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cryptography

In cryptography, an adversary (rarely opponent, enemy) is a malicious entity whose aim is to prevent the users of the cryptosystem from achieving their goal (primarily privacy, integrity, and availability of data). An adversary's efforts might take the form of attempting to discover secret data, corrupting someof the data in the system, spoofing the identity of a message senderor receiver, or forcing system downtime. Actual adversaries, as opposed to idealized ones, are referred to as attackers. Not surprisingly, the former term predominates in the cryptographic and the latter in the computer security literature. Eve, Mallory, Oscar and Trudy are all adversarial characters widely used in both types of texts. This notion of an adversary helps both intuitive and formal reasoning about cryptosystems by casting security analysis ofcryptosystems as a 'game' between the users and a centrally co-ordinated enemy. The notion of security of a cryptosystem is meaningful only with respect to particular attacks (usually presumedto be carried out by particular sorts of adversaries). There are several types of adversaries depending on what capabilities or intentions they are presumed to have. Adversaries may be[1]

computationally bounded or unbounded (i.e. in terms of time and storage resources),eavesdropping or Byzantine (i.e. passively listening on or actively corrupting data in the channel), static or adaptive (i.e. having fixed or changing behavior),mobile or non-mobile (e.g. in the context of network security)and so on. In actualsecurity practice, the attacks assigned to such adversaries are often seen, so such notional analysis is not merely theoretical.How successful an adversary is at breaking a system is measured by its advantage. An adversary's advantage is the difference between the adversary's probability of breaking the system and the probability that the system can be broken by simply guessing. The advantage is specified as a function of the security parameter.

In telecommunications, a communications protocol is a system of rules that allow two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. These are the rules or standard that defines the syntax, semantics and synchronization of communication and possible error recovery methods. Protocols may be implemented by hardware, software, or a combination of both.[1] Communicating systems use well-defined formats (protocol) for exchanging messages. Each message has an exact meaning intended to elicit a response from a range of possible responses pre-determined for that particular situation. The specified behavior is typically independent of how itis to be implemented. Communications protocols have to be agreed upon by the parties involved.[2] To reach agreement, a protocol may be developed into a technical standard. A programming language describes the same for computations, so there is a close analogy between protocols and programming languages: protocols are to communications as programming languages are to computations.[3] Information security, sometimes shortened to InfoSec, is the practice of defending information from unauthorized access, use, disclosure, disruption, modification, perusal, inspection, recordingor destruction. It is a general term that can be used regardless of the form the data may take (e.g. electronic, physical).[1] For the information security attribute CIA (confidentiality, integrity, and availability), see Information security. "Confidential" redirects here. For other uses, see Confidential (disambiguation). Confidentiality is a set of rules or a promise that limits access orplaces restrictions on certain types of information. Contents,, 1 Legal confidentiality, 1.1 History of the English law about

confidentiality, 2 Medical confidentiality, 3 Clinical and counseling psychology, 4 See also, 5 References. Legal confidentiality Main article: Privacy law Lawyers are often requiredby law to keep confidential anything pertaining to the representation of a client. The duty of confidentiality is much broader than the attorney–client evidentiary privilege, which only covers communications between the attorney and the client. Both the privilege and the duty serve the purpose of encouraging clients to speak frankly about their cases. This way, lawyers will be able to carry out their duty to provide clients with zealous representation.Otherwise, the opposing side may be able to surprise the lawyer in court with something which he did not know about his client, which may weaken the client's position. Also, a distrustful client might hide a relevant fact which he thinks is incriminating, but which a skilled lawyer could turn to the client's advantage (for example, byraising affirmative defenses like self-defense) However, most jurisdictions have exceptions for situations where the lawyer has reason to believe that the client may kill or seriously injure someone, may cause substantial injury to the financial interest or property of another, or is using (or seeking to use) the lawyer's services to perpetrate a crime or fraud.

In such situations the lawyer has the discretion, but not the obligation, to disclose information designed to prevent the planned action. Most states have a version of this discretionary disclosure rule under Rules of Professional Conduct, Rule 1.6 (or its equivalent). A few jurisdictions have made this traditionally discretionary duty mandatory. For example, see the New Jersey and Virginia Rules of Professional Conduct, Rule 1.6. In some jurisdictions the lawyer must try to convince the client to conform his or her conduct to the boundaries of the law before disclosing any otherwise confidential information. Note that these exceptions generally do not cover crimes that have already occurred, even in extreme cases where murderers have confessed the location of missingbodies to their lawyers but the police are still looking for those bodies. The U.S. Supreme Court and many state supreme courts have affirmed the right of a lawyer to withhold information in such situations. Otherwise, it would be impossible for any criminal defendant to obtain a zealous defense. California is famous for having one of the strongest duties of confidentiality in the world; its lawyers must protect client confidences at "every peril to

himself [or herself]" under former California Business and Professions Code section 6068(e). Until an amendment in 2004 (which turned subsection (e) into subsection (e)(1) and added subsection (e)(2) to section 6068), California lawyers were not even permitted to disclose that a client was about to commit murder or assault. TheSupreme Court of California promptly amended the California Rules ofProfessional Conduct to conform to the new exception in the revised statute. Recent legislation in the UK curtails the confidentiality professionals like lawyers and accountants can maintain at the expense of the state.[citation needed] Accountants, for example, arerequired to disclose to the state any suspicions of fraudulent accounting and, even, the legitimate use of tax saving schemes if those schemes are not already known to the tax authorities.

History of the English law about confidentiality The modern English law of confidence stems from the judgment of the Lord Chancellor, Lord Cottenham,[1] in which he restrained the defendant from publishing a catalogue of private etchings made by Queen Victoria and Prince Albert (Prince Albert v Strange). However, the jurisprudential basis of confidentiality remained largely unexamineduntil the case of Saltman Engineering Co. Ltd. v Campbell Engineering Co. Ltd.,[2] in which the Court of Appeal upheld the existence of an equitable doctrine of confidence, independent of contract. In Coco v A.N.Clark (Engineers) Ltd [1969] R.P.C. 41, Megarry J developed an influential tri-partite analysis of the essential ingredients of the cause of action for breach of confidence: the information must be confidential in quality,[3] and nature.[4][5] it must be imparted so as to import an obligation of confidence,[6][7] and there must be an unauthorised use[8][9] of that information resulting in the detriment[10] of the party communicating it.[11] The law in its then current state of development was authoritatively summarised by Lord Goff in the Spycatcher case.[12] He identified three qualifications limiting thebroad general principle that a duty of confidence arose when confidential information came to the knowledge of a person (the confidant) in circumstances where he had notice that the informationwas confidential, with the effect that it would be just in all the circumstances that he should be precluded from disclosing the information to others. First, once information had entered the public domain, it could no longer be protected as confidential. Secondly, the duty of confidence applied neither to useless

information, nor to trivia. Thirdly, the public interest in the preservation of a confidence might be outweighed by a greater publicinterest favouring disclosure.

The incorporation into domestic law of Article 8 of the European Convention on Human Rights by the Human Rights Act 1998 hassince had a profound effect on the development of the English law ofconfidentiality. Article 8 provides that everyone has the right to respect for his private and family life, his home and his correspondence. In Campbell v MGN Ltd,[13] the House of Lords held that the Daily Mirror had breached Naomi Campbell’s confidentiality rights by publishing reports and pictures of her attendance at Narcotics Anonymous meetings. Although their lordships were divided 3–2 as to the result of the appeal and adopted slightly different formulations of the applicable principles, there was broad agreementthat, in confidentiality cases involving issues of privacy, the focus shifted from the nature of the relationship between claimant and defendant to (a) an examination of the nature of the informationitself and (b) a balancing exercise between the claimant's rights under Article 8 and the defendant's competing rights (for example, under Article 10, to free speech). It presently remains unclear to what extent and how this judge-led development of a partial law of privacy will impact on the equitable principles of confidentiality as traditionally understood. Medical confidentiality It has been suggested that HIV confidentiality be merged into this article. (Discuss) Proposed since January 2015. Confidentiality is commonly applied to conversations between doctors and patients. Legal protections prevent physicians from revealing certain discussions with patients, even under oath in court.[14] This physician-patient privilege only applies to secrets shared between physician and patient during the course of providing medical care.[14] The rule dates back to at least the Hippocratic Oath, which reads: Whatever, in connection with my professional service, or not in connection with it, I see or hear, in the life of men, which ought not to be spoken of abroad, I will not divulge, as reckoning that all such should be kept secret. Traditionally, medical ethics has viewed the duty of confidentiality as a relatively non-negotiable tenet of medical practice. In the UK information about an individual's HIV status is kept confidential within the NHS. This is based in law, in

the NHS Constitution and in key NHS rules and procedures. It is alsooutlined in every NHS employee’s contract of employment and in professional standards set by regulatory bodies. The National AIDS Trust's Confidentiality in the NHS: Your Information, Your Rights[15] outlines these rights. However, there are a few limited instances when a healthcare worker can share personal information without consent if it is in the public interest. These instances areset out in guidance from the General Medical Council[16] which is the regulatory body for doctors. Sometimes the healthcare worker hasto provide the information - if required by law or in response to a court order.

Confidentiality is mandated in America by HIPAA laws, specifically the Privacy Rule, and various state laws, some more rigorous than HIPAA. However, numerous exceptions to the rules have been carved out over the years. For example, many American states require physicians to report gunshot wounds to the police and impaired drivers to the Department of Motor Vehicles. Confidentiality is also challenged in cases involving the diagnosis of a sexually transmitted disease in a patient who refuses to revealthe diagnosis to a spouse, and in the termination of a pregnancy in an underage patient, without the knowledge of the patient's parents.Many states in the U.S. have laws governing parental notification inunderage abortion.[17] Clinical and counseling psychology The ethical principle of confidentiality requires that information shared by the client with the therapist in the course of treatment is not shared with others. This is important for the therapeutic alliance, as it promotes an environment of trust. There are important exceptions to confidentiality, namely where it conflicts with the clinician's duty to warn or duty to protect. This includes instances of suicidal behavior or homicidal plans, child abuse, elder abuse and dependent adult abuse. [18] On 26 June 2012, a judgeof Oslo District Court apologized for the court's hearing of testimony (on 14 June, regarding contact with Child Welfare Services(Norway)) that was covered by confidentiality (that had not been waived at that point of the trial of Anders Behring Breivik).[19] Data integrity refers to maintaining and assuring the accuracy and consistency of data over its entire life-cycle,[1] and is a criticalaspect to the design, implementation and usage of any system which

stores, processes, or retrieves data. The term data integrity is broad in scope and may have widely different meanings depending on the specific context – even under the same general umbrella of computing. This article provides only a broad overview of some of the different types and concerns of data integrity.

Data integrity is the opposite of data corruption, which is a form of data loss. The overall intent of any data integrity technique is the same: ensure data is recorded exactly as intended (such as a database correctly rejecting mutually exclusive possibilities,) and upon later retrieval, ensure the data is the same as it was when it was originally recorded. In short, data integrity aims to prevent unintentional changes to information. Dataintegrity is not to be confused with data security, the discipline of protecting data from unauthorized parties. Any unintended changesto data as the result of a storage, retrieval or processing operation, including malicious intent, unexpected hardware failure, and human error, is failure of data integrity. If the changes are the result of unauthorized access, it may also be a failure of data security. Depending on the data involved this could manifest itself as benign as a single pixel in an image appearing a different color than was originally recorded, to the loss of vacation pictures or a business-critical database, to even catastrophic loss of human life in a life-critical system. Contents 1 Integrity types 1.1 Physical integrity 1.2 Logical integrity 2 Databases 2.1 Types of integrity constraints 2.2 Examples 3 File systems 4 Data storage 5 See also 6 References 7 Further readin Integrity types Physical integrity, Physical integrity deals with challenges associated with correctly storing and fetching the data itself. Challenges with physical integrity may include electromechanical faults, design flaws, material fatigue, corrosion, power outages, natural disasters, acts of war and terrorism, and other special environmental hazards such as ionizing radiation, extreme temperatures, pressures and g-forces.Ensuring physical integrity includes methods such as redundant hardware, an uninterruptible power supply, certain types of RAID arrays, radiation hardened chips, error-correcting memory, use of a clustered file system, using file systems that employ block level checksums such as ZFS, storage arrays that compute parity

calculations such as exclusive or or use a cryptographic hash function and even having a watchdog timer on critical subsystems.

Physical integrity often makes extensive use of error detecting algorithms known as error-correcting codes. Human-induced data integrity errors are often detected through the use of simpler checks and algorithms, such as the Damm algorithm or Luhn algorithm.These are used to maintain data integrity after manual transcriptionfrom one computer system to another by a human intermediary (e.g. credit card or bank routing numbers). Computer-induced transcriptionerrors can be detected through hash functions. In production systemsthese techniques are used together to ensure various degrees of dataintegrity. For example, a computer file system may be configured on a fault-tolerant RAID array, but might not provide block-level checksums to detect and prevent silent data corruption. As another example, a database management system might be compliant with the ACID properties, but the RAID controller or hard disk drive's internal write cache might not be Logical integrity See also: Mutex and Copy-on-write This type of integrity is concerned with the correctness or rationality of a piece of data, given a particular context. This includes topics such as referential integrity and entity integrity in a relational database or correctly ignoring impossible sensor data in robotic systems. These concerns involve ensuring that the data "makes sense" given its environment. Challenges include software bugs, design flaws, and human errors. Common methods of ensuring logical integrity include things such as a check constraints, foreign key constraints, program assertions, and other run-time sanity checks. Both physical and logical integrity often share many common challenges such as human errors and design flaws, and both must appropriately deal with concurrent requests to record and retrieve data, the latter of which is entirely a subject on its own. Databases

Data integrity contains guidelines for data retention, specifying or guaranteeing the length of time data can be retained in a particular database. It specifies what can be done with data values when their validity or usefulness expires. In order to achieve data integrity, these rules are consistently and routinely

applied to all data entering the system, and any relaxation of enforcement could cause errors in the data. Implementing checks on the data as close as possible to the source of input (such as human data entry), causes less erroneous data to enter the system. Strict enforcement of data integrity rules causes the error rates to be lower, resulting in time saved troubleshooting and tracing erroneousdata and the errors it causes algorithms. Data integrity also includes rules defining the relations a piece of data can have, to other pieces of data, such as a Customer record being allowed to link to purchased Products, but not to unrelated data such as Corporate Assets. Data integrity often includes checks and correction for invalid data, based on a fixed schema or a predefinedset of rules. An example being textual data entered where a date-time value is required. Rules for data derivation are also applicable, specifying how a data value is derived based on algorithm, contributors and conditions. It also specifies the conditions on how the data value could be re-derived. Types of integrity constraints Data integrity is normally enforced in a database system by a series of integrity constraints or rules. Threetypes of integrity constraints are an inherent part of the relational data model: entity integrity, referential integrity and domain integrity:

Entity integrity concerns the concept of a primary key. Entity integrity is an integrity rule which states that every table must have a primary key and that the column or columns chosen to be the primary key should be unique and not null. Referential integrityconcerns the concept of a foreign key. The referential integrity rule states that any foreign-key value can only be in one of two states. The usual state of affairs is that the foreign-key value refers to a primary key value of some table in the database. Occasionally, and this will depend on the rules of the data owner, aforeign-key value can be null. In this case we are explicitly sayingthat either there is no relationship between the objects representedin the database or that this relationship is unknown. Domain integrity specifies that all columns in a relational database must be declared upon a defined domain. The primary unit of data in the relational data model is the data item. Such data items are said to be non-decomposable or atomic. A domain is a set of values of the

same type. Domains are therefore pools of values from which actual values appearing in the columns of a table are drawn. User-defined integrity refers to a set of rules specified by a user, which do notbelong to the entity, domain and referential integrity categories. If a database supports these features it is the responsibility of the database to insure data integrity as well as the consistency model for the data storage and retrieval. If a database does not support these features it is the responsibility of the applications to ensure data integrity while the database supports the consistencymodel for the data storage and retrieval. Having a single, well-controlled, and well-defined data-integrity system increases stability (one centralized system performs all data integrity operations) performance (all data integrity operations are performedin the same tier as the consistency model) re-usability (all applications benefit from a single centralized data integrity system) maintainability (one centralized system for all data integrity administration).

As of 2012, since all modern databases support these features (see Comparison of relational database management systems), it has become the de facto responsibility of the database to ensure data integrity. Out-dated and legacy systems that use filesystems (text, spreadsheets, ISAM, flat files, etc.) for their consistency model lack any[citation needed] kind of data-integrity model. This requires organizations to invest a large amount of time,money and personnel in building data-integrity systems on a per-application basis that needlessly duplicate the existing data integrity systems found in modern databases. Many companies, and indeed many database systems themselves, offer products and servicesto migrate out-dated and legacy systems to modern databases to provide these data-integrity features. This offers organizations substantial savings in time, money and resources because they do nothave to develop per-application data-integrity systems that must be refactored each time the business requirements change. Examples An example of a data-integrity mechanism is the parent-and-child relationship of related records. If a parent record owns one or morerelated child records all of the referential integrity processes arehandled by the database itself, which automatically ensures the accuracy and integrity of the data so that no child record can existwithout a parent (also called being orphaned) and that no parent loses their child records. It also ensures that no parent record can

be deleted while the parent record owns any child records. All of this is handled at the database level and does not require coding integrity checks into each applications. File systems Various research results show that neither widespread filesystems (includingUFS, Ext, XFS, JFS and NTFS) nor hardware RAID solutions provide sufficient protection against data integrity problems.[2][3][4][5][6] Some filesystems (including Btrfs and ZFS) provide internal dataand metadata checksumming, what is used for detecting silent data corruption and improving data integrity. If a corruption is detectedthat way and internal RAID mechanisms provided by those filesystems are also used, such filesystems can additionally reconstruct corrupted data in a transparent way.[7] This approach allows improved data integrity protection covering the entire data paths, which is usually known as end-to-end data protection.[8] Data storage Main article: Data Integrity Field Apart from data in databases, standards exist to address the integrity of data on storage devices.[9] Methods Main article: Provenance

Authentication has relevance to multiple fields. In art, antiques, and anthropology, a common problem is verifying that a given artifact was produced by a certain person or was produced in acertain place or period of history. In computer science, verifying aperson's identity is often required to secure access to confidentialdata or systems. Authentication can be considered to be of three types: The first type of authentication is accepting proof of identity given by a credible person who has first-hand evidence thatthe identity is genuine. When authentication is required of art or physical objects, this proof could be a friend, family member or colleague attesting to the item's provenance, perhaps by having witnessed the item in its creator's possession. With autographed sports memorabilia, this could involve someone attesting that they witnessed the object being signed. A vendor selling branded items implies authenticity, while he or she may not have evidence that every step in the supply chain was authenticated. Authority based trust relationships (centralized) drive the majority of secured internet communication through known public certificate authorities;peer based trust (decentralized, web of trust) is used for personal services like email or files (pretty good privacy, GNU Privacy Guard) and trust is established by known individuals signing each

other's keys (proof of identity) or at Key signing parties, for example. The second type of authentication is comparing the attributes of the object itself to what is known about objects of that origin. For example, an art expert might look for similarities in the style of painting, check the location and form of a signature, or compare the object to an old photograph. An archaeologist might use carbon dating to verify the age of an artifact, do a chemical analysis of the materials used, or compare the style of construction or decoration to other artifacts of similar origin. The physics of sound and light, and comparison with a known physical environment, can be used to examine the authenticity of audio recordings, photographs, or videos. Documents can be verified as being created on ink or paper readily available at the time of the item's implied creation.

Attribute comparison may be vulnerable to forgery. In general,it relies on the facts that creating a forgery indistinguishable from a genuine artifact requires expert knowledge, that mistakes areeasily made, and that the amount of effort required to do so is considerably greater than the amount of profit that can be gained from the forgery. In art and antiques, certificates are of great importance for authenticating an object of interest and value. Certificates can, however, also be forged, and the authentication ofthese poses a problem. For instance, the son of Han van Meegeren, the well-known art-forger, forged the work of his father and provided a certificate for its provenance as well; see the article Jacques van Meegeren. Criminal and civil penalties for fraud, forgery, and counterfeiting can reduce the incentive for falsification, depending on the risk of getting caught. Currency andother financial instruments commonly use this second type of authentication method. Bills, coins, and cheques incorporate hard-to-duplicate physical features, such as fine printing or engraving, distinctive feel, watermarks, and holographic imagery, which are easy for trained receivers to verify. The third type of authentication relies on documentation or other external affirmations. In criminal courts, the rules of evidence often require establishing the chain of custody of evidence presented. This can be accomplished through a written evidence log, or by testimony from the police detectives and forensics staff that

handled it. Some antiques are accompanied by certificates attesting to their authenticity. Signed sports memorabilia is usually accompanied by a certificate of authenticity. These external recordshave their own problems of forgery and perjury, and are also vulnerable to being separated from the artifact and lost. In computer science, a user can be given access to secure systems basedon user credentials that imply authenticity. A network administratorcan give a user a password, or provide the user with a key card or other access device to allow system access. In this case, authenticity is implied but not guaranteed.

Consumer goods such as pharmaceuticals, perfume, fashion clothing can use all three forms of authentication to prevent counterfeit goods from taking advantage of a popular brand's reputation (damaging the brand owner's sales and reputation). As mentioned above, having an item for sale in a reputable store implicitly attests to it being genuine, the first type of authentication. The second type of authentication might involve comparing the quality and craftsmanship of an item, such as an expensive handbag, to genuine articles. The third type of authentication could be the presence of a trademark on the item, which is a legally protected marking, or any other identifying feature which aids consumers in the identification of genuine brand-name goods. With software, companies have taken great steps to protect from counterfeiters, including adding holograms, security rings, security threads and color shifting ink.[1] Factors and identity The ways in which someone may be authenticated fall into three categories, based on what are known as the factors of authentication: something the user knows, something the user has, and something the user is. Each authentication factor covers a rangeof elements used to authenticate or verify a person's identity priorto being granted access, approving a transaction request, signing a document or other work product, granting authority to others, and establishing a chain of authority. Security research has determined that for a positive authentication, elements from at least two, and preferably all three, factors should be verified.[2] The three factors (classes) and some of elements of each factor are: This is apicture of the front (top) and back (bottom) of an ID Card. the knowledge factors: Something the user knows (e.g., a password, pass

phrase, or personal identification number (PIN), challenge response (the user must answer a question, or pattern) the ownership factors:Something the user has (e.g., wrist band, ID card, security token, cell phone with built-in hardware token, software token, or cell phone holding a software token) the inherence factors: Something theuser is or does (e.g., fingerprint, retinal pattern, DNA sequence (there are assorted definitions of what is sufficient), signature, face, voice, unique bio-electric signals, or other biometric identifier). Two-factor authentication Main article: Two-factor authentication

When elements representing two factors are required for authentication, the term two-factor authentication is applied — e.g. a bankcard (something the user has) and a PIN (something the user knows). Business networks may require users to provide a password (knowledge factor) and a pseudorandom number froma security token (ownership factor). Access to a very-high-security system might require a mantrap screening of height, weight, facial, and fingerprint checks (several inherence factor elements) plus a PIN and a day code (knowledge factor elements), but this is still a two-factor authentication. Product authentication A Security hologram label on an electronics box for authentication Counterfeit products are often offered to consumers as being authentic. Counterfeit consumer goods such as electronics, music, apparel, and Counterfeit medications have been sold as being legitimate. Efforts to control the supply chain and educate consumers help ensure that authentic products are sold and used. Even security printing on packages, labels, and nameplates, however, is subject to counterfeiting. A secure key storage device can be used for authentication in consumer electronics, network authentication, license management, supply chain management, etc. Generally the device to be authenticated needs some sort of wireless or wired digital connection to either a host system or a network. Nonetheless, the component being authenticated need not be electronic in nature as an authentication chip can be mechanically attached and read through a connector to the host e.g. an authenticated ink tank for use with a printer. For products and services that these Secure Coprocessors can be applied to, they can offer a solution that can be much more difficult to counterfeit thanmost other options while at the same time being more easily verified. Packaging, Packaging and labeling can be engineered to

help reduce the risks of counterfeit consumer goods or the theft andresale of products.[3][4] Some package constructions are more difficult to copy and some have pilfer indicating seals. Counterfeitgoods, unauthorized sales (diversion), material substitution and tampering can all be reduced with these anti-counterfeiting technologies. Packages may include authentication seals and use security printing to help indicate that the package and contents arenot counterfeit; these too are subject to counterfeiting. Packages also can include anti-theft devices, such as dye-packs, RFID tags, or electronic article surveillance[5] tags that can be activated or detected by devices at exit points and require specialized tools to deactivate. Anti-counterfeiting technologies that can be used with packaging include:

Taggant fingerprinting - uniquely coded microscopic materials that are verified from a database. Encrypted micro-particles - unpredictably placed markings (numbers, layers and colors) not visible to the human eye Holograms - graphics printed onseals, patches, foils or labels and used at point of sale for visualverification Micro-printing - second line authentication often used on currencies Serialized barcodes UV printing - marks only visible under UV light Track and trace systems - use codes to link products to database tracking system Water indicators - become visible when contacted with water DNA tracking - genes embedded onto labels that can be traced Color shifting ink or film - visible marks that switchcolors or texture when tilted Tamper evident seals and tapes - destructible or graphically verifiable at point of sale 2d barcodes - data codes that can be tracked RFID chips Information content. Theauthentication of information can pose special problems with electronic communication, such as vulnerability to man-in-the-middleattacks, whereby a third party taps into the communication stream, and poses as each of the two other communicating parties, in order to intercept information from each. Extra identity factors can be required to authenticate each party's identity. Literary forgery caninvolve imitating the style of a famous author. If an original manuscript, typewritten text, or recording is available, then the medium itself (or its packaging — anything from a box to e-mail headers) can help prove or disprove the authenticity of the document. However, text, audio, and video can be copied into new

media, possibly leaving only the informational content itself to usein authentication. Various systems have been invented to allow authors to provide a means for readers to reliably authenticate thata given message originated from or was relayed by them. These involve authentication factors like: A difficult-to-reproduce physical artifact, such as a seal, signature, watermark, special stationery, or fingerprint. A shared secret, such as a passphrase, in the content of the message. An electronic signature; public-key infrastructure is often used to cryptographically guarantee that a message has been signed by the holder of a particular private key.The opposite problem is detection of plagiarism, where information from a different author is passed off as a person's own work. A common technique for proving plagiarism is the discovery of another copy of the same or very similar text, which has different attribution. In some cases, excessively high quality or a style mismatch may raise suspicion of plagiarism.

Factual verification Determining the truth or factual accuracyof information in a message is generally considered a separate problem from authentication. A wide range of techniques, from detective work, to fact checking in journalism, to scientific experiment might be employed. Video authentication It is sometimes necessary to authenticate the veracity of video recordings used as evidence in judicial proceedings. Proper chain-of-custody records and secure storage facilities can help ensure the admissibility of digital or analog recordings by the Court. Literacy & Literature authentication In literacy, authentication is a readers’ process of questioning the veracity of an aspect of literature and then verifying those questions via research. The fundamental question forauthentication of literature is - Do you believe it? Related to that, an authentication project is therefore a reading and writing activity which students documents the relevant research process ([6]). It builds students' critical literacy. The documentation materials for literature go beyond narrative texts and likely include informational texts, primary sources, and multimedia. The process typically involves both internet and hands-on library research. When authenticating historical fiction in particular, readers considers the extent that the major historical events, as well as the culture portrayed (e.g., the language, clothing, food, gender roles), are believable for the time period. ([7]). History and state-of-the-art Historically, fingerprints have been used as

the most authoritative method of authentication, but recent court cases in the US and elsewhere have raised fundamental doubts about fingerprint reliability.[citation needed] Outside of the legal system as well, fingerprints have been shown to be easily spoofable,with British Telecom's top computer-security official noting that "few" fingerprint readers have not already been tricked by one spoofor another.[8] Hybrid or two-tiered authentication methods offer a compelling solution, such as private keys encrypted by fingerprint inside of a USB device. In a computer data context, cryptographic methods have been developed (see digital signature and challenge-response authentication) which are currently not spoofable if and only if the originator's key has not been compromised. That the originator (or anyone other than an attacker) knows (or doesn't know) about a compromise is irrelevant. It is not known whether these cryptographically based authentication methods are provably secure, since unanticipated mathematical developments may make them vulnerable to attack in future. If that were to occur, it may call into question much of the authentication in the past. In particular,a digitally signed contract may be questioned when a new attack on the cryptography underlying the signature is discovered.

Strong authentication The U.S. Government's National Information Assurance Glossary defines strong authentication as layered authentication approach relying on two or more authenticators to establish the identity of an originator or receiver of information. The above definition is consistent with that of the European Central Bank, as discussed in the strong authentication entry. Authorization Main article: Authorization A soldier checks a driver's identification card before allowing her toenter a military base. The process of authorization is distinct fromthat of authentication. Whereas authentication is the process of verifying that "you are who you say you are", authorization is the process of verifying that "you are permitted to do what you are trying to do". Authorization thus presupposes authentication. For example, a client showing proper identification credentials to a bank teller is asking to be authenticated that he really is the one whose identification he is showing. A client whose authentication request is approved becomes authorized to access the accounts of that account holder, but no others. However note that if a stranger tries to access someone else's account with his own identification credentials, the stranger's identification credentials will still be

successfully authenticated because they are genuine and not counterfeit, however the stranger will not be successfully authorized to access the account, as the stranger's identification credentials had not been previously set to be eligible to access theaccount, even if valid (i.e. authentic). Similarly when someone tries to log on a computer, they are usually first requested to identify themselves with a login name and support that with a password. Afterwards, this combination is checked against an existing login-password validity record to check if the combination is authentic. If so, the user becomes authenticated (i.e. the identification he supplied in step 1 is valid, or authentic). Finally, a set of pre-defined permissions and restrictions for that particular login name is assigned to this user, which completes the final step, authorization. Even though authorization cannot occur without authentication, the former term is sometimes used to mean the combination of both. To distinguish "authentication" from the closely related "authorization", the shorthand notations A1 (authentication), A2 (authorization) as well as AuthN / AuthZ (AuthR) or Au / Az are used in some communities.[9] Normally delegation was considered to be a part of authorization domain. Recently authentication is also used for various type of delegation tasks. Delegation in IT network is also a new but evolving field.[10] Access control Main article: Access control, One familiar use of authentication and authorization is access control. A computer system that is supposed to be used only by those authorized must attempt to detect and exclude the unauthorized. Access to it is therefore usually controlled by insisting on an authentication procedure to establish with some degree of confidence the identity of the user, granting privileges established for that identity. One such procedure involves the usage of Layer 8 which allows IT administrators to identify users, control Internet activity of usersin the network, set user based policies and generate reports by username. Common examples of access control involving authenticationinclude:

Asking for photoID when a contractor first arrives at a house to perform work. Using captcha as a means of asserting that a user is a human being and not a computer program. By using One Time Password (OTP), received on a tele-network enabled device like

mobile phone, as an authentication password/PIN. A computer program using a blind credential to authenticate to another program Enteringa country with a passport Logging in to a computer Using a confirmation E-mail to verify ownership of an e-mail address Using an Internet banking system Withdrawing cash from an ATM In some cases, ease of access is balanced against the strictness of access checks. For example, the credit card network does not require a personal identification number for authentication of the claimed identity; and a small transaction usually does not even require a signature of the authenticated person for proof of authorization of the transaction. The security of the system is maintained by limiting distribution of credit card numbers, and by the threat of punishment for fraud. Security experts argue that it is impossible to prove the identity of a computer user with absolute certainty. Itis only possible to apply one or more tests which, if passed, have been previously declared to be sufficient to proceed. The problem isto determine which tests are sufficient, and many such are inadequate. Any given test can be spoofed one way or another, with varying degrees of difficulty. Computer security experts are now also recognising that despite extensive efforts, as a business, research and network community, we still do not have a secure understanding of the requirements for authentication, in a range of circumstances. Lacking this understanding is a significant barrier to identifying optimum methods of authentication. major questions are:

What is authentication for? Who benefits fromauthentication/who is disadvantaged by authentication failures? Whatdisadvantages can effective authentication actually guard against? Non-repudiation refers to a state of affairs where the author of a statement will not be able to successfully challenge the authorship of the statement or validity of an associated contract. The term is often seen in a legal setting wherein the authenticity of a signature is being challenged. In such an instance, the authenticityis being "repudiated". Contents 1 In security 1.1 In digital security 2 Trusted third parties (TTPs) 3 See also 4 References 5 External links In security In a general sense non-repudiation involves associating actions or changes to a unique individual. For a secure area, for example, it may be desirable to implement a key card access system. Non-repudiation would be violated if it were notalso a strictly enforced policy to prohibit sharing of the key cards

and to immediately report lost or stolen cards. Otherwise determining who performed the action of opening the door cannot be trivially determined. Similarly, for computer accounts, the individual owner of the account must not allow others to use that account, especially, for instance, by giving away their account's password, and a policy should be implemented to enforce this. This prevents the owner of the account from denying actions performed by the account.[1] In digital security Regarding digital security, thecryptological meaning and application of non-repudiation shifts to mean:[2] A service that provides proof of the integrity and origin of data. An authentication that can be asserted to be genuine with high assurance. Proof of data integrity is typically the easiest of these requirements to accomplish. A data hash, such as SHA2, is usually sufficient to establish that the likelihood of data being undetectably changed is extremely low. Even with this safeguard, it is still possible to tamper with data in transit, either through a man-in-the-middle attack or phishing. Due to this flaw, data integrity is best asserted when the recipient already possesses the necessary verification information. The most common method of asserting the digital origin of data is through digital certificates, a form of public key infrastructure, to which digital signatures belong. Note that the public key scheme is not used for encryption in this form, confidentiality is not achieved by signing a message with a private key (since anyone can obtain the public keyto reverse the signature). Verifying the digital origin means that the certified/signed data can be, with reasonable certainty, trustedto be from somebody who possesses the private key corresponding to the signing certificate. If the key is not properly safeguarded by the original owner, digital forgery can become a major concern.

Trusted third parties (TTPs) The ways in which a party may attempt to repudiate a signature present a challenge to the trustworthiness of the signatures themselves. The standard approach to mitigating these risks is to involve a trusted third party. The two most common TTPs are forensic analysts and notaries. A forensic analyst specializing in handwriting can look at a signature, compareit to a known valid signature, and make a reasonable assessment of the legitimacy of the first signature. A notary provides a witness whose job is to verify the identity of an individual by checking other credentials and affixing their certification that the party signing is who they claim to be. Further, a notary provides the

extra benefit of maintaining independent logs of their transactions,complete with the type of credential checked and another signature that can independently be verified by the preceding forensic analyst. For this double security, notaries are the preferred form of verification. On the digital side, the only TTP is the repositoryfor public key certificates. This provides the recipient with the ability to verify the origin of an item even if no direct exchange of the public information has ever been made. The digital signature,however, is forensically identical in both legitimate and forged uses - if someone possesses the private key they can create a "real"signature. The protection of the private key is the idea behind the United States Department of Defense's Common Access Card (CAC), which never allows the key to leave the card and therefore necessitates the possession of the card in addition to the personal identification number (PIN) code necessary to unlock the card for permission to use it for encryption and digital signatures. This article is about the study of topics such as quantity and structure.For other uses, see Mathematics (disambiguation). "Math" redirects here. For other uses, see Math (disambiguation). Euclid (holding calipers), Greek mathematician, 3rd century BC, as imagined by Raphael in this detail from The School of Athens.[1] Mathematics (from Greek μάθημα máthēma, “knowledge, study, learning”) is the study of topics such as quantity (numbers),[2] structure,[3] space,[2] and change.[4][5][6] There is a range of views among mathematicians and philosophers as to the exact scope and definitionof mathematics.[7][8] Mathematicians seek out patterns[9][10] and use them to formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proof. When mathematical structures are good models of real phenomena, then mathematical reasoning can provide insight or predictions about nature. Through the use of abstraction and logic, mathematics developed from counting, calculation, measurement, and the systematic study of the shapes and motions of physical objects. Practical mathematics has been a human activity for as far back as written records exist. The research required to solve mathematical problems can take years or even centuries of sustained inquiry.

Rigorous arguments first appeared in Greek mathematics, most notably in Euclid's Elements. Since the pioneering work of Giuseppe

Peano (1858–1932), David Hilbert (1862–1943), and others on axiomatic systems in the late 19th century, it has become customary to view mathematical research as establishing truth by rigorous deduction from appropriately chosen axioms and definitions. Mathematics developed at a relatively slow pace until the Renaissance, when mathematical innovations interacting with new scientific discoveries led to a rapid increase in the rate of mathematical discovery that has continued to the present day.[11] Galileo Galilei (1564–1642) said, "The universe cannot be read untilwe have learned the language and become familiar with the charactersin which it is written. It is written in mathematical language, and the letters are triangles, circles and other geometrical figures, without which means it is humanly impossible to comprehend a single word. Without these, one is wandering about in a dark labyrinth."[12] Carl Friedrich Gauss (1777–1855) referred to mathematics as "the Queen of the Sciences".[13] Benjamin Peirce (1809–1880) called mathematics "the science that draws necessary conclusions".[14] David Hilbert said of mathematics: "We are not speaking here of arbitrariness in any sense. Mathematics is not likea game whose tasks are determined by arbitrarily stipulated rules. Rather, it is a conceptual system possessing internal necessity thatcan only be so and by no means otherwise."[15] Albert Einstein (1879–1955) stated that "as far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality."[16] French mathematician Claire Voisin states "There is creative drive in mathematics, it's all about movement trying to express itself." [17] Mathematics is used throughout the world as an essential tool in many fields, including natural science, engineering, medicine, finance and the social sciences. Applied mathematics, the branch of mathematics concerned with application of mathematical knowledge to other fields, inspiresand makes use of new mathematical discoveries, which has led to the development of entirely new mathematical disciplines, such as statistics and game theory. Mathematicians also engage in pure mathematics, or mathematics for its own sake, without having any application in mind. There is no clear line separating pure and applied mathematics, and practical applications for what began as pure mathematics are often discovered.[18]

Contents

1 History

1.1 Evolution

1.2 Etymology

2 Definitions of mathematics

2.1 Mathematics as science

3 Inspiration, pure and applied mathematics, and aesthetics

4 Notation, language, and rigor

5 Fields of mathematics

5.1 Foundations and philosophy

5.2 Pure mathematics 5.3 Applied mathematics 6 Mathematical awards

7 See also

8 Notes

9 References

10 Further reading

11 External links

History

Evolution

Main article: History of mathematics

The evolution of mathematics can be seen as an ever-increasingseries of abstractions. The first abstraction, which is shared by many animals,[19] was probably that of numbers: the realization thata collection of two apples and a collection of two oranges (for example) have something in common, namely quantity of their members.

Greek mathematician Pythagoras (c. 570 – c. 495 BC), commonly credited with discovering the Pythagorean theorem

Mayan numerals

As evidenced by tallies found on bone, in addition to recognizing how to count physical objects, prehistoric peoples may have also recognized how to count abstract quantities, like time – days, seasons, years.[20]

More complex mathematics did not appear until around 3000 BC, when the Babylonians and Egyptians began using arithmetic, algebra and geometry for taxation and other financial calculations, for building and construction, and for astronomy.[21] The earliest uses of mathematics were in trading, land measurement, painting and weaving patterns and the recording of time.

In Babylonian mathematics elementary arithmetic (addition, subtraction, multiplication and division) first appears in the archaeological record. Numeracy pre-dated writing and numeral systems have been many and diverse, with the first known written numerals created by Egyptians in Middle Kingdom texts such as the Rhind Mathematical Papyrus.[citation needed]

Between 600 and 300 BC the Ancient Greeks began a systematic study of mathematics in its own right with Greek mathematics.[22]

Mathematics has since been greatly extended, and there has been a fruitful interaction between mathematics and science, to the benefit of both. Mathematical discoveries continue to be made today.According to Mikhail B. Sevryuk, in the January 2006 issue of the Bulletin of the American Mathematical Society, "The number of papersand books included in the Mathematical Reviews database since 1940 (the first year of operation of MR) is now more than 1.9 million, and more than 75 thousand items are added to the database each year.

The overwhelming majority of works in this ocean contain new mathematical theorems and their proofs."[23]

Etymology

The word mathematics comes from the Greek μάθημα (máthēma), which, in the ancient Greek language, means "that which is learnt",[24] "what one gets to know", hence also "study" and "science", and in modern Greek just "lesson". The word máthēma is derived from μανθάνω (manthano), while the modern Greek equivalent is μαθαίνω (mathaino), both of which mean "to learn". In Greece, the word for "mathematics" came to have the narrower and more technical meaning "mathematical study" even in Classical times.[25] Its adjective is μαθηματικός (mathēmatikós), meaning "related to learning" or "studious", which likewise further came to mean "mathematical". In particular, μαθηματικὴ τέχνη (mathēmatikḗ tékhnē), Latin: ars mathematica, meant "the mathematical art".

In Latin, and in English until around 1700, the term mathematics more commonly meant "astrology" (or sometimes "astronomy") rather than "mathematics"; the meaning gradually changed to its present one from about 1500 to 1800. This has resulted in several mistranslations: a particularly notorious one isSaint Augustine's warning that Christians should beware of mathematici meaning astrologers, which is sometimes mistranslated asa condemnation of mathematicians.[26]

The apparent plural form in English, like the French plural form les mathématiques (and the less commonly used singular derivative la mathématique), goes back to the Latin neuter plural mathematica (Cicero), based on the Greek plural τα μαθηματικά (ta mathēmatiká), used by Aristotle (384–322 BC), and meaning roughly "all things mathematical"; although it is plausible that English borrowed only the adjective mathematic(al) and formed the noun mathematics anew, after the pattern of physics and metaphysics, which were inherited from the Greek.[27] In English, the noun

mathematics takes singular verb forms. It is often shortened to maths or, in English-speaking North America, math.[28]

Definitions of mathematics

Main article: Definitions of mathematics

Leonardo Fibonacci, the Italian mathematician who established the Hindu–Arabic numeral system to the Western World

Aristotle defined mathematics as "the science of quantity", and this definition prevailed until the 18th century.[29] Starting in the 19th century, when the study of mathematics increased in rigor and began to address abstract topics such as group theory and projective geometry, which have no clear-cut relation to quantity and measurement, mathematicians and philosophers began to propose a variety of new definitions.[30] Some of these definitions emphasize the deductive character of much of mathematics, some emphasize its abstractness, some emphasize certain topics within mathematics. Today, no consensus on the definition of mathematics prevails, even among professionals.[7] There is not even consensus on whether mathematics is an art or a science.[8] A great many professional mathematicians take no interest in a definition of mathematics, or consider it undefinable.[7] Some just say, "Mathematics is what mathematicians do."[7]

Three leading types of definition of mathematics are called logicist, intuitionist, and formalist, each reflecting a different philosophical school of thought.[31] All have severe problems, none has widespread acceptance, and no reconciliation seems possible.[31]

An early definition of mathematics in terms of logic was Benjamin Peirce's "the science that draws necessary conclusions" (1870).[32] In the Principia Mathematica, Bertrand Russell and Alfred North Whitehead advanced the philosophical program known as logicism, and attempted to prove that all mathematical concepts, statements, and principles can be defined and proven entirely in

terms of symbolic logic. A logicist definition of mathematics is Russell's "All Mathematics is Symbolic Logic" (1903).[33]

Intuitionist definitions, developing from the philosophy of mathematician L.E.J. Brouwer, identify mathematics with certain mental phenomena. An example of an intuitionist definition is "Mathematics is the mental activity which consists in carrying out constructs one after the other."[31] A peculiarity of intuitionism is that it rejects some mathematical ideas considered valid according to other definitions. In particular, while other philosophies of mathematics allow objects that can be proven to exist even though they cannot be constructed, intuitionism allows only mathematical objects that one can actually construct.

Formalist definitions identify mathematics with its symbols and the rules for operating on them. Haskell Curry defined mathematics simply as "the science of formal systems".[34] A formal system is a set of symbols, or tokens, and some rules telling how the tokens may be combined into formulas. In formal systems, the word axiom has a special meaning, different from the ordinary meaning of "a self-evident truth". In formal systems, an axiom is a combination of tokens that is included in a given formal system without needing to be derived using the rules of the system.

Mathematics as science

Carl Friedrich Gauss, known as the prince of mathematicians

Gauss referred to mathematics as "the Queen of the Sciences".[13] In the original Latin Regina Scientiarum, as well as in German Königin der Wissenschaften, the word corresponding to science means a "field of knowledge", and this was the original meaning of "science" in English, also; mathematics is in this sense a field of knowledge. The specialization restricting the meaning of "science" to natural science follows the rise of Baconian science, which contrasted "natural science" to scholasticism, the Aristotelean method of inquiring from first principles. The role of empirical

experimentation and observation is negligible in mathematics, compared to natural sciences such as psychology, biology, or physics. Albert Einstein stated that "as far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality."[16] More recently, Marcus du Sautoy has called mathematics "the Queen of Science ... the main driving force behind scientific discovery".[35]

Many philosophers believe that mathematics is not experimentally falsifiable, and thus not a science according to the definition of Karl Popper.[36] However, in the 1930s Gödel's incompleteness theorems convinced many mathematicians[who?] that mathematics cannot be reduced to logic alone, and Karl Popper concluded that "most mathematical theories are, like those of physics and biology, hypothetico-deductive: pure mathematics therefore turns out to be much closer to the natural sciences whose hypotheses are conjectures, than it seemed even recently."[37] Otherthinkers, notably Imre Lakatos, have applied a version of falsificationism to mathematics itself.

An alternative view is that certain scientific fields (such astheoretical physics) are mathematics with axioms that are intended to correspond to reality. The theoretical physicist J.M. Ziman proposed that science is public knowledge, and thus includes mathematics.[38] Mathematics shares much in common with many fields in the physical sciences, notably the exploration of the logical consequences of assumptions. Intuition and experimentation also playa role in the formulation of conjectures in both mathematics and the(other) sciences. Experimental mathematics continues to grow in importance within mathematics, and computation and simulation are playing an increasing role in both the sciences and mathematics.

The opinions of mathematicians on this matter are varied. Manymathematicians[who?] feel that to call their area a science is to downplay the importance of its aesthetic side, and its history in the traditional seven liberal arts; others[who?] feel that to ignoreits connection to the sciences is to turn a blind eye to the fact

that the interface between mathematics and its applications in science and engineering has driven much development in mathematics. One way this difference of viewpoint plays out is in the philosophical debate as to whether mathematics is created (as in art) or discovered (as in science). It is common to see universitiesdivided into sections that include a division of Science and Mathematics, indicating that the fields are seen as being allied butthat they do not coincide. In practice, mathematicians are typicallygrouped with scientists at the gross level but separated at finer levels. This is one of many issues considered in the philosophy of mathematics.[citation needed]

Inspiration, pure and applied mathematics, and aesthetics

Main article: Mathematical beauty

Isaac Newton

Gottfried Wilhelm von Leibniz

Isaac Newton (left) and Gottfried Wilhelm Leibniz (right), developers of infinitesimal calculus

Mathematics arises from many different kinds of problems. At first these were found in commerce, land measurement, architecture and later astronomy; today, all sciences suggest problems studied bymathematicians, and many problems arise within mathematics itself. For example, the physicist Richard Feynman invented the path integral formulation of quantum mechanics using a combination of mathematical reasoning and physical insight, and today's string theory, a still-developing scientific theory which attempts to unifythe four fundamental forces of nature, continues to inspire new mathematics.[39]

Some mathematics is relevant only in the area that inspired it, and is applied to solve further problems in that area. But oftenmathematics inspired by one area proves useful in many areas, and joins the general stock of mathematical concepts. A distinction is often made between pure mathematics and applied mathematics. Howeverpure mathematics topics often turn out to have applications, e.g.

number theory in cryptography. This remarkable fact, that even the "purest" mathematics often turns out to have practical applications,is what Eugene Wigner has called "the unreasonable effectiveness of mathematics".[40] As in most areas of study, the explosion of knowledge in the scientific age has led to specialization: there arenow hundreds of specialized areas in mathematics and the latest Mathematics Subject Classification runs to 46 pages.[41] Several areas of applied mathematics have merged with related traditions outside of mathematics and become disciplines in their own right, including statistics, operations research, and computer science.

For those who are mathematically inclined, there is often a definite aesthetic aspect to much of mathematics. Many mathematicians talk about the elegance of mathematics, its intrinsicaesthetics and inner beauty. Simplicity and generality are valued. There is beauty in a simple and elegant proof, such as Euclid's proof that there are infinitely many prime numbers, and in an elegant numerical method that speeds calculation, such as the fast Fourier transform. G.H. Hardy in A Mathematician's Apology expressedthe belief that these aesthetic considerations are, in themselves, sufficient to justify the study of pure mathematics. He identified criteria such as significance, unexpectedness, inevitability, and economy as factors that contribute to a mathematical aesthetic.[42] Mathematicians often strive to find proofs that are particularly elegant, proofs from "The Book" of God according to Paul Erdős.[43][44] The popularity of recreational mathematics is another sign of the pleasure many find in solving mathematical questions.

Notation, language, and rigor

Main article: Mathematical notation

Leonhard Euler, who created and popularized much of the mathematical notation used today

Most of the mathematical notation in use today was not invented until the 16th century.[45] Before that, mathematics was written out in words, a painstaking process that limited mathematical discovery.[46] Euler (1707–1783) was responsible for

many of the notations in use today. Modern notation makes mathematics much easier for the professional, but beginners often find it daunting. It is extremely compressed: a few symbols contain a great deal of information. Like musical notation, modern mathematical notation has a strict syntax (which to a limited extentvaries from author to author and from discipline to discipline) and encodes information that would be difficult to write in any other way.

Mathematical language can be difficult to understand for beginners. Words such as or and only have more precise meanings thanin everyday speech. Moreover, words such as open and field have beengiven specialized mathematical meanings. Technical terms such as homeomorphism and integrable have precise meanings in mathematics. Additionally, shorthand phrases such as iff for "if and only if" belong to mathematical jargon. There is a reason for special notation and technical vocabulary: mathematics requires more precision than everyday speech. Mathematicians refer to this precision of language and logic as "rigor".

Mathematical proof is fundamentally a matter of rigor. Mathematicians want their theorems to follow from axioms by means ofsystematic reasoning. This is to avoid mistaken "theorems", based onfallible intuitions, of which many instances have occurred in the history of the subject.[47] The level of rigor expected in mathematics has varied over time: the Greeks expected detailed arguments, but at the time of Isaac Newton the methods employed wereless rigorous. Problems inherent in the definitions used by Newton would lead to a resurgence of careful analysis and formal proof in the 19th century. Misunderstanding the rigor is a cause for some of the common misconceptions of mathematics. Today, mathematicians continue to argue among themselves about computer-assisted proofs. Since large computations are hard to verify, such proofs may not be sufficiently rigorous.[48]

Axioms in traditional thought were "self-evident truths", but that conception is problematic.[49] At a formal level, an axiom is

just a string of symbols, which has an intrinsic meaning only in thecontext of all derivable formulas of an axiomatic system. It was thegoal of Hilbert's program to put all of mathematics on a firm axiomatic basis, but according to Gödel's incompleteness theorem every (sufficiently powerful) axiomatic system has undecidable formulas; and so a final axiomatization of mathematics is impossible. Nonetheless mathematics is often imagined to be (as far as its formal content) nothing but set theory in some axiomatization, in the sense that every mathematical statement or proof could be cast into formulas within set theory.[50]

Fields of mathematics

See also: Areas of mathematics and Glossary of areas of mathematics

An abacus, a simple calculating tool used since ancient times

Mathematics can, broadly speaking, be subdivided into the study of quantity, structure, space, and change (i.e. arithmetic, algebra, geometry, and analysis). In addition to these main concerns, there are also subdivisions dedicated to exploring links from the heart of mathematics to other fields: to logic, to set theory (foundations), to the empirical mathematics of the various sciences (applied mathematics), and more recently to the rigorous study of uncertainty. While some areas might seem unrelated, the Langlands program has found connections between areas previously thought unconnected, such as Galois groups, Riemann surfaces and number theory.

Foundations and philosophy

In order to clarify the foundations of mathematics, the fieldsof mathematical logic and set theory were developed. Mathematical logic includes the mathematical study of logic and the applications of formal logic to other areas of mathematics; set theory is the branch of mathematics that studies sets or collections of objects. Category theory, which deals in an abstract way with mathematical structures and relationships between them, is still in development.

The phrase "crisis of foundations" describes the search for a rigorous foundation for mathematics that took place from approximately 1900 to 1930.[51] Some disagreement about the foundations of mathematics continues to the present day. The crisis of foundations was stimulated by a number of controversies at the time, including the controversy over Cantor's set theory and the Brouwer–Hilbert controversy.

Mathematical logic is concerned with setting mathematics within a rigorous axiomatic framework, and studying the implicationsof such a framework. As such, it is home to Gödel's incompleteness theorems which (informally) imply that any effective formal system that contains basic arithmetic, if sound (meaning that all theorems that can be proven are true), is necessarily incomplete (meaning that there are true theorems which cannot be proved in that system).Whatever finite collection of number-theoretical axioms is taken as a foundation, Gödel showed how to construct a formal statement that is a true number-theoretical fact, but which does not follow from those axioms. Therefore, no formal system is a complete axiomatization of full number theory. Modern logic is divided into recursion theory, model theory, and proof theory, and is closely linked to theoretical computer science,[citation needed] as well as to category theory.

Theoretical computer science includes computability theory, computational complexity theory, and information theory. Computability theory examines the limitations of various theoreticalmodels of the computer, including the most well-known model – the Turing machine. Complexity theory is the study of tractability by computer; some problems, although theoretically solvable by computer, are so expensive in terms of time or space that solving them is likely to remain practically unfeasible, even with the rapidadvancement of computer hardware. A famous problem is the "P = NP?" problem, one of the Millennium Prize Problems.[52] Finally, information theory is concerned with the amount of data that can be stored on a given medium, and hence deals with concepts such as compression and entropy.

p \Rightarrow q \, Venn A intersect B.svg Commutative diagram for morphism.svg DFAexample.svg

Mathematical logic Set theory Category theory Theory of computation

Pure mathematics

Quantity

The study of quantity starts with numbers, first the familiar natural numbers and integers ("whole numbers") and arithmetical operations on them, which are characterized in arithmetic. The deeper properties of integers are studied in number theory, from which come such popular results as Fermat's Last Theorem. The twin prime conjecture and Goldbach's conjecture are two unsolved problemsin number theory.

As the number system is further developed, the integers are recognized as a subset of the rational numbers ("fractions"). These,in turn, are contained within the real numbers, which are used to represent continuous quantities. Real numbers are generalized to complex numbers. These are the first steps of a hierarchy of numbersthat goes on to include quaternions and octonions. Consideration of the natural numbers also leads to the transfinite numbers, which formalize the concept of "infinity". Another area of study is size, which leads to the cardinal numbers and then to another conception of infinity: the aleph numbers, which allow meaningful comparison ofthe size of infinitely large sets.

1, 2, 3,\ldots\! \ldots,-2, -1, 0, 1, 2\,\ldots\! -2, \frac{2}{3}, 1.21\,\! -e, \sqrt{2}, 3, \pi\,\! 2, i, -2+3i, 2e^{i\frac{4\pi}{3}}\,\!

Natural numbers Integers Rational numbers Real numbers Complex numbers

Structure

Many mathematical objects, such as sets of numbers and functions, exhibit internal structure as a consequence of operationsor relations that are defined on the set. Mathematics then studies properties of those sets that can be expressed in terms of that structure; for instance number theory studies properties of the set of integers that can be expressed in terms of arithmetic operations.Moreover, it frequently happens that different such structured sets (or structures) exhibit similar properties, which makes it possible,by a further step of abstraction, to state axioms for a class of structures, and then study at once the whole class of structures satisfying these axioms. Thus one can study groups, rings, fields and other abstract systems; together such studies (for structures defined by algebraic operations) constitute the domain of abstract algebra.

By its great generality, abstract algebra can often be appliedto seemingly unrelated problems; for instance a number of ancient problems concerning compass and straightedge constructions were finally solved using Galois theory, which involves field theory and group theory. Another example of an algebraic theory is linear algebra, which is the general study of vector spaces, whose elementscalled vectors have both quantity and direction, and can be used to model (relations between) points in space. This is one example of the phenomenon that the originally unrelated areas of geometry and algebra have very strong interactions in modern mathematics. Combinatorics studies ways of enumerating the number of objects thatfit a given structure.

\begin{matrix} (1,2,3) & (1,3,2) \\ (2,1,3) & (2,3,1) \\ (3,1,2) & (3,2,1) \end{matrix} Elliptic curve simple.svg Rubik's

cube.svg Group diagdram D6.svg Lattice of the divisibility of60.svg Braid-modular-group-cover.svg

Combinatorics Number theory Group theory Graph theory Order theory Algebra

Space

The study of space originates with geometry – in particular, Euclidean geometry. Trigonometry is the branch of mathematics that deals with relationships between the sides and the angles of triangles and with the trigonometric functions; it combines space and numbers, and encompasses the well-known Pythagorean theorem. Themodern study of space generalizes these ideas to include higher-dimensional geometry, non-Euclidean geometries (which play a centralrole in general relativity) and topology. Quantity and space both play a role in analytic geometry, differential geometry, and algebraic geometry. Convex and discrete geometry were developed to solve problems in number theory and functional analysis but now are pursued with an eye on applications in optimization and computer science. Within differential geometry are the concepts of fiber bundles and calculus on manifolds, in particular, vector and tensor calculus. Within algebraic geometry is the description of geometric objects as solution sets of polynomial equations, combining the concepts of quantity and space, and also the study of topological groups, which combine structure and space. Lie groups are used to study space, structure, and change. Topology in all its many ramifications may have been the greatest growth area in 20th-centurymathematics; it includes point-set topology, set-theoretic topology,algebraic topology and differential topology. In particular, instances of modern-day topology are metrizability theory, axiomaticset theory, homotopy theory, and Morse theory. Topology also includes the now solved Poincaré conjecture, and the still unsolved areas of the Hodge conjecture. Other results in geometry and topology, including the four color theorem and Kepler conjecture, have been proved only with the help of computers.

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Geometry Trigonometry Differential geometry Topology Fractal geometry Measure theory

Change

Understanding and describing change is a common theme in the natural sciences, and calculus was developed as a powerful tool to investigate it. Functions arise here, as a central concept describing a changing quantity. The rigorous study of real numbers and functions of a real variable is known as real analysis, with complex analysis the equivalent field for the complex numbers. Functional analysis focuses attention on (typically infinite-dimensional) spaces of functions. One of many applications of functional analysis is quantum mechanics. Many problems lead naturally to relationships between a quantity and its rate of change, and these are studied as differential equations. Many phenomena in nature can be described by dynamical systems; chaos theory makes precise the ways in which many of these systems exhibitunpredictable yet still deterministic behavior.

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Calculus Vector calculus Differential equations Dynamical systems Chaos theory Complex

analysis

Applied mathematics

Applied mathematics concerns itself with mathematical methods that are typically used in science, engineering, business, and industry. Thus, "applied mathematics" is a mathematical science with

specialized knowledge. The term applied mathematics also describes the professional specialty in which mathematicians work on practicalproblems; as a profession focused on practical problems, applied mathematics focuses on the "formulation, study, and use of mathematical models" in science, engineering, and other areas of mathematical practice.

In the past, practical applications have motivated the development of mathematical theories, which then became the subject of study in pure mathematics, where mathematics is developed primarily for its own sake. Thus, the activity of applied mathematics is vitally connected with research in pure mathematics.

Statistics and other decision sciences

Applied mathematics has significant overlap with the discipline of statistics, whose theory is formulated mathematically,especially with probability theory. Statisticians (working as part of a research project) "create data that makes sense" with random sampling and with randomized experiments;[53] the design of a statistical sample or experiment specifies the analysis of the data (before the data be available). When reconsidering data from experiments and samples or when analyzing data from observational studies, statisticians "make sense of the data" using the art of modelling and the theory of inference – with model selection and estimation; the estimated models and consequential predictions should be tested on new data.[54]

Statistical theory studies decision problems such as minimizing the risk (expected loss) of a statistical action, such asusing a procedure in, for example, parameter estimation, hypothesis testing, and selecting the best. In these traditional areas of mathematical statistics, a statistical-decision problem is formulated by minimizing an objective function, like expected loss or cost, under specific constraints: For example, designing a surveyoften involves minimizing the cost of estimating a population mean with a given level of confidence.[55] Because of its use of

optimization, the mathematical theory of statistics shares concerns with other decision sciences, such as operations research, control theory, and mathematical economics.[56]

Computational mathematics

Computational mathematics proposes and studies methods for solving mathematical problems that are typically too large for humannumerical capacity. Numerical analysis studies methods for problems in analysis using functional analysis and approximation theory; numerical analysis includes the study of approximation and discretization broadly with special concern for rounding errors. Numerical analysis and, more broadly, scientific computing also study non-analytic topics of mathematical science, especially algorithmic matrix and graph theory. Other areas of computational mathematics include computer algebra and symbolic computation.

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Mathematical physics Fluid dynamics Numerical analysis Optimization Probability theory Statistics Cryptography

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Mathematical finance Game theory Mathematical biology Mathematical chemistry Mathematical economics Control theory

Mathematical awards

Arguably the most prestigious award in mathematics is the Fields Medal,[57][58] established in 1936 and now awarded every four

years. The Fields Medal is often considered a mathematical equivalent to the Nobel Prize.

The Wolf Prize in Mathematics, instituted in 1978, recognizes lifetime achievement, and another major international award, the Abel Prize, was introduced in 2003. The Chern Medal was introduced in 2010 to recognize lifetime achievement. These accolades are awarded in recognition of a particular body of work, which may be innovational, or provide a solution to an outstanding problem in an established field.

A famous list of 23 open problems, called "Hilbert's problems", was compiled in 1900 by German mathematician David Hilbert. This list achieved great celebrity among mathematicians, and at least nine of the problems have now been solved. A new list of seven important problems, titled the "Millennium Prize Problems",was published in 2000. A solution to each of these problems carries a $1 million reward, and only one (the Riemann hypothesis) is duplicated in Hilbert's problems.

Computer science is the scientific and practical approach to computation and its applications. It is the systematic study of the feasibility, structure, expression, and mechanization of the methodical procedures (or algorithms) that underlie the acquisition,representation, processing, storage, communication of, and access toinformation, whether such information is encoded as bits in a computer memory or transcribed in genes and protein structures in a biological cell.[1] An alternate, more succinct definition of computer science is the study of automating algorithmic processes that scale. A computer scientist specializes in the theory of computation and the design of computational systems.[2]

Its subfields can be divided into a variety of theoretical andpractical disciplines. Some fields, such as computational complexitytheory (which explores the fundamental properties of computational and intractable problems), are highly abstract, while fields such ascomputer graphics emphasize real-world visual applications. Still

other fields focus on the challenges in implementing computation. For example, programming language theory considers various approaches to the description of computation, while the study of computer programming itself investigates various aspects of the use of programming language and complex systems. Human–computer interaction considers the challenges in making computers and computations useful, usable, and universally accessible to humans.

Contents

1 History

1.1 Contributions

2 Philosophy

2.1 Name of the field

3 Areas of computer science

3.1 Theoretical computer science

3.1.1 Theory of computation

3.1.2 Information and coding theory

3.1.3 Algorithms and data structures

3.1.4 Programming language theory

3.1.5 Formal methods

3.2 Applied computer science

3.2.1 Artificial intelligence

3.2.2 Computer architecture and engineering

3.2.3 Computer performance analysis

3.2.4 Computer graphics and visualization

3.2.5 Computer security and cryptography

3.2.6 Computational science

3.2.7 Computer networks

3.2.8 Concurrent, parallel and distributed systems

3.2.9 Databases

3.2.10 Software engineering

4 The great insights of computer science

5 Academia

6 Education

7 See also

8 Notes

9 References

10 Further reading

11 External links

History

Main article: History of computer science

Charles Babbage is credited with inventing the first mechanical computer.

Ada Lovelace is credited with writing the first algorithm intended for processing on a computer.

The earliest foundations of what would become computer sciencepredate the invention of the modern digital computer. Machines for calculating fixed numerical tasks such as the abacus have existed since antiquity, aiding in computations such as multiplication and division. Further, algorithms for performing computations have existed since antiquity, even before the development of sophisticated computing equipment. The ancient Sanskrit treatise Shulba Sutras, or "Rules of the Chord", is a book of algorithms written in 800 BCE for constructing geometric objects like altars using a peg and chord, an early precursor of the modern field of computational geometry.

Blaise Pascal designed and constructed the first working mechanical calculator, Pascal's calculator, in 1642.[3] In 1673 Gottfried Leibniz demonstrated a digital mechanical calculator, called the 'Stepped Reckoner'.[4] He may be considered the first computer scientist and information theorist, for, among other reasons, documenting the binary number system. In 1820, Thomas de Colmar launched the mechanical calculator industry[note 1] when he released his simplified arithmometer, which was the first calculating machine strong enough and reliable enough to be used daily in an office environment. Charles Babbage started the design of the first automatic mechanical calculator, his difference engine,in 1822, which eventually gave him the idea of the first programmable mechanical calculator, his Analytical Engine.[5] He started developing this machine in 1834 and "in less than two years he had sketched out many of the salient features of the modern computer. A crucial step was the adoption of a punched card system derived from the Jacquard loom"[6] making it infinitely programmable.[note 2] In 1843, during the translation of a French article on the analytical engine, Ada Lovelace wrote, in one of the many notes she included, an algorithm to compute the Bernoulli numbers, which is considered to be the first computer program.[7] Around 1885, Herman Hollerith invented the tabulator, which used punched cards to process statistical information; eventually his company became part of IBM. In 1937, one hundred years after Babbage's impossible dream, Howard Aiken convinced IBM, which was making all kinds of punched card equipment and was also in the calculator business[8] to develop his giant programmable calculator,the ASCC/Harvard Mark I, based on Babbage's analytical engine, whichitself used cards and a central computing unit. When the machine wasfinished, some hailed it as "Babbage's dream come true".[9]

During the 1940s, as new and more powerful computing machines were developed, the term computer came to refer to the machines rather than their human predecessors.[10] As it became clear that computers could be used for more than just mathematical calculations, the field of computer science broadened to study computation in general. Computer science began to be established as

a distinct academic discipline in the 1950s and early 1960s.[11][12]The world's first computer science degree program, the Cambridge Diploma in Computer Science, began at the University of Cambridge Computer Laboratory in 1953. The first computer science degree program in the United States was formed at Purdue University in 1962.[13] Since practical computers became available, many applications of computing have become distinct areas of study in their own rights.

Although many initially believed it was impossible that computers themselves could actually be a scientific field of study, in the late fifties it gradually became accepted among the greater academic population.[14][15] It is the now well-known IBM brand thatformed part of the computer science revolution during this time. IBM(short for International Business Machines) released the IBM 704[16]and later the IBM 709[17] computers, which were widely used during the exploration period of such devices. "Still, working with the IBM[computer] was frustrating ... if you had misplaced as much as one letter in one instruction, the program would crash, and you would have to start the whole process over again".[14] During the late 1950s, the computer science discipline was very much in its developmental stages, and such issues were commonplace.[15]

Time has seen significant improvements in the usability and effectiveness of computing technology. Modern society has seen a significant shift in the users of computer technology, from usage only by experts and professionals, to a near-ubiquitous user base. Initially, computers were quite costly, and some degree of human aidwas needed for efficient use - in part from professional computer operators. As computer adoption became more widespread and affordable, less human assistance was needed for common usage.

Contributions

The German military used the Enigma machine (shown here) during World War II for communications they wanted kept secret. The large-scale decryption of Enigma traffic at Bletchley Park was an important factor that contributed to Allied victory in WWII.[18]

Despite its short history as a formal academic discipline, computer science has made a number of fundamental contributions to science and society - in fact, along with electronics, it is a founding science of the current epoch of human history called the Information Age and a driver of the Information Revolution, seen as the third major leap in human technological progress after the Industrial Revolution (1750-1850 CE) and the Agricultural Revolution(8000-5000 BCE).

These contributions include:

The start of the "digital revolution", which includes the current Information Age and the Internet.[19]

A formal definition of computation and computability, and proof that there are computationally unsolvable and intractable problems.[20]

The concept of a programming language, a tool for the precise expression of methodological information at various levels of abstraction.[21]

In cryptography, breaking the Enigma code was an importantfactor contributing to the Allied victory in World War II.[18]

Scientific computing enabled practical evaluation of processes and situations of great complexity, as well as experimentation entirely by software. It also enabled advanced studyof the mind, and mapping of the human genome became possible with the Human Genome Project.[19] Distributed computing projects such asFolding@home explore protein folding.

Algorithmic trading has increased the efficiency and liquidity of financial markets by using artificial intelligence, machine learning, and other statistical and numerical techniques on a large scale.[22] High frequency algorithmic trading can also exacerbate volatility.[23]

Computer graphics and computer-generated imagery have become ubiquitous in modern entertainment, particularly in television, cinema, advertising, animation and video games. Even films that feature no explicit CGI are usually "filmed" now on digital cameras, or edited or postprocessed using a digital video editor.[citation needed]

Simulation of various processes, including computational fluid dynamics, physical, electrical, and electronic systems and circuits, as well as societies and social situations (notably war games) along with their habitats, among many others. Modern computers enable optimization of such designs as complete aircraft. Notable in electrical and electronic circuit design are SPICE, as well as software for physical realization of new (or modified) designs. The latter includes essential design software for integrated circuits.[citation needed]

Artificial intelligence is becoming increasingly importantas it gets more efficient and complex. There are many applications of AI, some of which can be seen at home, such as robotic vacuum cleaners. It is also present in video games and on the modern battlefield in drones, anti-missile systems, and squad support robots.

Philosophy

Main article: Philosophy of computer science

A number of computer scientists have argued for the distinction of three separate paradigms in computer science. Peter Wegner argued that those paradigms are science, technology, and mathematics.[24] Peter Denning's working group argued that they are theory, abstraction (modeling), and design.[25] Amnon H. Eden described them as the "rationalist paradigm" (which treats computer science as a branch of mathematics, which is prevalent in theoretical computer science, and mainly employs deductive reasoning), the "technocratic paradigm" (which might be found in engineering approaches, most prominently in software engineering), and the "scientific paradigm" (which approaches computer-related

artifacts from the empirical perspective of natural sciences, identifiable in some branches of artificial intelligence).[26]

Name of the field

Although first proposed in 1956,[15] the term "computer science" appears in a 1959 article in Communications of the ACM,[27]in which Louis Fein argues for the creation of a Graduate School in Computer Sciences analogous to the creation of Harvard Business School in 1921,[28] justifying the name by arguing that, like management science, the subject is applied and interdisciplinary in nature, while having the characteristics typical of an academic discipline.[27] His efforts, and those of others such as numerical analyst George Forsythe, were rewarded: universities went on to create such programs, starting with Purdue in 1962.[29] Despite its name, a significant amount of computer science does not involve the study of computers themselves. Because of this, several alternative names have been proposed.[30] Certain departments of major universities prefer the term computing science, to emphasize precisely that difference. Danish scientist Peter Naur suggested theterm datalogy,[31] to reflect the fact that the scientific discipline revolves around data and data treatment, while not necessarily involving computers. The first scientific institution touse the term was the Department of Datalogy at the University of Copenhagen, founded in 1969, with Peter Naur being the first professor in datalogy. The term is used mainly in the Scandinavian countries. An alternative term, also proposed by Naur, is data science; this is now used for a distinct field of data analysis, including statistics and databases.

Also, in the early days of computing, a number of terms for the practitioners of the field of computing were suggested in the Communications of the ACM – turingineer, turologist, flow-charts-man, applied meta-mathematician, and applied epistemologist.[32] Three months later in the same journal, comptologist was suggested, followed next year by hypologist.[33] The term computics has also been suggested.[34] In Europe, terms derived from contracted translations of the expression "automatic information" (e.g.

"informazione automatica" in Italian) or "information and mathematics" are often used, e.g. informatique (French), Informatik (German), informatica (Italy, The Netherlands), informática (Spain, Portugal), informatika (Slavic languages and Hungarian) or pliroforiki (πληροφορική, which means informatics) in Greek. Similarwords have also been adopted in the UK (as in the School of Informatics of the University of Edinburgh).[35]

A folkloric quotation, often attributed to—but almost certainly not first formulated by—Edsger Dijkstra, states that "computer science is no more about computers than astronomy is abouttelescopes."[note 3] The design and deployment of computers and computer systems is generally considered the province of disciplinesother than computer science. For example, the study of computer hardware is usually considered part of computer engineering, while the study of commercial computer systems and their deployment is often called information technology or information systems. However,there has been much cross-fertilization of ideas between the variouscomputer-related disciplines. Computer science research also often intersects other disciplines, such as philosophy, cognitive science,linguistics, mathematics, physics, biology, statistics, and logic.

Computer science is considered by some to have a much closer relationship with mathematics than many scientific disciplines, withsome observers saying that computing is a mathematical science.[11] Early computer science was strongly influenced by the work of mathematicians such as Kurt Gödel and Alan Turing, and there continues to be a useful interchange of ideas between the two fieldsin areas such as mathematical logic, category theory, domain theory,and algebra.[15]

The relationship between computer science and software engineering is a contentious issue, which is further muddied by disputes over what the term "software engineering" means, and how computer science is defined.[36] David Parnas, taking a cue from therelationship between other engineering and science disciplines, has claimed that the principal focus of computer science is studying the

properties of computation in general, while the principal focus of software engineering is the design of specific computations to achieve practical goals, making the two separate but complementary disciplines.[37]

The academic, political, and funding aspects of computer science tend to depend on whether a department formed with a mathematical emphasis or with an engineering emphasis. Computer science departments with a mathematics emphasis and with a numericalorientation consider alignment with computational science. Both types of departments tend to make efforts to bridge the field educationally if not across all research.

Areas of computer science

Further information: Outline of computer science

As a discipline, computer science spans a range of topics fromtheoretical studies of algorithms and the limits of computation to the practical issues of implementing computing systems in hardware and software.[38][39] CSAB, formerly called Computing Sciences Accreditation Board – which is made up of representatives of the Association for Computing Machinery (ACM), and the IEEE Computer Society (IEEE-CS)[40] – identifies four areas that it considers crucial to the discipline of computer science: theory of computation, algorithms and data structures, programming methodologyand languages, and computer elements and architecture. In addition to these four areas, CSAB also identifies fields such as software engineering, artificial intelligence, computer networking and telecommunications, database systems, parallel computation, distributed computation, computer-human interaction, computer graphics, operating systems, and numerical and symbolic computation as being important areas of computer science.[38]

Theoretical computer science

Main article: Theoretical computer science

The broader field of theoretical computer science encompasses both the classical theory of computation and a wide range of other topics that focus on the more abstract, logical, and mathematical aspects of computing.

Theory of computation

Main article: Theory of computation

According to Peter J. Denning, the fundamental question underlying computer science is, "What can be (efficiently) automated?"[11] The study of the theory of computation is focused onanswering fundamental questions about what can be computed and what amount of resources are required to perform those computations. In an effort to answer the first question, computability theory examines which computational problems are solvable on various theoretical models of computation. The second question is addressed by computational complexity theory, which studies the time and spacecosts associated with different approaches to solving a multitude ofcomputational problems.

The famous "P=NP?" problem, one of the Millennium Prize Problems,[41] is an open problem in the theory of computation.

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Automata theory Computability theory Computational complexitytheory Cryptography Quantum computing theory

Information and coding theory

Main articles: Information theory and Coding theory

Information theory is related to the quantification of information. This was developed by Claude E. Shannon to find fundamental limits on signal processing operations such as compressing data and on reliably storing and communicating data.[42]Coding theory is the study of the properties of codes (systems for

converting information from one form to another) and their fitness for a specific application. Codes are used for data compression, cryptography, error detection and correction, and more recently alsofor network coding. Codes are studied for the purpose of designing efficient and reliable data transmission methods.

Algorithms and data structures

Algorithms and data structures is the study of commonly used computational methods and their computational efficiency.

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Analysis of algorithms Algorithms Data structures Combinatorial optimization Computational geometry

Programming language theory

Main article: Programming language theory

Programming language theory is a branch of computer science that deals with the design, implementation, analysis, characterization, and classification of programming languages and their individual features. It falls within the discipline of computer science, both depending on and affecting mathematics, software engineering and linguistics. It is an active research area,with numerous dedicated academic journals.

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Type theory Compiler design Programming languages

Formal methods

Main article: Formal methods

Formal methods are a particular kind of mathematically based technique for the specification, development and verification of

software and hardware systems. The use of formal methods for software and hardware design is motivated by the expectation that, as in other engineering disciplines, performing appropriate mathematical analysis can contribute to the reliability and robustness of a design. They form an important theoretical underpinning for software engineering, especially where safety or security is involved. Formal methods are a useful adjunct to software testing since they help avoid errors and can also give a framework for testing. For industrial use, tool support is required.However, the high cost of using formal methods means that they are usually only used in the development of high-integrity and life-critical systems, where safety or security is of utmost importance. Formal methods are best described as the application of a fairly broad variety of theoretical computer science fundamentals, in particular logic calculi, formal languages, automata theory, and program semantics, but also type systems and algebraic data types toproblems in software and hardware specification and verification.

Applied computer science

Applied computer science aims at identifying certain computer science concepts that can be used directly in solving real world problems.

Artificial intelligence

Main article: Artificial intelligence

This branch of computer science aims to or is required to synthesise goal-orientated processes such as problem-solving, decision-making, environmental adaptation, learning and communication found in humans and animals. From its origins in cybernetics and in the Dartmouth Conference (1956), artificial intelligence (AI) research has been necessarily cross-disciplinary, drawing on areas of expertise such as applied mathematics, symbolic logic, semiotics, electrical engineering, philosophy of mind, neurophysiology, and social intelligence. AI is associated in the popular mind with robotic development, but the main field of practical application has been as an embedded component in areas of

software development, which require computational understanding. Thestarting-point in the late 1940s was Alan Turing's question "Can computers think?", and the question remains effectively unanswered although the "Turing test" is still used to assess computer output on the scale of human intelligence. But the automation of evaluativeand predictive tasks has been increasingly successful as a substitute for human monitoring and intervention in domains of computer application involving complex real-world data.

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Machine learning Computer vision Image processing

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Pattern recognition Data mining Evolutionary computation

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Knowledge representation Natural language processing Robotics

Computer architecture and engineering

Main articles: Computer architecture and Computer engineering

Computer architecture, or digital computer organization, is the conceptual design and fundamental operational structure of a computer system. It focuses largely on the way by which the central processing unit performs internally and accesses addresses in memory.[43] The field often involves disciplines of computer engineering and electrical engineering, selecting and interconnecting hardware components to create computers that meet functional, performance, and cost goals.

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Digital logic Microarchitecture Multiprocessing

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Ubiquitous computing Systems architecture Operating systems

Computer performance analysis

Main article: Computer performance

Computer performance analysis is the study of work flowing through computers with the general goals of improving throughput, controlling response time, using resources efficiently, eliminating bottlenecks, and predicting performance under anticipated peak loads.[44]

Computer graphics and visualization

Main article: Computer graphics (computer science)

Computer graphics is the study of digital visual contents, andinvolves synthese and manipulations of image data. The study is connected to many other fields in computer science, including computer vision, image processing, and computational geometry, and is heavily applied in the fields of special effects and video games.

Computer security and cryptography

Main articles: Computer security and Cryptography

Computer security is a branch of computer technology, whose objective includes protection of information from unauthorized access, disruption, or modification while maintaining the accessibility and usability of the system for its intended users. Cryptography is the practice and study of hiding (encryption) and therefore deciphering (decryption) information. Modern cryptography is largely related to computer science, for many encryption and decryption algorithms are based on their computational complexity.

Computational science

Computational science (or scientific computing) is the field of study concerned with constructing mathematical models and

quantitative analysis techniques and using computers to analyze and solve scientific problems. In practical use, it is typically the application of computer simulation and other forms of computation toproblems in various scientific disciplines.

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Numerical analysis Computational physics Computationalchemistry Bioinformatics

Computer networks

Main article: Computer network

This branch of computer science aims to manage networks between computers worldwide.

Concurrent, parallel and distributed systems

Main articles: Concurrency (computer science) and Distributed computing

Concurrency is a property of systems in which several computations are executing simultaneously, and potentially interacting with each other. A number of mathematical models have been developed for general concurrent computation including Petri nets, process calculi and the Parallel Random Access Machine model. A distributed system extends the idea of concurrency onto multiple computers connected through a network. Computers within the same distributed system have their own private memory, and information isoften exchanged among themselves to achieve a common goal.

Databases

Main article: Database

A database is intended to organize, store, and retrieve large amounts of data easily. Digital databases are managed using database

management systems to store, create, maintain, and search data, through database models and query languages.

Software engineering

Main article: Software engineering

See also: Computer programming

Software engineering is the study of designing, implementing, and modifying software in order to ensure it is of high quality, affordable, maintainable, and fast to build. It is a systematic approach to software design, involving the application of engineering practices to software. Software engineering deals with the organizing and analyzing of software— it doesn't just deal with the creation or manufacture of new software, but its internal maintenance and arrangement. Both computer applications software engineers and computer systems software engineers are projected to be among the fastest growing occupations from 2008 and 2018.

The great insights of computer science

The philosopher of computing Bill Rapaport noted three Great Insights of Computer Science[45]

Leibniz's, Boole's, Alan Turing's, Shannon's, & Morse's insight: There are only two objects that a computer has to deal within order to represent "anything"

All the information about any computable problem can be represented using only 0 and 1 (or any other bistable pair that can flip-flop between two easily distinguishable states, such as "on"/"off", "magnetized/de-magnetized", "high-voltage/low-voltage", etc.).

See also: Digital physics

Alan Turing's insight: There are only five actions that a computer has to perform in order to do "anything"

Every algorithm can be expressed in a language for a computer consisting of only five basic instructions:

* move left one location

* move right one location

* read symbol at current location

* print 0 at current location

* print 1 at current location

See also: Turing machine

Böhm and Jacopini's insight: There are only three ways of combining these actions (into more complex ones) that are needed in order for a computer to do "anything"

Only three rules are needed to combine any set of basic instructions into more complex ones:

sequence:

first do this; then do that

selection :

IF such-and-such is the case,

THEN do this

ELSE do that

repetition:

WHILE such-and-such is the case DO this

Note that the three rules of Boehm's and Jacopini's insight can be further simplified with the use of goto (which means it is more elementary than structured programming).

See also: Elementary function arithmetic § Friedman's grand conjecture

Academia

Further information: List of computer science conferences and Category:Computer science journals

Conferences are important events for computer science research. During these conferences, researchers from the public and private sectors present their recent work and meet. Unlike in most other academic fields, in computer science, the prestige of conference papers is greater than that of journal publications.[46][47] One proposed explanation for this is the quick development of this relatively new field requires rapid review and distribution of results, a task better handled by conferences than by journals.[48]

Education

See also: Women in computing

Since computer science is a relatively new field, it is not aswidely taught in schools and universities as other academic

subjects. For example, in 2014, Code.org estimated that only 10 percent of high schools in the United States offered computer science education.[49] A 2010 report by Association for Computing Machinery (ACM) and Computer Science Teachers Association (CSTA) revealed that only 14 out of 50 states have adopted significant education standards for high school computer science.[50] However, computer science education is growing. Some countries, such as Israel, New Zealand and South Korea, have already included computer science in their respective national secondary education curriculum.[51][52] Several countries are following suit.[53]

In most countries, there is a significant gender gap in computer science education. For example, in the U.S. about 20% of computer science degrees in 2012 were conferred to women.[54] This gender gap also exists in other Western countries.[55] However, in some parts of the world, the gap is small or nonexistent. In 2011, approximately half of all computer science degrees in Malaysia were conferred to women.[56] In 2001, women made up 54.5% of computer science graduates in Guyana.[55]

"Electrical and computer engineering" redirects here. For contents about computer engineering, see Computer engineering.

Electrical engineers design complex power systems ...

... and electronic circuits.

Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics, and electromagnetism. This field first became an identifiable occupation in the latter half of the 19th century aftercommercialization of the electric telegraph, the telephone, and electric power distribution and use. Subsequently, broadcasting and recording media made electronics part of daily life. The invention of the transistor, and later the integrated circuit, brought down the cost of electronics to the point where they can be used in almost any household object.

Electrical engineering has now subdivided into a wide range ofsubfields including electronics, digital computers, power engineering, telecommunications, control systems, radio-frequency engineering, signal processing, instrumentation, and microelectronics. The subject of electronic engineering is often treated as its own subfield but it intersects with all the other subfields, including the power electronics of power engineering.

Electrical engineers typically hold a degree in electrical engineering or electronic engineering. Practicing engineers may haveprofessional certification and be members of a professional body. Such bodies include the Institute of Electrical and Electronic Engineers (IEEE) and the Institution of Engineering and Technology (IET).

Electrical engineers work in a very wide range of industries and the skills required are likewise variable. These range from basic circuit theory to the management skills required of a project manager. The tools and equipment that an individual engineer may need are similarly variable, ranging from a simple voltmeter to a top end analyzer to sophisticated design and manufacturing software.

Contents

1 History

1.1 19th century

1.2 More modern developments

1.3 Solid-state transistors

2 Subdisciplines

2.1 Power

2.2 Control

2.3 Electronics

2.4 Microelectronics

2.5 Signal processing

2.6 Telecommunications

2.7 Instrumentation

2.8 Computers

2.9 Related disciplines

3 Education

4 Practicing engineers

5 Tools and work

6 See also

7 Notes

8 References

9 Further reading

10 External links

History

Main article: History of electrical engineering

Electricity has been a subject of scientific interest since atleast the early 17th century. The first electrical engineer was probably William Gilbert who designed the versorium: a device that detected the presence of statically charged objects. He was also thefirst to draw a clear distinction between magnetism and static electricity and is credited with establishing the term electricity.[1] In 1775 Alessandro Volta's scientific experimentations devised the electrophorus, a device that produced a static electric charge, and by 1800 Volta developed the voltaic pile, a forerunner of the electric battery.[2]

19th century

The discoveries of Michael Faraday formed the foundation of electric motor technology

However, it was not until the 19th century that research into the subject started to intensify. Notable developments in this century include the work of Georg Ohm, who in 1827 quantified the relationship between the electric current and potential difference in a conductor, of Michael Faraday, the discoverer of electromagnetic induction in 1831, and of James Clerk Maxwell, who in 1873 published a unified theory of electricity and magnetism in his treatise Electricity and Magnetism.[3]

Beginning in the 1830s, efforts were made to apply electricityto practical use in the telegraph. By the end of the 19th century the world had been forever changed by the rapid communication made possible by the engineering development of land-lines, submarine cables, and, from about 1890, wireless telegraphy.

Practical applications and advances in such fields created an increasing need for standardized units of measure. They led to the international standardization of the units volt, ampere, coulomb, ohm, farad, and henry. This was achieved at an international conference in Chicago in 1893.[4] The publication of these standardsformed the basis of future advances in standardisation in various industries, and in many countries the definitions were immediately recognised in relevant legislation.[5]

During these years, the study of electricity was largely considered to be a subfield of physics. It was not until about 1885 that universities and institutes of technology such as MassachusettsInstitute of Technology (MIT) and Cornell University started to offer bachelor's degrees in electrical engineering. The Darmstadt University of Technology founded the first department of electrical engineering in the world in 1882. In that same year, under Professor

Charles Cross, MIT began offering the first option of electrical engineering within its physics department.[6] In 1883, Darmstadt University of Technology and Cornell University introduced the world's first bachelor's degree courses of study in electrical engineering, and in 1885 University College London founded the firstchair of electrical engineering in Great Britain.[7] The University of Missouri established the first department of electrical engineering in the United States in 1886.[8] Several other schools soon followed suit, including Cornell and the Georgia School of Technology in Atlanta, Georgia.

Thomas Edison, electric light and (DC) power supply networks

Károly Zipernowsky, Ottó Bláthy, Miksa Déri, the ZDB transformer

William Stanley, Jr., transformers

Galileo Ferraris, electrical theory, induction motor

Nikola Tesla, practical polyphase (AC) and induction motordesigns

Mikhail Dolivo-Dobrovolsky developed standard 3-phase (AC)systems

Charles Proteus Steinmetz, AC mathematical theories for engineers

Oliver Heaviside, developed theoretical models for electric circuits

During these decades use of electrical engineering increased dramatically. In 1882, Thomas Edison switched on the world's first large-scale electric power network that provided 110 volts — direct current (DC) — to 59 customers on Manhattan Island in New York City.In 1884, Sir Charles Parsons invented the steam turbine allowing formore efficient electric power generation. Alternating current, with its ability to transmit power more efficiently over long distances via the use of transformers, developed rapidly in the 1880s and 1890s with transformer designs by Károly Zipernowsky, Ottó Bláthy and Miksa Déri (later called ZBD transformers), Lucien Gaulard, JohnDixon Gibbs and William Stanley, Jr.. Practical AC motor designs including induction motors were independently invented by Galileo Ferraris and Nikola Tesla and further developed into a practical three-phase form by Mikhail Dolivo-Dobrovolsky and Charles Eugene Lancelot Brown.[9] Charles Steinmetz and Oliver Heaviside contributed to the theoretical basis of alternating current engineering.[10][11] The spread in the use of AC set off in the United States what has been called the War of Currents between a George Westinghouse backed AC system and a Thomas Edison backed DC power system, with AC being adopted as the overall standard.[12]

More modern developments

Guglielmo Marconi known for his pioneering work on long distance radio transmission

During the development of radio, many scientists and inventorscontributed to radio technology and electronics. The mathematical work of James Clerk Maxwell during the 1850s had shown the relationship of different forms of electromagnetic radiation including possibility of invisible airborne waves (later called "radio waves"). In his classic physics experiments of 1888, HeinrichHertz proved Maxwell's theory by transmitting radio waves with a spark-gap transmitter, and detected them by using simple electrical devices. Other physicists experimented with these new waves and in the process developed devices for transmitting and detecting them.

In 1895 Guglielmo Marconi began work on a way to adapt the known methods of transmitting and detecting these "Hertzian waves" into a purpose built commercial wireless telegraphic system. Early on, he sent wireless signals over a distance of one and a half miles. In December 1901, he sent wireless waves that were not affected by the curvature of the Earth. Marconi later transmitted the wireless signals across the Atlantic between Poldhu, Cornwall, and St. John's, Newfoundland, a distance of 2,100 miles (3,400 km).[13]

In 1897, Karl Ferdinand Braun introduced the cathode ray tube as part of an oscilloscope, a crucial enabling technology for electronic television.[14] John Fleming invented the first radio tube, the diode, in 1904. Two years later, Robert von Lieben and LeeDe Forest independently developed the amplifier tube, called the triode.[15]

In 1920 Albert Hull developed the magnetron which would eventually lead to the development of the microwave oven in 1946 by Percy Spencer.[16][17] In 1934 the British military began to make strides toward radar (which also uses the magnetron) under the direction of Dr Wimperis, culminating in the operation of the first radar station at Bawdsey in August 1936.[18]

In 1941 Konrad Zuse presented the Z3, the world's first fully functional and programmable computer using electromechanical parts. In 1943 Tommy Flowers designed and built the Colossus, the world's first fully functional, electronic, digital and programmable computer.[19] In 1946 the ENIAC (Electronic Numerical Integrator andComputer) of John Presper Eckert and John Mauchly followed, beginning the computing era. The arithmetic performance of these machines allowed engineers to develop completely new technologies and achieve new objectives, including the Apollo program which culminated in landing astronauts on the Moon.[20]

Solid-state transistors

The invention of the transistor in late 1947 by William B. Shockley, John Bardeen, and Walter Brattain of the Bell Telephone Laboratories opened the door for more compact devices and led to thedevelopment of the integrated circuit in 1958 by Jack Kilby and independently in 1959 by Robert Noyce.[21] Starting in 1968, Ted Hoff and a team at the Intel Corporation invented the first commercial microprocessor, which foreshadowed the personal computer.The Intel 4004 was a four-bit processor released in 1971, but in 1973 the Intel 8080, an eight-bit processor, made the first personalcomputer, the Altair 8800, possible.[22]

Subdisciplines

Electrical engineering has many subdisciplines, the most common of which are listed below. Although there are electrical engineers who focus exclusively on one of these subdisciplines, manydeal with a combination of them. Sometimes certain fields, such as electronic engineering and computer engineering, are considered separate disciplines in their own right.

Power

Main article: Power engineering

Power pole

Power engineering deals with the generation, transmission and distribution of electricity as well as the design of a range of related devices.[23] These include transformers, electric generators, electric motors, high voltage engineering, and power electronics. In many regions of the world, governments maintain an electrical network called a power grid that connects a variety of generators together with users of their energy. Users purchase electrical energy from the grid, avoiding the costly exercise of having to generate their own. Power engineers may work on the designand maintenance of the power grid as well as the power systems that connect to it.[24] Such systems are called on-grid power systems andmay supply the grid with additional power, draw power from the grid or do both. Power engineers may also work on systems that do not

connect to the grid, called off-grid power systems, which in some cases are preferable to on-grid systems. The future includes Satellite controlled power systems, with feedback in real time to prevent power surges and prevent blackouts.

Control

Main article: Control engineering

Control systems play a critical role in space flight.

Control engineering focuses on the modeling of a diverse rangeof dynamic systems and the design of controllers that will cause these systems to behave in the desired manner.[25] To implement suchcontrollers electrical engineers may use electrical circuits, digital signal processors, microcontrollers and PLCs (Programmable Logic Controllers). Control engineering has a wide range of applications from the flight and propulsion systems of commercial airliners to the cruise control present in many modern automobiles.[26] It also plays an important role in industrial automation.

Control engineers often utilize feedback when designing control systems. For example, in an automobile with cruise control the vehicle's speed is continuously monitored and fed back to the system which adjusts the motor's power output accordingly. Where there is regular feedback, control theory can be used to determine how the system responds to such feedback.[27]

Electronics

Main article: Electronic engineering

Electronic components

Electronic engineering involves the design and testing of electronic circuits that use the properties of components such as resistors, capacitors, inductors, diodes and transistors to achieve a particular functionality.[24] The tuned circuit, which allows the user of a radio to filter out all but a single station, is just one

example of such a circuit. Another example (of a pneumatic signal conditioner) is shown in the adjacent photograph.

Prior to the Second World War, the subject was commonly known as radio engineering and basically was restricted to aspects of communications and radar, commercial radio and early television.[24]Later, in post war years, as consumer devices began to be developed,the field grew to include modern television, audio systems, computers and microprocessors. In the mid-to-late 1950s, the term radio engineering gradually gave way to the name electronic engineering.

Before the invention of the integrated circuit in 1959,[28] electronic circuits were constructed from discrete components that could be manipulated by humans. These discrete circuits consumed much space and power and were limited in speed, although they are still common in some applications. By contrast, integrated circuits packed a large number—often millions—of tiny electrical components, mainly transistors,[29] into a small chip around the size of a coin.This allowed for the powerful computers and other electronic deviceswe see today.

Microelectronics

Main article: Microelectronics

Microprocessor

Microelectronics engineering deals with the design and microfabrication of very small electronic circuit components for usein an integrated circuit or sometimes for use on their own as a general electronic component.[30] The most common microelectronic components are semiconductor transistors, although all main electronic components (resistors, capacitors etc.) can be created ata microscopic level. Nanoelectronics is the further scaling of devices down to nanometer levels. Modern devices are already in the nanometer regime, with below 100 nm processing having been standard since about 2002.[31]

Microelectronic components are created by chemically fabricating wafers of semiconductors such as silicon (at higher frequencies, compound semiconductors like gallium arsenide and indium phosphide) to obtain the desired transport of electronic charge and control of current. The field of microelectronics involves a significant amount of chemistry and material science and requires the electronic engineer working in the field to have a verygood working knowledge of the effects of quantum mechanics.[32]

Signal processing

Main article: Signal processing

A Bayer filter on a CCD requires signal processing to get a red, green, and blue value at each pixel.

Signal processing deals with the analysis and manipulation of signals.[33] Signals can be either analog, in which case the signal varies continuously according to the information, or digital, in which case the signal varies according to a series of discrete values representing the information. For analog signals, signal processing may involve the amplification and filtering of audio signals for audio equipment or the modulation and demodulation of signals for telecommunications. For digital signals, signal processing may involve the compression, error detection and error correction of digitally sampled signals.[34]

Signal Processing is a very mathematically oriented and intensive area forming the core of digital signal processing and it is rapidly expanding with new applications in every field of electrical engineering such as communications, control, radar, audioengineering, broadcast engineering, power electronics and bio-medical engineering as many already existing analog systems are replaced with their digital counterparts. Analog signal processing is still important in the design of many control systems.

DSP processor ICs are found in every type of modern electronicsystems and products including, SDTV | HDTV sets,[35] radios and mobile communication devices, Hi-Fi audio equipment, Dolby noise reduction algorithms, GSM mobile phones, mp3 multimedia players, camcorders and digital cameras, automobile control systems, noise cancelling headphones, digital spectrum analyzers, intelligent missile guidance, radar, GPS based cruise control systems and all kinds of image processing, video processing, audio processing and speech processing systems.[36]

Telecommunications

Main article: Telecommunications engineering

Satellite dishes are a crucial component in the analysis of satellite information.

Telecommunications engineering focuses on the transmission of information across a channel such as a coax cable, optical fiber or free space.[37] Transmissions across free space require information to be encoded in a carrier wave to shift the information to a carrier frequency suitable for transmission, this is known as modulation. Popular analog modulation techniques include amplitude modulation and frequency modulation.[38] The choice of modulation affects the cost and performance of a system and these two factors must be balanced carefully by the engineer.

Once the transmission characteristics of a system are determined, telecommunication engineers design the transmitters and receivers needed for such systems. These two are sometimes combined to form a two-way communication device known as a transceiver. A keyconsideration in the design of transmitters is their power consumption as this is closely related to their signal strength.[39][40] If the signal strength of a transmitter is insufficient the signal's information will be corrupted by noise.

Instrumentation

Main article: Instrumentation engineering

Flight instruments provide pilots with the tools to control aircraft analytically.

Instrumentation engineering deals with the design of devices to measure physical quantities such as pressure, flow and temperature.[41] The design of such instrumentation requires a good understanding of physics that often extends beyond electromagnetic theory. For example, flight instruments measure variables such as wind speed and altitude to enable pilots the control of aircraft analytically. Similarly, thermocouples use the Peltier-Seebeck effect to measure the temperature difference between two points.[42]

Often instrumentation is not used by itself, but instead as the sensors of larger electrical systems. For example, a thermocouple might be used to help ensure a furnace's temperature remains constant.[43] For this reason, instrumentation engineering is often viewed as the counterpart of control engineering.

Computers

Main article: Computer engineering

Supercomputers are used in fields as diverse as computational biology and geographic information systems.

Computer engineering deals with the design of computers and computer systems. This may involve the design of new hardware, the design of PDAs, tablets and supercomputers or the use of computers to control an industrial plant.[44] Computer engineers may also workon a system's software. However, the design of complex software systems is often the domain of software engineering, which is usually considered a separate discipline.[45] Desktop computers represent a tiny fraction of the devices a computer engineer might work on, as computer-like architectures are now found in a range of devices including video game consoles and DVD players.

Related disciplines

The Bird VIP Infant ventilator

Mechatronics is an engineering discipline which deals with theconvergence of electrical and mechanical systems. Such combined systems are known as electromechanical systems and have widespread adoption. Examples include automated manufacturing systems,[46] heating, ventilation and air-conditioning systems[47] and various subsystems of aircraft and automobiles. [48]

The term mechatronics is typically used to refer to macroscopic systems but futurists have predicted the emergence of very small electromechanical devices. Already such small devices, known as Microelectromechanical systems (MEMS), are used in automobiles to tell airbags when to deploy,[49] in digital projectors to create sharper images and in inkjet printers to createnozzles for high definition printing. In the future it is hoped the devices will help build tiny implantable medical devices and improveoptical communication.[50]

Biomedical engineering is another related discipline, concerned with the design of medical equipment. This includes fixed equipment such as ventilators, MRI scanners[51] and electrocardiograph monitors as well as mobile equipment such as cochlear implants, artificial pacemakers and artificial hearts.

Aerospace engineering and robotics an example is the most recent electric propulsion and ion propulsion.

Education

Main article: Education and training of electrical and electronics engineers

Oscilloscope

Electrical engineers typically possess an academic degree witha major in electrical engineering, electronics engineering,

electrical engineering technology,[52] or electrical and electronic engineering.[53][54] The same fundamental principles are taught in all programs, though emphasis may vary according to title. The length of study for such a degree is usually four or five years and the completed degree may be designated as a Bachelor of Science in Electrical/Electronics Engineering Technology, Bachelor of Engineering, Bachelor of Science, Bachelor of Technology, or Bachelor of Applied Science depending on the university. The bachelor's degree generally includes units covering physics, mathematics, computer science, project management, and a variety of topics in electrical engineering.[55] Initially such topics cover most, if not all, of the subdisciplines of electrical engineering. At some schools, the students can then choose to emphasize one or more subdisciplines towards the end of their courses of study.

Typical electrical engineering diagram used as a troubleshooting tool

At many schools, electronic engineering is included as part ofan electrical award, sometimes explicitly, such as a Bachelor of Engineering (Electrical and Electronic), but in others electrical and electronic engineering are both considered to be sufficiently broad and complex that separate degrees are offered.[56]

Some electrical engineers choose to study for a postgraduate degree such as a Master of Engineering/Master of Science (M.Eng./M.Sc.), a Master of Engineering Management, a Doctor of Philosophy (Ph.D.) in Engineering, an Engineering Doctorate (Eng.D.), or an Engineer's degree. The master's and engineer's degrees may consist of either research, coursework or a mixture of the two. The Doctor of Philosophy and Engineering Doctorate degrees consist of a significant research component and are often viewed as the entry point to academia. In the United Kingdom and some other European countries, Master of Engineering is often considered to be an undergraduate degree of slightly longer duration than the Bachelor of Engineering rather than postgraduate.[57]

Practicing engineers

Belgian electrical engineers inspecting the rotor of a 40,000 kilowatt turbine of the General Electric Company in New York City

In most countries, a bachelor's degree in engineering represents the first step towards professional certification and thedegree program itself is certified by a professional body.[58] Aftercompleting a certified degree program the engineer must satisfy a range of requirements (including work experience requirements) before being certified. Once certified the engineer is designated the title of Professional Engineer (in the United States, Canada andSouth Africa), Chartered Engineer or Incorporated Engineer (in India, Pakistan, the United Kingdom, Ireland and Zimbabwe), Chartered Professional Engineer (in Australia and New Zealand) or European Engineer (in much of the European Union).

The IEEE corporate office is on the 17th floor of 3 Park Avenue in New York City

The advantages of certification vary depending upon location. For example, in the United States and Canada "only a licensed engineer may seal engineering work for public and private clients".[59] This requirement is enforced by state and provincial legislation such as Quebec's Engineers Act.[60] In other countries, no such legislation exists. Practically all certifying bodies maintain a code of ethics that they expect all members to abide by or risk expulsion.[61] In this way these organizations play an important role in maintaining ethical standards for the profession. Even in jurisdictions where certification has little or no legal bearing on work, engineers are subject to contract law. In cases where an engineer's work fails he or she may be subject to the tort of negligence and, in extreme cases, the charge of criminal negligence. An engineer's work must also comply with numerous other rules and regulations such as building codes and legislation pertaining to environmental law.

Professional bodies of note for electrical engineers include the Institute of Electrical and Electronics Engineers (IEEE) and the

Institution of Engineering and Technology (IET). The IEEE claims to produce 30% of the world's literature in electrical engineering, hasover 360,000 members worldwide and holds over 3,000 conferences annually.[62] The IET publishes 21 journals, has a worldwide membership of over 150,000, and claims to be the largest professional engineering society in Europe.[63][64] Obsolescence of technical skills is a serious concern for electrical engineers. Membership and participation in technical societies, regular reviewsof periodicals in the field and a habit of continued learning are therefore essential to maintaining proficiency. MIET(Member of the Institution of Engineering and Technology) is recognised in Europe as Electrical and computer (technology) engineer.[65]

In Australia, Canada and the United States electrical engineers make up around 0.25% of the labor force (see note).

Tools and work

From the Global Positioning System to electric power generation, electrical engineers have contributed to the developmentof a wide range of technologies. They design, develop, test and supervise the deployment of electrical systems and electronic devices. For example, they may work on the design of telecommunication systems, the operation of electric power stations,the lighting and wiring of buildings, the design of household appliances or the electrical control of industrial machinery.[66]

Satellite communications is typical of what electrical engineers work on.

Fundamental to the discipline are the sciences of physics and mathematics as these help to obtain both a qualitative and quantitative description of how such systems will work. Today most engineering work involves the use of computers and it is commonplaceto use computer-aided design programs when designing electrical systems. Nevertheless, the ability to sketch ideas is still invaluable for quickly communicating with others.

The Shadow robot hand system

Although most electrical engineers will understand basic circuit theory (that is the interactions of elements such as resistors, capacitors, diodes, transistors and inductors in a circuit), the theories employed by engineers generally depend upon the work they do. For example, quantum mechanics and solid state physics might be relevant to an engineer working on VLSI (the designof integrated circuits), but are largely irrelevant to engineers working with macroscopic electrical systems. Even circuit theory maynot be relevant to a person designing telecommunication systems thatuse off-the-shelf components. Perhaps the most important technical skills for electrical engineers are reflected in university programs, which emphasize strong numerical skills, computer literacyand the ability to understand the technical language and concepts that relate to electrical engineering.[67]

A laser bouncing down an acrylic rod, illustrating the total internal reflection of light in a multi-mode optical fiber.

A wide range of instrumentation is used by electrical engineers. For simple control circuits and alarms, a basic multimeter measuring voltage, current and resistance may suffice. Where time-varying signals need to be studied, the oscilloscope is also an ubiquitous instrument. In RF engineering and high frequency telecommunications spectrum analyzers and network analyzers are used. In some disciplines safety can be a particular concern with instrumentation. For instance medical electronics designers must take into account that much lower voltages than normal can be dangerous when electrodes are directly in contact with internal bodyfluids.[68] Power transmission engineering also has great safety concerns due to the high voltages used; although voltmeters may in principle be similar to their low voltage equivalents, safety and calibration issues make them very different.[69] Many disciplines ofelectrical engineering use tests specific to their discipline. Audioelectronics engineers use audio test sets consisting of a signal generator and a meter, principally to measure level but also other parameters such as harmonic distortion and noise. Likewise

information technology have their own test sets, often specific to aparticular data format, and the same is true of television broadcasting.

Radome at the Misawa Air Base Misawa Security Operations Center, Misawa, Japan

For many engineers, technical work accounts for only a fraction of the work they do. A lot of time may also be spent on tasks such as discussing proposals with clients, preparing budgets and determining project schedules.[70] Many senior engineers manage a team of technicians or other engineers and for this reason projectmanagement skills are important. Most engineering projects involve some form of documentation and strong written communication skills are therefore very important.

The workplaces of engineers are just as varied as the types ofwork they do. Electrical engineers may be found in the pristine lab environment of a fabrication plant, the offices of a consulting firmor on site at a mine. During their working life, electrical engineers may find themselves supervising a wide range of individuals including scientists, electricians, computer programmersand other engineers.[71]

Electrical engineering has an intimate relationship with the physical sciences. For instance the physicist Lord Kelvin played a major role in the engineering of the first transatlantic telegraph cable.[72] Conversely, the engineer Oliver Heaviside produced major work on the mathematics of transmission on telegraph cables.[73] Electrical engineers are often required on major science projects. For instance, large particle accelerators such as CERN need electrical engineers to deal with many aspects of the project: from the power distribution, to the instrumentation, to the manufacture and installation of the superconducting electromagnets.[74][75]

"Cash machine" redirects here. For the Hard-Fi song, see Cash Machine.

An NCR Personas 75-Series interior, multi-function ATM in the United States

Smaller indoor ATMs dispense money inside convenience stores and other busy areas, such as this off-premises Wincor Nixdorf mono-function ATM in Sweden.

An automated teller machine or automatic teller machine[1][2][3] (ATM, American, Australian, Malaysian, Singaporean, Indian, Maldivian, Hiberno, Philippine and Sri Lankan English), also known as an automated banking machine (ABM, Canadian English), cash machine, cashpoint, cashline, minibank, or colloquially hole in the wall (British and South African English), is an electronic telecommunications device that enables the customers of a financial institution to perform financial transactions, particularly cash withdrawal, without the need for a human cashier, clerk or bank teller.

On most modern ATMs, the customer is identified by inserting aplastic ATM card with a magnetic stripe or a plastic smart card witha chip that contains a unique card number and some security information such as an expiration date or CVVC (CVV). Authenticationis provided by the customer entering a personal identification number (PIN).

Using an ATM, customers can access their bank deposit or credit accounts in order to make a variety of transactions such as cash withdrawals, check balances, or credit mobile phones. If the currency being withdrawn from the ATM is different from that in which the bank account is denominated the money will be converted atan official exchange rate. Thus, ATMs often provide the best possible exchange rates for foreign travellers, and are widely used for this purpose.[4] Yet it seems on modern ATMs foreign cash currency is not processed or possibly rejected when deposited or at least is not originally expected by the machine.

Contents

1 History

1.1 Docutel United States 1969

1.2 Continued Improvements

2 Location

3 Financial networks

4 Global use

5 Hardware

6 Software

7 Security

7.1 Physical

7.2 Transactional secrecy and integrity

7.3 Customer identity integrity

7.4 Device operation integrity

7.5 Customer security

7.6 Uses

8 Reliability

9 Fraud

9.1 Card fraud

10 Related devices

11 In popular culture

12 See also

13 References

14 Further reading

15 External links

History

An old Nixdorf ATM

The idea of out-of-hours cash distribution developed from banker's needs in Asia (Japan), Europe (Sweden and the United Kingdom) and North America (the United States).[5][6] LIttle is known of the Japanese device. In the US patent record, Luther GeorgeSimjian has been credited with developing a "prior art device". Specifically his 132nd patent (US3079603), which was first filed on 30 June 1960 (and granted 26 February 1963). The roll-out of this machine, called Bankograph, was delayed by a couple of years, due inpart to Simjian's Reflectone Electronics Inc. being acquired by Universal Match Corporation.[7] An experimental Bankograph was installed in New York City in 1961 by the City Bank of New York, butremoved after six months due to the lack of customer acceptance. TheBankograph was an automated envelope deposit machine (accepting coins, cash and cheques) and did not have cash dispensing features.[8][9]

Actor Reg Varney using the world's first cash machine in Enfield Town, north London on 27 June 1967

It is widely accepted that the first ATM was put into use by Barclays Bank in its Enfield Town branch in north London, United Kingdom, on 27 June 1967.[10] This machine was inaugurated by English comedy actor Reg Varney.[11] This instance of the invention is credited to John Shepherd-Barron of printing firm De La Rue,[12] who was awarded an OBE in the 2005 New Year Honours.[13] This designused paper cheques issued by a teller or cashier, marked with carbon-14 for machine readability and security, which in a latter model were matched with a personal identification number (PIN).[12][14] Shepherd-Barron stated; "It struck me there must be a way I could get my own money, anywhere in the world or the UK. I hit upon the idea of a chocolate bar dispenser, but replacing chocolate with cash."[12]

The Barclays-De La Rue machine (called De La Rue Automatic Cash System or DACS)[15] beat the Swedish saving banks' and a company called Metior's machine (a device called Bankomat) by a merenine days and Westminster Bank’s-Smith Industries-Chubb system (called Chubb MD2) by a month.[16] The online version of the Swedishmachine is listed to have been operational on 6 May 1968, while claiming to be the first online cash machine in the world (ahead of a similar claim by IBM and Lloyds Bank in 1971).[17] The collaboration of a small start-up called Speytec and Midland Bank developed a fourth machine which was marketed after 1969 in Europe and the US by the Burroughs Corporation. The patent for this device (GB1329964) was filed on September 1969 (and granted in 1973) by John David Edwards, Leonard Perkins, John Henry Donald, Peter Lee Chappell, Sean Benjamin Newcombe & Malcom David Roe.

ATM of Sberbank in Tolyatti, Russia

Both the DACS and MD2 accepted only a single-use token or voucher which was retained by the machine while the Speytec worked with a card with a magnetic strip at the back. They used principles including Carbon-14 and low-coercivity magnetism in order to make fraud more difficult. The idea of a PIN stored on the card was developed by a British engineer working on the MD2 named James Goodfellow in 1965 (patent GB1197183 filed on 2 May 1966 with Anthony Davies). The essence of this system was that it enabled the verification of the customer with the debited account without human intervention. This patent is also the earliest instance of a complete "currency dispenser system" in the patent record. This patent was filed on 5 March 1968 in the US (US 3543904) and granted on 1 December 1970. It had a profound influence on the industry as awhole. Not only did future entrants into the cash dispenser market such as NCR Corporation and IBM licence Goodfellow’s PIN system, buta number of later patents reference this patent as "Prior Art Device".[18]

In January 9, 1969's ABC newspaper (Madrid edition) there was an article about the new Bancomat, a teller machine installed in

downtown Madrid, Spain, by Banesto, dispensing 1,000 peseta bills (1to 5 max). Each user had to introduce a security personal key using a combination of the ten numeric buttons.[19] In March of the same year an ad with the instructions to use the Bancomat was published in the same newspaper [20] Bancomat was the first cash machine installed in Spain, one of the first in Europe.

File:ABC ATMs.ogvPlay media

1969 ABC news report on the introduction of ATMs in Sydney, Australia. People could only receive AUS $25 at a time and the bank card was sent back to the user at a later date.

Docutel United States 1969

After looking first hand at the experiences in Europe, in 1968the networked ATM was pioneered in the US, in Dallas, Texas, by Donald Wetzel, who was a department head at an automated baggage-handling company called Docutel. Recognised by the United States Patent Office for having invented the ATM are Kenneth S. Goldstein and John D. White, under US Patent # 3,662,343. Recognised by the United States Patent Office for having invented the ATM network are Fred J. Gentile and Jack Wu Chang, under US Patent # 3,833,885. On September 2, 1969, Chemical Bank installed the first ATM in the U.S.at its branch in Rockville Centre, New York. The first ATMs were designed to dispense a fixed amount of cash when a user inserted a specially coded card.[21] A Chemical Bank advertisement boasted "On Sept. 2 our bank will open at 9:00 and never close again."[22] Chemical's ATM, initially known as a Docuteller was designed by Donald Wetzel and his company Docutel. Chemical executives were initially hesitant about the electronic banking transition given thehigh cost of the early machines. Additionally, executives were concerned that customers would resist having machines handling theirmoney.[23] In 1995, the Smithsonian National Museum of American History recognised Docutel and Wetzel as the inventors of the networked ATM.[24]

Continued Improvements

The first modern ATM was an IBM 2984 and came into use at Lloyds Bank, Brentwood High Street, Essex, England in December 1972.The IBM 2984 was designed at the request of Lloyds Bank. The 2984 Cash Issuing Terminal was the first true ATM, similar in function totoday's machines and named by Lloyds Bank: Cashpoint; Cashpoint is still a registered trademark of Lloyds TSB in the UK. All were online and issued a variable amount which was immediately deducted from the account. A small number of 2984s were supplied to a US bank. A couple of well known historical models of ATMs include the IBM 3614, IBM 3624 and 473x series, Diebold 10xx and TABS 9000 series, NCR 1780 and earlier NCR 770 series.

The first switching system to enable shared automated teller machines between banks went into production operation on February 3,1979 in Denver, Colorado, in an effort by Colorado National Bank of Denver and Kranzley and Company of Cherry Hill, New Jersey.[25]

The newest ATM at Royal Bank of Scotland allows customers to withdraw cash up to £100 without a card by inputting a six-digit code requested through their smartphones.[26]

Location

This section does not cite any references or sources.Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (February2011)

An ATM Encrypting PIN Pad (EPP) with German markings

ATM in Vatican City with menu in Latin

ATMs are placed not only near or inside the premises of banks,but also in locations such as shopping centers/malls, airports, grocery stores, petrol/gas stations, restaurants, or anywhere frequented by large numbers of people. There are two types of ATM installations: on- and off-premises. On-premises ATMs are typically more advanced, multi-function machines that complement a bank

branch's capabilities, and are thus more expensive. Off-premises machines are deployed by financial institutions and Independent Sales Organisations (ISOs) where there is a simple need for cash, sothey are generally cheaper single function devices. In Canada, ATMs (also known there as ABMs) not operated by a financial institution are known as "white-label ABMs".

In the U.S., Canada and some Gulf countries, banks often have drive-thru lanes providing access to ATMs using an automobile.

Many ATMs have a sign above them, indicating the name of the bank or organisation owning the ATM and possibly including the list of ATM networks to which that machine is connected.

ATMs can also be found in railway stations and metro stations.In recent times, countries like India and some countries in Africa are installing ATM's in rural areas which are solar powered and do not require air conditioning.[27]

Financial networks

An ATM in the Netherlands. The logos of a number of interbank networks this ATM is connected to are shown

Most ATMs are connected to interbank networks, enabling peopleto withdraw and deposit money from machines not belonging to the bank where they have their accounts or in the countries where their accounts are held (enabling cash withdrawals in local currency). Some examples of interbank networks include NYCE, PULSE, PLUS, Cirrus, AFFN, Interac, Interswitch, STAR, LINK, MegaLink and BancNet.

ATMs rely on authorisation of a financial transaction by the card issuer or other authorising institution on a communications

network. This is often performed through an ISO 8583 messaging system.

Many banks charge ATM usage fees. In some cases, these fees are charged solely to users who are not customers of the bank where the ATM is installed; in other cases, they apply to all users.

In order to allow a more diverse range of devices to attach totheir networks, some interbank networks have passed rules expanding the definition of an ATM to be a terminal that either has the vault within its footprint or utilises the vault or cash drawer within themerchant establishment, which allows for the use of a scrip cash dispenser.

A Diebold 1063ix with a dial-up modem visible at the base

ATMs typically connect directly to their host or ATM Controller on either ADSL or dial-up modem over a telephone line or directly on a leased line. Leased lines are preferable to plain old telephone service (POTS) lines because they require less time to establish a connection. Less-trafficked machines will usually rely on a dial-up modem on a POTS line rather than using a leased line, since a leased line may be comparatively more expensive to operate compared to a POTS line. That dilemma may be solved as high-speed Internet VPN connections become more ubiquitous. Common lower-level layer communication protocols used by ATMs to communicate back to the bank include SNA over SDLC, TC500 over Async, X.25, and TCP/IP over Ethernet.

In addition to methods employed for transaction security and secrecy, all communications traffic between the ATM and the Transaction Processor may also be encrypted using methods such as SSL.[28]

Global use

ATMs at the railway station in Poznań

There are no hard international or government-compiled numberstotaling the complete number of ATMs in use worldwide. Estimates developed by ATMIA place the number of ATMs in use currently at over2.2 million, or approximately 1 ATM per 3000 people in the world.[29]

To simplify the analysis of ATM usage around the world, financial institutions generally divide the world into seven regions, due to the penetration rates, usage statistics, and features deployed. Four regions (USA, Canada, Europe, and Japan) have high numbers of ATMs per million people.[30][31] Despite the large number of ATMs, there is additional demand for machines in theAsia/Pacific area as well as in Latin America.[32][33] ATMs have yetto reach high numbers in the Near East and Africa.[34]

One of the world's most northerly installed ATMs is located atLongyearbyen, Svalbard, Norway.

The world's most southerly installed ATM is located at McMurdoStation, located in New Zealand's Ross Dependency, in Antarctica since 1997.[35] There are two ATMs at McMurdo, but only one active at any time, that are owned by Wells Fargo[36] and serviced once every two years by NCR.[37]

According to international statistics, the highest installed ATM in the world is located at Nathu La Pass, in India, installed bythe Indian Axis Bank at 4,023 metres (13,199 ft).[38] According to the Mainland Chinese media and CPC statistics, the highest installedATM in the world is located in Nagchu County, Tibet, China, at 4500 metres, allegedly installed by the Agricultural Bank of China.[39][unreliable source?][40][unreliable source?]

Israel has the world's lowest installed ATM at Ein Bokek at the Dead Sea, installed independently by a grocery store at 421 metres below sea level.[41]

While ATMs are ubiquitous on modern cruise ships, ATMs can also be found on some US Navy ships.[42]

Welcome message displayed on the world's most northerly ATM located in the post office at Longyearbyen

Hardware

A block diagram of an ATM

An ATM is typically made up of the following devices:

CPU (to control the user interface and transaction devices)

Magnetic or chip card reader (to identify the customer)

PIN pad EEP4 (similar in layout to a touch tone or calculator keypad), manufactured as part of a secure enclosure

Secure cryptoprocessor, generally within a secure enclosure

Display (used by the customer for performing the transaction)

Function key buttons (usually close to the display) or a touchscreen (used to select the various aspects of the transaction)

Record printer (to provide the customer with a record of the transaction)

Vault (to store the parts of the machinery requiring restricted access)

Housing (for aesthetics and to attach signage to)

Sensors and indicators

Due to heavier computing demands and the falling price of personal computer–like architectures, ATMs have moved away from custom hardware architectures using microcontrollers or application-specific integrated circuits and have adopted the hardware architecture of a personal computer, such as USB connections for peripherals, Ethernet and IP communications, and use personal computer operating systems.

Business owners often lease ATM terminals from ATM service providers, however based on the economies of scale, the price of equipment has dropped to the point where many business owners are simply paying for ATMs using a credit card.

New ADA voice and text-to-speech guidelines imposed in 2010, but required by March 2012[43] have forced many ATM owners to eitherupgrade non-compliant machines or dispose them if they are not up-gradable, and purchase new compliant equipment. This has created an avenue for hackers and thieves to obtain ATM hardware at junkyards from improperly disposed decommissioned ATMs.[44]

Two Loomis employees refilling an ATM at the Downtown Seattle REI

The vault of an ATM is within the footprint of the device itself and is where items of value are kept. Scrip cash dispensers do not incorporate a vault.

Mechanisms found inside the vault may include:

Dispensing mechanism (to provide cash or other items of value)

Deposit mechanism including a check processing module and bulk note acceptor (to allow the customer to make deposits)

Security sensors (magnetic, thermal, seismic, gas)

Locks (to ensure controlled access to the contents of the vault)

Journaling systems; many are electronic (a sealed flash memory device based on in-house standards) or a solid-state device (an actual printer) which accrues all records of activity including access timestamps, number of notes dispensed, etc. This is considered sensitive data and is secured in similar fashion to the cash as it is a similar liability.

ATM vaults are supplied by manufacturers in several grades. Factors influencing vault grade selection include cost, weight, regulatory requirements, ATM type, operator risk avoidance practicesand internal volume requirements.[45] Industry standard vault configurations include Underwriters Laboratories UL-291 "Business Hours" and Level 1 Safes,[46] RAL TL-30 derivatives,[47] and CEN EN 1143-1 - CEN III and CEN IV.[48][49]

ATM manufacturers recommend that an ATM vault be attached to the floor to prevent theft,[50] though there is a record of a theft conducted by tunnelling into an ATM floor.[citation needed]

Software

With the migration to commodity Personal Computer hardware, standard commercial "off-the-shelf" operating systems, and programming environments can be used inside of ATMs. Typical platforms previously used in ATM development include RMX or OS/2.

A Wincor Nixdorf ATM running Windows 2000.

Today the vast majority of ATMs worldwide use a Microsoft Windows operating system, primarily Windows XP Professional or Windows XP Embedded.[citation needed] A small number of deployments

may still be running older versions of Windows OS such as Windows NT, Windows CE, or Windows 2000.

There is a computer industry security view that general publicdesktop operating systems(os) have greater risks as operating systems for cash dispensing machines than other types of operating systems like (secure) real-time operating systems (RTOS). RISKS Digest has many articles about cash machine operating system vulnerabilities.[51]

Linux is also finding some reception in the ATM marketplace. An example of this is Banrisul, the largest bank in the south of Brazil, which has replaced the MS-DOS operating systems in its ATMs with Linux. Banco do Brasil is also migrating ATMs to Linux. Indian-based Vortex Engineering is manufacturing ATMs which operate only with Linux. Common application layer transaction protocols, such as Diebold 91x (911 or 912) and NCR NDC or NDC+ provide emulation of older generations of hardware on newer platforms with incremental extensions made over time to address new capabilities, although companies like NCR continuously improve these protocols issuing newer versions (e.g. NCR's AANDC v3.x.y, where x.y are subversions).Most major ATM manufacturers provide software packages that implement these protocols. Newer protocols such as IFX have yet to find wide acceptance by transaction processors.[52]

With the move to a more standardised software base, financial institutions have been increasingly interested in the ability to pick and choose the application programs that drive their equipment.WOSA/XFS, now known as CEN XFS (or simply XFS), provides a common API for accessing and manipulating the various devices of an ATM. J/XFS is a Java implementation of the CEN XFS API.

While the perceived benefit of XFS is similar to the Java's "Write once, run anywhere" mantra, often different ATM hardware vendors have different interpretations of the XFS standard. The

result of these differences in interpretation means that ATM applications typically use a middleware to even out the differences between various platforms.

With the onset of Windows operating systems and XFS on ATM's, the software applications have the ability to become more intelligent. This has created a new breed of ATM applications commonly referred to as programmable applications. These types of applications allows for an entirely new host of applications in which the ATM terminal can do more than only communicate with the ATM switch. It is now empowered to connected to other content servers and video banking systems.

Notable ATM software that operates on XFS platforms include Triton PRISM, Diebold Agilis EmPower, NCR APTRA Edge, Absolute Systems AbsoluteINTERACT, KAL Kalignite Software Platform, Phoenix Interactive VISTAatm, Wincor Nixdorf ProTopas, Euronet EFTS and Intertech inter-ATM.

With the move of ATMs to industry-standard computing environments, concern has risen about the integrity of the ATM's software stack.[53]

Security

Main article: Security of automated teller machines

Security, as it relates to ATMs, has several dimensions. ATMs also provide a practical demonstration of a number of security systems and concepts operating together and how various security concerns are dealt with.

Physical

A Wincor Nixdorf Procash 2100xe Frontload that was opened withan angle grinder

Automated Teller Machine In Dezfull in southwest of Iran

Early ATM security focused on making the ATMs invulnerable to physical attack; they were effectively safes with dispenser mechanisms. A number of attacks on ATMs resulted, with thieves attempting to steal entire ATMs by ram-raiding.[54] Since late 1990s, criminal groups operating in Japan improved ram-raiding by stealing and using a truck loaded with heavy construction machinery to effectively demolish or uproot an entire ATM and any housing to steal its cash.[55]

Another attack method, plofkraak, is to seal all openings of the ATM with silicone and fill the vault with a combustible gas or to place an explosive inside, attached, or near the ATM. This gas orexplosive is ignited and the vault is opened or distorted by the force of the resulting explosion and the criminals can break in.[56]This type of theft has occurred in the Netherlands, Belgium, France,Denmark, Germany and Australia.[57][58] These types of attacks can be prevented by a number of gas explosion prevention devices also known as gas suppression system. These systems use explosive gas detection sensor to detect explosive gas and to neutralise it by releasing a special explosion suppression chemical which changes thecomposition of the explosive gas and renders it ineffective.

Several attacks in the UK (at least one of which was successful) have involved digging a concealed tunnel under the ATM and cutting through the reinforced base to remove the money.[59]

Modern ATM physical security, per other modern money-handling security, concentrates on denying the use of the money inside the machine to a thief, by using different types of Intelligent BanknoteNeutralisation Systems.

A common method is to simply rob the staff filling the machinewith money. To avoid this, the schedule for filling them is kept

secret, varying and random. The money is often kept in cassettes, which will dye the money if incorrectly opened.

Transactional secrecy and integrity

A Triton brand ATM with a dip style card reader and a triple DES keypad

The security of ATM transactions relies mostly on the integrity of the secure cryptoprocessor: the ATM often uses general commodity components that sometimes are not considered to be "trusted systems".

Encryption of personal information, required by law in many jurisdictions, is used to prevent fraud. Sensitive data in ATM transactions are usually encrypted with DES, but transaction processors now usually require the use of Triple DES.[60] Remote KeyLoading techniques may be used to ensure the secrecy of the initialisation of the encryption keys in the ATM. Message Authentication Code (MAC) or Partial MAC may also be used to ensure messages have not been tampered with while in transit between the ATM and the financial network.

Customer identity integrity

A BTMU ATM with a palm scanner (to the right of the screen)

There have also been a number of incidents of fraud by Man-in-the-middle attacks, where criminals have attached fake keypads or card readers to existing machines. These have then been used to record customers' PINs and bank card information in order to gain unauthorised access to their accounts. Various ATM manufacturers have put in place countermeasures to protect the equipment they manufacture from these threats.[61][62]

Alternative methods to verify cardholder identities have been tested and deployed in some countries, such as finger and palm vein

patterns,[63] iris, and facial recognition technologies. Cheaper mass-produced equipment has been developed and is being installed inmachines globally that detect the presence of foreign objects on thefront of ATMs, current tests have shown 99% detection success for all types of skimming devices.[64]

Device operation integrity

ATMs that are exposed to the outside must be vandal and weather resistant

Openings on the customer-side of ATMs are often covered by mechanical shutters to prevent tampering with the mechanisms when they are not in use. Alarm sensors are placed inside the ATM and in ATM servicing areas to alert their operators when doors have been opened by unauthorised personnel.

To protect against hackers, ATM's have a built-in firewall. Once the firewall has detected malicious attempts to break into the machine remotely, the firewall locks down the machine.[65]

Rules are usually set by the government or ATM operating body that dictate what happens when integrity systems fail. Depending on the jurisdiction, a bank may or may not be liable when an attempt ismade to dispense a customer's money from an ATM and the money eithergets outside of the ATM's vault, or was exposed in a non-secure fashion, or they are unable to determine the state of the money after a failed transaction.[66] Customers often commented that it isdifficult to recover money lost in this way, but this is often complicated by the policies regarding suspicious activities typical of the criminal element.[67]

Customer security

Dunbar Armored ATM Techs watching over ATMs that have been installed in a van

In some countries, multiple security cameras and security guards are a common feature.[68] In the United States, The New York State Comptroller's Office has advised the New York State Departmentof Banking to have more thorough safety inspections of ATMs in high crime areas.[69]

Consultants of ATM operators assert that the issue of customersecurity should have more focus by the banking industry;[70] it has been suggested that efforts are now more concentrated on the preventive measure of deterrent legislation than on the problem of ongoing forced withdrawals.[71]

At least as far back as July 30, 1986, consultants of the industry have advised for the adoption of an emergency PIN system for ATMs, where the user is able to send a silent alarm in response to a threat.[72] Legislative efforts to require an emergency PIN system have appeared in Illinois,[73] Kansas[74] and Georgia,[75] but none have succeeded yet. In January 2009, Senate Bill 1355 was proposed in the Illinois Senate that revisits the issue of the reverse emergency PIN system.[76] The bill is again supported by thepolice and denied by the banking lobby.[77]

In 1998 three towns outside the Cleveland, Ohio, in response to an ATM crime wave, adopted ATM Consumer Security Legislation requiring that an emergency telephone number switch be installed at all outside ATMs within their jurisdiction. In the wake of an ATM Murder in Sharon Hill, Pennsylvania, The City Council of Sharon Hillpassed an ATM Consumer Security Bill as well. As of July 2009, ATM Consumer Security Legislation is currently pending in New York, New Jersey, and Washington D.C.

In China and elsewhere, many efforts to promote security have been made. On-premises ATMs are often located inside the bank's lobby which may be accessible 24 hours a day. These lobbies have extensive security camera coverage, a courtesy telephone for

consulting with the bank staff, and a security guard on the premises. Bank lobbies that are not guarded 24 hours a day may also have secure doors that can only be opened from outside by swiping the bank card against a wall-mounted scanner, allowing the bank to identify which card enters the building. Most ATMs will also displayon-screen safety warnings and may also be fitted with convex mirrorsabove the display allowing the user to see what is happening behind them.

As of 2013, the only claim available about the extent of ATM connected homicides is that they range from 500 to 1000 per year in the US, covering only cases where the victim had an ATM card and thecard was used by the killer after the known time of death.[78]

Uses

Two NCR Personas 84 ATMs at a bank in Jersey dispensing two types of pound sterling banknotes: Bank of England on the left, and States of Jersey on the right

Although ATMs were originally developed as just cash dispensers, they have evolved to include many other bank-related functions:

Paying routine bills, fees, and taxes (utilities, phone bills, social security, legal fees, taxes, etc.)

Printing bank statements

Updating passbooks

Cash advances

Cheque Processing Module

Paying (in full or partially) the credit balance on a cardlinked to a specific current account.

Transferring money between linked accounts (such as transferring between checking and savings accounts)

Deposit currency recognition, acceptance, and recycling[79][80]

In some countries, especially those which benefit from a fullyintegrated cross-bank ATM network (e.g.: Multibanco in Portugal), ATMs include many functions which are not directly related to the management of one's own bank account, such as:

Gold vending ATM in New York City

Loading monetary value into stored value cards

Adding pre-paid cell phone / mobile phone credit.

Purchasing

Postage stamps.

Lottery tickets

Train tickets

Concert tickets

Movie tickets

Shopping mall gift certificates.

Gold[81]

Donating to charities[82]

Increasingly banks are seeking to use the ATM as a sales device to deliver pre approved loans and targeted advertising using products such as ITM (the Intelligent Teller Machine) from Aptra Relate from NCR.[83] ATMs can also act as an advertising channel forother companies.[84]*

A South Korean ATM with mobile bank port and bar code reader

However several different technologies on ATMs have not yet reached worldwide acceptance, such as:

Videoconferencing with human tellers, known as video tellers[85]

Biometrics, where authorisation of transactions is based on the scanning of a customer's fingerprint, iris, face, etc.[86][87][88]

Cheque/Cash Acceptance, where the ATM accepts and recognise cheques and/or currency without using envelopes[89] Expected to grow in importance in the US through Check 21 legislation.

Bar code scanning[90]

On-demand printing of "items of value" (such as movie tickets, traveler's cheques, etc.)

Dispensing additional media (such as phone cards)

Co-ordination of ATMs with mobile phones[91]

Integration with non-banking equipment[92][93]

Games and promotional features[94]

CRM at the ATM

E.g. In Canada, ATMs are called guichets automatiques in French and sometimes "Bank Machines" in English. The Interac shared cash network does not allow for the selling of goods from ATMs due to specific security requirements for PIN entry when buying goods.[95] CIBC machines in Canada, are able to top-up the minutes on certain pay as you go phones.

Reliability

An ATM running Microsoft Windows that has crashed due to a peripheral component failure

Before an ATM is placed in a public place, it typically has undergone extensive testing with both test money and the backend computer systems that allow it to perform transactions. Banking customers also have come to expect high reliability in their ATMs,[96] which provides incentives to ATM providers to minimise machine and network failures. Financial consequences of incorrect machine operation also provide high degrees of incentive to minimise malfunctions.[97]

ATMs and the supporting electronic financial networks are generally very reliable, with industry benchmarks typically producing 98.25% customer availability for ATMs[98] and up to 99.999% availability for host systems that manage the networks of ATMs. If ATM networks do go out of service, customers could be left without the ability to make transactions until the beginning of their bank's next time of opening hours.

This said, not all errors are to the detriment of customers; there have been cases of machines giving out money without debiting the account, or giving out higher value notes as a result of incorrect denomination of banknote being loaded in the money cassettes.[99] The result of receiving too much money may be influenced by the card holder agreement in place between the customer and the bank.[100][101]

Errors that can occur may be mechanical (such as card transport mechanisms; keypads; hard disk failures; envelope deposit mechanisms); software (such as operating system; device driver; application); communications; or purely down to operator error.

To aid in reliability, some ATMs print each transaction to a roll paper journal that is stored inside the ATM, which allows both the users of the ATMs and the related financial institutions to settle things based on the records in the journal in case there is adispute. In some cases, transactions are posted to an electronic

journal to remove the cost of supplying journal paper to the ATM andfor more convenient searching of data.

Improper money checking can cause the possibility of a customer receiving counterfeit banknotes from an ATM. While bank personnel are generally trained better at spotting and removing counterfeit cash,[102][103] the resulting ATM money supplies used bybanks provide no guarantee for proper banknotes, as the Federal Criminal Police Office of Germany has confirmed that there are regularly incidents of false banknotes having been dispensed throughbank ATMs.[104] Some ATMs may be stocked and wholly owned by outsidecompanies, which can further complicate this problem. Bill validation technology can be used by ATM providers to help ensure the authenticity of the cash before it is stocked in an ATM; ATMs that have cash recycling capabilities include this capability.[105]

Fraud

ATM lineup

Some ATMs may put up warning messages to customers to be vigilant of possible tampering.

Banknotes from a cash machine robbery made unusable with red paint.

As with any device containing objects of value, ATMs and the systems they depend on to function are the targets of fraud. Fraud against ATMs and people's attempts to use them takes several forms.

The first known instance of a fake ATM was installed at a shopping mall in Manchester, Connecticut in 1993. By modifying the inner workings of a Fujitsu model 7020 ATM, a criminal gang known asThe Bucklands Boys were able to steal information from cards inserted into the machine by customers.[106]

WAVY-TV reported an incident in Virginia Beach in September 2006 where a hacker who had probably obtained a factory-default administrator password for a gas station's white label ATM caused the unit to assume it was loaded with US$5 bills instead of $20s, enabling himself—and many subsequent customers—to walk away with four times the money they wanted to withdraw.[107] This type of scamwas featured on the TV series The Real Hustle.

ATM behavior can change during what is called "stand-in" time,where the bank's cash dispensing network is unable to access databases that contain account information (possibly for database maintenance). In order to give customers access to cash, customers may be allowed to withdraw cash up to a certain amount that may be less than their usual daily withdrawal limit, but may still exceed the amount of available money in their accounts, which could result in fraud if the customers intentionally withdraw more money than what they had in their accounts.[108]

Card fraud

In an attempt to prevent criminals from shoulder surfing the customer's personal identification number (PIN), some banks draw privacy areas on the floor.

For a low-tech form of fraud, the easiest is to simply steal acustomer's card along with its PIN. A later variant of this approachis to trap the card inside of the ATM's card reader with a device often referred to as a Lebanese loop. When the customer gets frustrated by not getting the card back and walks away from the machine, the criminal is able to remove the card and withdraw cash from the customer's account, using the card and its PIN.

This type of ATM fraud has spread globally. Although somewhat replaced in terms of volume by ATM skimming incidents, a re-emergence of card trapping has been noticed in regions such as

Europe, where EMV chip and PIN cards have increased in circulation.[109]

Another simple form of fraud involves attempting to get the customer's bank to issue a new card and its PIN and stealing them from their mail.[110]

By contrast, a newer high-tech method of operating, sometimes called card skimming or card cloning, involves the installation of amagnetic card reader over the real ATM's card slot and the use of a wireless surveillance camera or a modified digital camera or a falsePIN keypad to observe the user's PIN. Card data is then cloned into a duplicate card and the criminal attempts a standard cash withdrawal. The availability of low-cost commodity wireless cameras,keypads, card readers, and card writers has made it a relatively simple form of fraud, with comparatively low risk to the fraudsters.[111]

In an attempt to stop these practices, countermeasures againstcard cloning have been developed by the banking industry, in particular by the use of smart cards which cannot easily be copied or spoofed by unauthenticated devices, and by attempting to make theoutside of their ATMs tamper evident. Older chip-card security systems include the French Carte Bleue, Visa Cash, Mondex, Blue fromAmerican Express[112] and EMV '96 or EMV 3.11. The most actively developed form of smart card security in the industry today is knownas EMV 2000 or EMV 4.x.

EMV is widely used in the UK (Chip and PIN) and other parts ofEurope, but when it is not available in a specific area, ATMs must fall back to using the easy–to–copy magnetic strip to perform transactions. This fallback behaviour can be exploited.[113] Howeverthe fall-back option has been removed on the ATMs of some UK banks, meaning if the chip is not read, the transaction will be declined.

Card cloning and skimming can be detected by the implementation of magnetic card reader heads and firmware that can read a signature embedded in all magnetic strips during the card production process. This signature, known as a "MagnePrint" or "BluPrint", can be used in conjunction with common two-factor authentication schemes used in ATM, debit/retail point-of-sale and prepaid card applications.

The concept and various methods of copying the contents of an ATM card's magnetic strip onto a duplicate card to access other people's financial information was well known in the hacking communities by late 1990.[114]

In 1996, Andrew Stone, a computer security consultant from Hampshire in the UK, was convicted of stealing more than £1 million by pointing high-definition video cameras at ATMs from a considerable distance, and by recording the card numbers, expiry dates, etc. from the embossed detail on the ATM cards along with video footage of the PINs being entered. After getting all the information from the videotapes, he was able to produce clone cards which not only allowed him to withdraw the full daily limit for eachaccount, but also allowed him to sidestep withdrawal limits by usingmultiple copied cards. In court, it was shown that he could withdrawas much as £10,000 per hour by using this method. Stone was sentenced to five years and six months in prison.[115]

In February 2009, a group of criminals used counterfeit ATM cards to steal $9 million from 130 ATMs in 49 cities around the world, all within a period of 30 minutes.[116]

Related devices

A talking ATM is a type of ATM that provides audible instructions so that people who cannot read an ATM screen can independently use the machine, therefore effectively eliminating theneed for assistance from an external, potentially malevolent source.

All audible information is delivered privately through a standard headphone jack on the face of the machine. Alternatively, some bankssuch as the Nordea and Swedbank use a built-in external speaker which may be invoked by pressing the talk button on the keypad.[117]Information is delivered to the customer either through pre-recordedsound files or via text-to-speech speech synthesis.

A postal interactive kiosk may also share many of the same components as an ATM (including a vault), but only dispenses items related to postage.[118][119]

A scrip cash dispenser may share many of the same components as an ATM, but lacks the ability to dispense physical cash and consequently requires no vault. Instead, the customer requests a withdrawal transaction from the machine, which prints a receipt. Thecustomer then takes this receipt to a nearby sales clerk, who then exchanges it for cash from the till.[120]

A teller assist unit (TAU) may also share many of the same components as an ATM (including a vault), but they are distinct in that they are designed to be operated solely by trained personnel and not by the general public, they do not integrate directly into interbank networks, and are usually controlled by a computer that isnot directly integrated into the overall construction of the unit.

A web ATM is an online interface for ATM card banking that uses a smart card reader. All the usual ATM functions are available except for withdrawing cash. Most banks in Taiwan provide these online ATM services. [121][122]

In popular culture

One of the banking innovations that Arthur Hailey mentioned inhis 1975 bestselling novel The Moneychangers is Docutel, an

automated teller machine,(Hailey & 1975 308)[123] based on real technology that was issued a patent in 1974 in the United States.

In the novel, Jill Peacock, a journalist, interviewed First Mercantile American Bank executive VP Alexander Vandervoort in a suburban shopping plaza where the bank had installed the first two stainless-steel Docutel automatic tellers. Vandervoort, whose clothes looked like they were from the "fashion section of Esquire",was not at all like the classical solemn, cautious banker in a double-breasted, dark blue suit. Peacock compared him to the new ATMs which embodied modern banking.[123] In GTA Online, players can use ATMs to store their collected money into their bank account.

For other uses, see Password (disambiguation).

The sign in form for the English Wikipedia, which requests a username and password

A password is a word or string of characters used for user authentication to prove identity or access approval to gain access to a resource (example: an access code is a type of password), whichshould be kept secret from those not allowed access.

The use of passwords is known to be ancient. Sentries would challenge those wishing to enter an area or approaching it to supplya password or watchword, and would only allow a person or group to pass if they knew the password. In modern times, user names and passwords are commonly used by people during a log in process that controls access to protected computer operating systems, mobile phones, cable TV decoders, automated teller machines (ATMs), etc. A typical computer user has passwords for many purposes: logging into accounts, retrieving e-mail, accessing applications, databases, networks, web sites, and even reading the morning newspaper online.

Despite the name, there is no need for passwords to be actual words; indeed passwords which are not actual words may be harder to

guess, a desirable property. Some passwords are formed from multiplewords and may more accurately be called a passphrase. The terms passcode and passkey are sometimes used when the secret information is purely numeric, such as the personal identification number (PIN) commonly used for ATM access. Passwords are generally short enough to be easily memorized and typed.

Most organizations specify a password policy that sets requirements for the composition and usage of passwords, typically dictating minimum length, required categories (e.g. upper and lower case, numbers, and special characters), prohibited elements (e.g. own name, date of birth, address, telephone number). Some governments have national authentication frameworks[1] that define requirements for user authentication to government services, including requirements for passwords.

Contents

1 Choosing a secure and memorable password

2 Factors in the security of a password system

2.1 Rate at which an attacker can try guessed passwords

2.2 Limits on the number of password guesses

2.3 Form of stored passwords

2.4 Methods of verifying a password over a network

2.4.1 Simple transmission of the password

2.4.2 Transmission through encrypted channels

2.4.3 Hash-based challenge-response methods

2.4.4 Zero-knowledge password proofs

2.5 Procedures for changing passwords

2.6 Password longevity

2.7 Number of users per password

2.8 Password security architecture

2.9 Password reuse

2.10 Writing down passwords on paper

2.11 After death

3 Password cracking

3.1 Incidents

4 Alternatives to passwords for authentication

5 "The Password is dead"

6 Website password systems

7 History of passwords

8 See also

9 References

10 External links

Choosing a secure and memorable password

The easier a password is for the owner to remember generally means it will be easier for an attacker to guess.[2] However, passwords which are difficult to remember may also reduce the security of a system because (a) users might need to write down or electronically store the password, (b) users will need frequent password resets and (c) users are more likely to re-use the same password. Similarly, the more stringent requirements for password strength, e.g. "have a mix of uppercase and lowercase letters and digits" or "change it monthly", the greater the degree to which users will subvert the system.[3] Others argue longer passwords provide more security (e.g., entropy) than shorter passwords with a wide variety of characters.[4]

In The Memorability and Security of Passwords,[5] Jeff Yan et al. examine the effect of advice given to users about a good choice of password. They found that passwords based on thinking of a phraseand taking the first letter of each word are just as memorable as naively selected passwords, and just as hard to crack as randomly generated passwords. Combining two or more unrelated words is another good method, but a single dictionary word is not. Having a personally designed algorithm for generating obscure passwords is another good method.

However, asking users to remember a password consisting of a "mix of uppercase and lowercase characters" is similar to asking them to remember a sequence of bits: hard to remember, and only a little bit harder to crack (e.g. only 128 times harder to crack for 7-letter passwords, less if the user simply capitalises one of the letters). Asking users to use "both letters and digits" will often lead to easy-to-guess substitutions such as 'E' → '3' and 'I' → '1',substitutions which are well known to attackers. Similarly typing the password one keyboard row higher is a common trick known to attackers.[6]

A method to memorize a complex password is to remember a sentence like 'This year I go to Italy on Friday July 6!' and use the first characters as the actual password. In this case 'TyIgtIoFJ6!'.

In 2013, Google released a list of the most common password types, all of which are considered insecure because they are too easy to guess (especially after researching an individual on social media):[7]

The name of a pet, child, family member, or significant other

Anniversary dates and birthdays

Birthplace

Name of a favorite holiday

Something related to a favorite sports team

The word "password"

Factors in the security of a password system

The security of a password-protected system depends on severalfactors. The overall system must, of course, be designed for sound security, with protection against computer viruses, man-in-the-middle attacks and the like. Physical security issues are also a concern, from deterring shoulder surfing to more sophisticated physical threats such as video cameras and keyboard sniffers. And, of course, passwords should be chosen so that they are hard for an attacker to guess and hard for an attacker to discover using any (and all) of the available automatic attack schemes. See password strength and computer security.

Nowadays, it is a common practice for computer systems to hidepasswords as they are typed. The purpose of this measure is to avoidbystanders reading the password. However, some argue that this practice may lead to mistakes and stress, encouraging users to choose weak passwords. As an alternative, users should have the option to show or hide passwords as they type them.[8]

Effective access control provisions may force extreme measureson criminals seeking to acquire a password or biometric token.[9] Less extreme measures include extortion, rubber hose cryptanalysis, and side channel attack.

Here are some specific password management issues that must beconsidered in thinking about, choosing, and handling, a password.

Rate at which an attacker can try guessed passwords

The rate at which an attacker can submit guessed passwords to the system is a key factor in determining system security. Some systems impose a time-out of several seconds after a small number (e.g., three) of failed password entry attempts. In the absence of other vulnerabilities, such systems can be effectively secure with relatively simple passwords, if they have been well chosen and are not easily guessed.[10]

Many systems store a cryptographic hash of the password. If anattacker gets access to the file of hashed passwords guessing can bedone off-line, rapidly testing candidate passwords against the true password's hash value. In the example of a web-server, an online attacker can guess only at the rate at which the server will respond, while an off-line attacker (who gains access to the file) can guess at a rate limited only by the hardware that is brought to bear.

Passwords that are used to generate cryptographic keys (e.g., for disk encryption or Wi-Fi security) can also be subjected to highrate guessing. Lists of common passwords are widely available and can make password attacks very efficient. (See Password cracking.) Security in such situations depends on using passwords or passphrases of adequate complexity, making such an attack computationally infeasible for the attacker. Some systems, such as PGP and Wi-Fi WPA, apply a computation-intensive hash to the password to slow such attacks. See key stretching.

Limits on the number of password guesses

An alternative to limiting the rate at which an attacker can make guesses on a password is to limit the total number of guesses

that can be made. The password can be disabled, requiring a reset, after a small number of consecutive bad guesses (say 5); and the user may be required to change the password after a larger cumulative number of bad guesses (say 30), to prevent an attacker from making an arbitrarily large number of bad guesses by interspersing them between good guesses made by the legitimate password owner. [11] The username associated with the password can be changed to counter a denial of service attack.

Form of stored passwords

Some computer systems store user passwords as plaintext, against which to compare user log on attempts. If an attacker gains access to such an internal password store, all passwords—and so all user accounts—will be compromised. If some users employ the same password for accounts on different systems, those will be compromised as well.

More secure systems store each password in a cryptographicallyprotected form, so access to the actual password will still be difficult for a snooper who gains internal access to the system, while validation of user access attempts remains possible. The most secure don't store passwords at all, but a one-way derivation, such as a polynomial, modulus, or an advanced hash function.[4] Roger Needham invented the now common approach of storing only a “hashed” form of the plaintext password. When a user types in a password on such a system, the password handling software runs through a cryptographic hash algorithm, and if the hash value generated from the user’s entry matches the hash stored in the password database, the user is permitted access. The hash value is created by applying a cryptographic hash function to a string consisting of the submitted password and, in many implementations, another value knownas a salt. A salt prevents attackers from easily building a list of hash values for common passwords and prevents password cracking efforts from scaling across all users.[12] MD5 and SHA1 are frequently used cryptographic hash functions but they are not recommended for password hashing unless they are used as part of a larger construction such as in PBKDF2.[13]

The stored data—sometimes called the "password verifier" or the "password hash"—is often stored in Modular Crypt Format or RFC 2307 hash format, sometimes in the /etc/passwd file or the /etc/shadow file.[14]

The main storage formats for passwords are plaintext, hashed, hashed and salted, and reversibly encrypted.[15] If an attacker gains access to the password file then if it is plaintext no cracking is necessary. If it is hashed but not salted then it is subject to rainbow table attacks (which are more efficient than cracking). If it is reversibly encrypted then if the attacker gets the decryption key along with the file no cracking is necessary, while if he fails to get the key cracking is not possible (guesses cannot be verified without the key). Thus, of the common storage formats for passwords only when passwords have been salted and hashed is cracking both necessary and possible.[15]

If a cryptographic hash function is well designed, it is computationally infeasible to reverse the function to recover a plaintext password. An attacker can, however, use widely available tools to attempt to guess the passwords. These tools work by hashingpossible passwords and comparing the result of each guess to the actual password hashes. If the attacker finds a match, they know that their guess is the actual password for the associated user. Password cracking tools can operate by brute force (i.e. trying every possible combination of characters) or by hashing every word from a list; large lists of possible passwords in many languages arewidely available on the Internet.[4] The existence of password cracking tools allows attackers to easily recover poorly chosen passwords. In particular, attackers can quickly recover passwords that are short, dictionary words, simple variations on dictionary words or that use easily guessable patterns.[16] A modified version of the DES algorithm was used as the basis for the password hashing algorithm in early Unix systems.[17] The crypt algorithm used a 12-bit salt value so that each user’s hash was unique and iterated the DES algorithm 25 times in order to make the hash function slower,

both measures intended to frustrate automated guessing attacks.[17] The user’s password was used as a key to encrypt a fixed value. Morerecent Unix or Unix like systems (e.g., Linux or the various BSD systems) use more secure password hashing algorithms such as PBKDF2,bcrypt, and scrypt which have large salts and an adjustable cost or number of iterations.[18] A poorly designed hash function can make attacks feasible even if a strong password is chosen. See LM hash for a widely deployed, and insecure, example.[19]

Methods of verifying a password over a network

Simple transmission of the password

Passwords are vulnerable to interception (i.e., "snooping") while being transmitted to the authenticating machine or person. If the password is carried as electrical signals on unsecured physical wiring between the user access point and the central system controlling the password database, it is subject to snooping by wiretapping methods. If it is carried as packetized data over the Internet, anyone able to watch the packets containing the logon information can snoop with a very low probability of detection.

Email is sometimes used to distribute passwords but this is generally an insecure method. Since most email is sent as plaintext,a message containing a password is readable without effort during transport by any eavesdropper. Further, the message will be stored as plaintext on at least two computers: the sender's and the recipient's. If it passes through intermediate systems during its travels, it will probably be stored on there as well, at least for some time, and may be copied to backup, cache or history files on any of these systems.

Using client-side encryption will only protect transmission from the mail handling system server to the client machine. Previousor subsequent relays of the email will not be protected and the email will probably be stored on multiple computers, certainly on the originating and receiving computers, most often in cleartext.

Transmission through encrypted channels

The risk of interception of passwords sent over the Internet can be reduced by, among other approaches, using cryptographic protection. The most widely used is the Transport Layer Security (TLS, previously called SSL) feature built into most current Internet browsers. Most browsers alert the user of a TLS/SSL protected exchange with a server by displaying a closed lock icon, or some other sign, when TLS is in use. There are several other techniques in use; see cryptography.

Hash-based challenge-response methods

Unfortunately, there is a conflict between stored hashed-passwords and hash-based challenge-response authentication; the latter requires a client to prove to a server that they know what the shared secret (i.e., password) is, and to do this, the server must be able to obtain the shared secret from its stored form. On many systems (including Unix-type systems) doing remote authentication, the shared secret usually becomes the hashed form and has the serious limitation of exposing passwords to offline guessing attacks. In addition, when the hash is used as a shared secret, an attacker does not need the original password to authenticate remotely; they only need the hash.

Zero-knowledge password proofs

Rather than transmitting a password, or transmitting the hash of the password, password-authenticated key agreement systems can perform a zero-knowledge password proof, which proves knowledge of the password without exposing it.

Moving a step further, augmented systems for password-authenticated key agreement (e.g., AMP, B-SPEKE, PAK-Z, SRP-6) avoidboth the conflict and limitation of hash-based methods. An augmentedsystem allows a client to prove knowledge of the password to a

server, where the server knows only a (not exactly) hashed password,and where the unhashed password is required to gain access.

Procedures for changing passwords

Usually, a system must provide a way to change a password, either because a user believes the current password has been (or might have been) compromised, or as a precautionary measure. If a new password is passed to the system in unencrypted form, security can be lost (e.g., via wiretapping) before the new password can evenbe installed in the password database. And, of course, if the new password is given to a compromised employee, little is gained. Some web sites include the user-selected password in an unencrypted confirmation e-mail message, with the obvious increased vulnerability.

Identity management systems are increasingly used to automate issuance of replacements for lost passwords, a feature called self service password reset. The user's identity is verified by asking questions and comparing the answers to ones previously stored (i.e.,when the account was opened).

Some password reset questions ask for personal information that could be found on social media, such as mother's maiden name. As a result, some security experts recommend either making up one's own questions or giving false answers.[20]

Password longevity

"Password aging" is a feature of some operating systems which forces users to change passwords frequently (e.g., quarterly, monthly or even more often). Such policies usually provoke user protest and foot-dragging at best and hostility at worst. There is often an increase in the people who note down the password and leaveit where it can easily be found, as well as helpdesk calls to reset a forgotten password. Users may use simpler passwords or develop

variation patterns on a consistent theme to keep their passwords memorable.[21] Because of these issues, there is some debate[22] as to whether password aging is effective. The intended benefit is mainly that a stolen password will be made ineffective if it is reset; however in many cases, particularly with administrative or "root" accounts, once an attacker has gained access, they can make alterations to the operating system that will allow them future access even after the initial password they used expires. (See rootkit.)

The other less-frequently cited, and possibly more valid reason is that in the event of a long brute force attack, the password will be invalid by the time it has been cracked. Specifically, in an environment where it is considered important to know the probability of a fraudulent login in order to accept the risk, one can ensure that the total number of possible passwords multiplied by the time taken to try each one (assuming the greatest conceivable computing resources) is much greater than the password lifetime. However there is no documented evidence that the policy ofrequiring periodic changes in passwords increases system security.

Password aging may be required because of the nature of IT systems the password allows access to; if personal data is involved the EU Data Protection Directive is in force. Implementing such a policy, however, requires careful consideration of the relevant human factors. Humans memorize by association, so it is impossible to simply replace one memory with another. Two psychological phenomena interfere with password substitution. "Primacy" describes the tendency for an earlier memory to be retained more strongly thana later one. "Interference" is the tendency of two memories with thesame association to conflict. Because of these effects most users must resort to a simple password containing a number that can be incremented each time the password is changed.

Number of users per password

Sometimes a single password controls access to a device, for example, for a network router, or password-protected mobile phone. However, in the case of a computer system, a password is usually stored for each user account, thus making all access traceable (save, of course, in the case of users sharing passwords). A would-be user on most systems must supply a username as well as a password, almost always at account set up time, and periodically thereafter. If the user supplies a password matching the one stored for the supplied username, he or she is permitted further access into the computer system. This is also the case for a cash machine, except that the 'user name' is typically the account number stored on the bank customer's card, and the PIN is usually quite short (4 to 6 digits).

Allotting separate passwords to each user of a system is preferable to having a single password shared by legitimate users ofthe system, certainly from a security viewpoint. This is partly because users are more willing to tell another person (who may not be authorized) a shared password than one exclusively for their use.Single passwords are also much less convenient to change because many people need to be told at the same time, and they make removal of a particular user's access more difficult, as for instance on graduation or resignation. Per-user passwords are also essential if users are to be held accountable for their activities, such as making financial transactions or viewing medical records.

Password security architecture

Common techniques used to improve the security of computer systems protected by a password include:

Not displaying the password on the display screen as it isbeing entered or obscuring it as it is typed by using asterisks (*) or bullets (•).

Allowing passwords of adequate length. (Some legacy operating systems, including early versions[which?] of Unix and

Windows, limited passwords to an 8 character maximum,[23][24][25] reducing security.)

Requiring users to re-enter their password after a period of inactivity (a semi log-off policy).

Enforcing a password policy to increase password strength and security.

Requiring periodic password changes.

Assigning randomly chosen passwords.

Requiring minimum password lengths.[13]

Some systems require characters from various characterclasses in a password—for example, "must have at least one uppercaseand at least one lowercase letter". However, all-lowercase passwordsare more secure per keystroke than mixed capitalization passwords.[26]

Providing an alternative to keyboard entry (e.g., spoken passwords, or biometric passwords).

Requiring more than one authentication system, such as2-factor authentication (something a user has and something the userknows).

Using encrypted tunnels or password-authenticated key agreement to prevent access to transmitted passwords via network attacks

Limiting the number of allowed failures within a given time period (to prevent repeated password guessing). After the limitis reached, further attempts will fail (including correct password attempts) until the beginning of the next time period. However, thisis vulnerable to a form of denial of service attack.

Introducing a delay between password submission attempts to slow down automated password guessing programs.

Some of the more stringent policy enforcement measures can pose a risk of alienating users, possibly decreasing security as a result.

Password reuse

It is common practice amongst computer users to reuse the samepassword on multiple sites. This presents a substantial security risk, since an attacker need only compromise a single site in order to gain access to other sites the victim uses. This problem is exacerbated by also reusing usernames, and by websites requiring email logins, as it makes it easier for an attacker to track a single user across multiple sites. Password reuse can be avoided or minimused by using mnemonic techniques, writing passwords down on paper, or using a password manager.[27]

It has been argued by Redmond researchers Dinei Florencio and Cormac Herley, together with Paul C. van Oorschot of Carleton University, Canada, that password reuse is inevitable, and that users should reuse passwords for low-security websites (which contain little personal data and no financial information, for example) and instead focus their efforts on remember long, complex passwords for a few important accounts, such as banks accounts.[28] Similar arguments were made by Forbes cybersecurity columnist, Joseph Steinberg, who also argued that people should not change passwords as often as many "experts" advise, due to the same limiations in human memory.[21]

Writing down passwords on paper

Historically, many security experts asked people to memorize their passwords: "Never write down a password". More recently, many security experts such as Bruce Schneier recommend that people use passwords that are too complicated to memorize, write them down on paper, and keep them in a wallet.[29][30][31][32][33][34][35]

Password manager software can also store passwords relatively safely, in an encrypted file sealed with a single password.

After death

According to a survey by the University of London, one in ten people are now leaving their passwords in their wills to pass on this important information when they die. One third of people, according to the poll, agree that their password protected data is important enough to pass on in their will.[36]

Password cracking

Main article: Password cracking

Attempting to crack passwords by trying as many possibilities as time and money permit is a brute force attack. A related method, rather more efficient in most cases, is a dictionary attack. In a dictionary attack, all words in one or more dictionaries are tested.Lists of common passwords are also typically tested.

Password strength is the likelihood that a password cannot be guessed or discovered, and varies with the attack algorithm used. Cryptologists and computer scientists often refer to the strength or'hardness' in terms of entropy.[4]

Passwords easily discovered are termed weak or vulnerable; passwords very difficult or impossible to discover are considered strong. There are several programs available for password attack (oreven auditing and recovery by systems personnel) such as L0phtCrack,John the Ripper, and Cain; some of which use password design vulnerabilities (as found in the Microsoft LANManager system) to increase efficiency. These programs are sometimes used by system administrators to detect weak passwords proposed by users.

Studies of production computer systems have consistently shownthat a large fraction of all user-chosen passwords are readily guessed automatically. For example, Columbia University found 22% ofuser passwords could be recovered with little effort.[37] According to Bruce Schneier, examining data from a 2006 phishing attack, 55%

of MySpace passwords would be crackable in 8 hours using a commercially available Password Recovery Toolkit capable of testing 200,000 passwords per second in 2006.[38] He also reported that the single most common password was password1, confirming yet again the general lack of informed care in choosing passwords among users. (Henevertheless maintained, based on these data, that the general quality of passwords has improved over the years—for example, average length was up to eight characters from under seven in previous surveys, and less than 4% were dictionary words.[39])

Incidents

On July 16, 1998, CERT reported an incident where an attacker had found 186,126 encrypted passwords. At the time the attacker was discovered, 47,642 passwords had already been cracked.[40]

In September, 2001, after the deaths of 960 New York employees in the September 11 attacks, financial services firm Cantor Fitzgerald through Microsoft broke the passwords of deceased employees to gain access to files needed for servicing client accounts.[41] Technicians used brute-force attacks, and interviewerscontacted families to gather personalized information that might reduce the search time for weaker passwords.[41]

In December 2009, a major password breach of the Rockyou.com website occurred that led to the release of 32 million passwords. The hacker then leaked the full list of the 32 million passwords (with no other identifiable information) to the Internet. Passwords were stored in cleartext in the database and were extracted through a SQL injection vulnerability. The Imperva Application Defense Center (ADC) did an analysis on the strength of the passwords.[42]

In June, 2011, NATO (North Atlantic Treaty Organization) experienced a security breach that led to the public release of first and last names, usernames, and passwords for more than 11,000 registered users of their e-bookshop. The data was leaked as part ofOperation AntiSec, a movement that includes Anonymous, LulzSec, as well as other hacking groups and individuals. The aim of AntiSec is

to expose personal, sensitive, and restricted information to the world, using any means necessary.[43]

On July 11, 2011, Booz Allen Hamilton, a consulting firm that does work for the Pentagon, had their servers hacked by Anonymous and leaked the same day. "The leak, dubbed 'Military Meltdown Monday,' includes 90,000 logins of military personnel—including personnel from USCENTCOM, SOCOM, the Marine corps, variousAir Force facilities, Homeland Security, State Department staff, andwhat looks like private sector contractors."[44] These leaked passwords wound up being hashed in SHA1, and were later decrypted and analyzed by the ADC team at Imperva, revealing that even military personnel look for shortcuts and ways around the password requirements.[45]

Alternatives to passwords for authentication

The numerous ways in which permanent or semi-permanent passwords can be compromised has prompted the development of other techniques. Unfortunately, some are inadequate in practice, and in any case few have become universally available for users seeking a more secure alternative.[citation needed] A 2012 paper[46] examines why passwords have proved so hard to supplant (despite numerous predictions that they would soon be a thing of the past[47]); in examining thirty representative proposed replacements with respect to security, usability and deployability they conclude "none even retains the full set of benefits that legacy passwords already provide."

Single-use passwords. Having passwords which are only valid once makes many potential attacks ineffective. Most users findsingle use passwords extremely inconvenient. They have, however, been widely implemented in personal online banking, where they are known as Transaction Authentication Numbers (TANs). As most home users only perform a small number of transactions each week, the single use issue has not led to intolerable customer dissatisfactionin this case.

Time-synchronized one-time passwords are similar in some ways to single-use passwords, but the value to be entered is displayed on a small (generally pocketable) item and changes every minute or so.

PassWindow one-time passwords are used as single-use passwords, but the dynamic characters to be entered are visible onlywhen a user superimposes a unique printed visual key over a server generated challenge image shown on the user's screen.

Access controls based on public key cryptography e.g. ssh.The necessary keys are usually too large to memorize (but see proposal Passmaze)[48] and must be stored on a local computer, security token or portable memory device, such as a USB flash drive or even floppy disk.

Biometric methods promise authentication based on unalterable personal characteristics, but currently (2008) have higherror rates and require additional hardware to scan, for example, fingerprints, irises, etc. They have proven easy to spoof in some famous incidents testing commercially available systems, for example, the gummie fingerprint spoof demonstration,[49] and, because these characteristics are unalterable, they cannot be changed if compromised; this is a highly important consideration in access control as a compromised access token is necessarily insecure.

Single sign-on technology is claimed to eliminate the needfor having multiple passwords. Such schemes do not relieve user and administrators from choosing reasonable single passwords, nor systemdesigners or administrators from ensuring that private access control information passed among systems enabling single sign-on is secure against attack. As yet, no satisfactory standard has been developed.

Envaulting technology is a password-free way to secure data on e.g. removable storage devices such as USB flash drives. Instead of user passwords, access control is based on the user's access to a network resource.

Non-text-based passwords, such as graphical passwords or mouse-movement based passwords.[50] Graphical passwords are an alternative means of authentication for log-in intended to be used

in place of conventional password; they use images, graphics or colours instead of letters, digits or special characters. One systemrequires users to select a series of faces as a password, utilizing the human brain's ability to recall faces easily.[51] In some implementations the user is required to pick from a series of imagesin the correct sequence in order to gain access.[52] Another graphical password solution creates a one-time password using a randomly generated grid of images. Each time the user is required toauthenticate, they look for the images that fit their pre-chosen categories and enter the randomly generated alphanumeric character that appears in the image to form the one-time password.[53][54] So far, graphical passwords are promising, but are not widely used. Studies on this subject have been made to determine its usability inthe real world. While some believe that graphical passwords would beharder to crack, others suggest that people will be just as likely to pick common images or sequences as they are to pick common passwords.[citation needed]

2D Key (2-Dimensional Key)[55] is a 2D matrix-like key input method having the key styles of multiline passphrase, crossword, ASCII/Unicode art, with optional textual semantic noises,to create big password/key beyond 128 bits to realize the MePKC (Memorizable Public-Key Cryptography)[56] using fully memorizable private key upon the current private key management technologies like encrypted private key, split private key, and roaming private key.

Cognitive passwords use question and answer cue/response pairs to verify identity.

"The Password is dead"

That "the password is dead" is a recurring idea in Computer Security. It often accompanies arguments that the replacement of passwords by a more secure means of authentication is both necessaryand imminent. This claim has been made by numerous people at least since 2004. Notably, Bill Gates, speaking at the 2004 RSA Conferencepredicted the demise of passwords saying "they just don't meet the challenge for anything you really want to secure."[47] In 2011 IBM

predicted that, within five years, "You will never need a password again."[57] Matt Honan, a journalist at Wired, who was the victim ofa hacking incident, in 2012 wrote "The age of the password has come to an end."[58] Heather Adkins, manager of Information Security at Google, in 2013 said that "passwords are done at Google."[59] Eric Grosse, VP of security engineering at Google, states that "passwordsand simple bearer tokens, such as cookies, are no longer sufficient to keep users safe."[60] Christopher Mims, writing in the Wall Street Journal said the password "is finally dying" and predicted their replacement by device-based authentication.[61] Avivah Litan of Gartner said in 2014 "Passwords were dead a few years ago. Now they are more than dead."[62] The reasons given often include reference to the Usability as well as security problems of passwords.

The claim that "the password is dead" is often used by advocates of alternatives to passwords, such as Biometrics, Two-factor authentication or Single sign-on. Many initiatives have been launched with the explicit goal of eliminating passwords. These include Microsoft's Cardspace, the Higgins project, the Liberty Alliance, NSTIC, the FIDO Alliance and various Identity 2.0 proposals. Jeremy Grant, head of NSTIC initiative (the US Dept. of Commerce National Strategy for Trusted Identities in Cyberspace), declared "Passwords are a disaster from a security perspective, we want to shoot them dead."[63] The FIDO Alliance promises a "passwordless experience" in its 2015 specification document.[64]

In spite of these predictions and efforts to replace them passwords still appear the dominant form of authentication on the web. In "The Persistence of Passwords," Cormac Herley and Paul van Oorschot suggest that every effort should be made to end the "spectacularly incorrect assumption" that passwords are dead.[65] They argue that "no other single technology matches their combination of cost, immediacy and convenience" and that "passwords are themselves the bestfit for many of the scenarios in which they are currently used."

Website password systems

Passwords are used on websites to authenticate users and are usually maintained on the Web server, meaning the browser on a remote system sends a password to the server (by HTTP POST), the server checks the password and sends back the relevant content (or an access denied message). This process eliminates the possibility of local reverse engineering as the code used to authenticate the password does not reside on the local machine.

Transmission of the password, via the browser, in plaintext means it can be intercepted along its journey to the server. Many web authentication systems use SSL to establish an encrypted sessionbetween the browser and the server, and is usually the underlying meaning of claims to have a "secure Web site". This is done automatically by the browser and increases integrity of the session,assuming neither end has been compromised and that the SSL/TLS implementations used are high quality ones.

History of passwords

Passwords or watchwords have been used since ancient times. Polybius describes the system for the distribution of watchwords in the Roman military as follows:

The way in which they secure the passing round of the watchword for the night is as follows: from the tenth maniple of each class of infantry and cavalry, the maniple which is encamped atthe lower end of the street, a man is chosen who is relieved from guard duty, and he attends every day at sunset at the tent of the tribune, and receiving from him the watchword — that is a wooden tablet with the word inscribed on it – takes his leave, and on returning to his quarters passes on the watchword and tablet before witnesses to the commander of the next maniple, who in turn passes it to the one next him. All do the same until it reaches the first maniples, those encamped near the tents of the tribunes. These latter are obliged to deliver the tablet to the tribunes before

dark. So that if all those issued are returned, the tribune knows that the watchword has been given to all the maniples, and has passed through all on its way back to him. If any one of them is missing, he makes inquiry at once, as he knows by the marks from what quarter the tablet has not returned, and whoever is responsiblefor the stoppage meets with the punishment he merits.[66]

Passwords in military use evolved to include not just a password, but a password and a counterpassword; for example in the opening days of the Battle of Normandy, paratroopers of the U.S. 101st Airborne Division used a password — flash — which was presented as a challenge, and answered with the correct response — thunder. The challenge and response were changed every three days. American paratroopers also famously used a device known as a "cricket" on D-Day in place of a password system as a temporarily unique method of identification; one metallic click given by the device in lieu of a password was to be met by two clicks in reply.[67]

Passwords have been used with computers since the earliest days of computing. MIT's CTSS, one of the first time sharing systems, was introduced in 1961. It had a LOGIN command that requested a user password. "After typing PASSWORD, the system turns off the printing mechanism, if possible, so that the user may type in his password with privacy."[68] In the early 1970s, Robert Morrisdeveloped a system of storing login passwords in a hashed form as part of the Unix operating system. The system was based on a simulated Hagelin rotor crypto machine, and first appeared in 6th Edition Unix in 1974. A later version of his algorithm, known as crypt(3), used a 12-bit salt and invoked a modified form of the DES algorithm 25 times to reduce the risk of pre-computed dictionary attacks.[69]

E-commerce (also written as e-Commerce, eCommerce or similar variants), short for electronic commerce, is trading in products or services using computer networks, such as the Internet. Electronic commerce draws on technologies such as mobile commerce, electronic funds transfer, supply chain management, Internet marketing, online

transaction processing, electronic data interchange (EDI), inventorymanagement systems, and automated data collection systems. Modern electronic commerce typically uses the World Wide Web for at least one part of the transaction's life cycle, although it may also use other technologies such as e-mail.

E-commerce businesses may employ some or all of the following:

Online shopping web sites for retail sales direct to consumers

Providing or participating in online marketplaces, which process third-party business-to-consumer or consumer-to-consumer sales

Business-to-business buying and selling

Gathering and using demographic data through web contacts and social media

Business-to-business electronic data interchange

Marketing to prospective and established customers by e-mail or fax (for example, with newsletters)

Engaging in pretail for launching new products and services

Contents

1 Timeline

2 Business applications

3 Governmental regulation

4 Forms

5 Global trends

6 Impact on markets and retailers

7 Impact on supply chain management

8 The social impact of e-commerce

9 Distribution channels

10 Examples of new e-commerce systems

11 See also

12 References

13 Further reading

14 External links

Timeline

A timeline for the development of e-commerce:

1971 or 1972: The ARPANET is used to arrange a sale between students at the Stanford Artificial Intelligence Laboratory and the Massachusetts Institute of Technology, later described as "the seminal act of e-commerce" in John Markoff's book What the Dormouse Said.[1]

1979: Michael Aldrich demonstrates the first online shopping system.[2]

1981: Thomson Holidays UK is first business-to-business online shopping system to be installed.[3]

1982: Minitel was introduced nationwide in France by France Télécom and used for online ordering.

1983: California State Assembly holds first hearing on "electronic commerce" in Volcano, California.[4] Testifying are CPUC, MCI Mail, Prodigy, CompuServe, Volcano Telephone, and Pacific Telesis. (Not permitted to testify is Quantum Technology, later to become AOL.)

1984: Gateshead SIS/Tesco is first B2C online shopping system [5] and Mrs Snowball, 72, is the first online home shopper[6]

1984: In April 1984, CompuServe launches the Electronic Mall in the USA and Canada. It is the first comprehensive electroniccommerce service.[7]

1990: Tim Berners-Lee writes the first web browser, WorldWideWeb, using a NeXT computer.[8]

1992: Book Stacks Unlimited in Cleveland opens a commercial sales website (www.books.com) selling books online with credit card processing.

1992: St. Martin's Press publishes J.H. Snider and Terra Ziporyn's Future Shop: How New Technologies Will Change the Way We Shop and What We Buy.[9]

1993: Paget Press releases edition No. 3 [10] of the first[citation needed] app store, The Electronic AppWrapper [11]

1994: Netscape releases the Navigator browser in October under the code name Mozilla. Netscape 1.0 is introduced in late 1994with SSL encryption that made transactions secure.

1994: Ipswitch IMail Server becomes the first software available online for sale and immediate download via a partnership between Ipswitch, Inc. and OpenMarket.

1994: "Ten Summoner's Tales" by Sting becomes the first secure online purchase.[12]

1995: The US National Science Foundation lifts its former strict prohibition of commercial enterprise on the Internet.[13]

1995: Thursday 27 April 1995, the purchase of a book by Paul Stanfield, Product Manager for CompuServe UK, from W H Smith's shop within CompuServe's UK Shopping Centre is the UK's first national online shopping service secure transaction. The shopping service at launch featured W H Smith, Tesco, Virgin Megastores/Our Price, Great Universal Stores (GUS), Interflora, Dixons Retail, PastTimes, PC World (retailer) and Innovations.

1995: Jeff Bezos launches Amazon.com and the first commercial-free 24-hour, internet-only radio stations, Radio HK and

NetRadio start broadcasting. eBay is founded by computer programmer Pierre Omidyar as AuctionWeb.

1996: IndiaMART B2B marketplace established in India.

1996: ECPlaza B2B marketplace established in Korea.

1996: The UK e-commerce platform Sellerdeck, formerly Actinic, is established.[citation needed]

1998: Electronic postal stamps can be purchased and downloaded for printing from the Web.[14]

1998: Cbazaar formerly chennaibazaar.com, India's first B2C eCommerce portal launched by Rajesh Nahar and Ritesh Katariya.

1999: Alibaba Group is established in China. Business.com sold for US $7.5 million to eCompanies, which was purchased in 1997 for US $149,000. The peer-to-peer filesharing software Napster launches. ATG Stores launches to sell decorative items for the home online.

2000: The dot-com bust.

2001: Alibaba.com achieved profitability in December 2001.

2002: eBay acquires PayPal for $1.5 billion.[15] Niche retail companies Wayfair and NetShops are founded with the concept of selling products through several targeted domains, rather than a central portal.

2003: Amazon.com posts first yearly profit.

2003: Bossgoo B2B marketplace established in China.

2004: DHgate.com, China's first online b2b transaction platform, is established, forcing other b2b sites to move away from the "yellow pages" model.[16]

2007: Business.com acquired by R.H. Donnelley for $345 million.[17]

2009: Zappos.com acquired by Amazon.com for $928 million.[18] Retail Convergence, operator of private sale website RueLaLa.com, acquired by GSI Commerce for $180 million, plus up to

$170 million in earn-out payments based on performance through 2012.[19]

2010: Groupon reportedly rejects a $6 billion offer from Google. Instead, the group buying websites went ahead with an IPO on4 November 2011. It was the largest IPO since Google.[20][21]

2011: Quidsi.com, parent company of Diapers.com, acquired by Amazon.com for $500 million in cash plus $45 million in debt and other obligations.[22] GSI Commerce, a company specializing in creating, developing and running online shopping sites for brick andmortar businesses, acquired by eBay for $2.4 billion.[23]

2014: Overstock.com processes over $1 million in Bitcoin sales.[24] India’s e-commerce industry is estimated to have grown more than 30% from 2012 to $12.6 billion in 2013.[25] US eCommerce and Online Retail sales projected to reach $294 billion, an increaseof 12 percent over 2013 and 9% of all retail sales.[26] Alibaba Group has the largest Initial public offering ever, worth $25 billion.

Business applications

An example of an automated online assistant on a merchandisingwebsite.

Some common applications related to electronic commerce are:

Document automation in supply chain and logistics

Domestic and international payment systems

Enterprise content management

Group buying

Print on demand

Automated online assistant

Newsgroups

Online shopping and order tracking

Online banking

Online office suites

Shopping cart software

Teleconferencing

Electronic tickets

Social networking

Instant messaging

Pretail

Digital Wallet

Governmental regulation

In the United States, some electronic commerce activities are regulated by the Federal Trade Commission (FTC). These activities include the use of commercial e-mails, online advertising and consumer privacy. The CAN-SPAM Act of 2003 establishes national standards for direct marketing over e-mail. The Federal Trade Commission Act regulates all forms of advertising, including online advertising, and states that advertising must be truthful and non-deceptive.[27] Using its authority under Section 5 of the FTC Act, which prohibits unfair or deceptive practices, the FTC has brought anumber of cases to enforce the promises in corporate privacy statements, including promises about the security of consumers' personal information.[28] As result, any corporate privacy policy related to e-commerce activity may be subject to enforcement by the FTC.

The Ryan Haight Online Pharmacy Consumer Protection Act of 2008, which came into law in 2008, amends the Controlled Substances Act to address online pharmacies.[29]

Conflict of laws in cyberspace is a major hurdle for harmonisation of legal framework for e-commerce around the world. Inorder to give a uniformity to e-commerce law around the world, many countries adopted the UNCITRAL Model Law on Electronic Commerce (1996) [30]

Internationally there is the International Consumer Protectionand Enforcement Network (ICPEN), which was formed in 1991 from an informal network of government customer fair trade organisations. The purpose was stated as being to find ways of co-operating on tackling consumer problems connected with cross-border transactions in both goods and services, and to help ensure exchanges of information among the participants for mutual benefit and understanding. From this came Econsumer.gov, an ICPEN initiative since April 2001. It is a portal to report complaints about online and related transactions with foreign companies.

There is also Asia Pacific Economic Cooperation (APEC) was established in 1989 with the vision of achieving stability, securityand prosperity for the region through free and open trade and investment. APEC has an Electronic Commerce Steering Group as well as working on common privacy regulations throughout the APEC region.

In Australia, Trade is covered under Australian Treasury Guidelines for electronic commerce,[31] and the Australian Competition and Consumer Commission[32] regulates and offers advice on how to deal with businesses online,[33][34] and offers specific advice on what happens if things go wrong.[35]

In the United Kingdom, The Financial Services Authority (FSA)[36] was formerly the regulating authority for most aspects of the EU's Payment Services Directive (PSD), until its replacement in 2013by the Prudential Regulation Authority and the Financial Conduct Authority.[37] The UK implemented the PSD through the Payment

Services Regulations 2009 (PSRs), which came into effect on 1 November 2009. The PSR affects firms providing payment services and their customers. These firms include banks, non-bank credit card issuers and non-bank merchant acquirers, e-money issuers, etc. The PSRs created a new class of regulated firms known as payment institutions (PIs), who are subject to prudential requirements. Article 87 of the PSD requires the European Commission to report on the implementation and impact of the PSD by 1 November 2012.[38]

In India, the Information Technology Act 2000 governs the basic applicability of e-commerce.

In China, the Telecommunications Regulations of the People's Republic of China (promulgated on 25 September 2000), stipulated theMinistry of Industry and Information Technology (MIIT) as the government department regulating all telecommunications related activities, including electronic commerce.[39] On the same day, The Administrative Measures on Internet Information Services released, is the first administrative regulation to address profit-generating activities conducted through the Internet, and lay the foundation for future regulations governing e-commerce in China.[40] In 28 August 2004, the eleventh session of the tenth NPC Standing Committee adopted The Electronic Signature Law, which regulates datamessage, electronic signature authentication and legal liability issues. It is considered the first law in China’s e-commerce legislation. It was a milestone in the course of improving China’s electronic commerce legislation, and also marks the entering of China’s rapid development stage for electronic commerce legislation.[41]

Forms

Contemporary electronic commerce involves everything from ordering "digital" content for immediate online consumption, to ordering conventional goods and services, to "meta" services to facilitate other types of electronic commerce.

On the institutional level, big corporations and financial institutions use the internet to exchange financial data to facilitate domestic and international business. Data integrity and security are pressing issues for electronic commerce.

Aside from traditional e-Commerce, the terms m-Commerce (mobile commerce) as well (around 2013) t-Commerce[42] have also been used.

Global trends

In 2010, the United Kingdom had the biggest e-commerce market in the world when measured by the amount spent per capita.[43] The Czech Republic is the European country where ecommerce delivers the biggest contribution to the enterprises´ total revenue. Almost a quarter (24%) of the country’s total turnover is generated via the online channel.[44]

Among emerging economies, China's e-commerce presence continues to expand every year. With 384 million internet users, China's online shopping sales rose to $36.6 billion in 2009 and one of the reasons behind the huge growth has been the improved trust level for shoppers. The Chinese retailers have been able to help consumers feel more comfortable shopping online.[45] China's cross-border e-commerce is also growing rapidly. E-commerce transactions between China and other countries increased 32% to 2.3 trillion yuan($375.8 billion) in 2012 and accounted for 9.6% of China's total international trade [46] In 2013, Alibaba had an e-commerce market share of 80% in China.[47]

Other BRIC countries are witnessing the accelerated growth of eCommerce as well. Brazil's eCommerce is growing quickly with retaileCommerce sales expected to grow at a healthy double-digit pace through 2014. By 2016, eMarketer expects retail ecommerce sales in

Brazil to reach $17.3 billion.[48] India has an internet user base of about 243.2 million as of January 2014. Despite being third largest userbase in world, the penetration of Internet is low compared to markets like the United States, United Kingdom or Francebut is growing at a much faster rate, adding around 6 million new entrants every month. The industry consensus is that growth is at aninflection point. In India, cash on delivery is the most preferred payment method, accumulating 75% of the e-retail activities.

E-Commerce has become an important tool for small and large businesses worldwide, not only to sell to customers, but also to engage them.[49][50]

In 2012, ecommerce sales topped $1 trillion for the first timein history.[51]

Mobile devices are playing an increasing role in the mix of eCommerce. Some estimates show that purchases made on mobile deviceswill make up 25% of the market by 2017.[52] According to Cisco Visual Networking Index,[53] in 2014 the amount of mobile devices will outnumber the number of world population.

In the past 10 years, e-commerce is in a period of rapid development. Cross-border e-commerce is called the Internet thinkingalong with traditional import and export trade. Cross-border e-commerce enables international trade towards more convenient and free open to cooperate between different countries in the world, incorporating developed and developing countries. In the short term,developing countries may be limited to IT, but in the long term, they would change the barrier to develop their IT facilities, and continuing to close to developed countries.[54] The moment, developing countries like China and India are developing e-commerce very rapidly, such as China 's Alibaba, the financing capital (£15 billions) is the highest ever in e-commerce company. In addition, China is becoming the biggest e-commerce provider in the world.[55]

The number of Internet users in China which amounts to 600 millions,and which is doubled than USA users in total.[56]

For traditional businesses, one research stated that information technology and cross-border e-commerce is a good opportunity for the rapid development and growth of enterprises. Many companies have invested enormous volume of investment in mobileapplications.The DeLone and McLean Model stated that 3 perspectives are contributed to a successful e-business, including information system quality, service quality and users satisfaction.[57] There isno limit of time and space, there are more opportunities to reach out to customers around the world, and to cut down unnecessary intermediate links, thereby reducing the cost price, and can benefitfrom one on one large customer data analysis, to achieve a high degree of personal customization strategic plan, in order to fully enhance the core competitiveness of the products in company[58]

Impact on markets and retailers

Economists have theorized that e-commerce ought to lead to intensified price competition, as it increases consumers' ability togather information about products and prices. Research by four economists at the University of Chicago has found that the growth ofonline shopping has also affected industry structure in two areas that have seen significant growth in e-commerce, bookshops and travel agencies. Generally, larger firms are able to use economies of scale and offer lower prices. The lone exception to this pattern has been the very smallest category of bookseller, shops with between one and four employees, which appear to have withstood the trend.[59] Depending on the category, e-commerce may shift the switching costs—procedural, relational, and financial—experienced bycustomers.[60]

Individual or business involved in e-commerce whether buyers or sellers rely on Internet-based technology in order to accomplish their transactions. E-commerce is recognized for its ability to allow business to communicate and to form transaction anytime and

anyplace. Whether an individual is in the US or overseas, business can be conducted through the internet. The power of e-commerce allows geophysical barriers to disappear, making all consumers and businesses on earth potential customers and suppliers. Thus, switching barriers and switching costs my shift.[60] eBay is a good example of e-commerce business individuals and businesses are able to post their items and sell them around the Globe.[61]

In e-commerce activities, supply chain and logistics are two most crucial factors need to be considered. Typically, cross-border logistics need about few weeks time round. Based on this low efficiency of the supply chain service, customer satisfaction will be greatly reduced.[62] Some researcher stated that combining e-commerce competence and IT setup could well enhance company’s overall business worth.[63] Other researcher stated that e-commerce need to consider the establishment of warehouse centers in foreign countries, to create high efficiency of the logistics system, not only improve customers’ satisfaction, but also can improve customers’ loyalty.[weasel words]. A recently published comprehensive meta-analysis shows that e-service quality is determined by many different factors, and influences customer satisfaction and repurchase intentions among customers.[64]

Some researcher investigated that if a company want to enhanceinternational customers’ satisfaction, where cultural website need to be adapted in particular country, rather than solely depending onits local country. However, according to this research findings, theresearcher found that German company had treated its international website as the same local model, such as in UK and US online marketing.[65] A company could save money and make decision quickly via the identical strategy in different country. However, opportunity cost could be occurred, if the local strategy does not match to a new market, the company could lose its potential customer.[66]

Impact on supply chain management

For a long time, companies had been troubled by the gap between the benefits which supply chain technology has and the solutions to deliver those benefits. However, the emergence of e-commerce has provided a more practical and effective way of delivering the benefits of the new supply chain technologies.[67]

E-commerce has the capability to integrate all inter-company and intra-company functions, meaning that the three flows (physical flow, financial flow and information flow) of the supply chain couldbe also affected by e-commerce. The affections on physical flows improved the way of product and inventory movement level for companies. For the information flows, e-commerce optimised the capacity of information processing than companies used to have, and for the financial flows, e-commerce allows companies to have more efficient payment and settlement solutions.[67]

In addition, e-commerce has a more sophisticated level of impact on supply chains: Firstly, the performance gap will be eliminated since companies can identify gaps between different levels of supply chains by electronic means of solutions; Secondly, as a result of e-commerce emergence, new capabilities such implementing ERP systems have helped companies to manage operations with customers and suppliers. Yet these new capabilities are still not fully exploited. Thirdly, technology companies would keep investing on new e-commerce software solutions as they are expectinginvestment return. Fourthly, e-commerce would help to solve many aspects of issues that companies may feel difficult to cope with, such as political barriers or cross-country changes. Finally, e-commerce provides companies a more efficient and effective way to collaborate with each other within the supply chain.[67]

The social impact of e-commerce

Along with the e-commerce and its unique charm that has appeared gradually, virtual enterprise, virtual bank, network marketing, online shopping, payment and advertising, such this new vocabulary which is unheard-of and now has become as familiar to

people. This reflects that the e-commerce has huge impact on the economy and society from the other side.[68] For instance, B2B is a rapidly growing business in the world that leads to lower cost and then improves the economic efficiency and also bring along the growth of employment.[69]

To understand how the e-commerce has affected the society and economy, this article will mention three issues below:

1. The e-commerce has changed the relative importance of time,but as the pillars of indicator of the country’s economic state thatthe importance of time should not be ignored.

2. The e-commerce offers the consumer or enterprise various information they need, making information into total transparency, will force enterprise no longer is able to use the mode of space or advertisement to raise their competitive edge.[70] Moreover, in theory, perfect competition between the consumer sovereignty and industry will maximize social welfare.[71]

3. In fact, during the economic activity in the past, large enterprise frequently has advantage of information resource, and thus at the expense of consumers. Nowadays, the transparent and real-time information protects the rights of consumers, because the consumers can use internet to pick out the portfolio to the benefit of themselves. The competitiveness of enterprises will be much more obvious than before, consequently, social welfare would be improved by the development of the e-commerce.

4. The new economy led by the e-commerce change humanistic spirit as well, but above all, is the employee loyalty.[72] Due to the market with competition, the employee’s level of professionalismbecomes the crucial for enterprise in the niche market. The enterprises must pay attention to how to build up the enterprises

inner culture and a set of interactive mechanisms and it is the prime problem for them. Furthermore, though the mode of e-commerce decrease the information cost and transaction cost, however, its development also makes human being are overly computer literate. In hence, emphasized more humanistic attitude to work is another project for enterprise to development. Life is the root of all and high technology are merely an assistive tool to support our quality of life.

The e-commerce is not a kind of new industry, but it is creating a new economic model. Most of people agree that the e-commerce indeed to be important and significant for economic societyin the future, but actually that is a bit of clueless feeling at thebeginning, this problem is exactly prove the e-commerce is a sort ofincorporeal revolution.[73] Generally speaking, as a type of business active procedure, the e-commerce is going to leading an unprecedented revolution in the world, the influence of this model far exceeded the commercial affair itself.[74] Except the mentioned above, in the area of law, education, culture and also policy, the e-commerce will continue that rise in impact. The e-commerce is truly to take human beings into the information society.

Distribution channels

This section does not cite any references or sources.Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (June 2013)

E-commerce has grown in importance as companies have adopted pure-click and brick-and-click channel systems. We can distinguish pure-click and brick-and-click channel system adopted by companies.

Pure-click or pure-play companies are those that have launched a website without any previous existence as a firm.

Bricks-and-clicks companies are those existing companies that have added an online site for e-commerce.

Click-to-brick online retailers that later open physical locations to supplement their online efforts.[75]

Examples of new e-commerce systems

According to eMarketer research company, "by 2017, 65.8 per cent of Britons will use smartphones" (cited by Williams, 2014).

Bringing online experience into the real world, also allows the development of the economy and the interaction between stores and customers. A great example of this new e-commerce system is whatthe Burberry store in London did in 2012. They refurbished the entire store with numerous big screens, photo-studios, and also provided a stage for live acts. Moreover, on the digital screens which are across the store, some fashion shows´ images and advertising campaigns are displayed (William, 2014). In this way, the experience of purchasing becomes more vivid and entertaining while the online and offline components are working together.

Another example is the Kiddicare smartphone app, in which consumers can compare prices. The app allows people to identify the location of sale products and to check whether the item they are looking for is in stock, or if it can be ordered online without going to the `real´ store (William, 2014). In the United States, theWalmart app allows consumers to check product availability and prices both online and offline. Moreover, you can also add to your shopping list items by scanning them, see their details and information, and check purchasers´ ratings and reviews.

Secret Code is the debut major album of artist Aya Kamiki, released on July 12, 2006. It comes in a CD only version. Secret Code debuted at number 5 on the Oricon Weekly Charts for Japan and sold 65,004 copies in total. "Secret Code" was used as the ending theme song for JAPAN COUNTDOWN.

Cryptology is an album by American jazz saxophonist David S. Ware recorded in 1994 and released on Homestead.

Contents

1 Background

2 Reception

3 Track listing

4 Personnel

5 References

Background

In fall 1992, Steven Joerg took over as Homestead Records’ manager. While he continued the label’s indie-rock trajectory, Joergadopted a radically different vision integrating free jazz on the same label where Sonic Youth, Dinosaur Jr and Big Black recorded seminal records.[1] Pianist Matthew Shipp, who had a duo record withbassist William Parker on a Texas punk-rock label which had a deal with Homestead's parent company, talked him into signing the David S. Ware Quartet.[2] According to Ware, Cryptology was "a meditation on Coltrane's example of using music as a vehicle for transcendence."[3]

Reception

Professional ratings

Review scores

Source Rating

AllMusic 4/5 stars[4]

The Penguin Guide to Jazz 3/4 stars[5]

In his review for AllMusic, Thom Jurek says about the album "It is raw, unwavering, and intense almost beyond measure."[4] The Penguin Guide to Jazz states that "the long-form, linked improvisations on Cryptology is an impressive first draft."[5]

The album garnered a Lead Review slot in Rolling Stone by David Fricke, who says about the title piece "It's a sharp lesson for anyone who thinks free jazz is just a euphemism for no discipline".[6]

The Wire placed the album in their "50 Records Of The Year 1995" list.[7]

A designated verifier signature is a signature scheme in whichsignatures can only be verified by a single designated verifier who is chosen by the signer. Designated verifier signatures were first proposed in 1996 by Jakobsson Sako, Kazue Sako, and Russell Impagliazzo.[1] Proposed as a way to combine authentication and off-the-record messages, designated verifier signatures allow authenticated, private conversations to take place.

Unlike in undeniable signature scheme the protocol of verifying is non-interactive, i.e. the signer chooses the designatedverifier (or the set of designated verifiers) in advance and does not take part in the verification process.

This article is about the study of topics such as quantity andstructure. For other uses, see Mathematics (disambiguation)."Math" redirects here. For other uses, see Math (disambiguation).

Euclid (holding calipers), Greek mathematician, 3rd century BC, as imagined by Raphael in this detail from The School of Athens.[1]

Mathematics (from Greek μάθημα máthēma, “knowledge, study, learning”) is the study of topics such as quantity (numbers),[2] structure,[3] space,[2] and change.[4][5][6] There is a range of views among mathematicians and philosophers as to the exact scope and definition of mathematics.[7][8]

Mathematicians seek out patterns [9] [10] and use them to formulatenew conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proof. When mathematical structures are good models of real phenomena, then mathematical reasoning can provide insight or predictions about nature. Through the use of abstraction and logic, mathematics developed from counting, calculation, measurement,and the systematic study of the shapes and motions of physicalobjects. Practical mathematics has been a human activity for as far back as written records exist. The research required tosolve mathematical problems can take years or even centuries of sustained inquiry.

Rigorous arguments first appeared in Greek mathematics, most notably in Euclid's Elements. Since the pioneering work of Giuseppe Peano (1858–1932), David Hilbert (1862–1943), and others on axiomatic systems in the late 19th century, it has become customary to view mathematical research as establishingtruth by rigorous deduction from appropriately chosen axioms and definitions. Mathematics developed at a relatively slow pace until the Renaissance, when mathematical innovations interacting with new scientific discoveries led to a rapid increase in the rate of mathematical discovery that has continued to the present day.[11]

Galileo Galilei (1564–1642) said, "The universe cannot be readuntil we have learned the language and become familiar with the characters in which it is written. It is written in mathematical language, and the letters are triangles, circles and other geometrical figures, without which means it is humanly impossible to comprehend a single word. Without these,one is wandering about in a dark labyrinth."[12] Carl Friedrich Gauss (1777–1855) referred to mathematics as "the Queen of theSciences".[13] Benjamin Peirce (1809–1880) called mathematics "the science that draws necessary conclusions".[14] David Hilbert said of mathematics: "We are not speaking here of arbitrariness in any sense. Mathematics is not like a game whose tasks are determined by arbitrarily stipulated rules. Rather, it is a conceptual system possessing internal necessity that can only be so and by no means otherwise."[15] Albert Einstein (1879–1955) stated that "as far as the laws ofmathematics refer to reality, they are not certain; and as faras they are certain, they do not refer to reality."[16] French mathematician Claire Voisin states "There is creative drive inmathematics, it's all about movement trying to express itself." [17]

Mathematics is used throughout the world as an essential tool in many fields, including natural science, engineering, medicine, finance and the social sciences. Applied mathematics, the branch of mathematics concerned with application of mathematical knowledge to other fields, inspires and makes use of new mathematical discoveries, which has led to the development of entirely new mathematical disciplines, such as statistics and game theory. Mathematicians also engage in pure mathematics, or mathematicsfor its own sake, without having any application in mind. There is no clear line separating pure and applied mathematics, and practical applications for what began as puremathematics are often discovered.[18]

Contents 1 History

o 1.1 Evolutiono 1.2 Etymology

2 Definitions of mathematics

o 2.1 Mathematics as science 3 Inspiration, pure and applied mathematics, and

aesthetics 4 Notation, language, and rigor 5 Fields of mathematics

o 5.1 Foundations and philosophyo 5.2 Pure mathematics o 5.3 Applied mathematics

6 Mathematical awards 7 See also 8 Notes 9 References 10 Further reading 11 External links

HistoryEvolution

Main article: History of mathematics

The evolution of mathematics can be seen as an ever-increasingseries of abstractions. The first abstraction, which is sharedby many animals,[19] was probably that of numbers: the realization that a collection of two apples and a collection of two oranges (for example) have something in common, namely quantity of their members.

Greek mathematician Pythagoras (c. 570 – c. 495 BC), commonly credited with discovering the Pythagorean theorem

Mayan numerals

As evidenced by tallies found on bone, in addition to recognizing how to count physical objects, prehistoric peoplesmay have also recognized how to count abstract quantities, like time – days, seasons, years.[20]

More complex mathematics did not appear until around 3000 BC, when the Babylonians and Egyptians began using arithmetic, algebra and geometry for taxation and other financial calculations, for building and construction, and for astronomy.[21] The earliest uses of mathematics were in trading,land measurement, painting and weaving patterns and the recording of time.

In Babylonian mathematics elementary arithmetic (addition, subtraction, multiplication and division) first appears in thearchaeological record. Numeracy pre-dated writing and numeral systems have been many and diverse, with the first known written numerals created by Egyptians in Middle Kingdom texts such as the Rhind Mathematical Papyrus.[citation needed]

Between 600 and 300 BC the Ancient Greeks began a systematic study of mathematics in its own right with Greek mathematics.[22]

Mathematics has since been greatly extended, and there has been a fruitful interaction between mathematics and science, to the benefit of both. Mathematical discoveries continue to be made today. According to Mikhail B. Sevryuk, in the January2006 issue of the Bulletin of the American Mathematical Society, "The

number of papers and books included in the Mathematical Reviews database since 1940 (the first year of operation of MR) is nowmore than 1.9 million, and more than 75 thousand items are added to the database each year. The overwhelming majority of works in this ocean contain new mathematical theorems and their proofs."[23]

Etymology

The word mathematics comes from the Greek μάθημα (máthēma), which, in the ancient Greek language, means "that which is learnt",[24] "what one gets to know", hence also "study" and "science", and in modern Greek just "lesson". The word máthēmais derived from μανθάνω (manthano), while the modern Greek equivalent is μαθαίνω (mathaino), both of which mean "to learn". In Greece, the word for "mathematics" came to have thenarrower and more technical meaning "mathematical study" even in Classical times.[25] Its adjective is μαθηματικός (mathēmatikós), meaning "related to learning" or "studious", which likewise further came to mean "mathematical". In particular, μαθηματικὴ τέχνη (mathēmatikḗ tékhnē), Latin: ars mathematica, meant "the mathematical art".

In Latin, and in English until around 1700, the term mathematicsmore commonly meant "astrology" (or sometimes "astronomy") rather than "mathematics"; the meaning gradually changed to its present one from about 1500 to 1800. This has resulted in several mistranslations: a particularly notorious one is SaintAugustine's warning that Christians should beware of mathematicimeaning astrologers, which is sometimes mistranslated as a condemnation of mathematicians.[26]

The apparent plural form in English, like the French plural form les mathématiques (and the less commonly used singular derivative la mathématique), goes back to the Latin neuter plural mathematica (Cicero), based on the Greek plural τα μαθηματικά (ta mathēmatiká), used by Aristotle (384–322 BC), andmeaning roughly "all things mathematical"; although it is plausible that English borrowed only the adjective mathematic(al)and formed the noun mathematics anew, after the pattern of physics and metaphysics, which were inherited from the Greek.[27] In English, the noun mathematics takes singular verb forms.

It is often shortened to maths or, in English-speaking North America, math.[28]

Definitions of mathematicsMain article: Definitions of mathematics

Leonardo Fibonacci, the Italian mathematician who established the Hindu–Arabic numeral system to the Western World

Aristotle defined mathematics as "the science of quantity", and this definition prevailed until the 18th century.[29] Starting in the 19th century, when the study of mathematics increased in rigor and began to address abstract topics such as group theory and projective geometry, which have no clear-cut relation to quantity and measurement, mathematicians and philosophers began to propose a variety of new definitions.[30] Some of these definitions emphasize the deductive character ofmuch of mathematics, some emphasize its abstractness, some emphasize certain topics within mathematics. Today, no consensus on the definition of mathematics prevails, even among professionals.[7] There is not even consensus on whether mathematics is an art or a science.[8] A great many professional mathematicians take no interest in a definition of mathematics, or consider it undefinable.[7] Some just say, "Mathematics is what mathematicians do."[7]

Three leading types of definition of mathematics are called logicist, intuitionist, and formalist, each reflecting a different philosophical school of thought.[31] All have severe

problems, none has widespread acceptance, and no reconciliation seems possible.[31]

An early definition of mathematics in terms of logic was Benjamin Peirce's "the science that draws necessary conclusions" (1870).[32] In the Principia Mathematica, Bertrand Russell and Alfred North Whitehead advanced the philosophical program known as logicism, and attempted to prove that all mathematical concepts, statements, and principles can be defined and proven entirely in terms of symbolic logic. A logicist definition of mathematics is Russell's "All Mathematics is Symbolic Logic" (1903).[33]

Intuitionist definitions, developing from the philosophy of mathematician L.E.J. Brouwer, identify mathematics with certain mental phenomena. An example of an intuitionist definition is "Mathematics is the mental activity which consists in carrying out constructs one after the other."[31] A peculiarity of intuitionism is that it rejects some mathematical ideas considered valid according to other definitions. In particular, while other philosophies of mathematics allow objects that can be proven to exist even though they cannot be constructed, intuitionism allows only mathematical objects that one can actually construct.

Formalist definitions identify mathematics with its symbols and the rules for operating on them. Haskell Curry defined mathematics simply as "the science of formal systems".[34] A formal system is a set of symbols, or tokens, and some rules telling how the tokens may be combined into formulas. In formal systems, the word axiom has a special meaning, different from the ordinary meaning of "a self-evident truth". In formal systems, an axiom is a combination of tokens that is included in a given formal system without needing to be derived using the rules of the system.

Mathematics as science

Carl Friedrich Gauss, known as the prince of mathematicians

Gauss referred to mathematics as "the Queen of the Sciences".[13] In the original Latin Regina Scientiarum, as well as in German Königin der Wissenschaften, the word corresponding to science means a "field of knowledge", and this was the original meaning of "science" in English, also; mathematics is in this sense a field of knowledge. The specialization restricting the meaningof "science" to natural science follows the rise of Baconian science, which contrasted "natural science" to scholasticism, the Aristotelean method of inquiring from first principles. The role of empirical experimentation and observation is negligible in mathematics, compared to natural sciences such as psychology, biology, or physics. Albert Einstein stated that "as far as the laws of mathematics refer to reality, theyare not certain; and as far as they are certain, they do not refer to reality."[16] More recently, Marcus du Sautoy has called mathematics "the Queen of Science ... the main driving force behind scientific discovery".[35]

Many philosophers believe that mathematics is not experimentally falsifiable, and thus not a science according to the definition of Karl Popper.[36] However, in the 1930s Gödel's incompleteness theorems convinced many mathematicians[who?] that mathematics cannot be reduced to logic alone, and Karl Popper concluded that "most mathematical theories are, like those of physics and biology, hypothetico-deductive: pure mathematics therefore turns out to be much closer to the natural sciences whose hypotheses are conjectures, than it seemed even recently."[37] Other thinkers, notably Imre Lakatos, have applied a version of falsificationism to mathematics itself.

An alternative view is that certain scientific fields (such astheoretical physics) are mathematics with axioms that are intended to correspond to reality. The theoretical physicist J.M. Ziman proposed that science is public knowledge, and thus includes mathematics.[38] Mathematics shares much in common withmany fields in the physical sciences, notably the exploration of the logical consequences of assumptions. Intuition and experimentation also play a role in the formulation of conjectures in both mathematics and the (other) sciences. Experimental mathematics continues to grow in importance within mathematics, and computation and simulation are playingan increasing role in both the sciences and mathematics.

The opinions of mathematicians on this matter are varied. Manymathematicians[who?] feel that to call their area a science is todownplay the importance of its aesthetic side, and its historyin the traditional seven liberal arts; others[who?] feel that to ignore its connection to the sciences is to turn a blind eye to the fact that the interface between mathematics and its applications in science and engineering has driven much development in mathematics. One way this difference of viewpoint plays out is in the philosophical debate as to whether mathematics is created (as in art) or discovered (as in science). It is common to see universities divided into sections that include a division of Science and Mathematics, indicating that the fields are seen as being allied but that they do not coincide. In practice, mathematicians are typically grouped with scientists at the gross level but separated at finer levels. This is one of many issues considered in the philosophy of mathematics.[citation needed]

Inspiration, pure and applied mathematics, and aestheticsMain article: Mathematical beauty

Isaac Newton (left) and Gottfried Wilhelm Leibniz (right), developers of infinitesimal calculus

Mathematics arises from many different kinds of problems. At first these were found in commerce, land measurement, architecture and later astronomy; today, all sciences suggest problems studied by mathematicians, and many problems arise within mathematics itself. For example, the physicist Richard Feynman invented the path integral formulation of quantum mechanics using a combination of mathematical reasoning and physical insight, and today's string theory, a still-developing scientific theory which attempts to unify the four fundamental forces of nature, continues to inspire new mathematics.[39]

Some mathematics is relevant only in the area that inspired it, and is applied to solve further problems in that area. Butoften mathematics inspired by one area proves useful in many areas, and joins the general stock of mathematical concepts. A

distinction is often made between pure mathematics and appliedmathematics. However pure mathematics topics often turn out tohave applications, e.g. number theory in cryptography. This remarkable fact, that even the "purest" mathematics often turns out to have practical applications, is what Eugene Wigner has called "the unreasonable effectiveness of mathematics".[40] As in most areas of study, the explosion of knowledge in the scientific age has led to specialization: there are now hundreds of specialized areas in mathematics andthe latest Mathematics Subject Classification runs to 46 pages.[41] Several areas of applied mathematics have merged with related traditions outside of mathematics and become disciplines in their own right, including statistics, operations research, and computer science.

For those who are mathematically inclined, there is often a definite aesthetic aspect to much of mathematics. Many mathematicians talk about the elegance of mathematics, its intrinsic aesthetics and inner beauty. Simplicity and generality are valued. There is beauty in a simple and elegantproof, such as Euclid's proof that there are infinitely many prime numbers, and in an elegant numerical method that speeds calculation, such as the fast Fourier transform. G.H. Hardy inA Mathematician's Apology expressed the belief that these aestheticconsiderations are, in themselves, sufficient to justify the study of pure mathematics. He identified criteria such as significance, unexpectedness, inevitability, and economy as factors that contribute to a mathematical aesthetic.[42] Mathematicians often strive to find proofs that are particularly elegant, proofs from "The Book" of God according to Paul Erdős.[43][44] The popularity of recreational mathematics is another sign of the pleasure many find in solving mathematical questions.

Notation, language, and rigorMain article: Mathematical notation

Leonhard Euler, who created and popularized much of the mathematical notation used today

Most of the mathematical notation in use today was not invented until the 16th century.[45] Before that, mathematics was written out in words, a painstaking process that limited mathematical discovery.[46] Euler (1707–1783) was responsible for many of the notations in use today. Modern notation makes mathematics much easier for the professional, but beginners often find it daunting. It is extremely compressed: a few symbols contain a great deal of information. Like musical notation, modern mathematical notation has a strict syntax (which to a limited extent varies from author to author and from discipline to discipline) and encodes information that would be difficult to write in any other way.

Mathematical language can be difficult to understand for beginners. Words such as or and only have more precise meaningsthan in everyday speech. Moreover, words such as open and field have been given specialized mathematical meanings. Technical terms such as homeomorphism and integrable have precise meanings in mathematics. Additionally, shorthand phrases such as iff for "if and only if" belong to mathematical jargon. There is a reason for special notation and technical vocabulary: mathematics requires more precision than everyday speech. Mathematicians refer to this precision of language and logic as "rigor".

Mathematical proof is fundamentally a matter of rigor. Mathematicians want their theorems to follow from axioms by means of systematic reasoning. This is to avoid mistaken "theorems", based on fallible intuitions, of which many instances have occurred in the history of the subject.[47] The

level of rigor expected in mathematics has varied over time: the Greeks expected detailed arguments, but at the time of Isaac Newton the methods employed were less rigorous. Problemsinherent in the definitions used by Newton would lead to a resurgence of careful analysis and formal proof in the 19th century. Misunderstanding the rigor is a cause for some of the common misconceptions of mathematics. Today, mathematicians continue to argue among themselves about computer-assisted proofs. Since large computations are hard toverify, such proofs may not be sufficiently rigorous.[48]

Axioms in traditional thought were "self-evident truths", but that conception is problematic.[49] At a formal level, an axiom is just a string of symbols, which has an intrinsic meaning only in the context of all derivable formulas of an axiomatic system. It was the goal of Hilbert's program to put all of mathematics on a firm axiomatic basis, but according to Gödel's incompleteness theorem every (sufficiently powerful) axiomatic system has undecidable formulas; and so a final axiomatization of mathematics is impossible. Nonetheless mathematics is often imagined to be (as far as its formal content) nothing but set theory in some axiomatization, in thesense that every mathematical statement or proof could be castinto formulas within set theory.[50]

Fields of mathematicsSee also: Areas of mathematics and Glossary of areas of mathematics

An abacus, a simple calculating tool used since ancient times

Mathematics can, broadly speaking, be subdivided into the study of quantity, structure, space, and change (i.e. arithmetic, algebra, geometry, and analysis). In addition to these main concerns, there are also subdivisions dedicated to exploring links from the heart of mathematics to other fields:

to logic, to set theory (foundations), to the empirical mathematics of the various sciences (applied mathematics), andmore recently to the rigorous study of uncertainty. While someareas might seem unrelated, the Langlands program has found connections between areas previously thought unconnected, suchas Galois groups, Riemann surfaces and number theory.

Foundations and philosophy

In order to clarify the foundations of mathematics, the fieldsof mathematical logic and set theory were developed. Mathematical logic includes the mathematical study of logic and the applications of formal logic to other areas of mathematics; set theory is the branch of mathematics that studies sets or collections of objects. Category theory, whichdeals in an abstract way with mathematical structures and relationships between them, is still in development. The phrase "crisis of foundations" describes the search for a rigorous foundation for mathematics that took place from approximately 1900 to 1930.[51] Some disagreement about the foundations of mathematics continues to the present day. The crisis of foundations was stimulated by a number of controversies at the time, including the controversy over Cantor's set theory and the Brouwer–Hilbert controversy.

Mathematical logic is concerned with setting mathematics within a rigorous axiomatic framework, and studying the implications of such a framework. As such, it is home to Gödel's incompleteness theorems which (informally) imply that any effective formal system that contains basic arithmetic, ifsound (meaning that all theorems that can be proven are true), is necessarily incomplete (meaning that there are true theorems which cannot be proved in that system). Whatever finite collectionof number-theoretical axioms is taken as a foundation, Gödel showed how to construct a formal statement that is a true number-theoretical fact, but which does not follow from those axioms. Therefore, no formal system is a complete axiomatization of full number theory. Modern logic is divided into recursion theory, model theory, and proof theory, and is closely linked to theoretical computer science,[citation needed] as well as to category theory.

Theoretical computer science includes computability theory, computational complexity theory, and information theory. Computability theory examines the limitations of various theoretical models of the computer, including the most well-known model – the Turing machine. Complexity theory is the study of tractability by computer; some problems, although theoretically solvable by computer, are so expensive in terms of time or space that solving them is likely to remain practically unfeasible, even with the rapid advancement of computer hardware. A famous problem is the "P = NP ? " problem, one of the Millennium Prize Problems.[52] Finally, information theory is concerned with the amount of data that can be storedon a given medium, and hence deals with concepts such as compression and entropy.

Mathematicallogic Set theory Category

theoryTheory of

computation

Pure mathematics

Quantity

The study of quantity starts with numbers, first the familiar natural numbers and integers ("whole numbers") and arithmetical operations on them, which are characterized in arithmetic. The deeper properties of integers are studied in number theory, from which come such popular results as Fermat's Last Theorem. The twin prime conjecture and Goldbach's conjecture are two unsolved problems in number theory.

As the number system is further developed, the integers are recognized as a subset of the rational numbers ("fractions"). These, in turn, are contained within the real numbers, which are used to represent continuous quantities. Real numbers are generalized to complex numbers. These are the first steps of ahierarchy of numbers that goes on to include quaternions and octonions. Consideration of the natural numbers also leads to

the transfinite numbers, which formalize the concept of "infinity". Another area of study is size, which leads to the cardinal numbers and then to another conception of infinity: the aleph numbers, which allow meaningful comparison of the size of infinitely large sets.

Naturalnumbers Integers Rational

numbersReal

numbers Complex numbers

Structure

Many mathematical objects, such as sets of numbers and functions, exhibit internal structure as a consequence of operations or relations that are defined on the set. Mathematics then studies properties of those sets that can be expressed in terms of that structure; for instance number theory studies properties of the set of integers that can be expressed in terms of arithmetic operations. Moreover, it frequently happens that different such structured sets (or structures) exhibit similar properties, which makes it possible, by a further step of abstraction, to state axioms for a class of structures, and then study at once the whole class of structures satisfying these axioms. Thus one can study groups, rings, fields and other abstract systems; together such studies (for structures defined by algebraic operations) constitute the domain of abstract algebra.

By its great generality, abstract algebra can often be appliedto seemingly unrelated problems; for instance a number of ancient problems concerning compass and straightedge constructions were finally solved using Galois theory, which involves field theory and group theory. Another example of an algebraic theory is linear algebra, which is the general studyof vector spaces, whose elements called vectors have both quantity and direction, and can be used to model (relations between) points in space. This is one example of the phenomenon that the originally unrelated areas of geometry andalgebra have very strong interactions in modern mathematics. Combinatorics studies ways of enumerating the number of objects that fit a given structure.

Combinatorics Numbertheory

Grouptheory

Graphtheory

Ordertheory Algebra

Space

The study of space originates with geometry – in particular, Euclidean geometry. Trigonometry is the branch of mathematics that deals with relationships between the sides and the anglesof triangles and with the trigonometric functions; it combinesspace and numbers, and encompasses the well-known Pythagorean theorem. The modern study of space generalizes these ideas to include higher-dimensional geometry, non-Euclidean geometries (which play a central role in general relativity) and topology. Quantity and space both play a role in analytic geometry, differential geometry, and algebraic geometry. Convex and discrete geometry were developed to solve problems in number theory and functional analysis but now are pursued with an eye on applications in optimization and computer science. Within differential geometry are the concepts of fiber bundles and calculus on manifolds, in particular, vectorand tensor calculus. Within algebraic geometry is the description of geometric objects as solution sets of polynomial equations, combining the concepts of quantity and space, and also the study of topological groups, which combinestructure and space. Lie groups are used to study space, structure, and change. Topology in all its many ramifications may have been the greatest growth area in 20th-century mathematics; it includes point-set topology, set-theoretic topology, algebraic topology and differential topology. In particular, instances of modern-day topology are metrizabilitytheory, axiomatic set theory, homotopy theory, and Morse theory. Topology also includes the now solved Poincaré conjecture, and the still unsolved areas of the Hodge conjecture. Other results in geometry and topology, including the four color theorem and Kepler conjecture, have been provedonly with the help of computers.

Geometry Trigonometry

Differential

geometryTopology Fractal

geometryMeasuretheory

Change

Understanding and describing change is a common theme in the natural sciences, and calculus was developed as a powerful tool to investigate it. Functions arise here, as a central concept describing a changing quantity. The rigorous study of real numbers and functions of a real variable is known as realanalysis, with complex analysis the equivalent field for the complex numbers. Functional analysis focuses attention on (typically infinite-dimensional) spaces of functions. One of many applications of functional analysis is quantum mechanics.Many problems lead naturally to relationships between a quantity and its rate of change, and these are studied as differential equations. Many phenomena in nature can be described by dynamical systems; chaos theory makes precise theways in which many of these systems exhibit unpredictable yet still deterministic behavior.

Calculus Vectorcalculus

Differential

equations

Dynamicalsystems

Chaostheory

Complexanalysis

Applied mathematics

Applied mathematics concerns itself with mathematical methods that are typically used in science, engineering, business, andindustry. Thus, "applied mathematics" is a mathematical science with specialized knowledge. The term applied mathematics also describes the professional specialty in which

mathematicians work on practical problems; as a profession focused on practical problems, applied mathematics focuses on the "formulation, study, and use of mathematical models" in science, engineering, and other areas of mathematical practice.

In the past, practical applications have motivated the development of mathematical theories, which then became the subject of study in pure mathematics, where mathematics is developed primarily for its own sake. Thus, the activity of applied mathematics is vitally connected with research in puremathematics.

Statistics and other decision sciences

Applied mathematics has significant overlap with the discipline of statistics, whose theory is formulated mathematically, especially with probability theory. Statisticians (working as part of a research project) "create data that makes sense" with random sampling and with randomized experiments;[53] the design of a statistical sample or experiment specifies the analysis of the data (before the data be available). When reconsidering data from experiments and samples or when analyzing data from observational studies,statisticians "make sense of the data" using the art of modelling and the theory of inference – with model selection and estimation; the estimated models and consequential predictions should be tested on new data.[54]

Statistical theory studies decision problems such as minimizing the risk (expected loss) of a statistical action, such as using a procedure in, for example, parameter estimation, hypothesis testing, and selecting the best. In these traditional areas of mathematical statistics, a statistical-decision problem is formulated by minimizing an objective function, like expected loss or cost, under specificconstraints: For example, designing a survey often involves minimizing the cost of estimating a population mean with a given level of confidence.[55] Because of its use of optimization, the mathematical theory of statistics shares concerns with other decision sciences, such as operations research, control theory, and mathematical economics.[56]

Computational mathematics

Computational mathematics proposes and studies methods for solving mathematical problems that are typically too large forhuman numerical capacity. Numerical analysis studies methods for problems in analysis using functional analysis and approximation theory; numerical analysis includes the study ofapproximation and discretization broadly with special concern for rounding errors. Numerical analysis and, more broadly, scientific computing also study non-analytic topics of mathematical science, especially algorithmic matrix and graph theory. Other areas of computational mathematics include computer algebra and symbolic computation.

Mathematical physics

Fluiddynamics

Numericalanalysis

Optimization

Probability theory

Statistics

Cryptography

Mathematical finance

Gametheory

Mathematical

biology

Mathematical

chemistry

Mathematical

economics

Controltheory

Mathematical awardsArguably the most prestigious award in mathematics is the Fields Medal,[57][58] established in 1936 and now awarded every four years. The Fields Medal is often considered a mathematical equivalent to the Nobel Prize.

The Wolf Prize in Mathematics, instituted in 1978, recognizes lifetime achievement, and another major international award, the Abel Prize, was introduced in 2003. The Chern Medal was introduced in 2010 to recognize lifetime achievement. These accolades are awarded in recognition of a particular body of

work, which may be innovational, or provide a solution to an outstanding problem in an established field.

A famous list of 23 open problems, called "Hilbert's problems", was compiled in 1900 by German mathematician David Hilbert. This list achieved great celebrity among mathematicians, and at least nine of the problems have now been solved. A new list of seven important problems, titled the "Millennium Prize Problems", was published in 2000. A solution to each of these problems carries a $1 million reward, and only one (the Riemann hypothesis) is duplicated inHilbert's problems.

Computer science is the scientific and practical approach to computation and its applications. It is the systematic study of the feasibility, structure, expression, and mechanization of the methodical procedures (or algorithms) that underlie theacquisition, representation, processing, storage, communication of, and access to information, whether such information is encoded as bits in a computer memory or transcribed in genes and protein structures in a biological cell.[1] An alternate, more succinct definition of computer science is the study of automating algorithmic processes that scale. A computer scientist specializes in the theory of computation and the design of computational systems.[2]

Its subfields can be divided into a variety of theoretical andpractical disciplines. Some fields, such as computational complexity theory (which explores the fundamental properties of computational and intractable problems), are highly abstract, while fields such as computer graphics emphasize real-world visual applications. Still other fields focus on the challenges in implementing computation. For example, programming language theory considers various approaches to the description of computation, while the study of computer programming itself investigates various aspects of the use of programming language and complex systems. Human–computer interaction considers the challenges in making computers and computations useful, usable, and universally accessible to humans.

Contents

1 History o 1.1 Contributions

2 Philosophy o 2.1 Name of the field

3 Areas of computer science o 3.1 Theoretical computer science

3.1.1 Theory of computation 3.1.2 Information and coding theory 3.1.3 Algorithms and data structures 3.1.4 Programming language theory 3.1.5 Formal methods

o 3.2 Applied computer science 3.2.1 Artificial intelligence 3.2.2 Computer architecture and engineering 3.2.3 Computer performance analysis 3.2.4 Computer graphics and visualization 3.2.5 Computer security and cryptography 3.2.6 Computational science 3.2.7 Computer networks 3.2.8 Concurrent, parallel and distributed

systems 3.2.9 Databases 3.2.10 Software engineering

4 The great insights of computer science 5 Academia 6 Education 7 See also 8 Notes 9 References 10 Further reading 11 External links

HistoryMain article: History of computer science

Charles Babbage is credited with inventing the first mechanical computer.

Ada Lovelace is credited with writing the first algorithm intended for processing on a computer.

The earliest foundations of what would become computer sciencepredate the invention of the modern digital computer. Machinesfor calculating fixed numerical tasks such as the abacus have existed since antiquity, aiding in computations such as multiplication and division. Further, algorithms for performing computations have existed since antiquity, even before the development of sophisticated computing equipment. The ancient Sanskrit treatise Shulba Sutras, or "Rules of the Chord", is a book of algorithms written in 800 BCE for constructing geometric objects like altars using a peg and chord, an early precursor of the modern field of computationalgeometry.

Blaise Pascal designed and constructed the first working mechanical calculator, Pascal's calculator, in 1642.[3] In 1673Gottfried Leibniz demonstrated a digital mechanical calculator, called the 'Stepped Reckoner'.[4] He may be considered the first computer scientist and information theorist, for, among other reasons, documenting the binary

number system. In 1820, Thomas de Colmar launched the mechanical calculator industry[note 1] when he released his simplified arithmometer, which was the first calculating machine strong enough and reliable enough to be used daily in an office environment. Charles Babbage started the design of the first automatic mechanical calculator, his difference engine, in 1822, which eventually gave him the idea of the first programmable mechanical calculator, his Analytical Engine.[5] He started developing this machine in 1834 and "in less than two years he had sketched out many of the salient features of the modern computer. A crucial step was the adoption of a punched card system derived from the Jacquard loom"[6] making it infinitely programmable.[note 2] In 1843, during the translation of a French article on the analytical engine, Ada Lovelace wrote, in one of the many notes she included, an algorithm to computethe Bernoulli numbers, which is considered to be the first computer program.[7] Around 1885, Herman Hollerith invented thetabulator, which used punched cards to process statistical information; eventually his company became part of IBM. In 1937, one hundred years after Babbage's impossible dream, Howard Aiken convinced IBM, which was making all kinds of punched card equipment and was also in the calculator business[8] to develop his giant programmable calculator, the ASCC/Harvard Mark I, based on Babbage's analytical engine, which itself used cards and a central computing unit. When the machine was finished, some hailed it as "Babbage's dream come true".[9]

During the 1940s, as new and more powerful computing machines were developed, the term computer came to refer to the machinesrather than their human predecessors.[10] As it became clear that computers could be used for more than just mathematical calculations, the field of computer science broadened to studycomputation in general. Computer science began to be established as a distinct academic discipline in the 1950s andearly 1960s.[11][12] The world's first computer science degree program, the Cambridge Diploma in Computer Science, began at the University of Cambridge Computer Laboratory in 1953. The first computer science degree program in the United States wasformed at Purdue University in 1962.[13] Since practical computers became available, many applications of computing have become distinct areas of study in their own rights.

Although many initially believed it was impossible that computers themselves could actually be a scientific field of study, in the late fifties it gradually became accepted among the greater academic population.[14][15] It is the now well-known IBM brand that formed part of the computer science revolution during this time. IBM (short for International Business Machines) released the IBM 704[16] and later the IBM 709[17] computers, which were widely used during the exploration period of such devices. "Still, working with the IBM [computer] was frustrating ... if you had misplaced as much asone letter in one instruction, the program would crash, and you would have to start the whole process over again".[14] During the late 1950s, the computer science discipline was very much in its developmental stages, and such issues were commonplace.[15]

Time has seen significant improvements in the usability and effectiveness of computing technology. Modern society has seena significant shift in the users of computer technology, from usage only by experts and professionals, to a near-ubiquitous user base. Initially, computers were quite costly, and some degree of human aid was needed for efficient use - in part from professional computer operators. As computer adoption became more widespread and affordable, less human assistance was needed for common usage.

Contributions

The German military used the Enigma machine (shown here) during World War II for communications they wanted kept secret. The large-scale decryption of Enigma traffic at

Bletchley Park was an important factor that contributed to Allied victory in WWII.[18]

Despite its short history as a formal academic discipline, computer science has made a number of fundamental contributions to science and society - in fact, along with electronics, it is a founding science of the current epoch of human history called the Information Age and a driver of the Information Revolution, seen as the third major leap in human technological progress after the Industrial Revolution (1750-1850 CE) and the Agricultural Revolution (8000-5000 BCE).

These contributions include:

The start of the "digital revolution", which includes thecurrent Information Age and the Internet.[19]

A formal definition of computation and computability, andproof that there are computationally unsolvable and intractable problems.[20]

The concept of a programming language, a tool for the precise expression of methodological information at various levels of abstraction.[21]

In cryptography, breaking the Enigma code was an important factor contributing to the Allied victory in World War II.[18]

Scientific computing enabled practical evaluation of processes and situations of great complexity, as well as experimentation entirely by software. It also enabled advanced study of the mind, and mapping of the human genome became possible with the Human Genome Project.[19] Distributed computing projects such as Folding@home explore protein folding.

Algorithmic trading has increased the efficiency and liquidity of financial markets by using artificial intelligence, machine learning, and other statistical andnumerical techniques on a large scale.[22] High frequency algorithmic trading can also exacerbate volatility.[23]

Computer graphics and computer-generated imagery have become ubiquitous in modern entertainment, particularly in television, cinema, advertising, animation and video games. Even films that feature no explicit CGI are usually "filmed" now on digital cameras, or edited or postprocessed using a digital video editor.[citation needed]

Simulation of various processes, including computational fluid dynamics, physical, electrical, and electronic systems and circuits, as well as societies and social situations (notably war games) along with their habitats,among many others. Modern computers enable optimization of such designs as complete aircraft. Notable in electrical and electronic circuit design are SPICE, as well as software for physical realization of new (or modified) designs. The latter includes essential design software for integrated circuits.[citation needed]

Artificial intelligence is becoming increasingly important as it gets more efficient and complex. There are many applications of AI, some of which can be seen athome, such as robotic vacuum cleaners. It is also presentin video games and on the modern battlefield in drones, anti-missile systems, and squad support robots.

PhilosophyMain article: Philosophy of computer science

A number of computer scientists have argued for the distinction of three separate paradigms in computer science. Peter Wegner argued that those paradigms are science, technology, and mathematics.[24] Peter Denning's working group argued that they are theory, abstraction (modeling), and design.[25] Amnon H. Eden described them as the "rationalist paradigm" (which treats computer science as a branch of mathematics, which is prevalent in theoretical computer science, and mainly employs deductive reasoning), the "technocratic paradigm" (which might be found in engineering approaches, most prominently in software engineering), and the"scientific paradigm" (which approaches computer-related artifacts from the empirical perspective of natural sciences, identifiable in some branches of artificial intelligence).[26]

Name of the field

Although first proposed in 1956,[15] the term "computer science"appears in a 1959 article in Communications of the ACM,[27] in whichLouis Fein argues for the creation of a Graduate School in Computer Sciences analogous to the creation of Harvard Business School in

1921,[28] justifying the name by arguing that, like management science, the subject is applied and interdisciplinary in nature, while having the characteristics typical of an academic discipline.[27] His efforts, and those of others such as numerical analyst George Forsythe, were rewarded: universities went on to create such programs, starting with Purdue in 1962.[29] Despite its name, a significant amount of computer science does not involve the study of computers themselves. Because of this, several alternative names have been proposed.[30] Certain departments of major universities prefer the term computing science, to emphasize precisely that difference. Danish scientist Peter Naur suggested the term datalogy,[31] to reflect the fact that the scientific discipline revolves around data and data treatment, while not necessarilyinvolving computers. The first scientific institution to use the term was the Department of Datalogy at the University of Copenhagen, founded in 1969, with Peter Naur being the first professor in datalogy. The term is used mainly in the Scandinavian countries. An alternative term, also proposed by Naur, is data science; this is now used for a distinct field of data analysis, including statistics and databases.

Also, in the early days of computing, a number of terms for the practitioners of the field of computing were suggested in the Communications of the ACM – turingineer, turologist, flow-charts-man, applied meta-mathematician, and applied epistemologist.[32] Three months later in the same journal, comptologist was suggested, followed next year by hypologist.[33] The term computics has also been suggested.[34] In Europe, terms derived from contracted translations of the expression "automatic information" (e.g. "informazione automatica" in Italian) or "information and mathematics" are often used, e.g. informatique (French), Informatik(German), informatica (Italy, The Netherlands), informática (Spain,Portugal), informatika (Slavic languages and Hungarian) or pliroforiki (πληροφορική, which means informatics) in Greek. Similar words have also been adopted in the UK (as in the School of Informatics of the University of Edinburgh).[35]

A folkloric quotation, often attributed to—but almost certainly not first formulated by—Edsger Dijkstra, states that"computer science is no more about computers than astronomy isabout telescopes."[note 3] The design and deployment of computers

and computer systems is generally considered the province of disciplines other than computer science. For example, the study of computer hardware is usually considered part of computer engineering, while the study of commercial computer systems and their deployment is often called information technology or information systems. However, there has been much cross-fertilization of ideas between the various computer-related disciplines. Computer science research also often intersects other disciplines, such as philosophy, cognitive science, linguistics, mathematics, physics, biology,statistics, and logic.

Computer science is considered by some to have a much closer relationship with mathematics than many scientific disciplines, with some observers saying that computing is a mathematical science.[11] Early computer science was strongly influenced by the work of mathematicians such as Kurt Gödel and Alan Turing, and there continues to be a useful interchange of ideas between the two fields in areas such as mathematical logic, category theory, domain theory, and algebra.[15]

The relationship between computer science and software engineering is a contentious issue, which is further muddied by disputes over what the term "software engineering" means, and how computer science is defined.[36] David Parnas, taking a cue from the relationship between other engineering and science disciplines, has claimed that the principal focus of computer science is studying the properties of computation in general, while the principal focus of software engineering is the design of specific computations to achieve practical goals, making the two separate but complementary disciplines.[37]

The academic, political, and funding aspects of computer science tend to depend on whether a department formed with a mathematical emphasis or with an engineering emphasis. Computer science departments with a mathematics emphasis and with a numerical orientation consider alignment with computational science. Both types of departments tend to make efforts to bridge the field educationally if not across all research.

Areas of computer scienceFurther information: Outline of computer science

As a discipline, computer science spans a range of topics fromtheoretical studies of algorithms and the limits of computation to the practical issues of implementing computing systems in hardware and software.[38][39] CSAB, formerly called Computing Sciences Accreditation Board – which is made up of representatives of the Association for Computing Machinery (ACM), and the IEEE Computer Society (IEEE-CS)[40] – identifies four areas that it considers crucial to the discipline of computer science: theory of computation, algorithms and data structures, programming methodology and languages, and computer elements and architecture. In addition to these four areas, CSAB also identifies fields such as software engineering, artificial intelligence, computer networking and telecommunications, database systems, parallel computation, distributed computation, computer-human interaction, computer graphics, operating systems, and numerical and symbolic computation as being important areas of computer science.[38]

Theoretical computer science

Main article: Theoretical computer science

The broader field of theoretical computer science encompasses both the classical theory of computation and a wide range of other topics that focus on the more abstract, logical, and mathematical aspects of computing.

Theory of computation

Main article: Theory of computation

According to Peter J. Denning, the fundamental question underlying computer science is, "What can be (efficiently) automated?"[11]The study of the theory of computation is focused on answeringfundamental questions about what can be computed and what amount of resources are required to perform those computations. In an effort to answer the first question, computability theory examines which computational problems aresolvable on various theoretical models of computation. The

second question is addressed by computational complexity theory, which studies the time and space costs associated withdifferent approaches to solving a multitude of computational problems.

The famous "P=NP?" problem, one of the Millennium Prize Problems,[41] is an open problem in the theory of computation.

P = NP ? GNITIRW-TERCES

Automatatheory

Computability theory

Computationalcomplexitytheory

Cryptography

Quantumcomputingtheory

Information and coding theory

Main articles: Information theory and Coding theory

Information theory is related to the quantification of information. This was developed by Claude E. Shannon to find fundamental limits on signal processing operations such as compressing data and on reliably storing and communicating data.[42] Coding theory is the study of the properties of codes (systems for converting information from one form to another) and their fitness for a specific application. Codes are used for data compression, cryptography, error detection and correction, and more recently also for network coding. Codes are studied for the purpose of designing efficient and reliable data transmission methods.

Algorithms and data structures

Algorithms and data structures is the study of commonly used computational methods and their computational efficiency.

Analysis of Algorithms Data Combinatorial Computational

algorithms structures optimization geometry

Programming language theory

Main article: Programming language theory

Programming language theory is a branch of computer science that deals with the design, implementation, analysis, characterization, and classification of programming languages and their individual features. It falls within the discipline of computer science, both depending on and affecting mathematics, software engineering and linguistics. It is an active research area, with numerous dedicated academic journals.

Type theory Compilerdesign

Programminglanguages

Formal methods

Main article: Formal methods

Formal methods are a particular kind of mathematically based technique for the specification, development and verification of software and hardware systems. The use of formal methods for software and hardware design is motivated by the expectation that, as in other engineering disciplines, performing appropriate mathematical analysis can contribute tothe reliability and robustness of a design. They form an important theoretical underpinning for software engineering, especially where safety or security is involved. Formal methods are a useful adjunct to software testing since they help avoid errors and can also give a framework for testing. For industrial use, tool support is required. However, the high cost of using formal methods means that they are usually only used in the development of high-integrity and life-critical systems, where safety or security is of utmost importance. Formal methods are best described as the

application of a fairly broad variety of theoretical computer science fundamentals, in particular logic calculi, formal languages, automata theory, and program semantics, but also type systems and algebraic data types to problems in software and hardware specification and verification.

Applied computer science

Applied computer science aims at identifying certain computer science concepts that can be used directly in solving real world problems.

Artificial intelligence

Main article: Artificial intelligence

This branch of computer science aims to or is required to synthesise goal-orientated processes such as problem-solving, decision-making, environmental adaptation, learning and communication found in humans and animals. From its origins incybernetics and in the Dartmouth Conference (1956), artificialintelligence (AI) research has been necessarily cross-disciplinary, drawing on areas of expertise such as applied mathematics, symbolic logic, semiotics, electrical engineering, philosophy of mind, neurophysiology, and social intelligence. AI is associated in the popular mind with robotic development, but the main field of practical application has been as an embedded component in areas of software development, which require computational understanding. The starting-point in the late 1940s was Alan Turing's question "Can computers think?", and the question remains effectively unanswered although the "Turing test" is still used to assess computer output on the scale of human intelligence. But the automation of evaluative and predictive tasks has been increasingly successful as a substitute for human monitoring and intervention in domains of computer application involving complex real-world data.

Machine learning Computer vision Image processing

Pattern recognition Data mining Evolutionarycomputation

Knowledgerepresentation

Natural languageprocessing Robotics

Computer architecture and engineering

Main articles: Computer architecture and Computer engineering

Computer architecture, or digital computer organization, is the conceptual design and fundamental operational structure ofa computer system. It focuses largely on the way by which the central processing unit performs internally and accesses addresses in memory.[43] The field often involves disciplines ofcomputer engineering and electrical engineering, selecting andinterconnecting hardware components to create computers that meet functional, performance, and cost goals.

Digital logic Microarchitecture

Multiprocessing

Ubiquitouscomputing

Systemsarchitecture

Operatingsystems

Computer performance analysis

Main article: Computer performance

Computer performance analysis is the study of work flowing through computers with the general goals of improving throughput, controlling response time, using resources efficiently, eliminating bottlenecks, and predicting performance under anticipated peak loads.[44]

Computer graphics and visualization

Main article: Computer graphics (computer science)

Computer graphics is the study of digital visual contents, andinvolves synthese and manipulations of image data. The study is connected to many other fields in computer science, including computer vision, image processing, and computationalgeometry, and is heavily applied in the fields of special effects and video games.

Computer security and cryptography

Main articles: Computer security and Cryptography

Computer security is a branch of computer technology, whose objective includes protection of information from unauthorizedaccess, disruption, or modification while maintaining the accessibility and usability of the system for its intended users. Cryptography is the practice and study of hiding (encryption) and therefore deciphering (decryption) information. Modern cryptography is largely related to computer science, for many encryption and decryption algorithms are based on their computational complexity.

Computational science

Computational science (or scientific computing) is the field of study concerned with constructing mathematical models and quantitative analysis techniques and using computers to analyze and solve scientific problems. In practical use, it istypically the application of computer simulation and other forms of computation to problems in various scientific disciplines.

Numericalanalysis

Computationalphysics

Computationalchemistry

Bioinformatics

Computer networks

Main article: Computer network

This branch of computer science aims to manage networks between computers worldwide.

Concurrent, parallel and distributed systems

Main articles: Concurrency (computer science) and Distributed computing

Concurrency is a property of systems in which several computations are executing simultaneously, and potentially interacting with each other. A number of mathematical models have been developed for general concurrent computation including Petri nets, process calculi and the Parallel Random Access Machine model. A distributed system extends the idea ofconcurrency onto multiple computers connected through a network. Computers within the same distributed system have their own private memory, and information is often exchanged among themselves to achieve a common goal.

Databases

Main article: Database

A database is intended to organize, store, and retrieve large amounts of data easily. Digital databases are managed using database management systems to store, create, maintain, and search data, through database models and query languages.

Software engineering

Main article: Software engineeringSee also: Computer programming

Software engineering is the study of designing, implementing, and modifying software in order to ensure it is of high quality, affordable, maintainable, and fast to build. It is a systematic approach to software design, involving the application of engineering practices to software. Software engineering deals with the organizing and analyzing of software— it doesn't just deal with the creation or manufacture of new software, but its internal maintenance and arrangement. Both computer applications software engineers andcomputer systems software engineers are projected to be among the fastest growing occupations from 2008 and 2018.

"Electrical and computer engineering" redirects here. For contents about computer engineering, see Computer engineering.

Electrical engineers design complex power systems ...

... and electronic circuits.

Electrical engineering is a field of engineering that generally deals with the study and application of electricity,electronics, and electromagnetism. This field first became an identifiable occupation in the latter half of the 19th centuryafter commercialization of the electric telegraph, the telephone, and electric power distribution and use. Subsequently, broadcasting and recording media made electronics part of daily life. The invention of the transistor, and later the integrated circuit, brought down the

cost of electronics to the point where they can be used in almost any household object.

Electrical engineering has now subdivided into a wide range ofsubfields including electronics, digital computers, power engineering, telecommunications, control systems, radio-frequency engineering, signal processing, instrumentation, andmicroelectronics. The subject of electronic engineering is often treated as its own subfield but it intersects with all the other subfields, including the power electronics of power engineering.

Electrical engineers typically hold a degree in electrical engineering or electronic engineering. Practicing engineers may have professional certification and be members of a professional body. Such bodies include the Institute of Electrical and Electronic Engineers (IEEE) and the Institutionof Engineering and Technology (IET).

Electrical engineers work in a very wide range of industries and the skills required are likewise variable. These range from basic circuit theory to the management skills required ofa project manager. The tools and equipment that an individual engineer may need are similarly variable, ranging from a simple voltmeter to a top end analyzer to sophisticated designand manufacturing software.

Contents 1 History

o 1.1 19th century o 1.2 More modern developments o 1.3 Solid-state transistors

2 Subdisciplines o 2.1 Power o 2.2 Control o 2.3 Electronics o 2.4 Microelectronics o 2.5 Signal processing o 2.6 Telecommunications o 2.7 Instrumentation o 2.8 Computers

o 2.9 Related disciplines 3 Education 4 Practicing engineers 5 Tools and work 6 See also 7 Notes 8 References 9 Further reading 10 External links

HistoryMain article: History of electrical engineering

Electricity has been a subject of scientific interest since atleast the early 17th century. The first electrical engineer was probably William Gilbert who designed the versorium: a device that detected the presence of statically charged objects. He was also the first to draw a clear distinction between magnetism and static electricity and is credited with establishing the term electricity.[1] In 1775 Alessandro Volta's scientific experimentations devised the electrophorus,a device that produced a static electric charge, and by 1800 Volta developed the voltaic pile, a forerunner of the electricbattery.[2]

19th century

The discoveries of Michael Faraday formed the foundation of electric motor technology

However, it was not until the 19th century that research into the subject started to intensify. Notable developments in this

century include the work of Georg Ohm, who in 1827 quantified the relationship between the electric current and potential difference in a conductor, of Michael Faraday, the discoverer of electromagnetic induction in 1831, and of James Clerk Maxwell, who in 1873 published a unified theory of electricityand magnetism in his treatise Electricity and Magnetism.[3]

Beginning in the 1830s, efforts were made to apply electricityto practical use in the telegraph. By the end of the 19th century the world had been forever changed by the rapid communication made possible by the engineering development of land-lines, submarine cables, and, from about 1890, wireless telegraphy.

Practical applications and advances in such fields created an increasing need for standardized units of measure. They led tothe international standardization of the units volt, ampere, coulomb, ohm, farad, and henry. This was achieved at an international conference in Chicago in 1893.[4] The publicationof these standards formed the basis of future advances in standardisation in various industries, and in many countries the definitions were immediately recognised in relevant legislation.[5]

During these years, the study of electricity was largely considered to be a subfield of physics. It was not until about1885 that universities and institutes of technology such as Massachusetts Institute of Technology (MIT) and Cornell University started to offer bachelor's degrees in electrical engineering. The Darmstadt University of Technology founded the first department of electrical engineering in the world in1882. In that same year, under Professor Charles Cross, MIT began offering the first option of electrical engineering within its physics department.[6] In 1883, Darmstadt Universityof Technology and Cornell University introduced the world's first bachelor's degree courses of study in electrical engineering, and in 1885 University College London founded thefirst chair of electrical engineering in Great Britain.[7] The University of Missouri established the first department of electrical engineering in the United States in 1886.[8] Severalother schools soon followed suit, including Cornell and the Georgia School of Technology in Atlanta, Georgia.

Thomas Edison, electric light and (DC) power supply networks

Károly Zipernowsky, Ottó Bláthy, Miksa Déri, the ZDB transformer

William Stanley, Jr., transformers

Galileo Ferraris, electrical theory, induction motor

Nikola Tesla, practical polyphase (AC) and induction motor designs

Mikhail Dolivo-Dobrovolsky developed standard 3-phase (AC) systems

Charles Proteus Steinmetz, AC mathematical theories for engineers

Oliver Heaviside, developed theoretical models for electric circuits

During these decades use of electrical engineering increased dramatically. In 1882, Thomas Edison switched on the world's first large-scale electric power network that provided 110 volts — direct current (DC) — to 59 customers on Manhattan Island in New York City. In 1884, Sir Charles Parsons inventedthe steam turbine allowing for more efficient electric power generation. Alternating current, with its ability to transmit power more efficiently over long distances via the use of transformers, developed rapidly in the 1880s and 1890s with transformer designs by Károly Zipernowsky, Ottó Bláthy and Miksa Déri (later called ZBD transformers), Lucien Gaulard, John Dixon Gibbs and William Stanley, Jr.. Practical AC motor designs including induction motors were independently inventedby Galileo Ferraris and Nikola Tesla and further developed

into a practical three-phase form by Mikhail Dolivo-Dobrovolsky and Charles Eugene Lancelot Brown.[9] Charles Steinmetz and Oliver Heaviside contributed to the theoretical basis of alternating current engineering.[10][11] The spread in the use of AC set off in the United States what has been called the War of Currents between a George Westinghouse backed AC system and a Thomas Edison backed DC power system, with AC being adopted as the overall standard.[12]

More modern developments

Guglielmo Marconi known for his pioneering work on long distance radio transmission

During the development of radio, many scientists and inventorscontributed to radio technology and electronics. The mathematical work of James Clerk Maxwell during the 1850s had shown the relationship of different forms of electromagnetic radiation including possibility of invisible airborne waves (later called "radio waves"). In his classic physics experiments of 1888, Heinrich Hertz proved Maxwell's theory bytransmitting radio waves with a spark-gap transmitter, and detected them by using simple electrical devices. Other physicists experimented with these new waves and in the process developed devices for transmitting and detecting them.In 1895 Guglielmo Marconi began work on a way to adapt the known methods of transmitting and detecting these "Hertzian waves" into a purpose built commercial wireless telegraphic system. Early on, he sent wireless signals over a distance of one and a half miles. In December 1901, he sent wireless wavesthat were not affected by the curvature of the Earth. Marconi later transmitted the wireless signals across the Atlantic

between Poldhu, Cornwall, and St. John's, Newfoundland, a distance of 2,100 miles (3,400 km).[13]

In 1897, Karl Ferdinand Braun introduced the cathode ray tube as part of an oscilloscope, a crucial enabling technology for electronic television.[14] John Fleming invented the first radiotube, the diode, in 1904. Two years later, Robert von Lieben and Lee De Forest independently developed the amplifier tube, called the triode.[15]

In 1920 Albert Hull developed the magnetron which would eventually lead to the development of the microwave oven in 1946 by Percy Spencer.[16][17] In 1934 the British military began to make strides toward radar (which also uses the magnetron) under the direction of Dr Wimperis, culminating in the operation of the first radar station at Bawdsey in August 1936.[18]

In 1941 Konrad Zuse presented the Z3, the world's first fully functional and programmable computer using electromechanical parts. In 1943 Tommy Flowers designed and built the Colossus, the world's first fully functional, electronic, digital and programmable computer.[19] In 1946 the ENIAC (Electronic Numerical Integrator and Computer) of John Presper Eckert and John Mauchly followed, beginning the computing era. The arithmetic performance of these machines allowed engineers to develop completely new technologies and achieve new objectives, including the Apollo program which culminated in landing astronauts on the Moon.[20]

Solid-state transistors

The invention of the transistor in late 1947 by William B. Shockley, John Bardeen, and Walter Brattain of the Bell Telephone Laboratories opened the door for more compact devices and led to the development of the integrated circuit in 1958 by Jack Kilby and independently in 1959 by Robert Noyce.[21] Starting in 1968, Ted Hoff and a team at the Intel Corporation invented the first commercial microprocessor, which foreshadowed the personal computer. The Intel 4004 was afour-bit processor released in 1971, but in 1973 the Intel 8080, an eight-bit processor, made the first personal computer, the Altair 8800, possible.[22]

SubdisciplinesElectrical engineering has many subdisciplines, the most common of which are listed below. Although there are electrical engineers who focus exclusively on one of these subdisciplines, many deal with a combination of them. Sometimes certain fields, such as electronic engineering and computer engineering, are considered separate disciplines in their own right.

Power

Main article: Power engineering

Power pole

Power engineering deals with the generation, transmission and distribution of electricity as well as the design of a range of related devices.[23] These include transformers, electric generators, electric motors, high voltage engineering, and power electronics. In many regions of the world, governments maintain an electrical network called a power grid that connects a variety of generators together with users of their energy. Users purchase electrical energy from the grid, avoiding the costly exercise of having to generate their own. Power engineers may work on the design and maintenance of the power grid as well as the power systems that connect to it.[24] Such systems are called on-grid power systems and may supply thegrid with additional power, draw power from the grid or do both. Power engineers may also work on systems that do not connect to the grid, called off-grid power systems, which in somecases are preferable to on-grid systems. The future includes Satellite controlled power systems, with feedback in real timeto prevent power surges and prevent blackouts.

Control

Main article: Control engineering

Control systems play a critical role in space flight.

Control engineering focuses on the modeling of a diverse rangeof dynamic systems and the design of controllers that will cause these systems to behave in the desired manner.[25] To implement such controllers electrical engineers may use electrical circuits, digital signal processors, microcontrollers and PLCs (Programmable Logic Controllers). Control engineering has a wide range of applications from the flight and propulsion systems of commercial airliners to the cruise control present in many modern automobiles.[26] It also plays an important role in industrial automation.

Control engineers often utilize feedback when designing control systems. For example, in an automobile with cruise control the vehicle's speed is continuously monitored and fed back to the system which adjusts the motor's power output accordingly. Where there is regular feedback, control theory can be used to determine how the system responds to such feedback.[27]

Electronics

Main article: Electronic engineering

Electronic components

Electronic engineering involves the design and testing of electronic circuits that use the properties of components suchas resistors, capacitors, inductors, diodes and transistors toachieve a particular functionality.[24] The tuned circuit, whichallows the user of a radio to filter out all but a single station, is just one example of such a circuit. Another example (of a pneumatic signal conditioner) is shown in the adjacent photograph.

Prior to the Second World War, the subject was commonly known as radio engineering and basically was restricted to aspects of communications and radar, commercial radio and early television.[24] Later, in post war years, as consumer devices began to be developed, the field grew to include modern television, audio systems, computers and microprocessors. In the mid-to-late 1950s, the term radio engineering gradually gave way to the name electronic engineering.

Before the invention of the integrated circuit in 1959,[28] electronic circuits were constructed from discrete components that could be manipulated by humans. These discrete circuits consumed much space and power and were limited in speed, although they are still common in some applications. By contrast, integrated circuits packed a large number—often millions—of tiny electrical components, mainly transistors,[29] into a small chip around the size of a coin. This allowed for the powerful computers and other electronic devices we see today.

Microelectronics

Main article: Microelectronics

Microprocessor

Microelectronics engineering deals with the design and microfabrication of very small electronic circuit components for use in an integrated circuit or sometimes for use on theirown as a general electronic component.[30] The most common microelectronic components are semiconductor transistors, although all main electronic components (resistors, capacitorsetc.) can be created at a microscopic level. Nanoelectronics is the further scaling of devices down to nanometer levels. Modern devices are already in the nanometer regime, with below100 nm processing having been standard since about 2002.[31]

Microelectronic components are created by chemically fabricating wafers of semiconductors such as silicon (at higher frequencies, compound semiconductors like gallium arsenide and indium phosphide) to obtain the desired transportof electronic charge and control of current. The field of microelectronics involves a significant amount of chemistry and material science and requires the electronic engineer working in the field to have a very good working knowledge of the effects of quantum mechanics.[32]

Signal processing

Main article: Signal processing

A Bayer filter on a CCD requires signal processing to get a red, green, and blue value at each pixel.

Signal processing deals with the analysis and manipulation of signals.[33] Signals can be either analog, in which case the signal varies continuously according to the information, or digital, in which case the signal varies according to a seriesof discrete values representing the information. For analog signals, signal processing may involve the amplification and filtering of audio signals for audio equipment or the modulation and demodulation of signals for telecommunications.For digital signals, signal processing may involve the

compression, error detection and error correction of digitallysampled signals.[34]

Signal Processing is a very mathematically oriented and intensive area forming the core of digital signal processing and it is rapidly expanding with new applications in every field of electrical engineering such as communications, control, radar, audio engineering, broadcast engineering, power electronics and bio-medical engineering as many already existing analog systems are replaced with their digital counterparts. Analog signal processing is still important in the design of many control systems.

DSP processor ICs are found in every type of modern electronicsystems and products including, SDTV | HDTV sets,[35] radios andmobile communication devices, Hi-Fi audio equipment, Dolby noise reduction algorithms, GSM mobile phones, mp3 multimedia players, camcorders and digital cameras, automobile control systems, noise cancelling headphones, digital spectrum analyzers, intelligent missile guidance, radar, GPS based cruise control systems and all kinds of image processing, video processing, audio processing and speech processing systems.[36]

Telecommunications

Main article: Telecommunications engineering

Satellite dishes are a crucial component in the analysis of satellite information.

Telecommunications engineering focuses on the transmission of information across a channel such as a coax cable, optical fiber or free space.[37] Transmissions across free space requireinformation to be encoded in a carrier wave to shift the

information to a carrier frequency suitable for transmission, this is known as modulation. Popular analog modulation techniques include amplitude modulation and frequency modulation.[38] The choice of modulation affects the cost and performance of a system and these two factors must be balancedcarefully by the engineer.

Once the transmission characteristics of a system are determined, telecommunication engineers design the transmitters and receivers needed for such systems. These two are sometimes combined to form a two-way communication device known as a transceiver. A key consideration in the design of transmitters is their power consumption as this is closely related to their signal strength.[39][40] If the signal strength of a transmitter is insufficient the signal's information willbe corrupted by noise.

Instrumentation

Main article: Instrumentation engineering

Flight instruments provide pilots with the tools to control aircraft analytically.

Instrumentation engineering deals with the design of devices to measure physical quantities such as pressure, flow and temperature.[41] The design of such instrumentation requires a good understanding of physics that often extends beyond electromagnetic theory. For example, flight instruments measure variables such as wind speed and altitude to enable pilots the control of aircraft analytically. Similarly, thermocouples use the Peltier-Seebeck effect to measure the temperature difference between two points.[42]

Often instrumentation is not used by itself, but instead as the sensors of larger electrical systems. For example, a thermocouple might be used to help ensure a furnace's temperature remains constant.[43] For this reason, instrumentation engineering is often viewed as the counterpartof control engineering.

Computers

Main article: Computer engineering

Supercomputers are used in fields as diverse as computational biology and geographic information systems.

Computer engineering deals with the design of computers and computer systems. This may involve the design of new hardware,the design of PDAs, tablets and supercomputers or the use of computers to control an industrial plant.[44] Computer engineersmay also work on a system's software. However, the design of complex software systems is often the domain of software engineering, which is usually considered a separate discipline.[45] Desktop computers represent a tiny fraction of the devices a computer engineer might work on, as computer-like architectures are now found in a range of devices including video game consoles and DVD players.

Related disciplines

The Bird VIP Infant ventilator

Mechatronics is an engineering discipline which deals with theconvergence of electrical and mechanical systems. Such combined systems are known as electromechanical systems and have widespread adoption. Examples include automated manufacturing systems,[46] heating, ventilation and air-conditioning systems [47] and various subsystems of aircraft and automobiles. [48]

The term mechatronics is typically used to refer to macroscopic systems but futurists have predicted the emergence of very small electromechanical devices. Already such small devices, known as Microelectromechanical systems (MEMS), are used in automobiles to tell airbags when to deploy,[49] in digital projectors to create sharper images and in inkjet printers to create nozzles for high definition printing. In the future it is hoped the devices will help build tiny implantable medical devices and improve optical communication.[50]

Biomedical engineering is another related discipline, concerned with the design of medical equipment. This includes fixed equipment such as ventilators, MRI scanners [51] and electrocardiograph monitors as well as mobile equipment such as cochlear implants, artificial pacemakers and artificial hearts.

Aerospace engineering and robotics an example is the most recent electric propulsion and ion propulsion.

Education

Main article: Education and training of electrical and electronics engineers

Oscilloscope

Electrical engineers typically possess an academic degree witha major in electrical engineering, electronics engineering, electrical engineering technology,[52] or electrical and electronic engineering.[53][54] The same fundamental principles are taught in all programs, though emphasis may vary accordingto title. The length of study for such a degree is usually four or five years and the completed degree may be designated as a Bachelor of Science in Electrical/Electronics EngineeringTechnology, Bachelor of Engineering, Bachelor of Science, Bachelor of Technology, or Bachelor of Applied Science depending on the university. The bachelor's degree generally includes units covering physics, mathematics, computer science, project management, and a variety of topics in electrical engineering.[55] Initially such topics cover most, ifnot all, of the subdisciplines of electrical engineering. At some schools, the students can then choose to emphasize one ormore subdisciplines towards the end of their courses of study.

Typical electrical engineering diagram used as a troubleshooting tool

At many schools, electronic engineering is included as part ofan electrical award, sometimes explicitly, such as a Bachelor of Engineering (Electrical and Electronic), but in others electrical and electronic engineering are both considered to be sufficiently broad and complex that separate degrees are offered.[56]

Some electrical engineers choose to study for a postgraduate degree such as a Master of Engineering/Master of Science (M.Eng./M.Sc.), a Master of Engineering Management, a Doctor of Philosophy (Ph.D.) in Engineering, an Engineering Doctorate(Eng.D.), or an Engineer's degree. The master's and engineer'sdegrees may consist of either research, coursework or a mixture of the two. The Doctor of Philosophy and Engineering Doctorate degrees consist of a significant research component and are often viewed as the entry point to academia. In the United Kingdom and some other European countries, Master of Engineering is often considered to be an undergraduate degree of slightly longer duration than the Bachelor of Engineering rather than postgraduate.[57]

Practicing engineersBelgian electrical engineers inspecting the rotor of a 40,000 kilowatt turbine of the General Electric Company in New York City

In most countries, a bachelor's degree in engineering represents the first step towards professional certification and the degree program itself is certified by a professional body.[58] After completing a certified degree program the engineer must satisfy a range of requirements (including work experience requirements) before being certified. Once certified the engineer is designated the title of ProfessionalEngineer (in the United States, Canada and South Africa), Chartered Engineer or Incorporated Engineer (in India, Pakistan, the United Kingdom, Ireland and Zimbabwe), CharteredProfessional Engineer (in Australia and New Zealand) or European Engineer (in much of the European Union).

The IEEE corporate office is on the 17th floor of 3 Park Avenue in New York City

The advantages of certification vary depending upon location. For example, in the United States and Canada "only a licensed engineer may seal engineering work for public and private clients".[59] This requirement is enforced by state and provincial legislation such as Quebec's Engineers Act.[60] In other countries, no such legislation exists. Practically all certifying bodies maintain a code of ethics that they expect all members to abide by or risk expulsion.[61] In this way theseorganizations play an important role in maintaining ethical standards for the profession. Even in jurisdictions where certification has little or no legal bearing on work, engineers are subject to contract law. In cases where an engineer's work fails he or she may be subject to the tort of negligence and, in extreme cases, the charge of criminal negligence. An engineer's work must also comply with numerous other rules and regulations such as building codes and legislation pertaining to environmental law.

Professional bodies of note for electrical engineers include the Institute of Electrical and Electronics Engineers (IEEE) and the Institution of Engineering and Technology (IET). The IEEE claims to produce 30% of the world's literature in electrical engineering, has over 360,000 members worldwide andholds over 3,000 conferences annually.[62] The IET publishes 21 journals, has a worldwide membership of over 150,000, and claims to be the largest professional engineering society in

Europe.[63][64] Obsolescence of technical skills is a serious concern for electrical engineers. Membership and participationin technical societies, regular reviews of periodicals in the field and a habit of continued learning are therefore essential to maintaining proficiency. MIET(Member of the Institution of Engineering and Technology) is recognised in Europe as Electrical and computer (technology) engineer.[65]

In Australia, Canada and the United States electrical engineers make up around 0.25% of the labor force (see note).

Tools and workFrom the Global Positioning System to electric power generation, electrical engineers have contributed to the development of a wide range of technologies. They design, develop, test and supervise the deployment of electrical systems and electronic devices. For example, they may work on the design of telecommunication systems, the operation of electric power stations, the lighting and wiring of buildings,the design of household appliances or the electrical control of industrial machinery.[66]

Satellite communications is typical of what electrical engineers work on.

Fundamental to the discipline are the sciences of physics and mathematics as these help to obtain both a qualitative and quantitative description of how such systems will work. Today most engineering work involves the use of computers and it is commonplace to use computer-aided design programs when designing electrical systems. Nevertheless, the ability to sketch ideas is still invaluable for quickly communicating with others.

The Shadow robot hand system

Although most electrical engineers will understand basic circuit theory (that is the interactions of elements such as resistors, capacitors, diodes, transistors and inductors in a circuit), the theories employed by engineers generally depend upon the work they do. For example, quantum mechanics and solid state physics might be relevant to an engineer working on VLSI (the design of integrated circuits), but are largely irrelevant to engineers working with macroscopic electrical systems. Even circuit theory may not be relevant to a person designing telecommunication systems that use off-the-shelf components. Perhaps the most important technical skills for electrical engineers are reflected in university programs, which emphasize strong numerical skills, computer literacy andthe ability to understand the technical language and concepts that relate to electrical engineering.[67]

A laser bouncing down an acrylic rod, illustrating the total internal reflection of light in a multi-mode optical fiber.

A wide range of instrumentation is used by electrical engineers. For simple control circuits and alarms, a basic multimeter measuring voltage, current and resistance may suffice. Where time-varying signals need to be studied, the oscilloscope is also an ubiquitous instrument. In RF engineering and high frequency telecommunications spectrum analyzers and network analyzers are used. In some disciplines safety can be a particular concern with instrumentation. For instance medical electronics designers must take into account that much lower voltages than normal can be dangerous when electrodes are directly in contact with internal body fluids.[68] Power transmission engineering also has great safety concerns due to the high voltages used; although voltmeters may in principle be similar to their low voltage equivalents, safety and calibration issues make them very different.[69] Manydisciplines of electrical engineering use tests specific to their discipline. Audio electronics engineers use audio test sets consisting of a signal generator and a meter, principallyto measure level but also other parameters such as harmonic distortion and noise. Likewise information technology have their own test sets, often specific to a particular data format, and the same is true of television broadcasting.

Radome at the Misawa Air Base Misawa Security Operations Center, Misawa, Japan

For many engineers, technical work accounts for only a fraction of the work they do. A lot of time may also be spent on tasks such as discussing proposals with clients, preparing budgets and determining project schedules.[70] Many senior engineers manage a team of technicians or other engineers and for this reason project management skills are important. Most engineering projects involve some form of documentation and strong written communication skills are therefore very important.

The workplaces of engineers are just as varied as the types ofwork they do. Electrical engineers may be found in the pristine lab environment of a fabrication plant, the offices of a consulting firm or on site at a mine. During their working life, electrical engineers may find themselves supervising a wide range of individuals including scientists, electricians, computer programmers and other engineers.[71]

Electrical engineering has an intimate relationship with the physical sciences. For instance the physicist Lord Kelvin played a major role in the engineering of the first transatlantic telegraph cable.[72] Conversely, the engineer Oliver Heaviside produced major work on the mathematics of transmission on telegraph cables.[73] Electrical engineers are often required on major science projects. For instance, large particle accelerators such as CERN need electrical engineers to deal with many aspects of the project: from the power distribution, to the instrumentation, to the manufacture and installation of the superconducting electromagnets.[74][75]

"Cash machine" redirects here. For the Hard-Fi song, see Cash Machine.

An NCR Personas 75-Series interior, multi-function ATM in the United States

Smaller indoor ATMs dispense money inside convenience stores and other busy areas, such as this off-premises Wincor Nixdorfmono-function ATM in Sweden.

An automated teller machine or automatic teller machine[1][2][3] (ATM, American, Australian, Malaysian, Singaporean, Indian, Maldivian, Hiberno, Philippine and Sri Lankan English), also known as an automated banking machine (ABM, Canadian English),cash machine, cashpoint, cashline, minibank, or colloquially hole in the wall (British and South African English), is an electronic telecommunications device that enables the customers of a financial institution to perform financial transactions, particularly cash withdrawal, without the need for a human cashier, clerk or bank teller.

On most modern ATMs, the customer is identified by inserting aplastic ATM card with a magnetic stripe or a plastic smart card with a chip that contains a unique card number and some security information such as an expiration date or CVVC (CVV).Authentication is provided by the customer entering a personalidentification number (PIN).

Using an ATM, customers can access their bank deposit or credit accounts in order to make a variety of transactions such as cash withdrawals, check balances, or credit mobile phones. If the currency being withdrawn from the ATM is different from that in which the bank account is denominated the money will be converted at an official exchange rate. Thus, ATMs often provide the best possible exchange rates for foreign travellers, and are widely used for this purpose.[4] Yet it seems on modern ATMs foreign cash currency is not

processed or possibly rejected when deposited or at least is not originally expected by the machine.

Contents 1 History

o 1.1 Docutel United States 1969 o 1.2 Continued Improvements

2 Location 3 Financial networks 4 Global use 5 Hardware 6 Software 7 Security

o 7.1 Physical o 7.2 Transactional secrecy and integrity o 7.3 Customer identity integrity o 7.4 Device operation integrity o 7.5 Customer security o 7.6 Uses

8 Reliability 9 Fraud

o 9.1 Card fraud 10 Related devices 11 In popular culture 12 See also 13 References 14 Further reading 15 External links

History

An old Nixdorf ATM

The idea of out-of-hours cash distribution developed from banker's needs in Asia (Japan), Europe (Sweden and the United Kingdom) and North America (the United States).[5][6] LIttle is known of the Japanese device. In the US patent record, Luther George Simjian has been credited with developing a "prior art device". Specifically his 132nd patent (US3079603), which was first filed on 30 June 1960 (and granted 26 February 1963). The roll-out of this machine, called Bankograph, was delayed by a couple of years, due in part to Simjian's Reflectone Electronics Inc. being acquired by Universal Match Corporation.[7] An experimental Bankograph was installed in NewYork City in 1961 by the City Bank of New York, but removed after six months due to the lack of customer acceptance. The Bankograph was an automated envelope deposit machine (accepting coins, cash and cheques) and did not have cash dispensing features.[8][9]

Actor Reg Varney using the world's first cash machine in Enfield Town, north London on 27 June 1967

It is widely accepted that the first ATM was put into use by Barclays Bank in its Enfield Town branch in north London, United Kingdom, on 27 June 1967.[10] This machine was inaugurated by English comedy actor Reg Varney.[11] This instance of the invention is credited to John Shepherd-Barron of printing firm De La Rue,[12] who was awarded an OBE in the 2005 New Year Honours.[13] This design used paper cheques issuedby a teller or cashier, marked with carbon-14 for machine readability and security, which in a latter model were matchedwith a personal identification number (PIN).[12][14] Shepherd-Barron stated; "It struck me there must be a way I could get my own money, anywhere in the world or the UK. I hit upon the idea of a chocolate bar dispenser, but replacing chocolate with cash."[12]

The Barclays-De La Rue machine (called De La Rue Automatic Cash System or DACS)[15] beat the Swedish saving banks' and a company called Metior's machine (a device called Bankomat) by a mere nine days and Westminster Bank’s-Smith Industries-Chubbsystem (called Chubb MD2) by a month.[16] The online version of the Swedish machine is listed to have been operational on 6 May 1968, while claiming to be the first online cash machine in the world (ahead of a similar claim by IBM and Lloyds Bank in 1971).[17] The collaboration of a small start-up called Speytec and Midland Bank developed a fourth machine which was marketed after 1969 in Europe and the US by the Burroughs Corporation. The patent for this device (GB1329964) was filed on September 1969 (and granted in 1973) by John David Edwards,Leonard Perkins, John Henry Donald, Peter Lee Chappell, Sean Benjamin Newcombe & Malcom David Roe.

ATM of Sberbank in Tolyatti, Russia

Both the DACS and MD2 accepted only a single-use token or voucher which was retained by the machine while the Speytec worked with a card with a magnetic strip at the back. They used principles including Carbon-14 and low-coercivity magnetism in order to make fraud more difficult. The idea of aPIN stored on the card was developed by a British engineer working on the MD2 named James Goodfellow in 1965 (patent GB1197183 filed on 2 May 1966 with Anthony Davies). The essence of this system was that it enabled the verification ofthe customer with the debited account without human

intervention. This patent is also the earliest instance of a complete "currency dispenser system" in the patent record. This patent was filed on 5 March 1968 in the US (US 3543904) and granted on 1 December 1970. It had a profound influence onthe industry as a whole. Not only did future entrants into thecash dispenser market such as NCR Corporation and IBM licence Goodfellow’s PIN system, but a number of later patents reference this patent as "Prior Art Device".[18]

In January 9, 1969's ABC newspaper (Madrid edition) there was an article about the new Bancomat, a teller machine installed in downtown Madrid, Spain, by Banesto, dispensing 1,000 pesetabills (1 to 5 max). Each user had to introduce a security personal key using a combination of the ten numeric buttons.[19]

In March of the same year an ad with the instructions to use the Bancomat was published in the same newspaper [20] Bancomat was the first cash machine installed in Spain, one of the first in Europe.

Play media1969 ABC news report on the introduction of ATMs in Sydney, Australia. People could only receive AUS $25 at a time and thebank card was sent back to the user at a later date.

Docutel United States 1969

After looking first hand at the experiences in Europe, in 1968the networked ATM was pioneered in the US, in Dallas, Texas, by Donald Wetzel, who was a department head at an automated baggage-handling company called Docutel. Recognised by the United States Patent Office for having invented the ATM are Kenneth S. Goldstein and John D. White, under US Patent # 3,662,343. Recognised by the United States Patent Office for having invented the ATM network are Fred J. Gentile and Jack Wu Chang, under US Patent # 3,833,885. On September 2, 1969, Chemical Bank installed the first ATM in the U.S. at its branch in Rockville Centre, New York. The first ATMs were designed to dispense a fixed amount of cash when a user

inserted a specially coded card.[21] A Chemical Bank advertisement boasted "On Sept. 2 our bank will open at 9:00 and never close again."[22] Chemical's ATM, initially known as aDocuteller was designed by Donald Wetzel and his company Docutel. Chemical executives were initially hesitant about theelectronic banking transition given the high cost of the earlymachines. Additionally, executives were concerned that customers would resist having machines handling their money.[23]

In 1995, the Smithsonian National Museum of American History recognised Docutel and Wetzel as the inventors of the networked ATM.[24]

Continued Improvements

The first modern ATM was an IBM 2984 and came into use at Lloyds Bank, Brentwood High Street, Essex, England in December1972. The IBM 2984 was designed at the request of Lloyds Bank.The 2984 Cash Issuing Terminal was the first true ATM, similarin function to today's machines and named by Lloyds Bank: Cashpoint; Cashpoint is still a registered trademark of LloydsTSB in the UK. All were online and issued a variable amount which was immediately deducted from the account. A small number of 2984s were supplied to a US bank. A couple of well known historical models of ATMs include the IBM 3614, IBM 3624and 473x series, Diebold 10xx and TABS 9000 series, NCR 1780 and earlier NCR 770 series.

The first switching system to enable shared automated teller machines between banks went into production operation on February 3, 1979 in Denver, Colorado, in an effort by ColoradoNational Bank of Denver and Kranzley and Company of Cherry Hill, New Jersey.[25]

The newest ATM at Royal Bank of Scotland allows customers to withdraw cash up to £100 without a card by inputting a six-digit code requested through their smartphones.[26]

LocationThis section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged

and removed. (February 2011)

An ATM Encrypting PIN Pad (EPP) with German markings

ATM in Vatican City with menu in Latin

ATMs are placed not only near or inside the premises of banks,but also in locations such as shopping centers/malls, airports, grocery stores, petrol/gas stations, restaurants, oranywhere frequented by large numbers of people. There are two types of ATM installations: on- and off-premises. On-premises ATMs are typically more advanced, multi-function machines thatcomplement a bank branch's capabilities, and are thus more expensive. Off-premises machines are deployed by financial institutions and Independent Sales Organisations (ISOs) where there is a simple need for cash, so they are generally cheapersingle function devices. In Canada, ATMs (also known there as ABMs) not operated by a financial institution are known as "white-label ABMs".

In the U.S., Canada and some Gulf countries, banks often have drive-thru lanes providing access to ATMs using an automobile.

Many ATMs have a sign above them, indicating the name of the bank or organisation owning the ATM and possibly including thelist of ATM networks to which that machine is connected.

ATMs can also be found in railway stations and metro stations.In recent times, countries like India and some countries in

Africa are installing ATM's in rural areas which are solar powered and do not require air conditioning.[27]

Financial networks

An ATM in the Netherlands. The logos of a number of interbank networks this ATM is connected to are shown

Most ATMs are connected to interbank networks, enabling peopleto withdraw and deposit money from machines not belonging to the bank where they have their accounts or in the countries where their accounts are held (enabling cash withdrawals in local currency). Some examples of interbank networks include NYCE, PULSE, PLUS, Cirrus, AFFN, Interac, Interswitch, STAR, LINK, MegaLink and BancNet.

ATMs rely on authorisation of a financial transaction by the card issuer or other authorising institution on a communications network. This is often performed through an ISO8583 messaging system.

Many banks charge ATM usage fees. In some cases, these fees are charged solely to users who are not customers of the bank where the ATM is installed; in other cases, they apply to all users.

In order to allow a more diverse range of devices to attach totheir networks, some interbank networks have passed rules expanding the definition of an ATM to be a terminal that either has the vault within its footprint or utilises the vault or cash drawer within the merchant establishment, which allows for the use of a scrip cash dispenser.

A Diebold 1063ix with a dial-up modem visible at the base

ATMs typically connect directly to their host or ATM Controller on either ADSL or dial-up modem over a telephone line or directly on a leased line. Leased lines are preferableto plain old telephone service (POTS) lines because they require less time to establish a connection. Less-trafficked machines will usually rely on a dial-up modem on a POTS line rather than using a leased line, since a leased line may be comparatively more expensive to operate compared to a POTS line. That dilemma may be solved as high-speed Internet VPN connections become more ubiquitous. Common lower-level layer communication protocols used by ATMs to communicate back to the bank include SNA over SDLC, TC500 over Async, X.25, and TCP/IP over Ethernet.

In addition to methods employed for transaction security and secrecy, all communications traffic between the ATM and the Transaction Processor may also be encrypted using methods suchas SSL.[28]

Global use

ATMs at the railway station in Poznań

There are no hard international or government-compiled numberstotaling the complete number of ATMs in use worldwide. Estimates developed by ATMIA place the number of ATMs in use currently at over 2.2 million, or approximately 1 ATM per 3000people in the world.[29]

To simplify the analysis of ATM usage around the world, financial institutions generally divide the world into seven regions, due to the penetration rates, usage statistics, and features deployed. Four regions (USA, Canada, Europe, and Japan) have high numbers of ATMs per million people.[30][31] Despite the large number of ATMs, there is additional demand for machines in the Asia/Pacific area as well as in Latin America.[32][33] ATMs have yet to reach high numbers in the Near East and Africa.[34]

One of the world's most northerly installed ATMs is located atLongyearbyen, Svalbard, Norway.

The world's most southerly installed ATM is located at McMurdoStation, located in New Zealand's Ross Dependency, in Antarctica since 1997.[35] There are two ATMs at McMurdo, but only one active at any time, that are owned by Wells Fargo [36] and serviced once every two years by NCR.[37]

According to international statistics, the highest installed ATM in the world is located at Nathu La Pass, in India, installed by the Indian Axis Bank at 4,023 metres (13,199 ft).[38] According to the Mainland Chinese media and CPC statistics,the highest installed ATM in the world is located in Nagchu County, Tibet, China, at 4500 metres, allegedly installed by the Agricultural Bank of China.[39][unreliable source?][40][unreliable source?]

Israel has the world's lowest installed ATM at Ein Bokek at the Dead Sea, installed independently by a grocery store at 421 metres below sea level.[41]

While ATMs are ubiquitous on modern cruise ships, ATMs can also be found on some US Navy ships.[42]

Welcome message displayed on the world's most northerly ATM located in the post office at Longyearbyen

Hardware

A block diagram of an ATM

An ATM is typically made up of the following devices:

CPU (to control the user interface and transaction devices)

Magnetic or chip card reader (to identify the customer) PIN pad EEP4 (similar in layout to a touch tone or

calculator keypad), manufactured as part of a secure enclosure

Secure cryptoprocessor , generally within a secure enclosure

Display (used by the customer for performing the transaction)

Function key buttons (usually close to the display) or a touchscreen (used to select the various aspects of the transaction)

Record printer (to provide the customer with a record of the transaction)

Vault (to store the parts of the machinery requiring restricted access)

Housing (for aesthetics and to attach signage to) Sensors and indicators

Due to heavier computing demands and the falling price of personal computer–like architectures, ATMs have moved away from custom hardware architectures using microcontrollers or application-specific integrated circuits and have adopted the hardware architecture of a personal computer, such as USB connections for peripherals, Ethernet and IP communications, and use personal computer operating systems.

Business owners often lease ATM terminals from ATM service providers, however based on the economies of scale, the price of equipment has dropped to the point where many business owners are simply paying for ATMs using a credit card.

New ADA voice and text-to-speech guidelines imposed in 2010, but required by March 2012[43] have forced many ATM owners to either upgrade non-compliant machines or dispose them if they are not up-gradable, and purchase new compliant equipment. This has created an avenue for hackers and thieves to obtain ATM hardware at junkyards from improperly disposed decommissioned ATMs.[44]

Two Loomis employees refilling an ATM at the Downtown Seattle REI

The vault of an ATM is within the footprint of the device itself and is where items of value are kept. Scrip cash dispensers do not incorporate a vault.

Mechanisms found inside the vault may include:

Dispensing mechanism (to provide cash or other items of value)

Deposit mechanism including a check processing module andbulk note acceptor (to allow the customer to make deposits)

Security sensors (magnetic, thermal, seismic, gas) Locks (to ensure controlled access to the contents of the

vault) Journaling systems; many are electronic (a sealed flash

memory device based on in-house standards) or a solid-state device (an actual printer) which accrues all records of activity including access timestamps, number of notes dispensed, etc. This is considered sensitive data and is secured in similar fashion to the cash as it is a similar liability.

ATM vaults are supplied by manufacturers in several grades. Factors influencing vault grade selection include cost, weight, regulatory requirements, ATM type, operator risk avoidance practices and internal volume requirements.[45] Industry standard vault configurations include Underwriters Laboratories UL-291 "Business Hours" and Level 1 Safes,[46] RAL TL-30 derivatives,[47] and CEN EN 1143-1 - CEN III and CEN IV.[48]

[49]

ATM manufacturers recommend that an ATM vault be attached to the floor to prevent theft,[50] though there is a record of a theft conducted by tunnelling into an ATM floor.[citation needed]

SoftwareWith the migration to commodity Personal Computer hardware, standard commercial "off-the-shelf" operating systems, and programming environments can be used inside of ATMs. Typical platforms previously used in ATM development include RMX or OS/2.

A Wincor Nixdorf ATM running Windows 2000.

Today the vast majority of ATMs worldwide use a Microsoft Windows operating system, primarily Windows XP Professional orWindows XP Embedded.[citation needed] A small number of deployments maystill be running older versions of Windows OS such as Windows NT, Windows CE, or Windows 2000.

There is a computer industry security view that general publicdesktop operating systems(os) have greater risks as operating systems for cash dispensing machines than other types of operating systems like (secure) real-time operating systems (RTOS). RISKS Digest has many articles about cash machine operating system vulnerabilities.[51]

Linux is also finding some reception in the ATM marketplace. An example of this is Banrisul, the largest bank in the south of Brazil, which has replaced the MS-DOS operating systems in its ATMs with Linux. Banco do Brasil is also migrating ATMs toLinux. Indian-based Vortex Engineering is manufacturing ATMs which operate only with Linux. Common application layer transaction protocols, such as Diebold 91x (911 or 912) and NCR NDC or NDC+ provide emulation of older generations of hardware on newer platforms with incremental extensions made over time to address new capabilities, although companies likeNCR continuously improve these protocols issuing newer versions (e.g. NCR's AANDC v3.x.y, where x.y are subversions).Most major ATM manufacturers provide software packages that implement these protocols. Newer protocols such as IFX have yet to find wide acceptance by transaction processors.[52]

With the move to a more standardised software base, financial institutions have been increasingly interested in the ability to pick and choose the application programs that drive their equipment. WOSA/XFS, now known as CEN XFS (or simply XFS),

provides a common API for accessing and manipulating the various devices of an ATM. J/XFS is a Java implementation of the CEN XFS API.

While the perceived benefit of XFS is similar to the Java's "Write once, run anywhere" mantra, often different ATM hardware vendors have different interpretations of the XFS standard. The result of these differences in interpretation means that ATM applications typically use a middleware to evenout the differences between various platforms.

With the onset of Windows operating systems and XFS on ATM's, the software applications have the ability to become more intelligent. This has created a new breed of ATM applications commonly referred to as programmable applications. These typesof applications allows for an entirely new host of applications in which the ATM terminal can do more than only communicate with the ATM switch. It is now empowered to connected to other content servers and video banking systems.

Notable ATM software that operates on XFS platforms include Triton PRISM, Diebold Agilis EmPower, NCR APTRA Edge, AbsoluteSystems AbsoluteINTERACT, KAL Kalignite Software Platform, Phoenix Interactive VISTAatm, Wincor Nixdorf ProTopas, EuronetEFTS and Intertech inter-ATM.

With the move of ATMs to industry-standard computing environments, concern has risen about the integrity of the ATM's software stack.[53]

SecurityMain article: Security of automated teller machines

Security, as it relates to ATMs, has several dimensions. ATMs also provide a practical demonstration of a number of securitysystems and concepts operating together and how various security concerns are dealt with.

Physical

A Wincor Nixdorf Procash 2100xe Frontload that was opened withan angle grinder

Automated Teller Machine In Dezfull in southwest of Iran

Early ATM security focused on making the ATMs invulnerable to physical attack; they were effectively safes with dispenser mechanisms. A number of attacks on ATMs resulted, with thievesattempting to steal entire ATMs by ram-raiding.[54] Since late 1990s, criminal groups operating in Japan improved ram-raidingby stealing and using a truck loaded with heavy construction machinery to effectively demolish or uproot an entire ATM and any housing to steal its cash.[55]

Another attack method, plofkraak, is to seal all openings of theATM with silicone and fill the vault with a combustible gas orto place an explosive inside, attached, or near the ATM. This gas or explosive is ignited and the vault is opened or distorted by the force of the resulting explosion and the criminals can break in.[56] This type of theft has occurred in the Netherlands, Belgium, France, Denmark, Germany and Australia.[57][58] These types of attacks can be prevented by a number of gas explosion prevention devices also known as gas

suppression system. These systems use explosive gas detection sensor to detect explosive gas and to neutralise it by releasing a special explosion suppression chemical which changes the composition of the explosive gas and renders it ineffective.

Several attacks in the UK (at least one of which was successful) have involved digging a concealed tunnel under theATM and cutting through the reinforced base to remove the money.[59]

Modern ATM physical security, per other modern money-handling security, concentrates on denying the use of the money inside the machine to a thief, by using different types of Intelligent Banknote Neutralisation Systems.

A common method is to simply rob the staff filling the machinewith money. To avoid this, the schedule for filling them is kept secret, varying and random. The money is often kept in cassettes, which will dye the money if incorrectly opened.

Transactional secrecy and integrity

A Triton brand ATM with a dip style card reader and a triple DES keypad

The security of ATM transactions relies mostly on the integrity of the secure cryptoprocessor: the ATM often uses general commodity components that sometimes are not consideredto be "trusted systems".

Encryption of personal information, required by law in many jurisdictions, is used to prevent fraud. Sensitive data in ATMtransactions are usually encrypted with DES, but transaction processors now usually require the use of Triple DES.[60] Remote

Key Loading techniques may be used to ensure the secrecy of the initialisation of the encryption keys in the ATM. Message Authentication Code (MAC) or Partial MAC may also be used to ensure messages have not been tampered with while in transit between the ATM and the financial network.

Customer identity integrity

A BTMU ATM with a palm scanner (to the right of the screen)

There have also been a number of incidents of fraud by Man-in-the-middle attacks, where criminals have attached fake keypadsor card readers to existing machines. These have then been used to record customers' PINs and bank card information in order to gain unauthorised access to their accounts. Various ATM manufacturers have put in place countermeasures to protectthe equipment they manufacture from these threats.[61][62]

Alternative methods to verify cardholder identities have been tested and deployed in some countries, such as finger and palmvein patterns,[63] iris, and facial recognition technologies. Cheaper mass-produced equipment has been developed and is being installed in machines globally that detect the presence of foreign objects on the front of ATMs, current tests have shown 99% detection success for all types of skimming devices.[64]

Device operation integrity

ATMs that are exposed to the outside must be vandal and weather resistant

Openings on the customer-side of ATMs are often covered by mechanical shutters to prevent tampering with the mechanisms when they are not in use. Alarm sensors are placed inside the ATM and in ATM servicing areas to alert their operators when doors have been opened by unauthorised personnel.

To protect against hackers, ATM's have a built-in firewall. Once the firewall has detected malicious attempts to break into the machine remotely, the firewall locks down the machine.[65]

Rules are usually set by the government or ATM operating body that dictate what happens when integrity systems fail. Depending on the jurisdiction, a bank may or may not be liablewhen an attempt is made to dispense a customer's money from anATM and the money either gets outside of the ATM's vault, or was exposed in a non-secure fashion, or they are unable to determine the state of the money after a failed transaction.[66]

Customers often commented that it is difficult to recover money lost in this way, but this is often complicated by the policies regarding suspicious activities typical of the criminal element.[67]

Customer security

Dunbar Armored ATM Techs watching over ATMs that have been installed in a van

In some countries, multiple security cameras and security guards are a common feature.[68] In the United States, The New York State Comptroller's Office has advised the New York StateDepartment of Banking to have more thorough safety inspectionsof ATMs in high crime areas.[69]

Consultants of ATM operators assert that the issue of customersecurity should have more focus by the banking industry;[70] it has been suggested that efforts are now more concentrated on the preventive measure of deterrent legislation than on the problem of ongoing forced withdrawals.[71]

At least as far back as July 30, 1986, consultants of the industry have advised for the adoption of an emergency PIN system for ATMs, where the user is able to send a silent alarmin response to a threat.[72] Legislative efforts to require an emergency PIN system have appeared in Illinois,[73] Kansas [74] andGeorgia,[75] but none have succeeded yet. In January 2009, Senate Bill 1355 was proposed in the Illinois Senate that revisits the issue of the reverse emergency PIN system.[76] The bill is again supported by the police and denied by the banking lobby.[77]

In 1998 three towns outside the Cleveland, Ohio, in response to an ATM crime wave, adopted ATM Consumer Security Legislation requiring that an emergency telephone number switch be installed at all outside ATMs within their jurisdiction. In the wake of an ATM Murder in Sharon Hill, Pennsylvania, The City Council of Sharon Hill passed an ATM Consumer Security Bill as well. As of July 2009, ATM Consumer Security Legislation is currently pending in New York, New Jersey, and Washington D.C.

In China and elsewhere, many efforts to promote security have been made. On-premises ATMs are often located inside the bank's lobby which may be accessible 24 hours a day. These lobbies have extensive security camera coverage, a courtesy telephone for consulting with the bank staff, and a security guard on the premises. Bank lobbies that are not guarded 24 hours a day may also have secure doors that can only be openedfrom outside by swiping the bank card against a wall-mounted scanner, allowing the bank to identify which card enters the building. Most ATMs will also display on-screen safety warnings and may also be fitted with convex mirrors above the display allowing the user to see what is happening behind them.

As of 2013, the only claim available about the extent of ATM connected homicides is that they range from 500 to 1000 per year in the US, covering only cases where the victim had an ATM card and the card was used by the killer after the known time of death.[78]

Uses

Two NCR Personas 84 ATMs at a bank in Jersey dispensing two types of pound sterling banknotes: Bank of England on the left, and States of Jersey on the right

Although ATMs were originally developed as just cash dispensers, they have evolved to include many other bank-related functions:

Paying routine bills, fees, and taxes (utilities, phone bills, social security, legal fees, taxes, etc.)

Printing bank statements Updating passbooks Cash advances Cheque Processing Module Paying (in full or partially) the credit balance on a

card linked to a specific current account.

Transferring money between linked accounts (such as transferring between checking and savings accounts)

Deposit currency recognition, acceptance, and recycling[79]

[80]

In some countries, especially those which benefit from a fullyintegrated cross-bank ATM network (e.g.: Multibanco in Portugal), ATMs include many functions which are not directly related to the management of one's own bank account, such as:

Gold vending ATM in New York City

Loading monetary value into stored value cards Adding pre-paid cell phone / mobile phone credit. Purchasing

o Postage stamps .o Lottery ticketso Train tickets o Concert ticketso Movie ticketso Shopping mall gift certificates.o Gold [81]

Donating to charities[82]

Increasingly banks are seeking to use the ATM as a sales device to deliver pre approved loans and targeted advertising using products such as ITM (the Intelligent Teller Machine) from Aptra Relate from NCR.[83] ATMs can also act as an advertising channel for other companies.[84]*

A South Korean ATM with mobile bank port and bar code reader

However several different technologies on ATMs have not yet reached worldwide acceptance, such as:

Videoconferencing with human tellers, known as video tellers[85]

Biometrics , where authorisation of transactions is based on the scanning of a customer's fingerprint, iris, face, etc.[86][87][88]

Cheque/Cash Acceptance, where the ATM accepts and recognise cheques and/or currency without using envelopes[89] Expected to grow in importance in the US through Check 21 legislation.

Bar code scanning [90] On-demand printing of "items of value" (such as movie

tickets, traveler's cheques, etc.) Dispensing additional media (such as phone cards) Co-ordination of ATMs with mobile phones[91]

Integration with non-banking equipment[92][93]

Games and promotional features[94]

CRM at the ATM

E.g. In Canada, ATMs are called guichets automatiques in French and sometimes "Bank Machines" in English. The Interac shared cash network does not allow for the selling of goods from ATMsdue to specific security requirements for PIN entry when buying goods.[95] CIBC machines in Canada, are able to top-up the minutes on certain pay as you go phones.

Reliability

An ATM running Microsoft Windows that has crashed due to a peripheral component failure

Before an ATM is placed in a public place, it typically has undergone extensive testing with both test money and the backend computer systems that allow it to perform transactions. Banking customers also have come to expect high reliability in their ATMs,[96] which provides incentives to ATM providers to minimise machine and network failures. Financial consequences of incorrect machine operation also provide high degrees of incentive to minimise malfunctions.[97]

ATMs and the supporting electronic financial networks are generally very reliable, with industry benchmarks typically producing 98.25% customer availability for ATMs[98] and up to 99.999% availability for host systems that manage the networksof ATMs. If ATM networks do go out of service, customers couldbe left without the ability to make transactions until the beginning of their bank's next time of opening hours.

This said, not all errors are to the detriment of customers; there have been cases of machines giving out money without debiting the account, or giving out higher value notes as a result of incorrect denomination of banknote being loaded in the money cassettes.[99] The result of receiving too much money may be influenced by the card holder agreement in place between the customer and the bank.[100][101]

Errors that can occur may be mechanical (such as card transport mechanisms; keypads; hard disk failures; envelope

deposit mechanisms); software (such as operating system; device driver; application); communications; or purely down tooperator error.

To aid in reliability, some ATMs print each transaction to a roll paper journal that is stored inside the ATM, which allowsboth the users of the ATMs and the related financial institutions to settle things based on the records in the journal in case there is a dispute. In some cases, transactions are posted to an electronic journal to remove thecost of supplying journal paper to the ATM and for more convenient searching of data.

Improper money checking can cause the possibility of a customer receiving counterfeit banknotes from an ATM. While bank personnel are generally trained better at spotting and removing counterfeit cash,[102][103] the resulting ATM money supplies used by banks provide no guarantee for proper banknotes, as the Federal Criminal Police Office of Germany has confirmed that there are regularly incidents of false banknotes having been dispensed through bank ATMs.[104] Some ATMs may be stocked and wholly owned by outside companies, which can further complicate this problem. Bill validation technology can be used by ATM providers to help ensure the authenticity of the cash before it is stocked in an ATM; ATMs that have cash recycling capabilities include this capability.[105]

Fraud

ATM lineup

Some ATMs may put up warning messages to customers to be vigilant of possible tampering.

Banknotes from a cash machine robbery made unusable with red paint.

As with any device containing objects of value, ATMs and the systems they depend on to function are the targets of fraud. Fraud against ATMs and people's attempts to use them takes several forms.

The first known instance of a fake ATM was installed at a shopping mall in Manchester, Connecticut in 1993. By modifyingthe inner workings of a Fujitsu model 7020 ATM, a criminal gang known as The Bucklands Boys were able to steal information from cards inserted into the machine by customers.[106]

WAVY-TV reported an incident in Virginia Beach in September 2006 where a hacker who had probably obtained a factory-default administrator password for a gas station's white labelATM caused the unit to assume it was loaded with US$5 bills instead of $20s, enabling himself—and many subsequent

customers—to walk away with four times the money they wanted to withdraw.[107] This type of scam was featured on the TV series The Real Hustle.

ATM behavior can change during what is called "stand-in" time,where the bank's cash dispensing network is unable to access databases that contain account information (possibly for database maintenance). In order to give customers access to cash, customers may be allowed to withdraw cash up to a certain amount that may be less than their usual daily withdrawal limit, but may still exceed the amount of availablemoney in their accounts, which could result in fraud if the customers intentionally withdraw more money than what they hadin their accounts.[108]

Card fraud

In an attempt to prevent criminals from shoulder surfing the customer's personal identification number (PIN), some banks draw privacy areas on the floor.

For a low-tech form of fraud, the easiest is to simply steal acustomer's card along with its PIN. A later variant of this approach is to trap the card inside of the ATM's card reader with a device often referred to as a Lebanese loop. When the customer gets frustrated by not getting the card back and walks away from the machine, the criminal is able to remove the card and withdraw cash from the customer's account, using the card and its PIN.

This type of ATM fraud has spread globally. Although somewhat replaced in terms of volume by ATM skimming incidents, a re-emergence of card trapping has been noticed in regions such asEurope, where EMV chip and PIN cards have increased in circulation.[109]

Another simple form of fraud involves attempting to get the customer's bank to issue a new card and its PIN and stealing them from their mail.[110]

By contrast, a newer high-tech method of operating, sometimes called card skimming or card cloning, involves the installation of a magnetic card reader over the real ATM's

card slot and the use of a wireless surveillance camera or a modified digital camera or a false PIN keypad to observe the user's PIN. Card data is then cloned into a duplicate card andthe criminal attempts a standard cash withdrawal. The availability of low-cost commodity wireless cameras, keypads, card readers, and card writers has made it a relatively simpleform of fraud, with comparatively low risk to the fraudsters.[111]

In an attempt to stop these practices, countermeasures againstcard cloning have been developed by the banking industry, in particular by the use of smart cards which cannot easily be copied or spoofed by unauthenticated devices, and by attempting to make the outside of their ATMs tamper evident. Older chip-card security systems include the French Carte Bleue, Visa Cash, Mondex, Blue from American Express [112] and EMV '96 or EMV 3.11. The most actively developed form of smartcard security in the industry today is known as EMV 2000 or EMV 4.x.

EMV is widely used in the UK (Chip and PIN) and other parts ofEurope, but when it is not available in a specific area, ATMs must fall back to using the easy–to–copy magnetic strip to perform transactions. This fallback behaviour can be exploited.[113] However the fall-back option has been removed onthe ATMs of some UK banks, meaning if the chip is not read, the transaction will be declined.

Card cloning and skimming can be detected by the implementation of magnetic card reader heads and firmware thatcan read a signature embedded in all magnetic strips during the card production process. This signature, known as a "MagnePrint" or "BluPrint", can be used in conjunction with common two-factor authentication schemes used in ATM, debit/retail point-of-sale and prepaid card applications.

The concept and various methods of copying the contents of an ATM card's magnetic strip onto a duplicate card to access other people's financial information was well known in the hacking communities by late 1990.[114]

In 1996, Andrew Stone, a computer security consultant from Hampshire in the UK, was convicted of stealing more than

£1 million by pointing high-definition video cameras at ATMs from a considerable distance, and by recording the card numbers, expiry dates, etc. from the embossed detail on the ATM cards along with video footage of the PINs being entered. After getting all the information from the videotapes, he was able to produce clone cards which not only allowed him to withdraw the full daily limit for each account, but also allowed him to sidestep withdrawal limits by using multiple copied cards. In court, it was shown that he could withdraw asmuch as £10,000 per hour by using this method. Stone was sentenced to five years and six months in prison.[115]

In February 2009, a group of criminals used counterfeit ATM cards to steal $9 million from 130 ATMs in 49 cities around the world, all within a period of 30 minutes.[116]

Related devicesA talking ATM is a type of ATM that provides audible instructions so that people who cannot read an ATM screen can independently use the machine, therefore effectively eliminating the need for assistance from an external, potentially malevolent source. All audible information is delivered privately through a standard headphone jack on the face of the machine. Alternatively, some banks such as the Nordea and Swedbank use a built-in external speaker which may be invoked by pressing the talk button on the keypad.[117] Information is delivered to the customer either through pre-recorded sound files or via text-to-speech speech synthesis.

A postal interactive kiosk may also share many of the same components as an ATM (including a vault), but only dispenses items related to postage.[118][119]

A scrip cash dispenser may share many of the same components as an ATM, but lacks the ability to dispense physical cash andconsequently requires no vault. Instead, the customer requestsa withdrawal transaction from the machine, which prints a receipt. The customer then takes this receipt to a nearby sales clerk, who then exchanges it for cash from the till.[120]

A teller assist unit (TAU) may also share many of the same components as an ATM (including a vault), but they are

distinct in that they are designed to be operated solely by trained personnel and not by the general public, they do not integrate directly into interbank networks, and are usually controlled by a computer that is not directly integrated into the overall construction of the unit.

A web ATM is an online interface for ATM card banking that uses a smart card reader. All the usual ATM functions are available except for withdrawing cash. Most banks in Taiwan provide these online ATM services. [121][122]

In popular cultureOne of the banking innovations that Arthur Hailey mentioned inhis 1975 bestselling novel The Moneychangers is Docutel, an automated teller machine,(Hailey & 1975 308)[123] based on real technology that was issued a patent in 1974 in the United States.

In the novel, Jill Peacock, a journalist, interviewed First Mercantile American Bank executive VP Alexander Vandervoort ina suburban shopping plaza where the bank had installed the first two stainless-steel Docutel automatic tellers. Vandervoort, whose clothes looked like they were from the "fashion section of Esquire", was not at all like the classical solemn, cautious banker in a double-breasted, dark blue suit. Peacock compared him to the new ATMs which embodiedmodern banking.[123]

In GTA Online, players can For other uses, see Password (disambiguation).

The sign in form for the English Wikipedia, which requests a username and password

A password is a word or string of characters used for user authentication to prove identity or access approval to gain access to a resource (example: an access code is a type of password), which should be kept secret from those not allowed access.

The use of passwords is known to be ancient. Sentries would challenge those wishing to enter an area or approaching it to supply a password or watchword, and would only allow a person or group to pass if they knew the password. In modern times, user names and passwords are commonly used by people during a log in process that controls access to protected computer operating systems, mobile phones, cable TV decoders, automatedteller machines (ATMs), etc. A typical computer user has passwords for many purposes: logging into accounts, retrievinge-mail, accessing applications, databases, networks, web sites, and even reading the morning newspaper online.

Despite the name, there is no need for passwords to be actual words; indeed passwords which are not actual words may be harder to guess, a desirable property. Some passwords are formed from multiple words and may more accurately be called apassphrase. The terms passcode and passkey are sometimes used when the secret information is purely numeric, such as the personal identification number (PIN) commonly used for ATM access. Passwords are generally short enough to be easily memorized and typed.

Most organizations specify a password policy that sets requirements for the composition and usage of passwords, typically dictating minimum length, required categories (e.g. upper and lower case, numbers, and special characters), prohibited elements (e.g. own name, date of birth, address, telephone number). Some governments have national authentication frameworks[1] that define requirements for user authentication to government services, including requirements for passwords.

Contents

1 Choosing a secure and memorable password 2 Factors in the security of a password system

o 2.1 Rate at which an attacker can try guessed passwords

o 2.2 Limits on the number of password guesseso 2.3 Form of stored passwordso 2.4 Methods of verifying a password over a network

2.4.1 Simple transmission of the password 2.4.2 Transmission through encrypted channels 2.4.3 Hash-based challenge-response methods 2.4.4 Zero-knowledge password proofs

o 2.5 Procedures for changing passwordso 2.6 Password longevityo 2.7 Number of users per passwordo 2.8 Password security architectureo 2.9 Password reuseo 2.10 Writing down passwords on papero 2.11 After death

3 Password cracking o 3.1 Incidents

4 Alternatives to passwords for authentication 5 "The Password is dead" 6 Website password systems 7 History of passwords 8 See also 9 References 10 External links

Choosing a secure and memorable passwordThe easier a password is for the owner to remember generally means it will be easier for an attacker to guess.[2] However, passwords which are difficult to remember may also reduce the security of a system because (a) users might need to write down or electronically store the password, (b) users will needfrequent password resets and (c) users are more likely to re-use the same password. Similarly, the more stringent requirements for password strength, e.g. "have a mix of uppercase and lowercase letters and digits" or "change it monthly", the greater the degree to which users will subvert the system.[3] Others argue longer passwords provide more

security (e.g., entropy) than shorter passwords with a wide variety of characters.[4]

In The Memorability and Security of Passwords,[5] Jeff Yan et al. examinethe effect of advice given to users about a good choice of password. They found that passwords based on thinking of a phrase and taking the first letter of each word are just as memorable as naively selected passwords, and just as hard to crack as randomly generated passwords. Combining two or more unrelated words is another good method, but a single dictionary word is not. Having a personally designed algorithmfor generating obscure passwords is another good method.

However, asking users to remember a password consisting of a "mix of uppercase and lowercase characters" is similar to asking them to remember a sequence of bits: hard to remember, and only a little bit harder to crack (e.g. only 128 times harder to crack for 7-letter passwords, less if the user simply capitalises one of the letters). Asking users to use "both letters and digits" will often lead to easy-to-guess substitutions such as 'E' → '3' and 'I' → '1', substitutions which are well known to attackers. Similarly typing the password one keyboard row higher is a common trick known to attackers.[6]

A method to memorize a complex password is to remember a sentence like 'This year I go to Italy on Friday July 6!' and use the first characters as the actual password. In this case 'TyIgtIoFJ6!'.

In 2013, Google released a list of the most common password types, all of which are considered insecure because they are too easy to guess (especially after researching an individual on social media):[7]

The name of a pet, child, family member, or significant other

Anniversary dates and birthdays Birthplace Name of a favorite holiday Something related to a favorite sports team The word "password"

Factors in the security of a password systemThe security of a password-protected system depends on severalfactors. The overall system must, of course, be designed for sound security, with protection against computer viruses, man-in-the-middle attacks and the like. Physical security issues are also a concern, from deterring shoulder surfing to more sophisticated physical threats such as video cameras and keyboard sniffers. And, of course, passwords should be chosen so that they are hard for an attacker to guess and hard for anattacker to discover using any (and all) of the available automatic attack schemes. See password strength and computer security.

Nowadays, it is a common practice for computer systems to hidepasswords as they are typed. The purpose of this measure is toavoid bystanders reading the password. However, some argue that this practice may lead to mistakes and stress, encouraging users to choose weak passwords. As an alternative,users should have the option to show or hide passwords as theytype them.[8]

Effective access control provisions may force extreme measureson criminals seeking to acquire a password or biometric token.[9] Less extreme measures include extortion, rubber hose cryptanalysis, and side channel attack.

Here are some specific password management issues that must beconsidered in thinking about, choosing, and handling, a password.

Rate at which an attacker can try guessed passwords

The rate at which an attacker can submit guessed passwords to the system is a key factor in determining system security. Some systems impose a time-out of several seconds after a small number (e.g., three) of failed password entry attempts. In the absence of other vulnerabilities, such systems can be effectively secure with relatively simple passwords, if they have been well chosen and are not easily guessed.[10]

Many systems store a cryptographic hash of the password. If anattacker gets access to the file of hashed passwords guessing can be done off-line, rapidly testing candidate passwords against the true password's hash value. In the example of a web-server, an online attacker can guess only at the rate at which the server will respond, while an off-line attacker (whogains access to the file) can guess at a rate limited only by the hardware that is brought to bear.

Passwords that are used to generate cryptographic keys (e.g., for disk encryption or Wi-Fi security) can also be subjected to high rate guessing. Lists of common passwords are widely available and can make password attacks very efficient. (See Password cracking.) Security in such situations depends on using passwords or passphrases of adequate complexity, making such an attack computationally infeasible for the attacker. Some systems, such as PGP and Wi-Fi WPA, apply a computation-intensive hash to the password to slow such attacks. See key stretching.

Limits on the number of password guesses

An alternative to limiting the rate at which an attacker can make guesses on a password is to limit the total number of guesses that can be made. The password can be disabled, requiring a reset, after a small number of consecutive bad guesses (say 5); and the user may be required to change the password after a larger cumulative number of bad guesses (say 30), to prevent an attacker from making an arbitrarily large number of bad guesses by interspersing them between good guesses made by the legitimate password owner. [11] The usernameassociated with the password can be changed to counter a denial of service attack.

Form of stored passwords

Some computer systems store user passwords as plaintext, against which to compare user log on attempts. If an attacker gains access to such an internal password store, all passwords—and so all user accounts—will be compromised. If some users employ the same password for accounts on different systems, those will be compromised as well.

More secure systems store each password in a cryptographicallyprotected form, so access to the actual password will still bedifficult for a snooper who gains internal access to the system, while validation of user access attempts remains possible. The most secure don't store passwords at all, but a one-way derivation, such as a polynomial, modulus, or an advanced hash function.[4] Roger Needham invented the now common approach of storing only a “hashed” form of the plaintext password. When a user types in a password on such a system, the password handling software runs through a cryptographic hash algorithm, and if the hash value generated from the user’s entry matches the hash stored in the password database, the user is permitted access. The hash value is created by applying a cryptographic hash function to a string consisting of the submitted password and, in many implementations, another value known as a salt. A salt prevents attackers from easily building a list of hash values for common passwords and prevents password cracking efforts from scaling across all users.[12] MD5 and SHA1 are frequently used cryptographic hash functions but they are not recommendedfor password hashing unless they are used as part of a larger construction such as in PBKDF2.[13]

The stored data—sometimes called the "password verifier" or the "password hash"—is often stored in Modular Crypt Format orRFC 2307 hash format, sometimes in the /etc/passwd file or the/etc/shadow file.[14]

The main storage formats for passwords are plaintext, hashed, hashed and salted, and reversibly encrypted.[15] If an attacker gains access to the password file then if it is plaintext no cracking is necessary. If it is hashed but not salted then it is subject to rainbow table attacks (which are more efficient than cracking). If it is reversibly encrypted then if the attacker gets the decryption key along with the file no cracking is necessary, while if he fails to get the key cracking is not possible (guesses cannot be verified without the key). Thus, of the common storage formats for passwords only when passwords have been salted and hashed is cracking both necessary and possible.[15]

If a cryptographic hash function is well designed, it is computationally infeasible to reverse the function to recover

a plaintext password. An attacker can, however, use widely available tools to attempt to guess the passwords. These toolswork by hashing possible passwords and comparing the result ofeach guess to the actual password hashes. If the attacker finds a match, they know that their guess is the actual password for the associated user. Password cracking tools can operate by brute force (i.e. trying every possible combinationof characters) or by hashing every word from a list; large lists of possible passwords in many languages are widely available on the Internet.[4] The existence of password cracking tools allows attackers to easily recover poorly chosen passwords. In particular, attackers can quickly recoverpasswords that are short, dictionary words, simple variations on dictionary words or that use easily guessable patterns.[16] Amodified version of the DES algorithm was used as the basis for the password hashing algorithm in early Unix systems.[17] The crypt algorithm used a 12-bit salt value so that each user’s hash was unique and iterated the DES algorithm 25 timesin order to make the hash function slower, both measures intended to frustrate automated guessing attacks.[17] The user’spassword was used as a key to encrypt a fixed value. More recent Unix or Unix like systems (e.g., Linux or the various BSD systems) use more secure password hashing algorithms such as PBKDF2, bcrypt, and scrypt which have large salts and an adjustable cost or number of iterations.[18] A poorly designed hash function can make attacks feasible even if a strong password is chosen. See LM hash for a widely deployed, and insecure, example.[19]

Methods of verifying a password over a network

Simple transmission of the password

Passwords are vulnerable to interception (i.e., "snooping") while being transmitted to the authenticating machine or person. If the password is carried as electrical signals on unsecured physical wiring between the user access point and the central system controlling the password database, it is subject to snooping by wiretapping methods. If it is carried as packetized data over the Internet, anyone able to watch thepackets containing the logon information can snoop with a verylow probability of detection.

Email is sometimes used to distribute passwords but this is generally an insecure method. Since most email is sent as plaintext, a message containing a password is readable withouteffort during transport by any eavesdropper. Further, the message will be stored as plaintext on at least two computers:the sender's and the recipient's. If it passes through intermediate systems during its travels, it will probably be stored on there as well, at least for some time, and may be copied to backup, cache or history files on any of these systems.

Using client-side encryption will only protect transmission from the mail handling system server to the client machine. Previous or subsequent relays of the email will not be protected and the email will probably be stored on multiple computers, certainly on the originating and receiving computers, most often in cleartext.

Transmission through encrypted channels

The risk of interception of passwords sent over the Internet can be reduced by, among other approaches, using cryptographicprotection. The most widely used is the Transport Layer Security (TLS, previously called SSL) feature built into most current Internet browsers. Most browsers alert the user of a TLS/SSL protected exchange with a server by displaying a closed lock icon, or some other sign, when TLS is in use. There are several other techniques in use; see cryptography.

Hash-based challenge-response methods

Unfortunately, there is a conflict between stored hashed-passwords and hash-based challenge-response authentication; the latter requires a client to prove to a server that they know what the shared secret (i.e., password) is, and to do this, the server must be able to obtain the shared secret fromits stored form. On many systems (including Unix-type systems)doing remote authentication, the shared secret usually becomesthe hashed form and has the serious limitation of exposing passwords to offline guessing attacks. In addition, when the hash is used as a shared secret, an attacker does not need theoriginal password to authenticate remotely; they only need thehash.

Zero-knowledge password proofs

Rather than transmitting a password, or transmitting the hash of the password, password-authenticated key agreement systems can perform a zero-knowledge password proof, which proves knowledge of the password without exposing it.

Moving a step further, augmented systems for password-authenticated key agreement (e.g., AMP, B-SPEKE, PAK-Z, SRP-6)avoid both the conflict and limitation of hash-based methods. An augmented system allows a client to prove knowledge of the password to a server, where the server knows only a (not exactly) hashed password, and where the unhashed password is required to gain access.

Procedures for changing passwords

Usually, a system must provide a way to change a password, either because a user believes the current password has been (or might have been) compromised, or as a precautionary measure. If a new password is passed to the system in unencrypted form, security can be lost (e.g., via wiretapping)before the new password can even be installed in the password database. And, of course, if the new password is given to a compromised employee, little is gained. Some web sites includethe user-selected password in an unencrypted confirmation e-mail message, with the obvious increased vulnerability.

Identity management systems are increasingly used to automate issuance of replacements for lost passwords, a feature called self service password reset. The user's identity is verified by asking questions and comparing the answers to ones previously stored (i.e., when the account was opened).

Some password reset questions ask for personal information that could be found on social media, such as mother's maiden name. As a result, some security experts recommend either making up one's own questions or giving false answers.[20]

Password longevity

"Password aging" is a feature of some operating systems which forces users to change passwords frequently (e.g., quarterly,

monthly or even more often). Such policies usually provoke user protest and foot-dragging at best and hostility at worst.There is often an increase in the people who note down the password and leave it where it can easily be found, as well ashelpdesk calls to reset a forgotten password. Users may use simpler passwords or develop variation patterns on a consistent theme to keep their passwords memorable.[21] Because of these issues, there is some debate[22] as to whether passwordaging is effective. The intended benefit is mainly that a stolen password will be made ineffective if it is reset; however in many cases, particularly with administrative or "root" accounts, once an attacker has gained access, they can make alterations to the operating system that will allow them future access even after the initial password they used expires. (See rootkit.)

The other less-frequently cited, and possibly more valid reason is that in the event of a long brute force attack, the password will be invalid by the time it has been cracked. Specifically, in an environment where it is considered important to know the probability of a fraudulent login in order to accept the risk, one can ensure that the total numberof possible passwords multiplied by the time taken to try eachone (assuming the greatest conceivable computing resources) ismuch greater than the password lifetime. However there is no documented evidence that the policy of requiring periodic changes in passwords increases system security.

Password aging may be required because of the nature of IT systems the password allows access to; if personal data is involved the EU Data Protection Directive is in force. Implementing such a policy, however, requires careful consideration of the relevant human factors. Humans memorize by association, so it is impossible to simply replace one memory with another. Two psychological phenomena interfere with password substitution. "Primacy" describes the tendency for an earlier memory to be retained more strongly than a later one. "Interference" is the tendency of two memories withthe same association to conflict. Because of these effects most users must resort to a simple password containing a number that can be incremented each time the password is changed.

Number of users per password

Sometimes a single password controls access to a device, for example, for a network router, or password-protected mobile phone. However, in the case of a computer system, a password is usually stored for each user account, thus making all access traceable (save, of course, in the case of users sharing passwords). A would-be user on most systems must supply a username as well as a password, almost always at account set up time, and periodically thereafter. If the user supplies a password matching the one stored for the supplied username, he or she is permitted further access into the computer system. This is also the case for a cash machine, except that the 'user name' is typically the account number stored on the bank customer's card, and the PIN is usually quite short (4 to 6 digits).

Allotting separate passwords to each user of a system is preferable to having a single password shared by legitimate users of the system, certainly from a security viewpoint. Thisis partly because users are more willing to tell another person (who may not be authorized) a shared password than one exclusively for their use. Single passwords are also much lessconvenient to change because many people need to be told at the same time, and they make removal of a particular user's access more difficult, as for instance on graduation or resignation. Per-user passwords are also essential if users are to be held accountable for their activities, such as making financial transactions or viewing medical records.

Password security architecture

Common techniques used to improve the security of computer systems protected by a password include:

Not displaying the password on the display screen as it is being entered or obscuring it as it is typed by using asterisks (*) or bullets (•).

Allowing passwords of adequate length. (Some legacy operating systems, including early versions[which?] of Unix and Windows, limited passwords to an 8 character maximum,[23][24][25] reducing security.)

Requiring users to re-enter their password after a periodof inactivity (a semi log-off policy).

Enforcing a password policy to increase password strengthand security.

o Requiring periodic password changes.o Assigning randomly chosen passwords.o Requiring minimum password lengths.[13]

o Some systems require characters from various character classes in a password—for example, "must have at least one uppercase and at least one lowercase letter". However, all-lowercase passwords are more secure per keystroke than mixed capitalization passwords.[26]

o Providing an alternative to keyboard entry (e.g., spoken passwords, or biometric passwords).

o Requiring more than one authentication system, such as 2-factor authentication (something a user has andsomething the user knows).

Using encrypted tunnels or password-authenticated key agreement to prevent access to transmitted passwords via network attacks

Limiting the number of allowed failures within a given time period (to prevent repeated password guessing). After the limit is reached, further attempts will fail (including correct password attempts) until the beginningof the next time period. However, this is vulnerable to aform of denial of service attack.

Introducing a delay between password submission attempts to slow down automated password guessing programs.

Some of the more stringent policy enforcement measures can pose a risk of alienating users, possibly decreasing security as a result.

Password reuse

It is common practice amongst computer users to reuse the samepassword on multiple sites. This presents a substantial security risk, since an attacker need only compromise a singlesite in order to gain access to other sites the victim uses. This problem is exacerbated by also reusing usernames, and by websites requiring email logins, as it makes it easier for an

attacker to track a single user across multiple sites. Password reuse can be avoided or minimused by using mnemonic techniques, writing passwords down on paper, or using a password manager.[27]

It has been argued by Redmond researchers Dinei Florencio and Cormac Herley, together with Paul C. van Oorschot of Carleton University, Canada, that password reuse is inevitable, and that users should reuse passwords for low-security websites (which contain little personal data and no financial information, for example) and instead focus their efforts on remember long, complex passwords for a few important accounts,such as banks accounts.[28] Similar arguments were made by Forbes cybersecurity columnist, Joseph Steinberg, who also argued that people should not change passwords as often as many "experts" advise, due to the same limiations in human memory.[21]

Writing down passwords on paper

Historically, many security experts asked people to memorize their passwords: "Never write down a password". More recently,many security experts such as Bruce Schneier recommend that people use passwords that are too complicated to memorize, write them down on paper, and keep them in a wallet.[29][30][31][32]

[33][34][35]

Password manager software can also store passwords relatively safely, in an encrypted file sealed with a single password.

After death

According to a survey by the University of London, one in ten people are now leaving their passwords in their wills to pass on this important information when they die. One third of people, according to the poll, agree that their password protected data is important enough to pass on in their will.[36]

Password crackingMain article: Password cracking

Attempting to crack passwords by trying as many possibilities as time and money permit is a brute force attack. A related method, rather more efficient in most cases, is a dictionary attack. In a dictionary attack, all words in one or more dictionaries are tested. Lists of common passwords are also typically tested.

Password strength is the likelihood that a password cannot be guessed or discovered, and varies with the attack algorithm used. Cryptologists and computer scientists often refer to thestrength or 'hardness' in terms of entropy.[4]

Passwords easily discovered are termed weak or vulnerable; passwords very difficult or impossible to discover are considered strong. There are several programs available for password attack (or even auditing and recovery by systems personnel) such as L0phtCrack, John the Ripper, and Cain; someof which use password design vulnerabilities (as found in the Microsoft LANManager system) to increase efficiency. These programs are sometimes used by system administrators to detectweak passwords proposed by users.

Studies of production computer systems have consistently shownthat a large fraction of all user-chosen passwords are readilyguessed automatically. For example, Columbia University found 22% of user passwords could be recovered with little effort.[37]

According to Bruce Schneier, examining data from a 2006 phishing attack, 55% of MySpace passwords would be crackable in 8 hours using a commercially available Password Recovery Toolkit capable of testing 200,000 passwords per second in 2006.[38] He also reported that the single most common password was password1, confirming yet again the general lack of informed care in choosing passwords among users. (He nevertheless maintained, based on these data, that the generalquality of passwords has improved over the years—for example, average length was up to eight characters from under seven in previous surveys, and less than 4% were dictionary words.[39])

Incidents

On July 16, 1998, CERT reported an incident where an attacker had found 186,126 encrypted passwords. At the

time the attacker was discovered, 47,642 passwords had already been cracked.[40]

In September, 2001, after the deaths of 960 New York employees in the September 11 attacks, financial servicesfirm Cantor Fitzgerald through Microsoft broke the passwords of deceased employees to gain access to files needed for servicing client accounts.[41] Technicians used brute-force attacks, and interviewers contacted families to gather personalized information that might reduce the search time for weaker passwords.[41]

In December 2009, a major password breach of the Rockyou.com website occurred that led to the release of 32 million passwords. The hacker then leaked the full list of the 32 million passwords (with no other identifiable information) to the Internet. Passwords werestored in cleartext in the database and were extracted through a SQL injection vulnerability. The Imperva Application Defense Center (ADC) did an analysis on the strength of the passwords.[42]

In June, 2011, NATO (North Atlantic Treaty Organization) experienced a security breach that led to the public release of first and last names, usernames, and passwordsfor more than 11,000 registered users of their e-bookshop. The data was leaked as part of Operation AntiSec, a movement that includes Anonymous, LulzSec, as well as other hacking groups and individuals. The aim of AntiSec is to expose personal, sensitive, and restricted information to the world, using any means necessary.[43]

On July 11, 2011, Booz Allen Hamilton, a consulting firm that does work for the Pentagon, had their servers hackedby Anonymous and leaked the same day. "The leak, dubbed 'Military Meltdown Monday,' includes 90,000 logins of military personnel—including personnel from USCENTCOM, SOCOM, the Marine corps, various Air Force facilities, Homeland Security, State Department staff, and what lookslike private sector contractors."[44] These leaked passwords wound up being hashed in SHA1, and were later decrypted and analyzed by the ADC team at Imperva, revealing that even military personnel look for shortcutsand ways around the password requirements.[45]

Alternatives to passwords for authenticationThe numerous ways in which permanent or semi-permanent passwords can be compromised has prompted the development of other techniques. Unfortunately, some are inadequate in practice, and in any case few have become universally available for users seeking a more secure alternative.[citation needed]

A 2012 paper[46] examines why passwords have proved so hard to supplant (despite numerous predictions that they would soon bea thing of the past[47]); in examining thirty representative proposed replacements with respect to security, usability and deployability they conclude "none even retains the full set ofbenefits that legacy passwords already provide."

Single-use passwords . Having passwords which are only valid once makes many potential attacks ineffective. Mostusers find single use passwords extremely inconvenient. They have, however, been widely implemented in personal online banking, where they are known as Transaction Authentication Numbers (TANs). As most home users only perform a small number of transactions each week, the single use issue has not led to intolerable customer dissatisfaction in this case.

Time-synchronized one-time passwords are similar in some ways to single-use passwords, but the value to be enteredis displayed on a small (generally pocketable) item and changes every minute or so.

PassWindow one-time passwords are used as single-use passwords, but the dynamic characters to be entered are visible only when a user superimposes a unique printed visual key over a server generated challenge image shown on the user's screen.

Access controls based on public key cryptography e.g. ssh. The necessary keys are usually too large to memorize(but see proposal Passmaze)[48] and must be stored on a local computer, security token or portable memory device,such as a USB flash drive or even floppy disk.

Biometric methods promise authentication based on unalterable personal characteristics, but currently (2008) have high error rates and require additional

hardware to scan, for example, fingerprints, irises, etc.They have proven easy to spoof in some famous incidents testing commercially available systems, for example, the gummie fingerprint spoof demonstration,[49] and, because these characteristics are unalterable, they cannot be changed if compromised; this is a highly important consideration in access control as a compromised access token is necessarily insecure.

Single sign-on technology is claimed to eliminate the need for having multiple passwords. Such schemes do not relieve user and administrators from choosing reasonable single passwords, nor system designers or administrators from ensuring that private access control information passed among systems enabling single sign-on is secure against attack. As yet, no satisfactory standard has beendeveloped.

Envaulting technology is a password-free way to secure data on e.g. removable storage devices such as USB flash drives. Instead of user passwords, access control is based on the user's access to a network resource.

Non-text-based passwords, such as graphical passwords or mouse-movement based passwords.[50] Graphical passwords arean alternative means of authentication for log-in intended to be used in place of conventional password; they use images, graphics or colours instead of letters, digits or special characters. One system requires users to select a series of faces as a password, utilizing the human brain's ability to recall faces easily.[51] In some implementations the user is required to pick from a series of images in the correct sequence in order to gainaccess.[52] Another graphical password solution creates a one-time password using a randomly generated grid of images. Each time the user is required to authenticate, they look for the images that fit their pre-chosen categories and enter the randomly generated alphanumeric character that appears in the image to form the one-time password.[53][54] So far, graphical passwords are promising, but are not widely used. Studies on this subject have been made to determine its usability in the real world. While some believe that graphical passwords would be harder to crack, others suggest that people will be just

as likely to pick common images or sequences as they are to pick common passwords.[citation needed]

2D Key (2-Dimensional Key)[55] is a 2D matrix-like key input method having the key styles of multiline passphrase, crossword, ASCII/Unicode art, with optional textual semantic noises, to create big password/key beyond 128 bits to realize the MePKC (Memorizable Public-Key Cryptography)[56] using fully memorizable private key upon the current private key management technologies likeencrypted private key, split private key, and roaming private key.

Cognitive passwords use question and answer cue/response pairs to verify identity.

"The Password is dead"That "the password is dead" is a recurring idea in Computer Security. It often accompanies arguments that the replacement of passwords by a more secure means of authentication is both necessary and imminent. This claim has been made by numerous people at least since 2004. Notably, Bill Gates, speaking at the 2004 RSA Conference predicted the demise of passwords saying "they just don't meet the challenge for anything you really want to secure."[47] In 2011 IBM predicted that, within five years, "You will never need a password again."[57] Matt Honan, a journalist at Wired, who was the victim of a hacking incident, in 2012 wrote "The age of the password has come to an end."[58] Heather Adkins, manager of Information Security at Google, in 2013 said that "passwords are done at Google."[59] Eric Grosse, VP of security engineering at Google, states that"passwords and simple bearer tokens, such as cookies, are no longer sufficient to keep users safe."[60] Christopher Mims, writing in the Wall Street Journal said the password "is finally dying" and predicted their replacement by device-basedauthentication.[61] Avivah Litan of Gartner said in 2014 "Passwords were dead a few years ago. Now they are more than dead."[62] The reasons given often include reference to the Usability as well as security problems of passwords.

The claim that "the password is dead" is often used by advocates of alternatives to passwords, such as Biometrics, Two-factor authentication or Single sign-on. Many initiatives

have been launched with the explicit goal of eliminating passwords. These include Microsoft's Cardspace, the Higgins project, the Liberty Alliance, NSTIC, the FIDO Alliance and various Identity 2.0 proposals. Jeremy Grant, head of NSTIC initiative (the US Dept. of Commerce National Strategy for Trusted Identities in Cyberspace), declared "Passwords are a disaster from a security perspective, we want to shoot them dead."[63] The FIDO Alliance promises a "passwordless experience" in its 2015 specification document.[64]

In spite of these predictions and efforts to replace them passwords still appear the dominant form of authentication on the web. In "The Persistence of Passwords," Cormac Herley and Paul van Oorschot suggest that every effort should be made to end the "spectacularly incorrect assumption" that passwords are dead.[65] They argue that "no other single technology matches their combination of cost, immediacy and convenience" and that "passwords are themselves the bestfit for many of thescenarios in which they are currently used."

Website password systemsPasswords are used on websites to authenticate users and are usually maintained on the Web server, meaning the browser on aremote system sends a password to the server (by HTTP POST), the server checks the password and sends back the relevant content (or an access denied message). This process eliminatesthe possibility of local reverse engineering as the code used to authenticate the password does not reside on the local machine.

Transmission of the password, via the browser, in plaintext means it can be intercepted along its journey to the server. Many web authentication systems use SSL to establish an encrypted session between the browser and the server, and is usually the underlying meaning of claims to have a "secure Website". This is done automatically by the browser and increasesintegrity of the session, assuming neither end has been compromised and that the SSL/TLS implementations used are highquality ones.

History of passwords

Passwords or watchwords have been used since ancient times. Polybius describes the system for the distribution of watchwords in the Roman military as follows:

The way in which they secure the passing round of the watchword for the night is as follows: from the tenth maniple of each class of infantry and cavalry, the maniple which is encamped at the lower end of the street,a man is chosen who is relieved from guard duty, and he attends every day at sunset at the tent of the tribune, and receiving from him the watchword — that is a wooden tablet with the word inscribed on it – takes his leave, and on returning to his quarters passes on the watchword and tablet before witnesses to the commander of the next maniple, who in turn passes it to the one next him. All do the same until it reaches the first maniples, those encamped near the tents of the tribunes. These latter areobliged to deliver the tablet to the tribunes before dark. So that if all those issued are returned, the tribune knows that the watchword has been given to all the maniples, and has passed through all on its way back to him. If any one of them is missing, he makes inquiry at once, as he knows by the marks from what quarter the tablet has not returned, and whoever is responsible for the stoppage meets with the punishment he merits.[66]

Passwords in military use evolved to include not just a password, but a password and a counterpassword; for example inthe opening days of the Battle of Normandy, paratroopers of the U.S. 101st Airborne Division used a password — flash — whichwas presented as a challenge, and answered with the correct response — thunder. The challenge and response were changed every three days. American paratroopers also famously used a device known as a "cricket" on D-Day in place of a password system as a temporarily unique method of identification; one metallic click given by the device in lieu of a password was to be met by two clicks in reply.[67]

Passwords have been used with computers since the earliest days of computing. MIT's CTSS, one of the first time sharing systems, was introduced in 1961. It had a LOGIN command that requested a user password. "After typing PASSWORD, the system turns off the printing mechanism, if possible, so that the

user may type in his password with privacy."[68] In the early 1970s, Robert Morris developed a system of storing login passwords in a hashed form as part of the Unix operating system. The system was based on a simulated Hagelin rotor crypto machine, and first appeared in 6th Edition Unix in 1974. A later version of his algorithm, known as crypt(3), used a 12-bit salt and invoked a modified form of the DES algorithm 25 times to reduce the risk of pre-computed dictionary attacks.[69]

use ATMs to store their collected money into their bank account.

E-commerce (also written as e-Commerce, eCommerce or similar variants), short for electronic commerce, is trading in products or services using computer networks, such as the Internet. Electronic commerce draws on technologies such as mobile commerce, electronic funds transfer, supply chain management, Internet marketing, online transaction processing,electronic data interchange (EDI), inventory management systems, and automated data collection systems. Modern electronic commerce typically uses the World Wide Web for at least one part of the transaction's life cycle, although it may also use other technologies such as e-mail.

E-commerce businesses may employ some or all of the following:

Online shopping web sites for retail sales direct to consumers

Providing or participating in online marketplaces, which process third-party business-to-consumer or consumer-to-consumer sales

Business-to-business buying and selling Gathering and using demographic data through web contacts

and social media Business-to-business electronic data interchange Marketing to prospective and established customers by e-

mail or fax (for example, with newsletters) Engaging in pretail for launching new products and

services

Contents

1 Timeline 2 Business applications 3 Governmental regulation 4 Forms 5 Global trends 6 Impact on markets and retailers 7 Impact on supply chain management 8 The social impact of e-commerce 9 Distribution channels 10 Examples of new e-commerce systems 11 See also 12 References 13 Further reading 14 External links

TimelineA timeline for the development of e-commerce:

1971 or 1972: The ARPANET is used to arrange a sale between students at the Stanford Artificial Intelligence Laboratory and the Massachusetts Institute of Technology,later described as "the seminal act of e-commerce" in John Markoff's book What the Dormouse Said.[1]

1979: Michael Aldrich demonstrates the first online shopping system.[2]

1981: Thomson Holidays UK is first business-to-business online shopping system to be installed.[3]

1982: Minitel was introduced nationwide in France by France Télécom and used for online ordering.

1983: California State Assembly holds first hearing on "electronic commerce" in Volcano, California.[4] Testifying are CPUC, MCI Mail, Prodigy, CompuServe, Volcano Telephone, and Pacific Telesis. (Not permitted totestify is Quantum Technology, later to become AOL.)

1984: Gateshead SIS/Tesco is first B2C online shopping system [5] and Mrs Snowball, 72, is the first online home shopper[6]

1984: In April 1984, CompuServe launches the Electronic Mall in the USA and Canada. It is the first comprehensiveelectronic commerce service.[7]

1990: Tim Berners-Lee writes the first web browser, WorldWideWeb, using a NeXT computer.[8]

1992: Book Stacks Unlimited in Cleveland opens a commercial sales website (www.books.com) selling books online with credit card processing.

1992: St. Martin's Press publishes J.H. Snider and Terra Ziporyn's Future Shop: How New Technologies Will Change the Way We Shop and What We Buy. [9]

1993: Paget Press releases edition No. 3 [10] of the first[citation needed] app store, The Electronic AppWrapper [11]

1994: Netscape releases the Navigator browser in October under the code name Mozilla. Netscape 1.0 is introduced in late 1994 with SSL encryption that made transactions secure.

1994: Ipswitch IMail Server becomes the first software available online for sale and immediate download via a partnership between Ipswitch, Inc. and OpenMarket.

1994: "Ten Summoner's Tales" by Sting becomes the first secure online purchase.[12]

1995: The US National Science Foundation lifts its formerstrict prohibition of commercial enterprise on the Internet.[13]

1995: Thursday 27 April 1995, the purchase of a book by Paul Stanfield, Product Manager for CompuServe UK, from WH Smith's shop within CompuServe's UK Shopping Centre is the UK's first national online shopping service secure transaction. The shopping service at launch featured W H Smith, Tesco, Virgin Megastores/Our Price, Great Universal Stores (GUS), Interflora, Dixons Retail, Past Times, PC World (retailer) and Innovations.

1995: Jeff Bezos launches Amazon.com and the first commercial-free 24-hour, internet-only radio stations, Radio HK and NetRadio start broadcasting. eBay is foundedby computer programmer Pierre Omidyar as AuctionWeb.

1996: IndiaMART B2B marketplace established in India. 1996: ECPlaza B2B marketplace established in Korea. 1996: The UK e-commerce platform Sellerdeck, formerly

Actinic, is established.[citation needed]

1998: Electronic postal stamps can be purchased and downloaded for printing from the Web.[14]

1998: Cbazaar formerly chennaibazaar.com, India's first B2C eCommerce portal launched by Rajesh Nahar and Ritesh Katariya.

1999: Alibaba Group is established in China. Business.comsold for US $7.5 million to eCompanies, which was purchased in 1997 for US $149,000. The peer-to-peer filesharing software Napster launches. ATG Stores launches to sell decorative items for the home online.

2000: The dot-com bust. 2001: Alibaba.com achieved profitability in December

2001. 2002: eBay acquires PayPal for $1.5 billion.[15] Niche

retail companies Wayfair and NetShops are founded with the concept of selling products through several targeted domains, rather than a central portal.

2003: Amazon.com posts first yearly profit. 2003: Bossgoo B2B marketplace established in China. 2004: DHgate.com, China's first online b2b transaction

platform, is established, forcing other b2b sites to moveaway from the "yellow pages" model.[16]

2007: Business.com acquired by R.H. Donnelley for $345 million.[17]

2009: Zappos.com acquired by Amazon.com for $928 million.[18] Retail Convergence, operator of private sale website RueLaLa.com, acquired by GSI Commerce for $180 million, plus up to $170 million in earn-out payments based on performance through 2012.[19]

2010: Groupon reportedly rejects a $6 billion offer from Google. Instead, the group buying websites went ahead with an IPO on 4 November 2011. It was the largest IPO since Google.[20][21]

2011: Quidsi.com, parent company of Diapers.com, acquiredby Amazon.com for $500 million in cash plus $45 million in debt and other obligations.[22] GSI Commerce, a company specializing in creating, developing and running online shopping sites for brick and mortar businesses, acquired by eBay for $2.4 billion.[23]

2014: Overstock.com processes over $1 million in Bitcoin sales.[24] India’s e-commerce industry is estimated to havegrown more than 30% from 2012 to $12.6 billion in 2013.[25]

US eCommerce and Online Retail sales projected to reach $294 billion, an increase of 12 percent over 2013 and 9%

of all retail sales.[26] Alibaba Group has the largest Initial public offering ever, worth $25 billion.

Business applications

An example of an automated online assistant on a merchandisingwebsite.

Some common applications related to electronic commerce are:

Document automation in supply chain and logistics Domestic and international payment systems Enterprise content management Group buying Print on demand Automated online assistant Newsgroups Online shopping and order tracking Online banking Online office suites Shopping cart software Teleconferencing Electronic tickets Social networking Instant messaging Pretail Digital Wallet

Governmental regulation

In the United States, some electronic commerce activities are regulated by the Federal Trade Commission (FTC). These activities include the use of commercial e-mails, online advertising and consumer privacy. The CAN-SPAM Act of 2003 establishes national standards for direct marketing over e-mail. The Federal Trade Commission Act regulates all forms of advertising, including online advertising, and states that advertising must be truthful and non-deceptive.[27] Using its authority under Section 5 of the FTC Act, which prohibits unfair or deceptive practices, the FTC has brought a number ofcases to enforce the promises in corporate privacy statements,including promises about the security of consumers' personal information.[28] As result, any corporate privacy policy relatedto e-commerce activity may be subject to enforcement by the FTC.

The Ryan Haight Online Pharmacy Consumer Protection Act of 2008, which came into law in 2008, amends the Controlled Substances Act to address online pharmacies.[29]

Conflict of laws in cyberspace is a major hurdle for harmonisation of legal framework for e-commerce around the world. In order to give a uniformity to e-commerce law around the world, many countries adopted the UNCITRAL Model Law on Electronic Commerce (1996) [30]

Internationally there is the International Consumer Protectionand Enforcement Network (ICPEN), which was formed in 1991 froman informal network of government customer fair trade organisations. The purpose was stated as being to find ways ofco-operating on tackling consumer problems connected with cross-border transactions in both goods and services, and to help ensure exchanges of information among the participants for mutual benefit and understanding. From this came Econsumer.gov, an ICPEN initiative since April 2001. It is a portal to report complaints about online and related transactions with foreign companies.

There is also Asia Pacific Economic Cooperation (APEC) was established in 1989 with the vision of achieving stability, security and prosperity for the region through free and open trade and investment. APEC has an Electronic Commerce Steering

Group as well as working on common privacy regulations throughout the APEC region.

In Australia, Trade is covered under Australian Treasury Guidelines for electronic commerce,[31] and the Australian Competition and Consumer Commission [32] regulates and offers advice on how to deal with businesses online,[33][34] and offers specific advice on what happens if things go wrong.[35]

In the United Kingdom, The Financial Services Authority (FSA)[36] was formerly the regulating authority for most aspects of the EU's Payment Services Directive (PSD), until its replacement in 2013 by the Prudential Regulation Authority andthe Financial Conduct Authority.[37] The UK implemented the PSD through the Payment Services Regulations 2009 (PSRs), which came into effect on 1 November 2009. The PSR affects firms providing payment services and their customers. These firms include banks, non-bank credit card issuers and non-bank merchant acquirers, e-money issuers, etc. The PSRs created a new class of regulated firms known as payment institutions (PIs), who are subject to prudential requirements. Article 87 of the PSD requires the European Commission to report on the implementation and impact of the PSD by 1 November 2012.[38]

In India, the Information Technology Act 2000 governs the basic applicability of e-commerce.

In China, the Telecommunications Regulations of the People's Republic of China (promulgated on 25 September 2000), stipulated the Ministry of Industry and Information Technology(MIIT) as the government department regulating all telecommunications related activities, including electronic commerce.[39] On the same day, The Administrative Measures on Internet Information Services released, is the first administrative regulation to address profit-generating activities conducted through the Internet, and lay the foundation for future regulations governing e-commerce in China.[40] In 28 August 2004, the eleventh session of the tenth NPC Standing Committee adopted The Electronic Signature Law, which regulates data message, electronic signature authentication and legal liability issues. It is considered the first law in China’s e-commerce legislation. It was a milestone in the course of improving China’s electronic

commerce legislation, and also marks the entering of China’s rapid development stage for electronic commerce legislation.[41]

FormsContemporary electronic commerce involves everything from ordering "digital" content for immediate online consumption, to ordering conventional goods and services, to "meta" services to facilitate other types of electronic commerce.

On the institutional level, big corporations and financial institutions use the internet to exchange financial data to facilitate domestic and international business. Data integrityand security are pressing issues for electronic commerce.

Aside from traditional e-Commerce, the terms m-Commerce (mobile commerce) as well (around 2013) t-Commerce [42] have alsobeen used.

Global trendsIn 2010, the United Kingdom had the biggest e-commerce market in the world when measured by the amount spent per capita.[43] The Czech Republic is the European country where ecommerce delivers the biggest contribution to the enterprises´ total revenue. Almost a quarter (24%) of the country’s total turnover is generated via the online channel.[44]

Among emerging economies, China's e-commerce presence continues to expand every year. With 384 million internet users, China's online shopping sales rose to $36.6 billion in 2009 and one of the reasons behind the huge growth has been the improved trust level for shoppers. The Chinese retailers have been able to help consumers feel more comfortable shopping online.[45] China's cross-border e-commerce is also growing rapidly. E-commerce transactions between China and other countries increased 32% to 2.3 trillion yuan ($375.8 billion) in 2012 and accounted for 9.6% of China's total international trade [46] In 2013, Alibaba had an e-commerce market share of 80% in China.[47]

Other BRIC countries are witnessing the accelerated growth of eCommerce as well. Brazil's eCommerce is growing quickly with retail eCommerce sales expected to grow at a healthy double-digit pace through 2014. By 2016, eMarketer expects retail ecommerce sales in Brazil to reach $17.3 billion.[48] India has an internet user base of about 243.2 million as of January 2014. Despite being third largest userbase in world, the penetration of Internet is low compared to markets like the United States, United Kingdom or France but is growing at a much faster rate, adding around 6 million new entrants every month. The industry consensus is that growth is at an inflection point. In India, cash on delivery is the most preferred payment method, accumulating 75% of the e-retail activities.

E-Commerce has become an important tool for small and large businesses worldwide, not only to sell to customers, but also to engage them.[49][50]

In 2012, ecommerce sales topped $1 trillion for the first timein history.[51]

Mobile devices are playing an increasing role in the mix of eCommerce. Some estimates show that purchases made on mobile devices will make up 25% of the market by 2017.[52] According toCisco Visual Networking Index,[53] in 2014 the amount of mobile devices will outnumber the number of world population.

In the past 10 years, e-commerce is in a period of rapid development. Cross-border e-commerce is called the Internet thinking along with traditional import and export trade. Cross-border e-commerce enables international trade towards more convenient and free open to cooperate between different countries in the world, incorporating developed and developingcountries. In the short term, developing countries may be limited to IT, but in the long term, they would change the barrier to develop their IT facilities, and continuing to close to developed countries.[54] The moment, developing countries like China and India are developing e-commerce very rapidly, such as China 's Alibaba, the financing capital (£15 billions) is the highest ever in e-commerce company. In addition, China is becoming the biggest e-commerce provider inthe world.[55] The number of Internet users in China which

amounts to 600 millions, and which is doubled than USA users in total.[56]

For traditional businesses, one research stated that information technology and cross-border e-commerce is a good opportunity for the rapid development and growth of enterprises. Many companies have invested enormous volume of investment in mobile applications.The DeLone and McLean Model stated that 3 perspectives are contributed to a successful e-business, including information system quality, service quality and users satisfaction.[57] There is no limit of time and space, there are more opportunities to reach out to customers around the world, and to cut down unnecessary intermediate links, thereby reducing the cost price, and can benefit from one on one large customer data analysis, to achieve a high degree of personal customization strategic plan, in order to fully enhance the core competitiveness of the products in company[58]

Impact on markets and retailersEconomists have theorized that e-commerce ought to lead to intensified price competition, as it increases consumers' ability to gather information about products and prices. Research by four economists at the University of Chicago has found that the growth of online shopping has also affected industry structure in two areas that have seen significant growth in e-commerce, bookshops and travel agencies. Generally, larger firms are able to use economies of scale andoffer lower prices. The lone exception to this pattern has been the very smallest category of bookseller, shops with between one and four employees, which appear to have withstoodthe trend.[59] Depending on the category, e-commerce may shift the switching costs—procedural, relational, and financial—experienced by customers.[60]

Individual or business involved in e-commerce whether buyers or sellers rely on Internet-based technology in order to accomplish their transactions. E-commerce is recognized for its ability to allow business to communicate and to form transaction anytime and anyplace. Whether an individual is in the US or overseas, business can be conducted through the

internet. The power of e-commerce allows geophysical barriers to disappear, making all consumers and businesses on earth potential customers and suppliers. Thus, switching barriers and switching costs my shift.[60] eBay is a good example of e-commerce business individuals and businesses are able to post their items and sell them around the Globe.[61]

In e-commerce activities, supply chain and logistics are two most crucial factors need to be considered. Typically, cross-border logistics need about few weeks time round. Based on this low efficiency of the supply chain service, customer satisfaction will be greatly reduced.[62] Some researcher statedthat combining e-commerce competence and IT setup could well enhance company’s overall business worth.[63] Other researcher stated that e-commerce need to consider the establishment of warehouse centers in foreign countries, to create high efficiency of the logistics system, not only improve customers’ satisfaction, but also can improve customers’ loyalty.[weasel words]. A recently published comprehensive meta-analysis shows that e-service quality is determined by many different factors, and influences customer satisfaction and repurchase intentions among customers.[64]

Some researcher investigated that if a company want to enhanceinternational customers’ satisfaction, where cultural website need to be adapted in particular country, rather than solely depending on its local country. However, according to this research findings, the researcher found that German company had treated its international website as the same local model,such as in UK and US online marketing.[65] A company could save money and make decision quickly via the identical strategy in different country. However, opportunity cost could be occurred, if the local strategy does not match to a new market, the company could lose its potential customer.[66]

Impact on supply chain managementFor a long time, companies had been troubled by the gap between the benefits which supply chain technology has and thesolutions to deliver those benefits. However, the emergence ofe-commerce has provided a more practical and effective way of

delivering the benefits of the new supply chain technologies.[67]

E-commerce has the capability to integrate all inter-company and intra-company functions, meaning that the three flows (physical flow, financial flow and information flow) of the supply chain could be also affected by e-commerce. The affections on physical flows improved the way of product and inventory movement level for companies. For the information flows, e-commerce optimised the capacity of information processing than companies used to have, and for the financial flows, e-commerce allows companies to have more efficient payment and settlement solutions.[67]

In addition, e-commerce has a more sophisticated level of impact on supply chains: Firstly, the performance gap will be eliminated since companies can identify gaps between differentlevels of supply chains by electronic means of solutions; Secondly, as a result of e-commerce emergence, new capabilities such implementing ERP systems have helped companies to manage operations with customers and suppliers. Yet these new capabilities are still not fully exploited. Thirdly, technology companies would keep investing on new e-commerce software solutions as they are expecting investment return. Fourthly, e-commerce would help to solve many aspects of issues that companies may feel difficult to cope with, suchas political barriers or cross-country changes. Finally, e-commerce provides companies a more efficient and effective wayto collaborate with each other within the supply chain.[67]

The social impact of e-commerceAlong with the e-commerce and its unique charm that has appeared gradually, virtual enterprise, virtual bank, network marketing, online shopping, payment and advertising, such thisnew vocabulary which is unheard-of and now has become as familiar to people. This reflects that the e-commerce has hugeimpact on the economy and society from the other side.[68] For instance, B2B is a rapidly growing business in the world that leads to lower cost and then improves the economic efficiency and also bring along the growth of employment.[69]

To understand how the e-commerce has affected the society and economy, this article will mention three issues below:

1. The e-commerce has changed the relative importance of time,but as the pillars of indicator of the country’s economic state that the importance of time should not be ignored.

2. The e-commerce offers the consumer or enterprise various information they need, making information into total transparency, will force enterprise no longer is able to use the mode of space or advertisement to raise their competitive edge.[70] Moreover, in theory, perfect competition between the consumer sovereignty and industry will maximize social welfare.[71]

3. In fact, during the economic activity in the past, large enterprise frequently has advantage of information resource, and thus at the expense of consumers. Nowadays, the transparent and real-time information protects the rights of consumers, because the consumers can use internet to pick out the portfolio to the benefit of themselves. The competitiveness of enterprises will be much more obvious than before, consequently, social welfare would be improved by the development of the e-commerce.

4. The new economy led by the e-commerce change humanistic spirit as well, but above all, is the employee loyalty.[72] Due to the market with competition, the employee’s level of professionalism becomes the crucial for enterprise in the niche market. The enterprises must pay attention to how to build up the enterprises inner culture and a set of interactive mechanisms and it is the prime problem for them. Furthermore, though the mode of e-commerce decrease the information cost and transaction cost, however, its development also makes human being are overly computer literate. In hence, emphasized more humanistic attitude to work is another project for enterprise to development. Life isthe root of all and high technology are merely an assistive tool to support our quality of life.

The e-commerce is not a kind of new industry, but it is creating a new economic model. Most of people agree that the e-commerce indeed to be important and significant for economic

society in the future, but actually that is a bit of clueless feeling at the beginning, this problem is exactly prove the e-commerce is a sort of incorporeal revolution.[73] Generally speaking, as a type of business active procedure, the e-commerce is going to leading an unprecedented revolution in the world, the influence of this model far exceeded the commercial affair itself.[74] Except the mentioned above, in thearea of law, education, culture and also policy, the e-commerce will continue that rise in impact. The e-commerce is truly to take human beings into the information society.

Distribution channelsThis section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (June 2013)

E-commerce has grown in importance as companies have adopted pure-click and brick-and-click channel systems. We can distinguish pure-click and brick-and-click channel system adopted by companies.

Pure-click or pure-play companies are those that have launched a website without any previous existence as a firm.

Bricks-and-clicks companies are those existing companies that have added an online site for e-commerce.

Click-to-brick online retailers that later open physical locations to supplement their online efforts.[75]

Examples of new e-commerce systemsAccording to eMarketer research company, "by 2017, 65.8 per cent of Britons will use smartphones" (cited by Williams, 2014).

Bringing online experience into the real world, also allows the development of the economy and the interaction between stores and customers. A great example of this new e-commerce system is what the Burberry store in London did in 2012. They refurbished the entire store with numerous big screens, photo-

studios, and also provided a stage for live acts. Moreover, onthe digital screens which are across the store, some fashion shows´ images and advertising campaigns are displayed (William, 2014). In this way, the experience of purchasing becomes more vivid and entertaining while the online and offline components are working together.

Another example is the Kiddicare smartphone app, in which consumers can compare prices. The app allows people to identify the location of sale products and to check whether the item they are looking for is in stock, or if it can be ordered online without going to the `real´ store (William, 2014). In the United States, the Walmart app allows consumers to check product availability and prices both online and offline. Moreover, you can also add to your shopping list items by scanning them, see their details and information, andcheck purchasers´ ratings and reviews.

"Computer technology" and "Computer system" redirect here. Forthe company, see Computer Technology Limited. For other uses, see Computer (disambiguation) and Computer system (disambiguation).

Computer

A computer is a general-purpose device that can be programmed to carry out a set of arithmetic or logical operations automatically. Since a sequence of operations can be readily changed, the computer can solve more than one kind of problem.

Conventionally, a computer consists of at least one processingelement, typically a central processing unit (CPU), and some form of memory. The processing element carries out arithmetic

and logic operations, and a sequencing and control unit can change the order of operations in response to stored information. Peripheral devices allow information to be retrieved from an external source, and the result of operations saved and retrieved.

Mechanical analog computers started appearing in the first century and were later used in the medieval era for astronomical calculations. In World War II, mechanical analog computers were used for specialized military applications suchas calculating torpedo aiming. During this time the first electronic digital computers were developed. Originally they were the size of a large room, consuming as much power as several hundred modern personal computers (PCs).[1]

Modern computers based on integrated circuits are millions to billions of times more capable than the early machines, and occupy a fraction of the space.[2] Computers are small enough to fit into mobile devices, and mobile computers can be powered by small batteries. Personal computers in their various forms are icons of the Information Age and are what most people consider as “computers.” However, the embedded computers found in many devices from MP3 players to fighter aircraft and from electronic toys to industrial robots are themost numerous.

Contents 1 Etymology 2 History

o 2.1 Pre-twentieth centuryo 2.2 First general-purpose computing deviceo 2.3 Later Analog computerso 2.4 Digital computer development

2.4.1 Electromechanical 2.4.2 Vacuum tubes and digital electronic

circuits 2.4.3 Stored programs 2.4.4 Transistors 2.4.5 Integrated circuits

o 2.5 Mobile computers become dominant 3 Programs

o 3.1 Stored program architectureo 3.2 Machine codeo 3.3 Programming language

3.3.1 Low-level languages 3.3.2 High-level languages/Third Generation

Languageo 3.4 Fourth Generation Languageso 3.5 Program designo 3.6 Bugs

4 Components o 4.1 Control unito 4.2 Central Processing unit (CPU)o 4.3 Arithmetic logic unit (ALU)o 4.4 Memoryo 4.5 Input/output (I/O)o 4.6 Multitaskingo 4.7 Multiprocessing

5 Networking and the Internet o 5.1 Computer architecture paradigms

6 Misconceptions o 6.1 Unconventional computing

7 Future 8 Further topics

o 8.1 Artificial intelligence 9 Hardware

o 9.1 History of computing hardwareo 9.2 Other hardware topics

10 Software 11 Languages

o 11.1 Firmwareo 11.2 Liveware

12 Types of computers o 12.1 Based on useso 12.2 Based on sizes

13 Input Devices 14 Output Devices 15 Professions and organizations 16 See also 17 Notes 18 References 19 External links

EtymologyThe first known use of the word "computer" was in 1613 in a book called The Yong Mans Gleanings by English writer Richard Braithwait: "I haue read the truest computer of Times, and thebest Arithmetician that euer breathed, and he reduceth thy dayes into a short number." It referred to a person who carried out calculations, or computations. The word continued with the same meaning until the middle of the 20th century. From the end of the 19th century the word began to take on itsmore familiar meaning, a machine that carries out computations.[3]

HistoryMain article: History of computing hardware

Pre-twentieth century

The Ishango bone

Devices have been used to aid computation for thousands of years, mostly using one-to-one correspondence with fingers. The earliest counting device was probably a form of tally stick. Later record keeping aids throughout the Fertile Crescent included calculi (clay spheres, cones, etc.) which represented counts of items, probably livestock or grains, sealed in hollow unbaked clay containers.[4][5] The use of counting rods is one example.

Suanpan (the number represented on this abacus is 6,302,715,408)

The abacus was initially used for arithmetic tasks. The Roman abacus was used in Babylonia as early as 2400 BC. Since then, many other forms of reckoning boards or tables have been invented. In a medieval European counting house, a checkered cloth would be placed on a table, and markers moved around on it according to certain rules, as an aid to calculating sums of money.

The ancient Greek-designed Antikythera mechanism, dating between 150 to 100 BC, is the world's oldest analog computer.

The Antikythera mechanism is believed to be the earliest mechanical analog "computer", according to Derek J. de Solla Price.[6] It was designed to calculate astronomical positions. It was discovered in 1901 in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete, and has been dated to circa 100 BC. Devices of a level of complexitycomparable to that of the Antikythera mechanism would not reappear until a thousand years later.

Many mechanical aids to calculation and measurement were constructed for astronomical and navigation use. The planisphere was a star chart invented by Abū Rayhān al-Bīrūnī in the early 11th century.[7] The astrolabe was invented in theHellenistic world in either the 1st or 2nd centuries BC and is

often attributed to Hipparchus. A combination of the planisphere and dioptra, the astrolabe was effectively an analog computer capable of working out several different kindsof problems in spherical astronomy. An astrolabe incorporatinga mechanical calendar computer[8][9] and gear-wheels was inventedby Abi Bakr of Isfahan, Persia in 1235.[10] Abū Rayhān al-Bīrūnīinvented the first mechanical geared lunisolar calendar astrolabe,[11] an early fixed-wired knowledge processing machine [12] with a gear train and gear-wheels,[13] circa 1000 AD.

The sector, a calculating instrument used for solving problemsin proportion, trigonometry, multiplication and division, and for various functions, such as squares and cube roots, was developed in the late 16th century and found application in gunnery, surveying and navigation.

The planimeter was a manual instrument to calculate the area of a closed figure by tracing over it with a mechanical linkage.

A slide rule

The slide rule was invented around 1620–1630, shortly after the publication of the concept of the logarithm. It is a hand-operated analog computer for doing multiplication and division. As slide rule development progressed, added scales provided reciprocals, squares and square roots, cubes and cuberoots, as well as transcendental functions such as logarithms and exponentials, circular and hyperbolic trigonometry and other functions. Aviation is one of the few fields where sliderules are still in widespread use, particularly for solving time–distance problems in light aircraft. To save space and for ease of reading, these are typically circular devices rather than the classic linear slide rule shape. A popular example is the E6B.

In the 1770s Pierre Jaquet-Droz, a Swiss watchmaker, built a mechanical doll (automata) that could write holding a quill pen. By switching the number and order of its internal wheels different letters, and hence different messages, could be

produced. In effect, it could be mechanically "programmed" to read instructions. Along with two other complex machines, the doll is at the Musée d'Art et d'Histoire of Neuchâtel, Switzerland, and still operates.[14]

The tide-predicting machine invented by Sir William Thomson in1872 was of great utility to navigation in shallow waters. It used a system of pulleys and wires to automatically calculate predicted tide levels for a set period at a particular location.

The differential analyser, a mechanical analog computer designed to solve differential equations by integration, used wheel-and-disc mechanisms to perform the integration. In 1876 Lord Kelvin had already discussed the possible construction ofsuch calculators, but he had been stymied by the limited output torque of the ball-and-disk integrators.[15] In a differential analyzer, the output of one integrator drove the input of the next integrator, or a graphing output. The torqueamplifier was the advance that allowed these machines to work.Starting in the 1920s, Vannevar Bush and others developed mechanical differential analyzers.

First general-purpose computing device

A portion of Babbage's Difference engine.

Charles Babbage, an English mechanical engineer and polymath, originated the concept of a programmable computer. Considered

the "father of the computer",[16] he conceptualized and inventedthe first mechanical computer in the early 19th century. Afterworking on his revolutionary difference engine, designed to aid in navigational calculations, in 1833 he realized that a much more general design, an Analytical Engine, was possible. The input of programs and data was to be provided to the machine via punched cards, a method being used at the time to direct mechanical looms such as the Jacquard loom. For output,the machine would have a printer, a curve plotter and a bell. The machine would also be able to punch numbers onto cards to be read in later. The Engine incorporated an arithmetic logic unit, control flow in the form of conditional branching and loops, and integrated memory, making it the first design for ageneral-purpose computer that could be described in modern terms as Turing-complete.[17][18]

The machine was about a century ahead of its time. All the parts for his machine had to be made by hand - this was a major problem for a device with thousands of parts. Eventually, the project was dissolved with the decision of theBritish Government to cease funding. Babbage's failure to complete the analytical engine can be chiefly attributed to difficulties not only of politics and financing, but also to his desire to develop an increasingly sophisticated computer and to move ahead faster than anyone else could follow. Nevertheless, his son, Henry Babbage, completed a simplified version of the analytical engine's computing unit (the mill) in1888. He gave a successful demonstration of its use in computing tables in 1906.

Later Analog computers

Sir William Thomson's third tide-predicting machine design, 1879–81

During the first half of the 20th century, many scientific computing needs were met by increasingly sophisticated analog computers, which used a direct mechanical or electrical model of the problem as a basis for computation. However, these werenot programmable and generally lacked the versatility and accuracy of modern digital computers.[19]

The first modern analog computer was a tide-predicting machine, invented by Sir William Thomson in 1872. The differential analyser, a mechanical analog computer designed to solve differential equations by integration using wheel-and-disc mechanisms, was conceptualized in 1876 by James Thomson, the brother of the more famous Lord Kelvin.[15]

The art of mechanical analog computing reached its zenith withthe differential analyzer, built by H. L. Hazen and Vannevar Bush at MIT starting in 1927. This built on the mechanical integrators of James Thomson and the torque amplifiers invented by H. W. Nieman. A dozen of these devices were built before their obsolescence became obvious.

By the 1950s the success of digital electronic computers had spelled the end for most analog computing machines, but analogcomputers remain in use in some specialized applications such as education (control systems) and aircraft (slide rule).

Digital computer development

The principle of the modern computer was first described by mathematician and pioneering computer scientist Alan Turing, who set out the idea in his seminal 1936 paper,[20] On Computable Numbers. Turing reformulated Kurt Gödel's 1931 results on the limits of proof and computation, replacing Gödel's universal arithmetic-based formal language with the formal and simple hypothetical devices that became known as Turing machines. He proved that some such machine would be capable of performing any conceivable mathematical computation if it were representable as an algorithm. He went on to prove that there was no solution to the Entscheidungsproblem by first showing thatthe halting problem for Turing machines is undecidable: in general, it is not possible to decide algorithmically whether a given Turing machine will ever halt.

He also introduced the notion of a 'Universal Machine' (now known as a Universal Turing machine), with the idea that such a machine could perform the tasks of any other machine, or in other words, it is provably capable of computing anything thatis computable by executing a program stored on tape, allowing the machine to be programmable. Von Neumann acknowledged that the central concept of the modern computer was due to this paper.[21] Turing machines are to this day a central object of study in theory of computation. Except for the limitations imposed by their finite memory stores, modern computers are said to be Turing-complete, which is to say, they have algorithm execution capability equivalent to a universal Turing machine.

Electromechanical

By 1938 the United States Navy had developed an electromechanical analog computer small enough to use aboard asubmarine. This was the Torpedo Data Computer, which used trigonometry to solve the problem of firing a torpedo at a moving target. During World War II similar devices were developed in other countries as well.

Replica of Zuse's Z3, the first fully automatic, digital (electromechanical) computer.

Early digital computers were electromechanical; electric switches drove mechanical relays to perform the calculation. These devices had a low operating speed and were eventually superseded by much faster all-electric computers, originally using vacuum tubes. The Z2, created by German engineer Konrad Zuse in 1939, was one of the earliest examples of an electromechanical relay computer.[22]

In 1941, Zuse followed his earlier machine up with the Z3, theworld's first working electromechanical programmable, fully

automatic digital computer.[23][24] The Z3 was built with 2000 relays, implementing a 22 bit word length that operated at a clock frequency of about 5–10 Hz.[25] Program code was supplied on punched film while data could be stored in 64 words of memory or supplied from the keyboard. It was quite similar to modern machines in some respects, pioneering numerous advancessuch as floating point numbers. Replacement of the hard-to-implement decimal system (used in Charles Babbage's earlier design) by the simpler binary system meant that Zuse's machines were easier to build and potentially more reliable, given the technologies available at that time.[26] The Z3 was probably a complete Turing machine.

Vacuum tubes and digital electronic circuits

Purely electronic circuit elements soon replaced their mechanical and electromechanical equivalents, at the same timethat digital calculation replaced analog. The engineer Tommy Flowers, working at the Post Office Research Station in Londonin the 1930s, began to explore the possible use of electronicsfor the telephone exchange. Experimental equipment that he built in 1934 went into operation 5 years later, converting a portion of the telephone exchange network into an electronic data processing system, using thousands of vacuum tubes.[19] In the US, John Vincent Atanasoff and Clifford E. Berry of Iowa State University developed and tested the Atanasoff–Berry Computer (ABC) in 1942,[27] the first "automatic electronic digital computer".[28] This design was also all-electronic and used about 300 vacuum tubes, with capacitors fixed in a mechanically rotating drum for memory.[29]

Colossus was the first electronic digital programmable computing device, and was used to break German ciphers during World War II.

During World War II, the British at Bletchley Park achieved a number of successes at breaking encrypted German military communications. The German encryption machine, Enigma, was first attacked with the help of the electro-mechanical bombes.To crack the more sophisticated German Lorenz SZ 40/42 machine, used for high-level Army communications, Max Newman and his colleagues commissioned Flowers to build the Colossus.[29] He spent eleven months from early February 1943 designing and building the first Colossus.[30] After a functional test in December 1943, Colossus was shipped to Bletchley Park, where it was delivered on 18 January 1944[31] and attacked its first message on 5 February.[29]

Colossus was the world's first electronic digital programmablecomputer.[19] It used a large number of valves (vacuum tubes). It had paper-tape input and was capable of being configured toperform a variety of boolean logical operations on its data, but it was not Turing-complete. Nine Mk II Colossi were built (The Mk I was converted to a Mk II making ten machines in total). Colossus Mark I contained 1500 thermionic valves (tubes), but Mark II with 2400 valves, was both 5 times fasterand simpler to operate than Mark 1, greatly speeding the decoding process.[32][33]

ENIAC was the first Turing-complete device, and performed ballistics trajectory calculations for the United States Army.

The US-built ENIAC [34] (Electronic Numerical Integrator and Computer) was the first electronic programmable computer builtin the US. Although the ENIAC was similar to the Colossus it was much faster and more flexible. It was unambiguously a Turing-complete device and could compute any problem that would fit into its memory. Like the Colossus, a "program" on the ENIAC was defined by the states of its patch cables and switches, a far cry from the stored program electronic

machines that came later. Once a program was written, it had to be mechanically set into the machine with manual resetting of plugs and switches.

It combined the high speed of electronics with the ability to be programmed for many complex problems. It could add or subtract 5000 times a second, a thousand times faster than anyother machine. It also had modules to multiply, divide, and square root. High speed memory was limited to 20 words (about 80 bytes). Built under the direction of John Mauchly and J. Presper Eckert at the University of Pennsylvania, ENIAC's development and construction lasted from 1943 to full operation at the end of 1945. The machine was huge, weighing 30 tons, using 200 kilowatts of electric power and contained over 18,000 vacuum tubes, 1,500 relays, and hundreds of thousands of resistors, capacitors, and inductors.[35]

Stored programs

A section of the Manchester Small-Scale Experimental Machine, the first stored-program computer.

Early computing machines had fixed programs. Changing its function required the re-wiring and re-structuring of the machine.[29] With the proposal of the stored-program computer this changed. A stored-program computer includes by design an instruction set and can store in memory a set of instructions (a program) that details the computation. The theoretical basis for the stored-program computer was laid by Alan Turing in his 1936 paper. In 1945 Turing joined the National PhysicalLaboratory and began work on developing an electronic stored-program digital computer. His 1945 report ‘Proposed ElectronicCalculator’ was the first specification for such a device. John von Neumann at the University of Pennsylvania, also circulated his First Draft of a Report on the EDVAC in 1945.[19]

Ferranti Mark 1, c. 1951.

The Manchester Small-Scale Experimental Machine, nicknamed Baby, was the world's first stored-program computer. It was built at the Victoria University of Manchester by Frederic C. Williams, Tom Kilburn and Geoff Tootill, and ran its first program on 21 June 1948.[36] It was designed as a testbed for the Williams tube the first random-access digital storage device.[37] Although the computer was considered "small and primitive" by the standards of its time, it was the first working machine to contain all of the elements essential to a modern electronic computer.[38] As soon as the SSEM had demonstrated the feasibility of its design, a project was initiated at the university to develop it into a more usable computer, the Manchester Mark 1.

The Mark 1 in turn quickly became the prototype for the Ferranti Mark 1, the world's first commercially available general-purpose computer.[39] Built by Ferranti, it was delivered to the University of Manchester in February 1951. Atleast seven of these later machines were delivered between 1953 and 1957, one of them to Shell labs in Amsterdam.[40] In October 1947, the directors of British catering company J. Lyons & Company decided to take an active role in promoting the commercial development of computers. The LEO I computer became operational in April 1951 [41] and ran the world's first regular routine office computer job.

Transistors

A bipolar junction transistor

The bipolar transistor was invented in 1947. From 1955 onwardstransistors replaced vacuum tubes in computer designs, giving rise to the "second generation" of computers. Compared to vacuum tubes, transistors have many advantages: they are smaller, and require less power than vacuum tubes, so give offless heat. Silicon junction transistors were much more reliable than vacuum tubes and had longer, indefinite, servicelife. Transistorized computers could contain tens of thousandsof binary logic circuits in a relatively compact space.

At the University of Manchester, a team under the leadership of Tom Kilburn designed and built a machine using the newly developed transistors instead of valves.[42] Their first transistorised computer and the first in the world, was operational by 1953, and a second version was completed there in April 1955. However, the machine did make use of valves to generate its 125 kHz clock waveforms and in the circuitry to read and write on its magnetic drum memory, so it was not the first completely transistorized computer. That distinction goes to the Harwell CADET of 1955,[43] built by the electronics division of the Atomic Energy Research Establishment at Harwell.[44][45]

Integrated circuits

The next great advance in computing power came with the adventof the integrated circuit. The idea of the integrated circuit was first conceived by a radar scientist working for the RoyalRadar Establishment of the Ministry of Defence, Geoffrey W.A. Dummer. Dummer presented the first public description of an integrated circuit at the Symposium on Progress in Quality Electronic Components in Washington,   D.C. on 7 May 1952.[46]

The first practical ICs were invented by Jack Kilby at Texas Instruments and Robert Noyce at Fairchild Semiconductor.[47] Kilby recorded his initial ideas concerning the integrated circuit in July 1958, successfully demonstrating the first working integrated example on 12 September 1958.[48] In his patent application of 6 February 1959, Kilby described his newdevice as “a body of semiconductor material ... wherein all the components of the electronic circuit are completely integrated.”[49][50] Noyce also came up with his own idea of an integrated circuit half a year later than Kilby.[51] His chip solved many practical problems that Kilby's had not. Produced at Fairchild Semiconductor, it was made of silicon, whereas Kilby's chip was made of germanium.

This new development heralded an explosion in the commercial and personal use of computers and led to the invention of the microprocessor. While the subject of exactly which device was the first microprocessor is contentious, partly due to lack ofagreement on the exact definition of the term "microprocessor", it is largely undisputed that the first single-chip microprocessor was the Intel 4004,[52] designed and realized by Ted Hoff, Federico Faggin, and Stanley Mazor at Intel.[53]

Mobile computers become dominant

With the continued miniaturization of computing resources, andadvancements in portable battery life, portable computers grewin popularity in the 2000s.[54] The same developments that spurred the growth of laptop computers and other portable computers allowed manufacturers to integrate computing resources into cellular phones. These so-called smartphones and tablets run on a variety of operating systems and have become the dominant computing device on the market, with manufacturers reporting having shipped an estimated 237 million devices in 2Q 2013.[55]

ProgramsThe defining feature of modern computers which distinguishes them from all other machines is that they can be programmed. That is to say that some type of instructions (the program)

can be given to the computer, and it will process them. Moderncomputers based on the von Neumann architecture often have machine code in the form of an imperative programming language.

In practical terms, a computer program may be just a few instructions or extend to many millions of instructions, as dothe programs for word processors and web browsers for example.A typical modern computer can execute billions of instructionsper second (gigaflops) and rarely makes a mistake over many years of operation. Large computer programs consisting of several million instructions may take teams of programmers years to write, and due to the complexity of the task almost certainly contain errors.

Stored program architecture

Main articles: Computer program and Computer programming

Replica of the Small-Scale Experimental Machine (SSEM), the world's first stored-program computer, at the Museum of Science and Industry in Manchester, England

This section applies to most common RAM machine-based computers.

In most cases, computer instructions are simple: add one number to another, move some data from one location to another, send a message to some external device, etc. These instructions are read from the computer's memory and are generally carried out (executed) in the order they were given.However, there are usually specialized instructions to tell the computer to jump ahead or backwards to some other place inthe program and to carry on executing from there. These are called “jump” instructions (or branches). Furthermore, jump instructions may be made to happen conditionally so that different sequences of instructions may be used depending on

the result of some previous calculation or some external event. Many computers directly support subroutines by providing a type of jump that “remembers” the location it jumped from and another instruction to return to the instruction following that jump instruction.

Program execution might be likened to reading a book. While a person will normally read each word and line in sequence, theymay at times jump back to an earlier place in the text or skipsections that are not of interest. Similarly, a computer may sometimes go back and repeat the instructions in some section of the program over and over again until some internal condition is met. This is called the flow of control within the program and it is what allows the computer to perform tasks repeatedly without human intervention.

Comparatively, a person using a pocket calculator can perform a basic arithmetic operation such as adding two numbers with just a few button presses. But to add together all of the numbers from 1 to 1,000 would take thousands of button pressesand a lot of time, with a near certainty of making a mistake. On the other hand, a computer may be programmed to do this with just a few simple instructions. The following example is written in the MIPS assembly language:

begin: addi $8, $0, 0 # initialize sum to 0 addi $9, $0, 1 # set first number to add = 1 loop: slti $10, $9, 1000 # check if the number is less than 1000 beq $10, $0, finish # if odd number is greater than n then exit add $8, $8, $9 # update sum addi $9, $9, 1 # get next number j loop # repeat the summing process finish: add $2, $8, $0 # put sum in output register

Once told to run this program, the computer will perform the repetitive addition task without further human intervention. It will almost never make a mistake and a modern PC can complete the task in a fraction of a second.

Machine code

In most computers, individual instructions are stored as machine code with each instruction being given a unique number(its operation code or opcode for short). The command to add two numbers together would have one opcode; the command to multiply them would have a different opcode, and so on. The simplest computers are able to perform any of a handful of different instructions; the more complex computers have several hundred to choose from, each with a unique numerical code. Since the computer's memory is able to store numbers, itcan also store the instruction codes. This leads to the important fact that entire programs (which are just lists of these instructions) can be represented as lists of numbers andcan themselves be manipulated inside the computer in the same way as numeric data. The fundamental concept of storing programs in the computer's memory alongside the data they operate on is the crux of the von Neumann, or stored program[citation needed], architecture. In some cases, a computer mightstore some or all of its program in memory that is kept separate from the data it operates on. This is called the Harvard architecture after the Harvard Mark I computer. Modernvon Neumann computers display some traits of the Harvard architecture in their designs, such as in CPU caches.

While it is possible to write computer programs as long lists of numbers (machine language) and while this technique was used with many early computers,[56] it is extremely tedious and potentially error-prone to do so in practice, especially for complicated programs. Instead, each basic instruction can be given a short name that is indicative of its function and easyto remember – a mnemonic such as ADD, SUB, MULT or JUMP. Thesemnemonics are collectively known as a computer's assembly language. Converting programs written in assembly language into something the computer can actually understand (machine language) is usually done by a computer program called an assembler.

A 1970s punched card containing one line from a FORTRAN program. The card reads: “Z(1) = Y + W(1)” and is labeled “PROJ039” for identification purposes.

Programming language

Main article: Programming language

Programming languages provide various ways of specifying programs for computers to run. Unlike natural languages, programming languages are designed to permit no ambiguity and to be concise. They are purely written languages and are oftendifficult to read aloud. They are generally either translated into machine code by a compiler or an assembler before being run, or translated directly at run time by an interpreter. Sometimes programs are executed by a hybrid method of the two techniques.

Low-level languages

Main article: Low-level programming language

Machine languages and the assembly languages that represent them (collectively termed low-level programming languages) tend to be unique to a particular type of computer. For instance, an ARM architecture computer (such as may be found in a PDA or a hand-held videogame) cannot understand the machine language ofan Intel Pentium or the AMD Athlon 64 computer that might be in a PC.[57]

High-level languages/Third Generation Language

Main article: High-level programming language

Though considerably easier than in machine language, writing long programs in assembly language is often difficult and is also error prone. Therefore, most practical programs are written in more abstract high-level programming languages thatare able to express the needs of the programmer more conveniently (and thereby help reduce programmer error). High level languages are usually “compiled” into machine language (or sometimes into assembly language and then into machine language) using another computer program called a compiler.[58]

High level languages are less related to the workings of the target computer than assembly language, and more related to the language and structure of the problem(s) to be solved by the final program. It is therefore often possible to use different compilers to translate the same high level language program into the machine language of many different types of computer. This is part of the means by which software like video games may be made available for different computer architectures such as personal computers and various video game consoles.

Fourth Generation Languages

These 4G languages are less procedural than 3G languages. The benefit of 4GL is that it provides ways to obtain information without requiring the direct help of a programmer. Example of 4GL is SQL.

Program design

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Program design of small programs is relatively simple and involves the analysis of the problem, collection of inputs, using the programming constructs within languages, devising orusing established procedures and algorithms, providing data for output devices and solutions to the problem as applicable.As problems become larger and more complex, features such as subprograms, modules, formal documentation, and new paradigms such as object-oriented programming are encountered. Large programs involving thousands of line of code and more require formal software methodologies. The task of developing large software systems presents a significant intellectual challenge. Producing software with an acceptably high reliability within a predictable schedule and budget has historically been difficult; the academic and professional discipline of software engineering concentrates specifically on this challenge.

Bugs

Main article: Software bug

The actual first computer bug, a moth found trapped on a relayof the Harvard Mark II computer

Errors in computer programs are called “bugs.” They may be benign and not affect the usefulness of the program, or have only subtle effects. But in some cases, they may cause the program or the entire system to “hang,” becoming unresponsive to input such as mouse clicks or keystrokes, to completely fail, or to crash. Otherwise benign bugs may sometimes be harnessed for malicious intent by an unscrupulous user writingan exploit, code designed to take advantage of a bug and disrupt a computer's proper execution. Bugs are usually not the fault of the computer. Since computers merely execute the instructions they are given, bugs are nearly always the resultof programmer error or an oversight made in the program's design.[59]

Admiral Grace Hopper, an American computer scientist and developer of the first compiler, is credited for having first used the term “bugs” in computing after a dead moth was found shorting a relay in the Harvard Mark II computer in September 1947.[60]

ComponentsMain articles: Central processing unit and Microprocessor

Play mediaVideo demonstrating the standard components of a "slimline" computer

A general purpose computer has four main components: the arithmetic logic unit (ALU), the control unit, the memory, andthe input and output devices (collectively termed I/O). These

parts are interconnected by buses, often made of groups of wires.

Inside each of these parts are thousands to trillions of smallelectrical circuits which can be turned off or on by means of an electronic switch. Each circuit represents a bit (binary digit) of information so that when the circuit is on it represents a “1”, and when off it represents a “0” (in positive logic representation). The circuits are arranged in logic gates so that one or more of the circuits may control the state of one or more of the other circuits.

Control unit

Main articles: CPU design and Control unit

Diagram showing how a particular MIPS architecture instructionwould be decoded by the control system

The control unit (often called a control system or central controller) manages the computer's various components; it reads and interprets (decodes) the program instructions, transforming them into control signals that activate other parts of the computer.[61] Control systems in advanced computersmay change the order of execution of some instructions to improve performance.

A key component common to all CPUs is the program counter, a special memory cell (a register) that keeps track of which location in memory the next instruction is to be read from.[62]

The control system's function is as follows—note that this is a simplified description, and some of these steps may be performed concurrently or in a different order depending on the type of CPU:

1. Read the code for the next instruction from the cell indicated by the program counter.

2. Decode the numerical code for the instruction into a set of commands or signals for each of the other systems.

3. Increment the program counter so it points to the next instruction.

4. Read whatever data the instruction requires from cells inmemory (or perhaps from an input device). The location ofthis required data is typically stored within the instruction code.

5. Provide the necessary data to an ALU or register.6. If the instruction requires an ALU or specialized

hardware to complete, instruct the hardware to perform the requested operation.

7. Write the result from the ALU back to a memory location or to a register or perhaps an output device.

8. Jump back to step (1).

Since the program counter is (conceptually) just another set of memory cells, it can be changed by calculations done in theALU. Adding 100 to the program counter would cause the next instruction to be read from a place 100 locations further downthe program. Instructions that modify the program counter are often known as “jumps” and allow for loops (instructions that are repeated by the computer) and often conditional instruction execution (both examples of control flow).

The sequence of operations that the control unit goes through to process an instruction is in itself like a short computer program, and indeed, in some more complex CPU designs, there is another yet smaller computer called a microsequencer, whichruns a microcode program that causes all of these events to happen.

Central Processing unit (CPU)

The control unit, ALU, and registers are collectively known asa central processing unit (CPU). Early CPUs were composed of many separate components but since the mid-1970s CPUs have typically been constructed on a single integrated circuit called a microprocessor.

Arithmetic logic unit (ALU)

Main article: Arithmetic logic unit

The ALU is capable of performing two classes of operations: arithmetic and logic.[63]

The set of arithmetic operations that a particular ALU supports may be limited to addition and subtraction, or might include multiplication, division, trigonometry functions such as sine, cosine, etc., and square roots. Some can only operateon whole numbers (integers) whilst others use floating point to represent real numbers, albeit with limited precision. However, any computer that is capable of performing just the simplest operations can be programmed to break down the more complex operations into simple steps that it can perform. Therefore, any computer can be programmed to perform any arithmetic operation—although it will take more time to do so if its ALU does not directly support the operation. An ALU mayalso compare numbers and return boolean truth values (true or false) depending on whether one is equal to, greater than or less than the other (“is 64 greater than 65?”).

Logic operations involve Boolean logic: AND, OR, XOR and NOT. These can be useful for creating complicated conditional statements and processing boolean logic.

Superscalar computers may contain multiple ALUs, allowing themto process several instructions simultaneously.[64] Graphics processors and computers with SIMD and MIMD features often contain ALUs that can perform arithmetic on vectors and matrices.

Memory

Main article: Computer data storage

Magnetic core memory was the computer memory of choice throughout the 1960s, until it was replaced by semiconductor memory.

A computer's memory can be viewed as a list of cells into which numbers can be placed or read. Each cell has a numbered “address” and can store a single number. The computer can be instructed to “put the number 123 into the cell numbered 1357”or to “add the number that is in cell 1357 to the number that is in cell 2468 and put the answer into cell 1595.” The information stored in memory may represent practically anything. Letters, numbers, even computer instructions can be placed into memory with equal ease. Since the CPU does not differentiate between different types of information, it is the software's responsibility to give significance to what thememory sees as nothing but a series of numbers.

In almost all modern computers, each memory cell is set up to store binary numbers in groups of eight bits (called a byte). Each byte is able to represent 256 different numbers (2^8 = 256); either from 0 to 255 or −128 to +127. To store larger numbers, several consecutive bytes may be used (typically, two, four or eight). When negative numbers are required, they are usually stored in two's complement notation. Other arrangements are possible, but are usually not seen outside ofspecialized applications or historical contexts. A computer can store any kind of information in memory if it can be represented numerically. Modern computers have billions or even trillions of bytes of memory.

The CPU contains a special set of memory cells called registers that can be read and written to much more rapidly than the main memory area. There are typically between two andone hundred registers depending on the type of CPU. Registers are used for the most frequently needed data items to avoid having to access main memory every time data is needed. As data is constantly being worked on, reducing the need to access main memory (which is often slow compared to the ALU and control units) greatly increases the computer's speed.

Computer main memory comes in two principal varieties:

random-access memory or RAM read-only memory or ROM

RAM can be read and written to anytime the CPU commands it, but ROM is preloaded with data and software that never

changes, therefore the CPU can only read from it. ROM is typically used to store the computer's initial start-up instructions. In general, the contents of RAM are erased when the power to the computer is turned off, but ROM retains its data indefinitely. In a PC, the ROM contains a specialized program called the BIOS that orchestrates loading the computer's operating system from the hard disk drive into RAM whenever the computer is turned on or reset. In embedded computers, which frequently do not have disk drives, all of the required software may be stored in ROM. Software stored inROM is often called firmware, because it is notionally more like hardware than software. Flash memory blurs the distinction between ROM and RAM, as it retains its data when turned off but is also rewritable. It is typically much slowerthan conventional ROM and RAM however, so its use is restricted to applications where high speed is unnecessary.[65]

In more sophisticated computers there may be one or more RAM cache memories, which are slower than registers but faster than main memory. Generally computers with this sort of cache are designed to move frequently needed data into the cache automatically, often without the need for any intervention on the programmer's part.

Input/output (I/O)

Main article: Input/output

Hard disk drives are common storage devices used with computers.

I/O is the means by which a computer exchanges information with the outside world.[66] Devices that provide input or outputto the computer are called peripherals.[67] On a typical personal computer, peripherals include input devices like the keyboard and mouse, and output devices such as the display andprinter. Hard disk drives, floppy disk drives and optical disc

drives serve as both input and output devices. Computer networking is another form of I/O.

I/O devices are often complex computers in their own right, with their own CPU and memory. A graphics processing unit might contain fifty or more tiny computers that perform the calculations necessary to display 3D graphics.[citation needed] Modern desktop computers contain many smaller computers that assist the main CPU in performing I/O.

Multitasking

Main article: Computer multitasking

While a computer may be viewed as running one gigantic programstored in its main memory, in some systems it is necessary to give the appearance of running several programs simultaneously. This is achieved by multitasking i.e. having the computer switch rapidly between running each program in turn.[68]

One means by which this is done is with a special signal called an interrupt, which can periodically cause the computerto stop executing instructions where it was and do something else instead. By remembering where it was executing prior to the interrupt, the computer can return to that task later. If several programs are running “at the same time,” then the interrupt generator might be causing several hundred interrupts per second, causing a program switch each time. Since modern computers typically execute instructions several orders of magnitude faster than human perception, it may appear that many programs are running at the same time even though only one is ever executing in any given instant. This method of multitasking is sometimes termed “time-sharing” since each program is allocated a “slice” of time in turn.[69]

Before the era of cheap computers, the principal use for multitasking was to allow many people to share the same computer.

Seemingly, multitasking would cause a computer that is switching between several programs to run more slowly, in direct proportion to the number of programs it is running, but

most programs spend much of their time waiting for slow input/output devices to complete their tasks. If a program is waiting for the user to click on the mouse or press a key on the keyboard, then it will not take a “time slice” until the event it is waiting for has occurred. This frees up time for other programs to execute so that many programs may be run simultaneously without unacceptable speed loss.

Multiprocessing

Main article: Multiprocessing

Cray designed many supercomputers that used multiprocessing heavily.

Some computers are designed to distribute their work across several CPUs in a multiprocessing configuration, a technique once employed only in large and powerful machines such as supercomputers, mainframe computers and servers. Multiprocessor and multi-core (multiple CPUs on a single integrated circuit) personal and laptop computers are now widely available, and are being increasingly used in lower-endmarkets as a result.

Supercomputers in particular often have highly unique architectures that differ significantly from the basic stored-program architecture and from general purpose computers.[70] They often feature thousands of CPUs, customized high-speed interconnects, and specialized computing hardware. Such designs tend to be useful only for specialized tasks due to the large scale of program organization required to successfully utilize most of the available resources at once. Supercomputers usually see usage in large-scale simulation, graphics rendering, and cryptography applications, as well as with other so-called “embarrassingly parallel” tasks.

Networking and the InternetMain articles: Computer networking and Internet

Visualization of a portion of the routes on the Internet

Computers have been used to coordinate information between multiple locations since the 1950s. The U.S. military's SAGE system was the first large-scale example of such a system, which led to a number of special-purpose commercial systems such as Sabre.[71]

In the 1970s, computer engineers at research institutions throughout the United States began to link their computers together using telecommunications technology. The effort was funded by ARPA (now DARPA), and the computer network that resulted was called the ARPANET.[72] The technologies that made the Arpanet possible spread and evolved.

In time, the network spread beyond academic and military institutions and became known as the Internet. The emergence of networking involved a redefinition of the nature and boundaries of the computer. Computer operating systems and applications were modified to include the ability to define and access the resources of other computers on the network, such as peripheral devices, stored information, and the like, as extensions of the resources of an individual computer. Initially these facilities were available primarily to people working in high-tech environments, but in the 1990s the spreadof applications like e-mail and the World Wide Web, combined with the development of cheap, fast networking technologies like Ethernet and ADSL saw computer networking become almost ubiquitous. In fact, the number of computers that are

networked is growing phenomenally. A very large proportion of personal computers regularly connect to the Internet to communicate and receive information. “Wireless” networking, often utilizing mobile phone networks, has meant networking isbecoming increasingly ubiquitous even in mobile computing environments.

Computer architecture paradigms

There are many types of computer architectures:

Quantum computer vs Chemical computer Scalar processor vs Vector processor Non-Uniform Memory Access (NUMA) computers Register machine vs Stack machine Harvard architecture vs von Neumann architecture Cellular architecture

Of all these abstract machines, a quantum computer holds the most promise for revolutionizing computing.[73]

Logic gates are a common abstraction which can apply to most of the above digital or analog paradigms.

The ability to store and execute lists of instructions called programs makes computers extremely versatile, distinguishing them from calculators. The Church–Turing thesis is a mathematical statement of this versatility: any computer with a minimum capability (being Turing-complete) is, in principle,capable of performing the same tasks that any other computer can perform. Therefore, any type of computer (netbook, supercomputer, cellular automaton, etc.) is able to perform the same computational tasks, given enough time and storage capacity.

MisconceptionsMain articles: Human computer and Harvard Computers

Women as computers in NACA High Speed Flight Station "Computer Room"

A computer does not need to be electronic, nor even have a processor, nor RAM, nor even a hard disk. While popular usage of the word “computer” is synonymous with a personal electronic computer, the modern[74] definition of a computer is literally “A device that computes, especially a programmable [usually] electronic machine that performs high-speed mathematical or logical operations or that assembles, stores, correlates, or otherwise processes information.”[75] Any device which processes information qualifies as a computer, especially if the processing is purposeful. Even a human is a computer, in this sense.

Unconventional computing

Main article: Unconventional computing

Historically, computers evolved from mechanical computers and eventually from vacuum tubes to transistors. However, conceptually computational systems as flexible as a personal computer can be built out of almost anything. For example, a computer can be made out of billiard balls (billiard ball computer); an often quoted example.[citation needed] More realistically, modern computers are made out of transistors made of photolithographed semiconductors.

FutureThere is active research to make computers out of many promising new types of technology, such as optical computers, DNA computers, neural computers, and quantum computers. Most computers are universal, and are able to calculate any computable function, and are limited only by their memory

capacity and operating speed. However different designs of computers can give very different performance for particular problems; for example quantum computers can potentially break some modern encryption algorithms (by quantum factoring) very quickly.

Further topics Glossary of computers

Artificial intelligence

A computer will solve problems in exactly the way it is programmed to, without regard to efficiency, alternative solutions, possible shortcuts, or possible errors in the code.Computer programs that learn and adapt are part of the emerging field of artificial intelligence and machine learning.

HardwareMain articles: Computer hardware and Personal computer hardware

The term hardware covers all of those parts of a computer that are tangible objects. Circuits, displays, power supplies, cables, keyboards, printers and mice are all hardware.

History of computing hardware

Main article: History of computing hardware

First generation (mechanical/electromechanical)

Calculators

Pascal's calculator, Arithmometer, Difference engine, Quevedo's analytical machines

Programmable devices

Jacquard loom, Analytical engine, IBM ASCC/Harvard MarkI, Harvard Mark II, IBM SSEC, Z1, Z2, Z3

Second generation Calculators Atanasoff–Berry

(vacuum tubes)

Computer, IBM 604, UNIVAC 60, UNIVAC 120

Programmable devices

Colossus, ENIAC, Manchester Small-Scale Experimental Machine, EDSAC, Manchester Mark 1, Ferranti Pegasus, Ferranti Mercury, CSIRAC, EDVAC, UNIVACI, IBM 701, IBM 702, IBM 650, Z22

Third generation (discrete transistors and SSI, MSI, LSI integrated circuits)

Mainframes IBM 7090, IBM 7080, IBM System/360, BUNCH

MinicomputerPDP-8, PDP-11, IBM System/32, IBM System/36

Fourth generation (VLSI integrated circuits)

Minicomputer VAX, IBM System i4-bit microcomputer

Intel 4004, Intel 4040

8-bit microcomputer

Intel 8008, Intel 8080, Motorola 6800, Motorola 6809, MOS Technology 6502, Zilog Z80

16-bit microcomputer

Intel 8088, Zilog Z8000, WDC 65816/65802

32-bit microcomputer

Intel 80386, Pentium,Motorola 68000, ARM

64-bit microcomputer[76]

Alpha, MIPS, PA-RISC,PowerPC, SPARC, x86-64, ARMv8-A

Embedded computer Intel 8048, Intel 8051Personal computer Desktop computer,

Home computer, Laptopcomputer, Personal digital assistant (PDA), Portable computer, Tablet PC,

Wearable computer

Theoretical/experimental

Quantum computer,Chemical computer, DNA computing, Optical computer,Spintronics basedcomputer

Other hardware topics

Peripheral device (input/output)

InputMouse, keyboard, joystick, image scanner, webcam, graphicstablet, microphone

Output Monitor, printer, loudspeaker

BothFloppy disk drive, hard disk drive, optical disc drive, teleprinter

Computer buses

Short range RS-232, SCSI, PCI, USBLong range (computer networking)

Ethernet, ATM, FDDI

SoftwareMain article: Computer software

Software refers to parts of the computer which do not have a material form, such as programs, data, protocols, etc. When software is stored in hardware that cannot easily be modified (such as BIOS ROM in an IBM PC compatible), it is sometimes called “firmware.”

Operating system /System Software

Unix and BSDUNIX System V, IBM AIX, HP-UX, Solaris(SunOS), IRIX, List of BSD operating systems

GNU/Linux List of Linux distributions, Comparison of Linux distributions

Microsoft Windows

Windows 95, Windows 98, Windows NT, Windows 2000, Windows Me, Windows XP, Windows Vista, Windows 7, Windows 8

DOS 86-DOS (QDOS), IBM PC DOS, MS-DOS, DR-DOS, FreeDOS

Mac OS Mac OS classic, Mac OS XEmbedded andreal-time List of embedded operating systems

Experimental Amoeba, Oberon/Bluebottle, Plan 9 fromBell Labs

LibraryMultimedia DirectX, OpenGL, OpenALProgramming library

C standard library, Standard Template Library

Data Protocol TCP/IP, Kermit, FTP, HTTP, SMTPFile format HTML, XML, JPEG, MPEG, PNG

User interface

Graphical user interface (WIMP)

Microsoft Windows, GNOME, KDE, QNX Photon, CDE, GEM, Aqua

Text-based user interface

Command-line interface, Text user interface

ApplicationSoftware

Office suite

Word processing, Desktop publishing, Presentation program, Database management system, Scheduling & Time management, Spreadsheet, Accounting software

Internet Access

Browser, E-mail client, Web server, Mail transfer agent, Instant messaging

Design and manufacturing

Computer-aided design, Computer-aided manufacturing, Plant management, Robotic manufacturing, Supply chain management

Graphics

Raster graphics editor, Vector graphics editor, 3D modeler, Animationeditor, 3D computer graphics, Video editing, Image processing

AudioDigital audio editor, Audio playback, Mixing, Audio synthesis, Computer music

Software engineering

Compiler, Assembler, Interpreter, Debugger, Text editor, Integrated development environment, Software performance analysis, Revision

control, Software configuration management

Educational Edutainment, Educational game, Seriousgame, Flight simulator

Games

Strategy, Arcade, Puzzle, Simulation, First-person shooter, Platform, Massively multiplayer, Interactive fiction

Misc

Artificial intelligence, Antivirus software, Malware scanner, Installer/Package management systems, File manager

LanguagesThere are thousands of different programming languages—some intended to be general purpose, others useful only for highly specialized applications.

Programming languages

Lists of programming languages

Timeline of programming languages, List of programming languages by category, Generational list of programming languages, List of programming languages, Non-English-based programming languages

Commonly used assembly languages

ARM, MIPS, x86

Commonly used high-level programming languages

Ada, BASIC, C, C++, C#, COBOL, Fortran, Java, Lisp, Pascal, Object Pascal

Commonly used scripting languages

Bourne script, JavaScript, Python, Ruby, PHP, Perl

Firmware

Firmware is the technology which has the combination of both hardware and software such as BIOS chip inside a computer.this

chip(hardware) is located on the motherboard and has the BIOS set up (software) stored in it.

Liveware

At times the user working on the system are termed as Liveware.

Types of computersComputer can be classified based on their uses

Based on uses

Analog compute r Digital computer Hybrid computer

Based on sizes

Micro computer Personal computer Mini Computer Mainframe computer Super computer

Input DevicesWhen unprocessed data goes to computer with the help of input devices and get output after the data has been processed.the input devices may be hand operated or automated. The act of processing is mainly regulated by CPU.Hand operated input devices are

Concept keyboard Track Ball Joysticks Digital Camera Microphone Touch Screen Video Digital Scanner

Graphic Tablet Keyboard Mouse

Output DevicesThe means through which computer gives output are known as output devices. Some of the output devices are:

Monitor Printer Projector Sound card Speaker Video card

Professions and organizationsAs the use of computers has spread throughout society, there are an increasing number of careers involving computers.

Computer-related professions

Hardware-related

Electrical engineering, Electronic engineering, Computer engineering, Telecommunications engineering, Optical engineering, Nanoengineering

Software-related

Computer science, Computer engineering, Desktop publishing, Human–computer interaction, Information technology, Information systems, Computational science, Software engineering, Video game industry, Web design

The need for computers to work well together and to be able toexchange information has spawned the need for many standards organizations, clubs and societies of both a formal and informal nature.

OrganizationsStandards groups ANSI, IEC, IEEE, IETF, ISO, W3CProfessional societies ACM, AIS, IET, IFIP, BCS

Free/open source software groups

Free Software Foundation, Mozilla Foundation, Apache Software Foundation

"Encrypt" redirects here. For the film, see Encrypt (film).This article is about algorithms for encryption and decryption. For an overview of cryptographic technology in general, see Cryptography.

In cryptography, encryption is the process of encoding messages or information in such a way that only authorized parties can read it.[1] Encryption does not of itself prevent interception, but denies the message content to the interceptor.[2]:374 In an encryption scheme, the intended communication information or message, referred to as plaintext, is encrypted using an encryption algorithm, generating ciphertext that can only be read if decrypted.[2] For technical reasons, an encryption scheme usually uses a pseudo-random encryption key generated by an algorithm. It is in principle possible to decrypt the message without possessing the key, but, for a well-designed encryption scheme, large computational resources and skill are required. An authorized recipient can easily decrypt the message with the key provided by the originator to recipients, but not to unauthorized interceptors.

Contents 1 Types of encryption

o 1.1 Symmetric key encryption o 1.2 Public key encryption

2 Uses of encryption o 2.1 Message verification

3 See also 4 References 5 Further reading

Types of encryptionSymmetric key encryption

In symmetric-key schemes,[3] the encryption and decryption keysare the same. Communicating parties must have the same key before they can achieve secure communication.

Public key encryption

Illustration of how a file or document is sent using Public key encryption.

In public-key encryption schemes, the encryption key is published for anyone to use and encrypt messages. However, only the receiving party has access to the decryption key thatenables messages to be read.[4] Public-key encryption was firstdescribed in a secret document in 1973;[5] before then all encryption schemes were symmetric-key (also called private-key).[2]:478

A publicly available public key encryption application called Pretty Good Privacy (PGP) was written in 1991 by Phil Zimmermann, and distributed free of charge with source code; it was purchased by Symantec in 2010 and is regularly updated.[6]

Uses of encryptionEncryption has long been used by military and governments to facilitate secret communication. It is now commonly used in protecting information within many kinds of civilian systems. For example, the Computer Security Institute reported that in 2007, 71% of companies surveyed utilized encryption for some of their data in transit, and 53% utilized encryption for someof their data in storage.[7] Encryption can be used to protect data "at rest", such as information stored on computers and storage devices (e.g. USB flash drives). In recent years therehave been numerous reports of confidential data such as customers' personal records being exposed through loss or theft of laptops or backup drives. Encrypting such files at rest helps protect them should physical security measures fail. Digital rights management systems, which prevent unauthorized use or reproduction of copyrighted material and protect software against reverse engineering (see also copy protection), is another somewhat different example of using encryption on data at rest.[8]

Encryption is also used to protect data in transit, for example data being transferred via networks (e.g. the Internet, e-commerce), mobile telephones, wireless microphones, wireless intercom systems, Bluetooth devices and bank automatic teller machines. There have been numerous reports of data in transit being intercepted in recent years.[9] Data should also be encrypted when transmitted across networks in order to protect against eavesdropping of network traffic by unauthorized users.[10]

Message verification

Encryption, by itself, can protect the confidentiality of messages, but other techniques are still needed to protect theintegrity and authenticity of a message; for example, verification of a message authentication code (MAC) or a digital signature. Standards for cryptographic software and hardware to perform encryption are widely available, but successfully using encryption to ensure security may be a challenging problem. A single error in system design or execution can allow successful attacks. Sometimes an adversarycan obtain unencrypted information without directly undoing the encryption. See, e.g., traffic analysis, TEMPEST, or Trojan horse.[11]

Digital signature and encryption must be applied to the ciphertext when it is created (typically on the same device used to compose the message) to avoid tampering; otherwise anynode between the sender and the encryption agent could potentially tamper with it. Encrypting at the time of creatioFor other uses, see Nonsense (disambiguation).

For Wikipedia policy regarding nonsense, see Wikipedia:Patent nonsense.

This article needs additional citations for verification.Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (September 2008)

Nonsense is a communication, via speech, writing, or any othersymbolic system, that lacks any coherent meaning. Sometimes inordinary usage, nonsense is synonymous with absurdity or the

ridiculous. Many poets, novelists and songwriters have used nonsense in their works, often creating entire works using it for reasons ranging from pure comic amusement or satire, to illustrating a point about language or reasoning. In the philosophy of language and philosophy of science, nonsense is distinguished from sense or meaningfulness, and attempts have been made to come up with a coherent and consistent method of distinguishing sense from nonsense. It is also an important field of study in cryptography regarding separating a signal from noise.

Contents 1 Literary nonsense

o 1.1 Nonsense verse 1.1.1 Examples

2 Philosophy of language and of science o 2.1 Logical positivism o 2.2 Wittgenstein

3 Cryptography 4 Teaching machines to talk nonsense 5 See also 6 Notes 7 References 8 External links

Literary nonsense

A Book of Nonsense (ca. 1875 James Miller edition) by Edward LearMain article: Literary nonsense

The phrase "Colorless green ideas sleep furiously" was coined by Noam Chomsky as an example of nonsense. However, this can be easily confused with poetic symbolism. The individual words make sense and are arranged according to proper grammatical

rules, yet the result is nonsense. The inspiration for this attempt at creating verbal nonsense came from the idea of contradiction and seemingly irrelevant and/or incompatible characteristics, which conspire to make the phrase meaningless, but is open to interpretation. The phrase "the square root of Tuesday" (not a similar example; the lemondrop sunshine is more comparable)[vague] operates on the latter principle. This principle is behind the inscrutability of the kōan "What is the sound of one hand clapping?", where one hand would presumably be insufficient for clapping without the intervention of another.

James Joyce’s final novel Finnegans Wake also uses nonsense: full of portmanteau and strong words, it appears to be pregnantwith multiple layers of meaning, but in many passages it is difficult to say whether any one human’s interpretation of a text could be the intended or unintended one.

Nonsense verse

Jabberwocky, a poem (of nonsense verse) found in Through the Looking-Glass, and What Alice Found There by Lewis Carroll (1871), is anonsense poem written in the English language. The word jabberwocky is also occasionally used as a synonym of nonsense.[citation needed]

Nonsense verse is the verse form of literary nonsense, a genrethat can manifest in many other ways. Its best-known exponent is Edward Lear, author of The Owl and the Pussycat and hundreds of limericks.

Nonsense verse is part of a long line of tradition predating Lear: the nursery rhyme Hey Diddle Diddle could also be termed a nonsense verse. There are also some works which appear to be nonsense verse, but actually are not, such as the popular 1940s song Mairzy Doats.

Lewis Carroll, seeking a nonsense riddle, once posed the question How is a raven like a writing desk?. Someone answered him, Because Poe wrote on both. However, there are other possible answers (e.g. both have inky quills).

Lines of nonsense frequently figure in the refrains of folksongs, where nonsense riddles and knock-knock jokes are often encountered.

Examples

The first verse of Jabberwocky by Lewis Carroll;

'Twas brillig, and the slithy tovesDid gyre and gimble in the wabe;All mimsy were the borogoves,And the mome raths outgrabe.

The first four lines of On the Ning Nang Nong by Spike Milligan;[1]

On the Ning Nang NongWhere the cows go Bong!and the monkeys all say BOO!There's a Nong Nang Ning

The first verse of Spirk Troll-Derisive by James Whitcomb Riley;[2]

The Crankadox leaned o'er the edge of the moon,And wistfully gazed on the seaWhere the Gryxabodill madly whistled a tuneTo the air of "Ti-fol-de-ding-dee."

The first four lines of The Mayor of Scuttleton by Mary Mapes Dodge;[2]

The Mayor of Scuttleton burned his noseTrying to warm his copper toes;He lost his money and spoiled his willBy signing his name with an icicle quill;

The first four lines of Oh Freddled Gruntbuggly by Prostetnic Vogon Jeltz; a creation of Douglas Adams

Oh freddled gruntbuggly,Thy micturations are to meAs plurdled gabbleblotchits on a lurgid bee.Groop I implore thee, my foonting turlingdromes

Philosophy of language and of scienceFurther information: Sense

In the philosophy of language and the philosophy of science, nonsense refers to a lack of sense or meaning. Different technical definitions of meaning delineate sense from nonsense.

Logical positivism

Further information: Logical positivism

Wittgenstein

Further information: Ludwig Wittgenstein

In Ludwig Wittgenstein's writings, the word "nonsense" carriesa special technical meaning which differs significantly from the normal use of the word. In this sense, "nonsense" does notrefer to meaningless gibberish, but rather to the lack of sense in the context of sense and reference. In this context, logical tautologies, and purely mathematical propositions may be regarded as "nonsense". For example, "1+1=2" is a nonsensical proposition.[3] Wittgenstein wrote in Tractatus Logico Philosophicus that some of the propositions contained in his own book should be regarded as nonsense.[4] Used in thisway, "nonsense" does not necessarily carry negative connotations.

Starting from Wittgenstein, but through an original perspective, the Italian philosopher Leonardo Vittorio Arena, in his book Nonsense as the meaning, highlights this positive meaning of nonsense to undermine every philosophical conception which does not take note of the absolute lack of meaning of the world and life. Nonsense implies the destruction of all views or opinions, on the wake of the Indian Buddhist philosopher Nagarjuna. In the name of nonsense, it is finally refused the conception of duality and the Aristotelian formal logic.

Cryptography

The problem of distinguishing sense from nonsense is importantin cryptography and other intelligence fields. For example, they need to distinguish signal from noise. Cryptanalysts havedevised algorithms to determine whether a given text is in fact nonsense or not. These algorithms typically analyze the presence of repetitions and redundancy in a text; in meaningful texts, certain frequently used words recur, for example, the, is and and in a text in the English language. A random scattering of letters, punctuation marks and spaces do not exhibit these regularities. Zipf's law attempts to state this analysis mathematically. By contrast, cryptographers typically seek to make their cipher texts resemble random distributions, to avoid telltale repetitions and patterns which may give an opening for cryptanalysis.

It is harder for cryptographers to deal with the presence or absence of meaning in a text in which the level of redundancy and repetition is higher than found in natural languages (for example, in the mysterious text of the Voynich manuscript).

Teaching machines to talk nonsenseScientists have attempted to teach machines to produce nonsense. The Markov chain technique is one method which has been used to generate texts by algorithm and randomizing techniques that seem meaningful. Another method is sometimes called the Mad Libs method: it involves the creation of templates for various sentence structures, and filling in the blanks with noun phrases or verb phrases; these phrase-generation procedures can be looped to add recursion, giving the output the appearance of greater complexity and sophistication. Racter was a computer program which generated nonsense texts by this method; however, Racter’s book, The Policeman’s Beard is Half Constructed, proved to have been the product of heavy human editing of the program's output.

n is only secure if the encryption device itself has not been tampered with.

The war drew in all the world's economic great powers,[6] assembled in two opposing alliances: the Allies (based on the Triple Entente of the United Kingdom, France and the Russian

Empire) and the Central Powers of Germany and Austria-Hungary.Although Italy had also been a member of the Triple Alliance alongside Germany and Austria-Hungary, it did not join the Central Powers, as Austria-Hungary had taken the offensive against the terms of the alliance.[7] These alliances were reorganised and expanded as more nations entered the war: Italy, Japan and the United States joined the Allies, and the Ottoman Empire and Bulgaria the Central Powers. More than 70 million military personnel, including 60 million Europeans,were mobilised in one of the largest wars in history.[8][9] The trigger for war was the 28 June 1914 assassination of ArchdukeFranz Ferdinand of Austria, heir to the throne of Austria-Hungary, by Yugoslav nationalist Gavrilo Princip in Sarajevo. This set off a diplomatic crisis when Austria-Hungary delivered an ultimatum to the Kingdom of Serbia,[10][11] and entangled international alliances formed over the previous decades were invoked. Within weeks, the major powers were at war and the conflict soon spread around the world.

On 28 July, the Austro-Hungarians declared war on Serbia and subsequently invaded.[12][13] As Russia mobilised in support of Serbia, Germany invaded neutral Belgium and Luxembourg before moving towards France, leading Britain to declare war on Germany. After the German march on Paris was halted, what became known as the Western Front settled into a battle of attrition, with a trench line that would change little until 1917. Meanwhile, on the Eastern Front, the Russian army was successful against the Austro-Hungarians, but was stopped in its invasion of East Prussia by the Germans. In November 1914,the Ottoman Empire joined the Central Powers, opening fronts in the Caucasus, Mesopotamia and the Sinai. Italy joined the Allies in 1915 and Bulgaria joined the Central Powers in the same year, while Romania joined the Allies in 1916, and the United States joined the Allies in 1917.

The Russian government collapsed in March 1917, and a subsequent revolution in November brought the Russians to terms with the Central Powers via the Treaty of Brest Litovsk,which constituted a massive German victory until nullified by the 1918 victory of the Western allies. After a stunning Spring 1918 German offensive along the Western Front, the Allies rallied and drove back the Germans in a series of

successful offensives. On 4 November 1918, the Austro-Hungarian empire agreed to an armistice, and Germany, which had its own trouble with revolutionaries, agreed to an armistice on 11 November 1918, ending the war in victory for the Allies.

By the end of the war, the German Empire, Russian Empire, Austro-Hungarian Empire and the Ottoman Empire had ceased to exist. National borders were redrawn, with several independentnations restored or created, and Germany's colonies were parceled out among the winners. During the Paris Peace conference of 1919, the Big Four (Britain, France, the United States and Italy) imposed their terms in a series of treaties.The League of Nations was formed with the aim of preventing any repetition of such a conflict. This, however, failed with weakened states, economic depression, renewed European nationalism, and the German feeling of humiliation contributing to the rise of Nazism. These conditions eventually contributed to World War II.

Contents 1 Etymology 2 Background

o 2.1 Political and military allianceso 2.2 Arms raceo 2.3 Conflicts in the Balkans

3 Prelude o 3.1 Sarajevo assassinationo 3.2 Escalation of violence in Bosnia and Herzegovinao 3.3 July Crisis

4 Progress of the war o 4.1 Opening hostilities

4.1.1 Confusion among the Central Powers 4.1.2 Serbian campaign 4.1.3 German forces in Belgium and France 4.1.4 Asia and the Pacific 4.1.5 African campaigns 4.1.6 Indian support for the Allies

o 4.2 Western Front 4.2.1 Trench warfare begins 4.2.2 Continuation of trench warfare

o 4.3 Naval waro 4.4 Southern theatres

4.4.1 War in the Balkans 4.4.2 Ottoman Empire 4.4.3 Italian participation 4.4.4 Romanian participation

o 4.5 Eastern Front 4.5.1 Initial actions 4.5.2 Russian Revolution 4.5.3 Czechoslovak Legion

o 4.6 Central Powers peace overtureso 4.7 1917–1918

4.7.1 Developments in 1917 4.7.2 Ottoman Empire conflict, 1917–1918 4.7.3 Entry of the United States 4.7.4 German Spring Offensive of 1918 4.7.5 New states under war zone

o 4.8 Allied victory: summer 1918 onwards 4.8.1 Hundred Days Offensive 4.8.2 Armistices and capitulations

5 Aftermath o 5.1 Formal end of the waro 5.2 Peace treaties and national boundarieso 5.3 National identitieso 5.4 Health effects

6 Technology o 6.1 Ground warfareo 6.2 Navalo 6.3 Aviation

7 War crimes o 7.1 Baralong incidentso 7.2 HMHS Llandovery Castleo 7.3 Chemical weapons in warfareo 7.4 Genocide and ethnic cleansing

7.4.1 Russian Empireo 7.5 Rape of Belgium

8 Soldiers' experiences o 8.1 Prisoners of waro 8.2 Military attachés and war correspondents

9 Support and opposition to the war o 9.1 Supporto 9.2 Opposition

9.2.1 Conscription 10 Legacy and memory

o 10.1 Historiographyo 10.2 Memorialso 10.3 Cultural memoryo 10.4 Social traumao 10.5 Discontent in Germanyo 10.6 Economic effects

11 Media 12 See also 13 Footnotes 14 Notes 15 References

o 15.1 Primary sourceso 15.2 Historiography and memory

16 External links o 16.1 Animated mapso 16.2 Library guides

EtymologyFrom the time of its start until the approach of World War II,it was called simply the World War or the Great War and thereafter the First World War or World War I.[14][15]

In Canada, Maclean's Magazine in October 1914 said, "Some wars name themselves. This is the Great War."[16] During the Interwarperiod (1918–1939), the war was most often called the World Warand the Great War in English-speaking countries.

The term "First World War" was first used in September 1914 bythe German philosopher Ernst Haeckel, who claimed that "there is no doubt that the course and character of the feared 'European War' ... will become the first world war in the fullsense of the word."[17] After the onset of the Second World War in 1939, the terms World War I or the First World War became standard, with British and Canadian historians favouring the First World War, and Americans World War I.

BackgroundMain article: Causes of World War I

Military alliances leading to World War I; Triple Entente in green; Central Powers in brown

Political and military alliances

In the 19th century, the major European powers had gone to great lengths to maintain a balance of power throughout Europe, resulting in the existence of a complex network of political and military alliances throughout the continent by 1900.[7] These had started in 1815, with the Holy Alliance between Prussia, Russia, and Austria. Then, in October 1873, German Chancellor Otto von Bismarck negotiated the League of the Three Emperors (German: Dreikaiserbund) between the monarchs of Austria-Hungary, Russia and Germany. This agreement failed because Austria-Hungary and Russia could not agree over Balkanpolicy, leaving Germany and Austria-Hungary in an alliance formed in 1879, called the Dual Alliance. This was seen as a method of countering Russian influence in the Balkans as the Ottoman Empire continued to weaken.[7] In 1882, this alliance was expanded to include Italy in what became the Triple Alliance.[18]

Bismarck had especially worked to hold Russia at Germany's side to avoid a two-front war with France and Russia. When Wilhelm II ascended to the throne as German Emperor (Kaiser), Bismarck was compelled to retire and his system of alliances was gradually de-emphasised. For example, the Kaiser refused to renew the Reinsurance Treaty with Russia in 1890. Two yearslater, the Franco-Russian Alliance was signed to counteract the force of the Triple Alliance. In 1904, Britain signed a series of agreements with France, the Entente Cordiale, and in1907, Britain and Russia signed the Anglo-Russian Convention. While these agreements did not formally ally Britain with France or Russia, they made British entry into any future

conflict involving France or Russia a possibility, and the system of interlocking bilateral agreements became known as the Triple Entente.[7]

Arms race

German industrial and economic power had grown greatly after unification and the foundation of the Empire in 1871 followingthe Franco-Prussian War. From the mid-1890s on, the governmentof Wilhelm II used this base to devote significant economic resources for building up the Kaiserliche Marine (Imperial German Navy), established by Admiral Alfred von Tirpitz, in rivalry with the British Royal Navy for world naval supremacy.[19] As a result, each nation strove to out-build the other in capital ships. With the launch of HMS   Dreadnought in 1906, the British Empire expanded on its significant advantage over its German rival.[19] The arms race between Britain and Germany eventually extended to the rest of Europe, with all the major powers devoting their industrial base to producing the equipment and weapons necessary for a pan-European conflict.[20] Between 1908 and 1913, the military spending of the European powers increased by 50%.[21]

Sarajevo citizens reading a poster with the proclamation of the Austrian annexation in 1908.

Conflicts in the Balkans

Austria-Hungary precipitated the Bosnian crisis of 1908–1909 by officially annexing the former Ottoman territory of Bosnia and Herzegovina, which it had occupied since 1878. This angered the Kingdom of Serbia and its patron, the Pan-Slavic and Orthodox Russian Empire.[22] Russian political manoeuvring in the region destabilised peace accords, which were already

fracturing in what was known as the "powder keg of Europe".[22] In 1912 and 1913, the First Balkan War was fought between the Balkan League and the fracturing Ottoman Empire. The resultingTreaty of London further shrank the Ottoman Empire, creating an independent Albanian State while enlarging the territorial holdings of Bulgaria, Serbia, Montenegro, and Greece. When Bulgaria attacked Serbia and Greece on 16 June 1913, it lost most of Macedonia to Serbia and Greece and Southern Dobruja toRomania in the 33-day Second Balkan War, further destabilisingthe region.[23]

Prelude

This picture is usually associated with the arrest of Gavrilo Princip, although some[24][25] believe it depicts Ferdinand Behr, a bystander.

Sarajevo assassination

Main article: Assassination of Archduke Franz Ferdinand

On 28 June 1914, Austrian Archduke Franz Ferdinand visited theBosnian capital, Sarajevo. A group of six assassins (Cvjetko Popović, Gavrilo Princip, Muhamed Mehmedbašić, Nedeljko Čabrinović, Trifko Grabež, Vaso Čubrilović) from the nationalist group Mlada Bosna, supplied by the Black Hand, hadgathered on the street where the Archduke's motorcade would pass. Čabrinović threw a grenade at the car, but missed. Some nearby were injured by the blast, but Franz Ferdinand's convoycarried on. The other assassins failed to act as the cars drove past them. About an hour later, when Franz Ferdinand wasreturning from a visit at the Sarajevo Hospital with those wounded in the assassination attempt, the convoy took a wrong turn into a street where, by coincidence, Princip stood. With a pistol, Princip shot and killed Franz Ferdinand and his wife

Sophie. The reaction among the people in Austria was mild, almost indifferent. As historian Zbyněk Zeman later wrote, "the event almost failed to make any impression whatsoever. OnSunday and Monday (28 and 29 June), the crowds in Vienna listened to music and drank wine, as if nothing had happened."[26][27]

Crowds on the streets in the aftermath of the anti-Serb riots in Sarajevo, 29 June 1914.

Escalation of violence in Bosnia and Herzegovina

Main articles: Anti-Serb riots in Sarajevo and Schutzkorps

However, in Sarajevo itself, Austrian authorities encouraged violence against the Serb residents, which resulted in anti-Serb riots in Sarajevo, in which Croats and Bosnian Muslims killed two ethnic Serbs and damaged numerous Serb-owned buildings.[28][29] The events have been described as having the characteristics of a pogrom. Writer Ivo Andrić referred to theviolence as the "Sarajevo frenzy of hate."[30] Violent actions against ethnic Serbs were organized not only in Sarajevo, but also in many other large Austro-Hungarian cities in modern-dayCroatia, and Bosnia and Herzegovina.[31] Austro-Hungarian authorities in Bosnia and Herzegovina imprisoned and extradited approximately 5,500 prominent Serbs, 700 to 2,200 of whom died in prison. A further 460 Serbs were sentenced to death and a predominantly Muslim special militia known as the Schutzkorps was established and carried out the persecution of Serbs.[32][33][34][35]

July Crisis

Main article: July Crisis

The assassination led to a month of diplomatic manoeuvring between Austria-Hungary, Germany, Russia, France, and Britain called the July Crisis. Believing correctly that Serbian officials (especially the officers of the Black Hand) were involved in the plot to murder the Archduke, and wanting to finally end Serbian interference in Bosnia,[36] Austria-Hungary delivered to Serbia on 23 July the July Ultimatum, a series often demands that were made intentionally unacceptable, in an effort to provoke a war with Serbia.[37] The next day, after theCouncil of Ministers of Russia was held under the chairmanshipof the Tsar at Krasnoe Selo, Russia ordered general mobilization for Odessa, Kiev, Kazan and Moscow military districts and fleets of the Baltic and the Black Sea. They also asked for other regions to accelerate preparations for general mobilization. Serbia decreed general mobilization on the 25th and that night, declared that they accepted all the terms of the ultimatum, except the one claiming that Austrian investigators visit the country. Following this, Austria brokeoff diplomatic relations with Serbia, and the next day ordereda partial mobilization. Finally, on 28 July 1914, Austria-Hungary declared war on Serbia.

On 29 July, Russia in support of its Serb protégé, unilaterally declared – outside of the conciliation procedure provided by the Franco-Russian military agreements – partial mobilization against Austria-Hungary. German Chancellor Bethmann-Hollweg was then allowed until the 31st for an appropriate response. On the 30th, Russia ordered general mobilization against Germany. In response, the following day, Germany declared a "state of danger of war." This also led to the general mobilization in Austria-Hungary on 4 August. Kaiser Wilhelm II asked his cousin, Tsar Nicolas II, to suspend the Russian general mobilization. When he refused, Germany issued an ultimatum demanding the arrest of its mobilization and commitment not to support Serbia. Another wassent to France, asking her not to support Russia if it were tocome to the defence of Serbia. On 1 August, after the Russian response, Germany mobilized and declared war on Russia.

The German government issued demands that France remain neutral as they had to decide which deployment plan to implement, it being difficult if not impossible to change the

deployment whilst it was underway. The modified German Schlieffen Plan, Aufmarsch II West, would deploy 80% of the army in the west, and Aufmarsch I Ost and Aufmarsch II Ost would deploy 60% in the west and 40% in the east as this was the maximum that the East Prussian railway infrastructure could carry. TheFrench did not respond but sent a mixed message by ordering their troops to withdraw 10 km (6 mi) from the border to avoidany incidents while ordering the mobilisation of her reserves.Germany responded by mobilising its own reserves and implementing Aufmarsch II West. Germany attacked Luxembourg on 2 August and on 3 August declared war on France.[38] On 4 August, after Belgium refused to permit German troops to cross its borders into France, Germany declared war on Belgium as well.[38][39][40] Britain declared war on Germany at 19:00 UTC on 4 August 1914 (effective from 11 pm), following an "unsatisfactory reply" to the British ultimatum that Belgium must be kept neutral.[41]

Progress of the warOpening hostilities

Confusion among the Central Powers

The strategy of the Central Powers suffered from miscommunication. Germany had promised to support Austria-Hungary's invasion of Serbia, but interpretations of what thismeant differed. Previously tested deployment plans had been replaced early in 1914, but had never been tested in exercises. Austro-Hungarian leaders believed Germany would cover its northern flank against Russia.[42] Germany, however, envisioned Austria-Hungary directing most of its troops against Russia, while Germany dealt with France. This confusion forced the Austro-Hungarian Army to divide its forces between the Russian and Serbian fronts.

Serbian campaign

Serbian Army Blériot XI "Oluj", 1915.Main article: Serbian Campaign (World War I)

Austria invaded and fought the Serbian army at the Battle of Cer and Battle of Kolubara beginning on 12 August. Over the next two weeks, Austrian attacks were thrown back with heavy losses, which marked the first major Allied victories of the war and dashed Austro-Hungarian hopes of a swift victory. As aresult, Austria had to keep sizable forces on the Serbian front, weakening its efforts against Russia.[43] Serbia's defeatof the Austro-Hungarian invasion of 1914 counts among the major upset victories of the last century.[44]

German forces in Belgium and France

Main article: Western Front (World War I)

British hospital at the Western Front.

At the outbreak of World War I, 80% of the German army (consisting in the West of seven field armies) was deployed inthe west according to the plan Aufmarsch II West. However, they were then assigned the operation of the retired deployment plan Aufmarsch I West, also known as the Schlieffen Plan. This would march German armies through northern Belgium and into France, in an attempt to encircle the French army and then breach the 'second defensive area' of the fortresses of Verdunand Paris and the Marne river.[10]

Aufmarsch I West was one of four deployment plans available to the German General Staff in 1914, each plan favouring but not specifying a certain operation that was well-known to the officers expected to carry it out under their own initiative with minimal oversight. Aufmarsch I West, designed for a one-front war with France, had been retired once it became clear that it was irrelevant to the wars Germany could expect to face; both Russia and Britain were expected to help France andthere was no possibility of Italian nor Austro-Hungarian troops being available for operations against France. But despite its unsuitability, and the availability of more sensible and decisive options, it retained a certain allure due to its offensive nature and the pessimism of pre-war thinking, which expected offensive operations to be short-lived, costly in casualties and unlikely to be decisive. Accordingly, the Aufmarsch II West deployment was changed for the offensive of 1914, despite its unrealistic goals and the insufficient forces Germany had available for decisive success.[45]

The plan called for the right flank of the German advance to bypass the French armies concentrated on the Franco-German border, defeat the French forces closer to Luxembourg and Belgium and move south to Paris. Initially the Germans were successful, particularly in the Battle of the Frontiers (14–24August). By 12 September, the French, with assistance from theBritish Expeditionary Force (BEF), halted the German advance east of Paris at the First Battle of the Marne (5–12 September), and pushed the German forces back some 50 km (31 mi). The French offensive into southern Alsace, launched on 20 August with the Battle of Mulhouse, had limited success.

German soldiers in a railway goods wagon on the way to the front in 1914. Early in the war, all sides expected the conflict to be a short one.

In the east, the Russians invaded with two armies. In response, Germany rapidly moved the 8th Field Army from its previous role as reserve for the invasion of France, to East Prussia by rail across the German Empire. This army, led by general Paul von Hindenburg defeated Russia in a series of battles collectively known as the First Battle of Tannenberg (17 August – 2 September). While the Russian invasion failed,

it caused the diversion of German troops to the east, allowingthe tactical Allied victory at the First Battle of the Marne. This meant that Germany failed to achieve its objective of avoiding a long two-front war. However, the German army had fought its way into a good defensive position inside France and effectively halved France's supply of coal. It had also killed or permanently crippled 230,000 more French and Britishtroops than it itself had lost. Despite this, communications problems and questionable command decisions cost Germany the chance of a more decisive outcome.[46]

Asia and the Pacific

Military recruitment in Melbourne, Australia, 1914.Main article: Asian and Pacific theatre of World War I

New Zealand occupied German Samoa (later Western Samoa) on 30 August 1914. On 11 September, the Australian Naval and Military Expeditionary Force landed on the island of Neu Pommern (later New Britain), which formed part of German New Guinea. On 28 October, the German cruiser SMS   Emden sank the Russian cruiser Zhemchug in the Battle of Penang. Japan seizedGermany's Micronesian colonies and, after the Siege of Tsingtao, the German coaling port of Qingdao on the Chinese Shandong peninsula. As Vienna refused to withdraw the Austro-Hungarian cruiser SMS   Kaiserin Elisabeth from Tsingtao, Japan declared war not only on Germany, but also on Austria-Hungary;the ship participated in the defense of Tsingtao where it was sunk in November 1914.[47] Within a few months, the Allied forces had seized all the German territories in the Pacific; only isolated commerce raiders and a few holdouts in New Guinea remained.[48][49]

African campaigns

Main article: African theatre of World War I

Some of the first clashes of the war involved British, French,and German colonial forces in Africa. On 6–7 August, French and British troops invaded the German protectorate of Togolandand Kamerun. On 10 August, German forces in South-West Africa attacked South Africa; sporadic and fierce fighting continued for the rest of the war. The German colonial forces in German East Africa, led by Colonel Paul von Lettow-Vorbeck, fought a guerrilla warfare campaign during World War I and only surrendered two weeks after the armistice took effect in Europe.[50]

Indian support for the Allies

Further information: Third Anglo-Afghan War and Hindu–German Conspiracy

Contrary to British fears of a revolt in India, the outbreak of the war saw an unprecedented outpouring of loyalty and goodwill towards Britain.[51][52] Indian political leaders from the Indian National Congress and other groups were eager to support the British war effort, since they believed that strong support for the war effort would further the cause of Indian Home Rule. The Indian Army in fact outnumbered the British Army at the beginning of the war; about 1.3 million Indian soldiers and labourers served in Europe, Africa, and the Middle East, while the central government and the princelystates sent large supplies of food, money, and ammunition. In all, 140,000 men served on the Western Front and nearly 700,000 in the Middle East. Casualties of Indian soldiers totalled 47,746 killed and 65,126 wounded during World War I.[53] The suffering engendered by the war, as well as the failureof the British government to grant self-government to India after the end of hostilities, bred disillusionment and fuelledthe campaign for full independence that would be led by Mohandas K. Gandhi and others.

Western Front

Main article: Western Front (World War I)

Trench warfare begins

Royal Irish Rifles in a communications trench, first day on the Somme, 1916.

Military tactics before World War I had failed to keep pace with advances in technology and had become obsolete. These advances had allowed the creation of strong defensive systems,which out-of-date military tactics could not break through formost of the war. Barbed wire was a significant hindrance to massed infantry advances, while artillery, vastly more lethal than in the 1870s, coupled with machine guns, made crossing open ground extremely difficult.[54] Commanders on both sides failed to develop tactics for breaching entrenched positions without heavy casualties. In time, however, technology began to produce new offensive weapons, such as gas warfare and the tank.[55]

Just after the First Battle of the Marne (5–12 September 1914), Entente and German forces repeatedly attempted manoeuvring to the north to outflank each other: this series of manoeuvres became known as the "Race to the Sea". When these outflanking efforts failed, Britain and France soon found themselves facing an uninterrupted line of entrenched German forces from Lorraine to Belgium's coast.[10] Britain and France sought to take the offensive, while Germany defended the occupied territories. Consequently, German trenches were much better constructed than those of their enemy; Anglo-French trenches were only intended to be "temporary" before their forces broke through the German defences.[56]

Both sides tried to break the stalemate using scientific and technological advances. On 22 April 1915, at the Second Battleof Ypres, the Germans (violating the Hague Convention) used chlorine gas for the first time on the Western Front. Several types of gas soon became widely used by both sides, and thoughit never proved a decisive, battle-winning weapon, poison gas

became one of the most-feared and best-remembered horrors of the war.[57][58] Tanks were first used in combat by the British during the Battle of Flers–Courcelette (part of the Battle of the Somme) on 15 September 1916, with only partial success. However, their effectiveness would grow as the war progressed;the Germans employed only small numbers of their own design, supplemented by captured Allied tanks.

French 87th regiment near Verdun, 1916.

Continuation of trench warfare

Canadian troops advancing with a British Mark II tank at the Battle of Vimy Ridge, 1917.

Neither side proved able to deliver a decisive blow for the next two years. Throughout 1915–17, the British Empire and France suffered more casualties than Germany, because of both the strategic and tactical stances chosen by the sides. Strategically, while the Germans only mounted one major offensive, the Allies made several attempts to break through the German lines.

In February 1916 the Germans attacked the French defensive positions at Verdun. Lasting until December 1916, the battle saw initial German gains, before French counter-attacks returned matters to near their starting point. Casualties weregreater for the French, but the Germans bled heavily as well, with anywhere from 700,000[59] to 975,000[60] casualties suffered between the two combatants. Verdun became a symbol of French determination and self-sacrifice.[61]

The Battle of the Somme was an Anglo-French offensive that ranfrom July to November 1916. The opening of this offensive (1 July 1916) saw the British Army endure the bloodiest day in its history, suffering 57,470 casualties, including 19,240 dead, on the first day alone. The entire Somme offensive cost the British Army some 420,000 casualties. The French suffered another estimated 200,000 casualties and the Germans an estimated 500,000.[62]

Protracted action at Verdun throughout 1916,[63] combined with the bloodletting at the Somme, brought the exhausted French army to the brink of collapse. Futile attempts at frontal assault came at a high price for both the British and the French and led to the widespread French Army Mutinies, after the failure of the costly Nivelle Offensive of April–May 1917.[64] The concurrent British Battle of Arras was more limited in scope, and more successful, although ultimately of little strategic value.[65][66] A smaller part of the Arras offensive, the capture of Vimy Ridge by the Canadian Corps, became highlysignificant to that country: the idea that Canada's national identity was born out of the battle is an opinion widely held in military and general histories of Canada.[67][68]

The last large-scale offensive of this period was a British attack (with French support) at Passchendaele (July–November 1917). This offensive opened with great promise for the Allies, before bogging down in the October mud. Casualties, though disputed, were roughly equal, at some 200,000–400,000 per side.

These years of trench warfare in the West saw no major exchanges of territory and, as a result, are often thought of as static and unchanging. However, throughout this period,

British, French, and German tactics constantly evolved to meetnew battlefield challenges.

Naval war

Battleships of the Hochseeflotte, 1917.Main article: Naval warfare of World War I

At the start of the war, the German Empire had cruisers scattered across the globe, some of which were subsequently used to attack Allied merchant shipping. The British Royal Navy systematically hunted them down, though not without some embarrassment from its inability to protect Allied shipping. For example, the German detached light cruiser SMS Emden, partof the East-Asia squadron stationed at Qingdao, seized or destroyed 15 merchantmen, as well as sinking a Russian cruiserand a French destroyer. However, most of the German East-Asia squadron—consisting of the armoured cruisers Scharnhorst and Gneisenau, light cruisers Nürnberg and Leipzig and two transport ships—did not have orders to raid shipping and was instead underway to Germany when it met British warships. The German flotilla and Dresden sank two armoured cruisers at the Battle of Coronel, but was almost destroyed at the Battle of the Falkland Islands in December 1914, with only Dresden and a few auxiliaries escaping, but at the Battle of Más a Tierra these too were destroyed or interned.[69]

Soon after the outbreak of hostilities, Britain began a naval blockade of Germany. The strategy proved effective, cutting off vital military and civilian supplies, although this blockade violated accepted international law codified by several international agreements of the past two centuries.[70] Britain mined international waters to prevent any ships from entering entire sections of ocean, causing danger to even neutral ships.[71] Since there was limited response to this tactic, Germany expected a similar response to its unrestricted submarine warfare.[72]

The 1916 Battle of Jutland (German: Skagerrakschlacht, or "Battle of the Skagerrak") developed into the largest naval battle of the war, the only full-scale clash of battleships during the war, and one of the largest in history. It took place on 31 May – 1 June 1916, in the North Sea off Jutland. The Kaiserliche Marine's High Seas Fleet, commanded by Vice Admiral Reinhard Scheer, squared off against the Royal Navy's Grand Fleet, led by Admiral Sir John Jellicoe. The engagement was a stand off, as the Germans, outmanoeuvred by the larger British fleet, managed to escape and inflicted more damage to the British fleet than they received. Strategically, however, the British asserted their control of the sea, and the bulk ofthe German surface fleet remained confined to port for the duration of the war.[73]

U-155 exhibited near Tower Bridge in London, after the 1918 Armistice.

German U-boats attempted to cut the supply lines between NorthAmerica and Britain.[74] The nature of submarine warfare meant that attacks often came without warning, giving the crews of the merchant ships little hope of survival.[74][75] The United States launched a protest, and Germany changed its rules of engagement. After the sinking of the passenger ship RMS Lusitania in 1915, Germany promised not to target passenger liners, while Britain armed its merchant ships, placing them beyond the protection of the "cruiser rules", which demanded warning and placing crews in "a place of safety" (a standard that lifeboats did not meet).[76] Finally, in early 1917, Germany adopted a policy of unrestricted submarine warfare, realising that the Americans would eventually enter the war.[74]

[77] Germany sought to strangle Allied sea lanes before the United States could transport a large army overseas, but couldmaintain only five long-range U-boats on station, to limited effect.[74]

The U-boat threat lessened in 1917, when merchant ships began travelling in convoys, escorted by destroyers. This tactic made it difficult for U-boats to find targets, which significantly lessened losses; after the hydrophone and depth charges were introduced, accompanying destroyers could attack a submerged submarine with some hope of success. Convoys slowed the flow of supplies, since ships had to wait as convoys were assembled. The solution to the delays was an extensive program of building new freighters. Troopships were too fast for the submarines and did not travel the North Atlantic in convoys.[78] The U-boats had sunk more than 5,000 Allied ships, at a cost of 199 submarines.[79] World War I also saw the first use of aircraft carriers in combat, with HMS   Furious launching Sopwith Camels in a successful raid against the Zeppelin hangars at Tondern in July 1918, as well as blimps for antisubmarine patrol.[80]

Southern theatres

War in the Balkans

Main articles: Balkans Campaign (World War I), Bulgaria duringWorld War I, Serbian Campaign (World War I) and Macedonian Front

Bulgarian soldiers in a trench, preparing to fire against an incoming airplane.

Austro-Hungarian troops executing captured Serbians, 1917. Serbia lost about 850,000 people during the war, a quarter of its pre-war population.[81]

Refugee transport from Serbia in Leibnitz, Styria, 1914.

Faced with Russia, Austria-Hungary could spare only one-third of its army to attack Serbia. After suffering heavy losses, the Austrians briefly occupied the Serbian capital, Belgrade. A Serbian counter-attack in the Battle of Kolubara succeeded in driving them from the country by the end of 1914. For the first ten months of 1915, Austria-Hungary used most of its military reserves to fight Italy. German and Austro-Hungarian diplomats, however, scored a coup by persuading Bulgaria to join the attack on Serbia on 6 September 1915 in Pless.[82] The Austro-Hungarian provinces of Slovenia, Croatia and Bosnia provided troops for Austria-Hungary, invading Serbia as well as fighting Russia and Italy. Montenegro allied itself with Serbia.[83]

Serbia was conquered in a little more than a month, as the Central Powers, now including Bulgaria, sent in 600,000 troops. The Serbian army, fighting on two fronts and facing certain defeat, retreated into northern Albania. The Serbs suffered defeat in the Battle of Kosovo. Montenegro covered the Serbian retreat towards the Adriatic coast in the Battle of Mojkovac in 6–7 January 1916, but ultimately the Austrians also conquered Montenegro. The surviving Serbian soldiers wereevacuated by ship to Greece.[84] After conquest, Serbia was divided between Austro-Hungary and Bulgaria.

In late 1915, a Franco-British force landed at Salonica in Greece, to offer assistance and to pressure its government to declare war against the Central Powers. However, the pro-German King Constantine I dismissed the pro-Allied government

of Eleftherios Venizelos before the Allied expeditionary forcearrived.[85] The friction between the King of Greece and the Allies continued to accumulate with the National Schism, whicheffectively divided Greece between regions still loyal to the king and the new provisional government of Venizelos in Salonica. After intense negotiations and an armed confrontation in Athens between Allied and royalist forces (anincident known as Noemvriana), the King of Greece resigned andhis second son Alexander took his place; Greece then officially joined the war on the side of the Allies.

In the beginning, the Macedonian Front was mostly static. French and Serbian forces retook limited areas of Macedonia byrecapturing Bitola on 19 November 1916 following the costly Monastir Offensive, which brought stabilization of the front.[86]

Serbian and French troops finally made a breakthrough in September 1918, after most of the German and Austro-Hungarian troops had been withdrawn. The Bulgarians suffered their only defeat of the war at the Battle of Dobro Pole. Bulgaria capitulated two weeks later, on 29 September 1918.[87] The German high command responded by despatching troops to hold the line, but these forces were far too weak to reestablish a front.[88]

The disappearance of the Macedonian Front meant that the road to Budapest and Vienna was now opened to Allied forces. Hindenburg and Ludendorff concluded that the strategic and operational balance had now shifted decidedly against the Central Powers and, a day after the Bulgarian collapse, insisted on an immediate peace settlement.[89]

Ottoman Empire

Main article: Middle Eastern theatre of World War I

Mustafa Kemal Atatürk at the trenches of Gallipoli during the Gallipoli Campaign.

Ottoman 3rd Army troopers with winter gear.

British artillery battery on Mount Scopus in the Battle of Jerusalem, 1917.

Russian forest trench at the 1914–1915 Battle of Sarikamish.

The Ottoman Empire joined the Central Powers in the war with the secret Ottoman–German Alliance signed in August 1914.[90]

The Ottomans threatened Russia's Caucasian territories and Britain's communications with India via the Suez Canal.

As the conflict progressed, the Ottoman Empire took advantage of the European powers' preoccupation with the war and conducted large-scale ethnic cleansing of the indigenous Greek, Assyrian and Armenian Christian populations, known as the Greek genocide, Assyrian Genocide and Armenian genocide.[91]

[92][93]

The British and French opened overseas fronts with the Gallipoli (1915) and Mesopotamian campaigns (1914). In Gallipoli, the Ottoman Empire successfully repelled the British, French, and Australian and New Zealand Army Corps (ANZACs). In Mesopotamia, by contrast, after the disastrous Siege of Kut (1915–16), British Imperial forces reorganised and captured Baghdad in March 1917. The British were aided in Mesopotamia by local Arab and Assyrian tribesmen, while the Ottomans employed local Kurdish and Turcoman tribes.[94]

Further to the west, the Suez Canal was defended from Ottoman attacks in 1915 and 1916; in August, a German and Ottoman force was defeated at the Battle of Romani by the ANZAC Mounted Division and the 52nd (Lowland) Infantry Division. Following this victory, a Egyptian Expeditionary Force advanced across the Sinai Peninsula, pushing Ottoman forces back in the Battle of Magdhaba in December and the Battle of Rafa on the border between the Egyptian Sinai and Ottoman Palestine in January 1917.[95]

Xmas card from British Mesopotamian Expeditionary Force with list of engagements, Basra, 1917

Russian armies generally saw success in the Caucasus. Enver Pasha, supreme commander of the Ottoman armed forces, was ambitious and dreamed of re-conquering central Asia and areas that had been lost to Russia previously. He was, however, a poor commander.[96] He launched an offensive against the Russians in the Caucasus in December 1914 with 100,000 troops;insisting on a frontal attack against mountainous Russian positions in winter. He lost 86% of his force at the Battle ofSarikamish.[97]

In December 1914 the Ottoman Empire, with German support, invaded Persia (modern Iran) in an effort to cut off British and Russian access to petroleum reservoirs around Baku near the Caspian Sea.[98] Persia, ostensibly neutral, had long been under the spheres of British and Russian influence. The Ottomans and Germans were aided by Kurdish and Azeri forces, together with a large number of major Iranian tribes, such as the Qashqai, Tangistanis, Luristanis, and Khamseh, while the Russians and British had the support of Assyrian and Armenian forces. The Persian Campaign was to last until 1918 and end infailure for the Ottomans and their allies, however the Russianwithdrawal from the war in 1917 led to Armenian and Assyrian forces, who had hitherto inflicted a series of defeats upon the forces of the Ottomans and their allies, being cut off from supply lines, outnumbered, outgunned and isolated, forcing them to fight and flee towards British lines in northern Mesopotamia.[99]

General Yudenich, the Russian commander from 1915 to 1916, drove the Turks out of most of the southern Caucasus with a string of victories.[97] In 1917, Russian Grand Duke Nicholas assumed command of the Caucasus front. Nicholas planned a railway from Russian Georgia to the conquered territories, so that fresh supplies could be brought up for a new offensive in1917. However, in March 1917 (February in the pre-revolutionary Russian calendar), the Czar abdicated in the course of the February Revolution and the Russian Caucasus Army began to fall apart.

Instigated by the Arab bureau of the British Foreign Office, the Arab Revolt started June 1916 at the Battle of Mecca, led by Sherif Hussein of Mecca, and ended with the Ottoman surrender of Damascus. Fakhri Pasha, the Ottoman commander of Medina, resisted for more than two and half years during the Siege of Medina before surrendering.[100]

Along the border of Italian Libya and British Egypt, the Senussi tribe, incited and armed by the Turks, waged a small-scale guerrilla war against Allied troops. The British were forced to dispatch 12,000 troops to oppose them in the SenussiCampaign. Their rebellion was finally crushed in mid-1916.[101]

Total Allied casualties on the Ottoman fronts amounted 650,000men. Total Ottoman casualties were 725,000 (325,000 dead and 400,000 wounded).[102]

Italian participation

Austro-Hungarian troops, Tyrol.

Depiction of the Battle of Doberdò, fought in August 1916 between the Italian and the Austro-Hungarian armies.

Main articles: Italian Campaign (World War I) and Albania during World War IFurther information: Battles of the Isonzo

Italy had been allied with the German and Austro-Hungarian Empires since 1882 as part of the Triple Alliance. However, the nation had its own designs on Austrian territory in Trentino, the Austrian Littoral, Fiume (Rijeka) and Dalmatia. Rome had a secret 1902 pact with France, effectively nullifying its alliance.[103] At the start of hostilities, Italyrefused to commit troops, arguing that the Triple Alliance wasdefensive and that Austria-Hungary was an aggressor. The Austro-Hungarian government began negotiations to secure Italian neutrality, offering the French colony of Tunisia in return. The Allies made a counter-offer in which Italy would receive the Southern Tyrol, Austrian Littoral and territory onthe Dalmatian coast after the defeat of Austria-Hungary. This was formalised by the Treaty of London. Further encouraged by the Allied invasion of Turkey in April 1915, Italy joined the Triple Entente and declared war on Austria-Hungary on 23 May. Fifteen months later, Italy declared war on Germany.[104]

The Italians had numerical superiority but this advantage was lost, not only because of the difficult terrain in which fighting took place, but also because of the strategies and tactics employed.[105] Field Marshal Luigi Cadorna, a staunch proponent of the frontal assault, had dreams of breaking into the Slovenian plateau, taking Ljubljana and threatening Vienna.

On the Trentino front, the Austro-Hungarians took advantage ofthe mountainous terrain, which favoured the defender. After aninitial strategic retreat, the front remained largely unchanged, while Austrian Kaiserschützen and Standschützen engaged Italian Alpini in bitter hand-to-hand combat throughout the summer. The Austro-Hungarians counterattacked in the Altopiano of Asiago, towards Verona and Padua, in the spring of 1916 (Strafexpedition), but made little progress.[106]

Beginning in 1915, the Italians under Cadorna mounted eleven offensives on the Isonzo front along the Isonzo (Soča) River, northeast of Trieste. All eleven offensives were repelled by the Austro-Hungarians, who held the higher ground. In the

summer of 1916, after the Battle of Doberdò, the Italians captured the town of Gorizia. After this minor victory, the front remained static for over a year, despite several Italianoffensives, centred on the Banjšice and Karst Plateau east of Gorizia.

The Central Powers launched a crushing offensive on 26 October1917, spearheaded by the Germans. They achieved a victory at Caporetto (Kobarid). The Italian Army was routed and retreatedmore than 100 kilometres (62 mi) to reorganise, stabilising the front at the Piave River. Since the Italian Army had suffered heavy losses in the Battle of Caporetto, the Italian Government called to arms the so-called '99 Boys (Ragazzi del '99):that is, all males born on 1899 and after, and so were 18 years old or older. In 1918, the Austro-Hungarians failed to break through in a series of battles on the Piave and were finally decisively defeated in the Battle of Vittorio Veneto in October of that year. On 1 November, the Italian Navy destroyed much of the Austro-Hungarian fleet stationed in Pula, preventing it from being handed over to the new State ofSlovenes, Croats and Serbs. On 3 November, the Italians occupied Trieste from the sea. On the same day, the Armistice of Villa Giusti was signed. By mid-November 1918, the Italian military occupied the entire former Austrian Littoral and had seized control of the portion of Dalmatia that had been guaranteed to Italy by the London Pact.[107] By the end of hostilities in November 1918,[108] Admiral Enrico Millo declaredhimself Italy's Governor of Dalmatia.[108] Austria-Hungary surrendered in early November 1918.[109][110]

Romanian participation

Main article: Romania during World War I

Marshal Joffre inspecting Romanian troops, 1916.

Romania had been allied with the Central Powers since 1882. When the war began, however, it declared its neutrality, arguing that because Austria-Hungary had itself declared war

on Serbia, Romania was under no obligation to join the war. When the Entente Powers promised Romania large territories of eastern Hungary (Transylvania and Banat), which had a large Romanian population, in exchange for Romania's declaring war on the Central Powers, the Romanian government renounced its neutrality and, on 27 August 1916, the Romanian Army launched an attack against Austria-Hungary, with limited Russian support. The Romanian offensive was initially successful, pushing back the Austro-Hungarian troops in Transylvania, but a counterattack by the forces of the Central Powers drove backthe Russo-Romanian forces.[111] As a result of the Battle of Bucharest, the Central Powers occupied Bucharest on 6 December1916. Fighting in Moldova continued in 1917, resulting in a costly stalemate for the Central Powers.[112][113] Russian withdrawal from the war in late 1917 as a result of the October Revolution meant that Romania was forced to sign an armistice with the Central Powers on 9 December 1917.

Romanian troops during the Battle of Mărăşeşti, 1917.

In January 1918, Romanian forces established control over Bessarabia as the Russian Army abandoned the province. Although a treaty was signed by the Romanian and the BolshevikRussian governments following talks from 5–9 March 1918 on thewithdrawal of Romanian forces from Bessarabia within two months, on 27 March 1918 Romania attached Bessarabia to its territory, formally based on a resolution passed by the local assembly of that territory on its unification with Romania.[114]

Romania officially made peace with the Central Powers by signing the Treaty of Bucharest on 7 May 1918. Under that treaty, Romania was obliged to end the war with the Central Powers and make small territorial concessions to Austria-Hungary, ceding control of some passes in the Carpathian Mountains, and to grant oil concessions to Germany. In exchange, the Central Powers recognised the sovereignty of

Romania over Bessarabia. The treaty was renounced in October 1918 by the Alexandru Marghiloman government, and Romania nominally re-entered the war on 10 November 1918. The next day, the Treaty of Bucharest was nullified by the terms of theArmistice of Compiègne.[115][116] Total Romanian deaths from 1914 to 1918, military and civilian, within contemporary borders, were estimated at 748,000.[117]

Eastern Front

Main article: Eastern Front (World War I)

Initial actions

Russian troops in a trench, awaiting a German attack, 1917.

While the Western Front had reached stalemate, the war continued in East Europe.[118] Initial Russian plans called for simultaneous invasions of Austrian Galicia and East Prussia. Although Russia's initial advance into Galicia was largely successful, it was driven back from East Prussia by Hindenburgand Ludendorff at the Battle of Tannenberg and the Masurian Lakes in August and September 1914.[119][120] Russia's less developed industrial base and ineffective military leadership was instrumental in the events that unfolded. By the spring of1915, the Russians had retreated to Galicia, and, in May, the Central Powers achieved a remarkable breakthrough on Poland's southern frontiers.[121] On 5 August, they captured Warsaw and forced the Russians to withdraw from Poland.

Russian Revolution

Main article: Russian Revolution

Despite the success of the June 1916 Brusilov Offensive in eastern Galicia,[122] dissatisfaction with the Russian government's conduct of the war grew. The offensive's success was undermined by the reluctance of other generals to commit their forces to support the victory. Allied and Russian forceswere revived only temporarily by Romania's entry into the war on 27 August. German forces came to the aid of embattled Austro-Hungarian units in Transylvania while a German-Bulgarian force attacked from the south, and Bucharest fell tothe Central Powers on 6 December. Meanwhile, unrest grew in Russia, as the Tsar remained at the front. Empress Alexandra'sincreasingly incompetent rule drew protests and resulted in the murder of her favourite, Rasputin, at the end of 1916.

In March 1917, demonstrations in Petrograd culminated in the abdication of Tsar Nicholas II and the appointment of a weak Provisional Government, which shared power with the Petrograd Soviet socialists. This arrangement led to confusion and chaosboth at the front and at home. The army became increasingly ineffective.[121]

Treaty of Brest-Litovsk, 1918.1. Count Ottokar von Czernin2. Richard von Kühlmann3. Vasil Radoslavov

Following the Tsar's abdication, Vladimir Lenin was allowed passage by train back into Russia from Switzerland, and financed by Germany. Discontent and the weaknesses of the Provisional Government led to a rise in the popularity of the Bolshevik Party, led by Lenin, which demanded an immediate endto the war. The Revolution of November was followed in December by an armistice and negotiations with Germany. At first, the Bolsheviks refused the German terms, but when

German troops began marching across the Ukraine unopposed, thenew government acceded to the Treaty of Brest-Litovsk on 3 March 1918. The treaty ceded vast territories, including Finland, the Baltic provinces, parts of Poland and Ukraine to the Central Powers.[123] Despite this enormous apparent German success, the manpower required for German occupation of formerRussian territory may have contributed to the failure of the Spring Offensive and secured relatively little food or other materiel for the Central Powers war effort.

With the adoption of the Treaty of Brest-Litovsk, the Entente no longer existed. The Allied powers led a small-scale invasion of Russia, partly to stop Germany from exploiting Russian resources, and to a lesser extent, to support the "Whites" (as opposed to the "Reds") in the Russian Civil War.[124] Allied troops landed in Arkhangelsk and in Vladivostok as part of the North Russia Intervention.

Czechoslovak Legion

Czechoslovak Legion, Vladivostok, 1918.Main article: Czechoslovak Legion

The Czechoslovak Legion fought with the Entente; their goal was to win support for the independence of Czechoslovakia. TheLegion in Russia was established in 1917, in December 1917 in France (including volunteers from America) and in April 1918 in Italy. Czechoslovak Legion troops defeated the Austro-Hungarian army at the Ukrainian village Zborov in July 1917. After this success, the number of Czechoslovak legionaries increased, as well as Czechoslovak military power. In the Battle of Bakhmach, the Legion defeated the Germans and forcedthem to make a truce.

In Russia, they were heavily involved in the Russian Civil Warfighting the Bolsheviks, at times controlling most of the Trans-Siberian railway and conquering all major cities in Siberia. The presence of the Czechoslovak Legion near the

Yekaterinburg appears to have been one of the motivating forces for the Bolshevik execution of the Tsar and his family in July 1918. Legionaries came less than a week afterwards andcaptured the city. Because Russia's European ports were not safe, the corps was to be evacuated by a long detour via the port of Vladivostok. The last transport was the American ship Heffron in September 1920.

Central Powers peace overtures

"They shall not pass", a phrase typically associated with the defense of Verdun.

In December 1916, after ten brutal months of the Battle of Verdun and a successful offensive against Romania, the Germansattempted to negotiate a peace with the Allies. Soon after, the US president, Woodrow Wilson, attempted to intervene as a peacemaker, asking in a note for both sides to state their demands. Lloyd George's War Cabinet considered the German offer to be a ploy to create divisions amongst the Allies. After initial outrage and much deliberation, they took Wilson's note as a separate effort, signalling that the UnitedStates was on the verge of entering the war against Germany following the "submarine outrages". While the Allies debated aresponse to Wilson's offer, the Germans chose to rebuff it in favour of "a direct exchange of views". Learning of the Germanresponse, the Allied governments were free to make clear demands in their response of 14 January. They sought restoration of damages, the evacuation of occupied territories, reparations for France, Russia and Romania, and arecognition of the principle of nationalities. This included the liberation of Italians, Slavs, Romanians, Czecho-Slovaks, and the creation of a "free and united Poland". On the question of security, the Allies sought guarantees that would prevent or limit future wars, complete with sanctions, as a

condition of any peace settlement.[125] The negotiations failed and the Entente powers rejected the German offer, because Germany did not state any specific proposals. To Wilson, the Entente powers stated that they would not start peace negotiations until the Central powers evacuated all occupied Allied territories and provided indemnities for all damage which had been done.[126]

1917–1918

Developments in 1917

German film crew recording the action.

Events of 1917 proved decisive in ending the war, although their effects were not fully felt until 1918.

The British naval blockade began to have a serious impact on Germany. In response, in February 1917, the German General Staff convinced Chancellor Theobald von Bethmann-Hollweg to declare unrestricted submarine warfare, with the goal of starving Britain out of the war. German planners estimated that unrestricted submarine warfare would cost Britain a monthly shipping loss of 600,000 tons. The General Staff acknowledged that the policy would almost certainly bring the United States into the conflict, but calculated that British shipping losses would be so high that they would be forced to sue for peace after 5 to 6 months, before American intervention could make an impact. In reality, tonnage sunk rose above 500,000 tons per month from February to July. It peaked at 860,000 tons in April. After July, the newly re-introduced convoy system became extremely effective in reducing the U-boat threat. Britain was safe from starvation, while German industrial output fell and the United States troops joined the war in large numbers far earlier than Germany had anticipated.

Haut-Rhin, France, 1917.

On 3 May 1917, during the Nivelle Offensive, the French 2nd Colonial Division, veterans of the Battle of Verdun, refused orders, arriving drunk and without their weapons. Their officers lacked the means to punish an entire division, and harsh measures were not immediately implemented. The French Army Mutinies eventually spread to a further 54 French divisions and saw 20,000 men desert. However, appeals to patriotism and duty, as well as mass arrests and trials, encouraged the soldiers to return to defend their trenches, although the French soldiers refused to participate in furtheroffensive action.[127] Robert Nivelle was removed from command by 15 May, replaced by General Philippe Pétain, who suspended bloody large-scale attacks.

The victory of Austria-Hungary and Germany at the Battle of Caporetto led the Allies to convene the Rapallo Conference at which they formed the Supreme War Council to coordinate planning. Previously, British and French armies had operated under separate commands.

In December, the Central Powers signed an armistice with Russia. This released large numbers of German troops for use in the west. With German reinforcements and new American troops pouring in, the outcome was to be decided on the Western Front. The Central Powers knew that they could not wina protracted war, but they held high hopes for success based on a final quick offensive. Furthermore, the leaders of the Central Powers and the Allies became increasingly fearful of social unrest and revolution in Europe. Thus, both sides urgently sought a decisive victory.[128]

In 1917, Emperor Charles I of Austria secretly attempted separate peace negotiations with Clemenceau, through his wife's brother Sixtus in Belgium as an intermediary, without the knowledge of Germany. Italy opposed the proposals. When the negotiations failed, his attempt was revealed to Germany resulting in a diplomatic catastrophe.[129][130]

Ottoman Empire conflict, 1917–1918

Main article: Sinai and Palestine Campaign

British troops on the march in Mesopotamia, 1917.

Ottoman troops in Mesopotamia.

In March and April 1917, at the First and Second Battles of Gaza, German and Ottoman forces stopped the advance of the Egyptian Expeditionary Force, which had begun in August 1916 at the Battle of Romani.[131][132] At the end of October, the Sinai and Palestine Campaign resumed, when General Edmund Allenby's XXth Corps, XXI Corps and Desert Mounted Corps won the Battle of Beersheba.[133] Two Ottoman armies were defeated afew weeks later at the Battle of Mughar Ridge and, early in December, Jerusalem was captured following another Ottoman defeat at the Battle of Jerusalem (1917).[134][135][136] About this time, Friedrich Freiherr Kress von Kressenstein was relieved of his duties as the Eighth Army's commander, replaced by Djevad Pasha, and a few months later the commander of the

Ottoman Army in Palestine, Erich von Falkenhayn, was replaced by Otto Liman von Sanders.[137][138]

Early in 1918, the front line was extended into the Jordan Valley, was occupied, following the First Transjordan and the Second Transjordan attack by British Empire forces in March and April 1918.[139] During March, most of the Egyptian Expeditionary Force's British infantry and Yeomanry cavalry were sent to fight on the Western Front as a consequence of the Spring Offensive. They were replaced by Indian Army units.During several months of reorganisation and training during the summer, a number of attacks were carried out on sections of the Ottoman front line. These pushed the front line north to more advantageous positions in preparation for an attack and to acclimatise the newly arrived Indian Army infantry. It was not until the middle of September that the integrated force was ready for large-scale operations.

The reorganised Egyptian Expeditionary Force, with an additional mounted division, broke Ottoman forces at the Battle of Megiddo in September 1918. In two days the British and Indian infantry, supported by a creeping barrage, broke the Ottoman front line and captured the headquarters of the Eighth Army (Ottoman Empire) at Tulkarm, the continuous trenchlines at Tabsor, Arara and the Seventh Army (Ottoman Empire) headquarters at Nablus. The Desert Mounted Corps rode through the break in the front line created by the infantry and, during virtually continuous operations by Australian Light Horse, British mounted Yeomanry, Indian Lancers and New Zealand Mounted Rifle brigades in the Jezreel Valley, they captured Nazareth, Afulah and Beisan, Jenin, along with Haifa on the Mediterranean coast and Daraa east of the Jordan River on the Hejaz railway. Samakh and Tiberias on the Sea of Galilee, were captured on the way northwards to Damascus. Meanwhile, Chaytor's Force of Australian light horse, New Zealand mounted rifles, Indian, British West Indies and Jewishinfantry captured the crossings of the Jordan River, Es Salt, Amman and at Ziza most of the Fourth Army (Ottoman Empire). The Armistice of Mudros, signed at the end of October, ended hostilities with the Ottoman Empire when fighting was continuing north of Aleppo.

Entry of the United States

Main article: American entry into World War I

President Wilson before Congress, announcing the break in official relations with Germany on 3 February 1917.

At the outbreak of the war, the United States pursued a policyof non-intervention, avoiding conflict while trying to broker a peace. When the German U-boat SM U-20 sank the British linerRMS Lusitania on 7 May 1915 with 128 Americans among the dead, President Woodrow Wilson insisted that "America is too proud to fight" but demanded an end to attacks on passenger ships. Germany complied. Wilson unsuccessfully tried to mediate a settlement. However, he also repeatedly warned that the UnitedStates would not tolerate unrestricted submarine warfare, in violation of international law. The former president Theodore Roosevelt denounced German acts as "piracy".[140] Wilson was narrowly reelected in 1916 as his supporters emphasized "he kept us out of war".

In January 1917, Germany resumed unrestricted submarine warfare, realizing it would mean American entry. The German Foreign Minister, in the Zimmermann Telegram, invited Mexico to join the war as Germany's ally against the United States. In return, the Germans would finance Mexico's war and help it recover the territories of Texas, New Mexico, and Arizona.[141] The United Kingdom intercepted the message and presented it tothe US embassy in the UK. From there it made its way to President Wilson who released the Zimmermann note to the public, and Americans saw it as casus belli. Wilson called on antiwar elements to end all wars, by winning this one and eliminating militarism from the globe. He argued that the war was so important that the US had to have a voice in the peace conference.[142] After the sinking of seven US merchant ships bysubmarines and the publication of the Zimmermann telegram, Wilson called for war on Germany,[143] which the US Congress declared on 6 April 1917.

The United States was never formally a member of the Allies but became a self-styled "Associated Power". The United Stateshad a small army, but, after the passage of the Selective Service Act, it drafted 2.8 million men,[144] and, by summer 1918, was sending 10,000 fresh soldiers to France every day. In 1917, the US Congress gave US citizenship to Puerto Ricans when they were drafted to participate in World War I, as part of the Jones Act. Germany had miscalculated, believing it would be many more months before American soldiers would arrive and that their arrival could be stopped by U-boats.[145]

The United States Navy sent a battleship group to Scapa Flow to join with the British Grand Fleet, destroyers to Queenstown, Ireland, and submarines to help guard convoys. Several regiments of US Marines were also dispatched to France. The British and French wanted American units used to reinforce their troops already on the battle lines and not waste scarce shipping on bringing over supplies. General John J. Pershing, American Expeditionary Forces (AEF) commander, refused to break up American units to be used as reinforcements for British Empire and French units. As an exception, he did allow African-American combat regiments to be used in French divisions. The Harlem Hellfighters fought aspart of the French 16th Division, and earned a unit Croix de Guerre for their actions at Château-Thierry, Belleau Wood, andSechault.[146] AEF doctrine called for the use of frontal assaults, which had long since been discarded by British Empire and French commanders because of the large loss of life.[147]

German Spring Offensive of 1918

Main article: Spring Offensive

British 55th Division soldiers, blinded by tear gas during theBattle of Estaires, 10 April 1918.

French soldiers under General Gouraud, with machine guns amongst the ruins of a cathedral near the Marne, 1918.

Ludendorff drew up plans (codenamed Operation Michael) for the1918 offensive on the Western Front. The Spring Offensive sought to divide the British and French forces with a series of feints and advances. The German leadership hoped to end thewar before significant US forces arrived. The operation commenced on 21 March 1918, with an attack on British forces near Amiens. German forces achieved an unprecedented advance of 60 kilometres (37 mi).[148]

British and French trenches were penetrated using novel infiltration tactics, also named Hutier tactics, after General Oskar von Hutier, by specially trained units called stormtroopers. Previously, attacks had been characterised by long artillery bombardments and massed assaults. However, in the Spring Offensive of 1918, Ludendorff used artillery only briefly and infiltrated small groups of infantry at weak points. They attacked command and logistics areas and bypassedpoints of serious resistance. More heavily armed infantry thendestroyed these isolated positions. This German success reliedgreatly on the element of surprise.[149]

The front moved to within 120 kilometres (75 mi) of Paris. Three heavy Krupp railway guns fired 183 shells on the capital, causing many Parisians to flee. The initial offensivewas so successful that Kaiser Wilhelm II declared 24 March a national holiday. Many Germans thought victory was near. Afterheavy fighting, however, the offensive was halted. Lacking tanks or motorised artillery, the Germans were unable to consolidate their gains. This situation was not helped by the now stretched supply lines as a result of their rapid advance over devastated ground.[150]

General Foch pressed to use the arriving American troops as individual replacements, whereas Pershing sought to field American units as an independent force. These units were assigned to the depleted French and British Empire commands on28 March. A Supreme War Council of Allied forces was created at the Doullens Conference on 5 November 1917.[151] General Fochwas appointed as supreme commander of the Allied forces. Haig,Petain, and Pershing retained tactical control of their respective armies; Foch assumed a coordinating rather than a directing role, and the British, French, and US commands operated largely independently.[151]

Following Operation Michael, Germany launched Operation Georgette against the northern English Channel ports. The Allies halted the drive after limited territorial gains by Germany. The German Army to the south then conducted Operations Blücher and Yorck, pushing broadly towards Paris. Operation Marne was launched on 15 July, in an attempt to encircle Reims and beginning the Second Battle of the Marne. The resulting counterattack, which started the Hundred Days Offensive, marked the first successful Allied offensive of thewar.

By 20 July, the Germans had retreated across the Marne to their starting lines,[152] having achieved little, and the German Army never regained the initiative. German casualties between March and April 1918 were 270,000, including many highly trained storm troopers.

Meanwhile, Germany was falling apart at home. Anti-war marchesbecame frequent and morale in the army fell. Industrial outputwas 53% of 1913 levels.

New states under war zone

In the late spring of 1918, three new states were formed in the South Caucasus: the First Republic of Armenia, the Azerbaijan Democratic Republic, and the Democratic Republic ofGeorgia, which declared their independence from the Russian Empire.[153] Two other minor entities were established, the Centrocaspian Dictatorship and South West Caucasian Republic (the former was liquidated by Azerbaijan in the autumn of 1918and the latter by a joint Armenian-British task force in early

1919). With the withdrawal of the Russian armies from the Caucasus front in the winter of 1917–18, the three major republics braced for an imminent Ottoman advance, which commenced in the early months of 1918. Solidarity was briefly maintained when the Transcaucasian Federative Republic was created in the spring of 1918, but this collapsed in May, whenthe Georgians asked and received protection from Germany and the Azerbaijanis concluded a treaty with the Ottoman Empire that was more akin to a military alliance. Armenia was left tofend for itself and struggled for five months against the threat of a full-fledged occupation by the Ottoman Turks.[153]

Allied victory: summer 1918 onwards

Allies increased their front-line rifle strength while German strength fell in half in 1918[154]

Hundred Days Offensive

Main articles: Hundred Days Offensive and Weimar RepublicAerial view of ruins of Vaux-devant-Damloup, France, 1918.

The Allied counteroffensive, known as the Hundred Days Offensive, began on 8 August 1918, with the Battle of Amiens. The battle involved over 400 tanks and 120,000 British, Dominion, and French troops, and by the end of its first day agap 15 mi (24 km) long had been created in the German lines. The defenders displayed a marked collapse in morale, causing Ludendorff to refer to this day as the "Black Day of the

German army".[155][156] After an advance as far as 14 miles (23 km), German resistance stiffened, and the battle was concluded on 12 August.

Rather than continuing the Amiens battle past the point of initial success, as had been done so many times in the past, the Allies shifted their attention elsewhere. Allied leaders had now realised that to continue an attack after resistance had hardened was a waste of lives, and it was better to turn aline than to try to roll over it. They began to undertake attacks in quick order to take advantage of successful advances on the flanks, then broke them off when each attack lost its initial impetus.[157]

Canadian Scottish, advancing during the Battle of the Canal duNord, 1918.

British and Dominion forces launched the next phase of the campaign with the Battle of Albert on 21 August.[158] The assault was widened by French[159] and then further British forces in the following days. During the last week of August the pressure along a 70-mile (113 km) front against the enemy was heavy and unrelenting. From German accounts, "Each day wasspent in bloody fighting against an ever and again on-stormingenemy, and nights passed without sleep in retirements to new lines."[157]

Faced with these advances, on 2 September the German Oberste Heeresleitung (OHL) issued orders to withdraw to the Hindenburg Line in the south. This ceded without a fight the salient seized the previous April.[160] According to Ludendorff "We had to admit the necessity ... to withdraw the entire front from the Scarpe to the Vesle."[161]

September saw the Allied advance to the Hindenburg Line in thenorth and centre. The Germans continued to fight strong rear-guard actions and launched numerous counterattacks on lost positions, but only a few succeeded, and then only temporarily. Contested towns, villages, heights, and trenches in the screening positions and outposts of the Hindenburg Linecontinued to fall to the Allies, with the BEF alone taking 30,441 prisoners in the last week of September. On 24 September an assault by both the British and French came within 2 miles (3.2 km) of St. Quentin.[159] The Germans had nowretreated to positions at or behind the Hindenburg Line.

An American major, piloting an observation balloon near the front, 1918.

In nearly four weeks of fighting beginning 8 August, over 100,000 German prisoners were taken, 75,000 by the BEF and therest by the French. As of "The Black Day of the German Army", the German High Command realised that the war was lost and made attempts to reach a satisfactory end. The day after that battle, Ludendorff said: "We cannot win the war any more, but we must not lose it either." On 11 August he offered his resignation to the Kaiser, who refused it, replying, "I see that we must strike a balance. We have nearly reached the limit of our powers of resistance. The war must be ended." On 13 August, at Spa, Hindenburg, Ludendorff, the Chancellor, andForeign Minister Hintz agreed that the war could not be ended

militarily and, on the following day, the German Crown Councildecided that victory in the field was now most improbable. Austria and Hungary warned that they could only continue the war until December, and Ludendorff recommended immediate peacenegotiations. Prince Rupprecht warned Prince Max of Baden: "Our military situation has deteriorated so rapidly that I no longer believe we can hold out over the winter; it is even possible that a catastrophe will come earlier." On 10 September Hindenburg urged peace moves to Emperor Charles of Austria, and Germany appealed to the Netherlands for mediation. On 14 September Austria sent a note to all belligerents and neutrals suggesting a meeting for peace talkson neutral soil, and on 15 September Germany made a peace offer to Belgium. Both peace offers were rejected, and on 24 September OHL informed the leaders in Berlin that armistice talks were inevitable.[159]

The final assault on the Hindenburg Line began with the Meuse-Argonne Offensive, launched by French and American troops on 26 September. The following week, cooperating French and American units broke through in Champagne at the Battle of Blanc Mont Ridge, forcing the Germans off the commanding heights, and closing towards the Belgian frontier.[162] On 8 October the line was pierced again by British and Dominion troops at the Battle of Cambrai.[163] The German army had to shorten its front and use the Dutch frontier as an anchor to fight rear-guard actions as it fell back towards Germany.

When Bulgaria signed a separate armistice on 29 September, Ludendorff, having been under great stress for months, suffered something similar to a breakdown. It was evident thatGermany could no longer mount a successful defence.[164][165]

Men of US 64th Regiment, 7th Infantry Division, celebrate the news of the Armistice, 11 November 1918.

News of Germany's impending military defeat spread throughout the German armed forces. The threat of mutiny was rife. Admiral Reinhard Scheer and Ludendorff decided to launch a last attempt to restore the "valour" of the German Navy. Knowing the government of Prince Maximilian of Baden would veto any such action, Ludendorff decided not to inform him. Nonetheless, word of the impending assault reached sailors at Kiel. Many, refusing to be part of a naval offensive, which they believed to be suicidal, rebelled and were arrested. Ludendorff took the blame; the Kaiser dismissed him on 26 October. The collapse of the Balkans meant that Germany was about to lose its main supplies of oil and food. Its reserves had been used up, even as US troops kept arriving at the rate of 10,000 per day.[166] The Americans supplied more than 80% of Allied oil during the war, meaning no such loss of supplies could affect the Allied effort.[167]

With the military faltering and with widespread loss of confidence in the Kaiser, Germany moved towards peace. Prince Maximilian of Baden took charge of a new government as Chancellor of Germany to negotiate with the Allies. Negotiations with President Wilson began immediately, in the hope that he would offer better terms than the British and French. Wilson demanded a constitutional monarchy and parliamentary control over the German military.[168] There was no resistance when the Social Democrat Philipp Scheidemann on 9 November declared Germany to be a republic. The Kaiser, kings and other hereditary rulers all were removed from power.Imperial Germany was dead; a new Germany had been born: the Weimar Republic.[169]

Armistices and capitulations

Main article: Armistice of 11 November 1918

Ferdinand Foch, second from right, pictured outside the carriage in Compiègne after agreeing to the armistice that ended the war there. The carriage was later chosen by Nazi Germany as the symbolic setting of Pétain's June 1940 armistice.[170]

The collapse of the Central Powers came swiftly. Bulgaria was the first to sign an armistice, on 29 September 1918 at Saloniki.[171] On 30 October, the Ottoman Empire capitulated, signing the Armistice of Mudros.[171]

On 24 October, the Italians began a push that rapidly recovered territory lost after the Battle of Caporetto. This culminated in the Battle of Vittorio Veneto, which marked the end of the Austro-Hungarian Army as an effective fighting force. The offensive also triggered the disintegration of the Austro-Hungarian Empire. During the last week of October, declarations of independence were made in Budapest, Prague, and Zagreb. On 29 October, the imperial authorities asked Italy for an armistice. But the Italians continued advancing, reaching Trento, Udine, and Trieste. On 3 November, Austria-Hungary sent a flag of truce to ask for an armistice. The terms, arranged by telegraph with the Allied Authorities in Paris, were communicated to the Austrian commander and accepted. The Armistice with Austria was signed in the Villa Giusti, near Padua, on 3 November. Austria and Hungary signed separate armistices following the overthrow of the Habsburg Monarchy. Following the outbreak of the German Revolution of

1918–1919, a republic was proclaimed on 9 November. The Kaiserfled to the Netherlands.

The New York Times of 11 November 1918.

On 11 November, at 5:00 am, an armistice with Germany was signed in a railroad carriage at Compiègne. At 11 am on 11 November 1918—"the eleventh hour of the eleventh day of the eleventh month"—a ceasefire came into effect. During the six hours between the signing of the armistice and its taking effect, opposing armies on the Western Front began to withdrawfrom their positions, but fighting continued along many areas of the front, as commanders wanted to capture territory beforethe war ended.

The occupation of the Rhineland took place following the Armistice. The occupying armies consisted of American, Belgian, British and French forces.

In November 1918, the Allies had ample supplies of men and materiel to invade Germany. Yet at the time of the armistice, no Allied force had crossed the German frontier; the Western

Front was still some 450 mi (720 km) from Berlin; and the Kaiser's armies had retreated from the battlefield in good order. These factors enabled Hindenburg and other senior German leaders to spread the story that their armies had not really been defeated. This resulted in the stab-in-the-back legend,[172][173] which attributed Germany's defeat not to its inability to continue fighting (even though up to a million soldiers were suffering from the 1918 flu pandemic and unfit to fight), but to the public's failure to respond to its "patriotic calling" and the supposed intentional sabotage of the war effort, particularly by Jews, Socialists, and Bolsheviks.

The Allies had much more potential wealth they could spend on the war. One estimate (using 1913 US dollars) is that the Allies spent $58 billion on the war and the Central Powers only $25 billion. Among the Allies, the UK spent $21 billion and the US $17 billion; among the Central Powers Germany spent$20 billion.[174]

AftermathMain article: Aftermath of World War I

The French military cemetery at the Douaumont ossuary, which contains the remains of more than 130,000 unknown soldiers.

In the aftermath of the war, four empires disappeared: the German, Austro-Hungarian, Ottoman, and Russian. Numerous nations regained their former independence, and new ones created. Four dynasties, together with their ancillary aristocracies, all fell after the war: the Hohenzollerns, the Habsburgs, and the Ottomans. Belgium and Serbia were badly damaged, as was France, with 1.4 million soldiers dead,[175] notcounting other casualties. Germany and Russia were similarly affected.[176]

Formal end of the war

A formal state of war between the two sides persisted for another seven months, until the signing of the Treaty of Versailles with Germany on 28 June 1919. The United States Senate did not ratify the treaty despite public support for it,[177][178] and did not formally end its involvement in the war until the Knox–Porter Resolution was signed on 2 July 1921 by President Warren G. Harding.[179] For the United Kingdom and theBritish Empire, the state of war ceased under the provisions of the Termination of the Present War (Definition) Act 1918 with respect to:

Germany on 10 January 1920.[180]

Austria on 16 July 1920.[181]

Bulgaria on 9 August 1920.[182]

Hungary on 26 July 1921.[183]

Turkey on 6 August 1924.[184]

After the Treaty of Versailles, treaties with Austria, Hungary, Bulgaria, and the Ottoman Empire were signed. However, the negotiation of the latter treaty with the OttomanEmpire was followed by strife (the Turkish War of Independence), and a final peace treaty between the Allied Powers and the country that would shortly become the Republic of Turkey was not signed until 24 July 1923, at Lausanne.

Some war memorials date the end of the war as being when the Versailles Treaty was signed in 1919, which was when many of the troops serving abroad finally returned to their home countries; by contrast, most commemorations of the war's end concentrate on the armistice of 11 November 1918. Legally, theformal peace treaties were not complete until the last, the Treaty of Lausanne, was signed. Under its terms, the Allied forces divested Constantinople on 23 August 1923.

Peace treaties and national boundaries

The Signing of Peace in the Hall of Mirrors, Versailles, 28th June 1919

After the war, the Paris Peace Conference imposed a series of peace treaties on the Central Powers officially ending the war. The 1919 Treaty of Versailles dealt with Germany, and building on Wilson's 14th point, brought into being the Leagueof Nations on 28 June 1919.[185][186]

The Central Powers had to acknowledge responsibility for "all the loss and damage to which the Allied and Associated Governments and their nationals have been subjected as a consequence of the war imposed upon them by" their aggression.In the Treaty of Versailles, this statement was Article 231. This article became known as War Guilt clause as the majority of Germans felt humiliated and resentful.[187] Overall the Germans felt they had been unjustly dealt by what they called the "diktat of Versailles." Schulze says, the Treaty placed Germany, "under legal sanctions, deprived of military power, economically ruined, and politically humiliated."[188] Belgian historian Laurence Van Ypersele emphasizes the central role played by memory of the war and the Versailles Treaty in German politics in the 1920s and 1930s:

Active denial of war guilt in Germany and German resentment at both reparations and continued Allied occupation of the Rhineland made widespread revision of the meaning and memory of the war problematic. The legendof the "stab in the back" and the wish to revise the "Versailles diktat", and the belief in an international threat aimed at the elimination of the German nation

persisted at the heart of German politics. Even a man of peace such as Stresemann publicly rejected German guilt. As for the Nazis, they waved the banners of domestic treason and international conspiracy in an attempt to galvanize the German nation into a spirit of revenge. Like a Fascist Italy, Nazi Germany sought to redirect thememory of the war to the benefit of its own policies.[189]

Meanwhile, new nations liberated from German rule viewed the treaty as recognition of wrongs committed against small nations by much larger aggressive neighbors.[190] The Peace Conference required all the defeated powers to pay reparationsfor all the damage done to civilians. However, owing to economic difficulties and Germany being the only defeated power with an intact economy, the burden fell largely on Germany.

Austria-Hungary was partitioned into several successor states,including Austria, Hungary, Czechoslovakia and Yugoslavia, largely but not entirely along ethnic lines. Transylvania was shifted from Hungary to Greater Romania. The details were contained in the Treaty of Saint-Germain and the Treaty of Trianon. As a result of the Treaty of Trianon, 3.3 million Hungarians came under foreign rule. Although the Hungarians made up 54% of the population of the pre-war Kingdom of Hungary, only 32% of its territory was left to Hungary. Between 1920 and 1924, 354,000 Hungarians fled former Hungarian territories attached to Romania, Czechoslovakia, andYugoslavia.[191]

The Russian Empire, which had withdrawn from the war in 1917 after the October Revolution, lost much of its western frontier as the newly independent nations of Estonia, Finland,Latvia, Lithuania, and Poland were carved from it. Romania took control of Bessarabia in April 1918.[192]

The Ottoman Empire disintegrated, and much of its non-Anatolian territory was awarded to various Allied powers as protectorates. The Turkish core in Anatolia was reorganised asthe Republic of Turkey. The Ottoman Empire was to be partitioned by the Treaty of Sèvres of 1920. This treaty was never ratified by the Sultan and was rejected by the Turkish National Movement, leading to the victorious Turkish War of

Independence and the much less stringent 1923 Treaty of Lausanne.

National identities

Further information: Sykes–Picot Agreement

Poland reemerged as an independent country, after more than a century. The Kingdom of Serbia and its dynasty, as a "minor Entente nation" and the country with the most casualties per capita,[193][194][195] became the backbone of a new multinational state, the Kingdom of Serbs, Croats and Slovenes, later renamed Yugoslavia. Czechoslovakia, combining the Kingdom of Bohemia with parts of the Kingdom of Hungary, became a new nation. Russia became the Soviet Union and lost Finland, Estonia, Lithuania, and Latvia, which became independent countries. The Ottoman Empire was soon replaced by Turkey and several other countries in the Middle East.

Map of territorial changes in Europe after World War I (as of 1923).

In the British Empire, the war unleashed new forms of nationalism. In Australia and New Zealand the Battle of Gallipoli became known as those nations' "Baptism of Fire". Itwas the first major war in which the newly established countries fought, and it was one of the first times that Australian troops fought as Australians, not just subjects of the British Crown. Anzac Day, commemorating the Australian andNew Zealand Army Corps, celebrates this defining moment.[196][197]

After the Battle of Vimy Ridge, where the Canadian divisions fought together for the first time as a single corps, Canadians began to refer to theirs as a nation "forged from fire".[198] Having succeeded on the same battleground where the "mother countries" had previously faltered, they were for the

first time respected internationally for their own accomplishments. Canada entered the war as a Dominion of the British Empire and remained so, although it emerged with a greater measure of independence.[199][200] When Britain declared war in 1914, the dominions were automatically at war; at the conclusion, Canada, Australia, New Zealand, and South Africa were individual signatories of the Treaty of Versailles.[201]

The establishment of the modern state of Israel and the roots of the continuing Israeli–Palestinian conflict are partially found in the unstable power dynamics of the Middle East that resulted from World War I.[202] Before the end of the war, the Ottoman Empire had maintained a modest level of peace and stability throughout the Middle East.[203] With the fall of the Ottoman government, power vacuums developed and conflicting claims to land and nationhood began to emerge.[204] The political boundaries drawn by the victors of World War I were quickly imposed, sometimes after only cursory consultation with the local population. These continue to be problematic inthe 21st-century struggles for national identity.[205][206] While the dissolution of the Ottoman Empire at the end of World War I was pivotal in contributing to the modern political situation of the Middle East, including the Arab-Israeli conflict,[207][208][209] the end of Ottoman rule also spawned lesserknown disputes over water and other natural resources.[210]

Health effects

Transporting Ottoman wounded at Sirkeci.

Emergency military hospital during the Spanish flu pandemic, which killed about 675,000 people in the United States alone. Camp Funston, Kansas, 1918.

The war had profound consequences in the health of soldiers. Of the 60 million European military personnel who were mobilized from 1914 to 1918, 8   million were killed , 7 million were permanently disabled, and 15 million were seriously injured. Germany lost 15.1% of its active male population, Austria-Hungary lost 17.1%, and France lost 10.5%.[211] In Germany civilian deaths were 474,000 higher than in peacetime,due in large part to food shortages and malnutrition that weakened resistance to disease.[212] By the end of the war, starvation caused by famine had killed approximately 100,000 people in Lebanon.[213] Between 5 and 10 million people died in the Russian famine of 1921.[214] By 1922, there were between 4.5 million and 7 million homeless children in Russia as a result of nearly a decade of devastation from World War I, the Russian Civil War, and the subsequent famine of 1920–1922.[215] Numerous anti-Soviet Russians fled the country after the Revolution; by the 1930s, the northern Chinese city of Harbin had 100,000 Russians.[216] Thousands more emigrated to France, England, and the United States.

In Australia, the effects of the war on the economy were no less severe. The Australian prime minister, Billy Hughes, wrote to the British prime minister, Lloyd George, "You have assured us that you cannot get better terms. I much regret it,and hope even now that some way may be found of securing agreement for demanding reparation commensurate with the tremendous sacrifices made by the British Empire and her Allies."[217] Australia received ₤5,571,720 war reparations, butthe direct cost of the war to Australia had been ₤376,993,052,and, by the mid-1930s, repatriation pensions, war gratuities, interest and sinking fund charges were ₤831,280,947.[217] Of

about 416,000 Australians who served, about 60,000 were killedand another 152,000 were wounded.[218]

Diseases flourished in the chaotic wartime conditions. In 1914alone, louse-borne epidemic typhus killed 200,000 in Serbia.[219] From 1918 to 1922, Russia had about 25 million infections and 3 million deaths from epidemic typhus.[220] In 1923, 13 million Russians contracted malaria, a sharp increase from thepre-war years.[221] In addition, a major influenza epidemic spread around the world. Overall, the 1918 flu pandemic killedat least 50 million people.[222][223]

Lobbying by Chaim Weizmann and fear that American Jews would encourage the United States to support Germany culminated in the British government's Balfour Declaration of 1917, endorsing creation of a Jewish homeland in Palestine.[224] A total of more than 1,172,000 Jewish soldiers served in the Allied and Central Power forces in World War I, including 275,000 in Austria-Hungary and 450,000 in Czarist Russia.[225]

The social disruption and widespread violence of the Russian Revolution of 1917 and the ensuing Russian Civil War sparked more than 2,000 pogroms in the former Russian Empire, mostly in Ukraine.[226] An estimated 60,000–200,000 civilian Jews were killed in the atrocities.[227]

In the aftermath of World War I, Greece fought against Turkishnationalists led by Mustafa Kemal, a war which eventually resulted in a massive population exchange between the two countries under the Treaty of Lausanne.[228] According to various sources,[229] several hundred thousand Greeks died during this period, which was tied in with the Greek Genocide.[230]

TechnologySee also: Technology during World War I and Weapons of World War I

Ground warfare

A Russian armoured car, 1919

World War I began as a clash of 20th-century technology and 19th-century tactics, with the inevitably large ensuing casualties. By the end of 1917, however, the major armies, nownumbering millions of men, had modernised and were making use of telephone, wireless communication,[231] armoured cars, tanks,[232] and aircraft. Infantry formations were reorganised, so that 100-man companies were no longer the main unit of manoeuvre; instead, squads of 10 or so men, under the command of a junior NCO, were favoured.

Artillery also underwent a revolution. In 1914, cannons were positioned in the front line and fired directly at their targets. By 1917, indirect fire with guns (as well as mortars and even machine guns) was commonplace, using new techniques for spotting and ranging, notably aircraft and the often overlooked field telephone.[233] Counter-battery missions becamecommonplace, also, and sound detection was used to locate enemy batteries.

Germany was far ahead of the Allies in utilising heavy indirect fire. The German Army employed 150 mm (6 in) and 210 mm (8 in) howitzers in 1914, when typical French and British guns were only 75 mm (3 in) and 105 mm (4 in). The British had a 6 inch (152 mm) howitzer, but it was so heavy ithad to be hauled to the field in pieces and assembled. The Germans also fielded Austrian 305 mm (12 in) and 420 mm (17 in) guns and, even at the beginning of the war, had inventories of various calibers of Minenwerfer, which were ideally suited for trench warfare.[234]

Much of the combat involved trench warfare, in which hundreds often died for each yard gained. Many of the deadliest battlesin history occurred during World War I. Such battles include Ypres, the Marne, Cambrai, the Somme, Verdun, and Gallipoli. The Germans employed the Haber process of nitrogen fixation to

provide their forces with a constant supply of gunpowder despite the British naval blockade.[235] Artillery was responsible for the largest number of casualties[236] and consumed vast quantities of explosives. The large number of head wounds caused by exploding shells and fragmentation forced the combatant nations to develop the modern steel helmet, led by the French, who introduced the Adrian helmet in1915. It was quickly followed by the Brodie helmet, worn by British Imperial and US troops, and in 1916 by the distinctiveGerman Stahlhelm, a design, with improvements, still in use today.

Gas! GAS! Quick, boys! – Anecstasy of fumbling,Fitting the clumsy helmets just in time;But someone still was yelling out and stumbling,And flound'ring like a man in fire or lime ...Dim, through the misty panes and thick green light,As under a green sea, I sawhim drowning.

—Wilfred Owen, Dulce et Decorum est, 1917[237]

A Canadian soldier with mustard gasburns, ca. 1917–1918.

The widespread use of chemical warfare was a distinguishing feature of the conflict. Gases used included chlorine, mustardgas and phosgene. Few war casualties were caused by gas,[238] aseffective countermeasures to gas attacks were quickly created,such as gas masks. The use of chemical warfare and small-scalestrategic bombing were both outlawed by the Hague Conventions of 1899 and 1907, and both proved to be of limited effectiveness,[239] though they captured the public imagination.[240]

The most powerful land-based weapons were railway guns, manufactured by the Krupp works, weighing hundreds of tons

apiece. These were nicknamed Big Berthas, even though the namesake was not a railway gun. Germany developed the Paris Gun, able to bombard Paris from over 100 kilometres (62 mi), though shells were relatively light at 94 kilograms (210 lb).

British Vickers machine gun, 1917.

Trenches, machine guns, air reconnaissance, barbed wire, and modern artillery with fragmentation shells helped bring the battle lines of World War I to a stalemate. The British and the French sought a solution with the creation of the tank andmechanised warfare. The British first tanks were used during the Battle of the Somme on 15 September 1916. Mechanical reliability was an issue, but the experiment proved its worth.Within a year, the British were fielding tanks by the hundreds, and they showed their potential during the Battle ofCambrai in November 1917, by breaking the Hindenburg Line, while combined arms teams captured 8,000 enemy soldiers and 100 guns. Meanwhile, the French introduced the first tanks with a rotating turret, the Renault FT, which became a decisive tool of the victory. The conflict also saw the introduction of light automatic weapons and submachine guns, such as the Lewis Gun, the Browning automatic rifle, and the Bergmann MP18.

Another new weapon, the flamethrower, was first used by the German army and later adopted by other forces. Although not ofhigh tactical value, the flamethrower was a powerful, demoralising weapon that caused terror on the battlefield.

Trench railways evolved to supply the enormous quantities of food, water, and ammunition required to support large numbers of soldiers in areas where conventional transportation systemshad been destroyed. Internal combustion engines and improved traction systems for automobiles and trucks/lorries eventuallyrendered trench railways obsolete.

Naval

Germany deployed U-boats (submarines) after the war began. Alternating between restricted and unrestricted submarine warfare in the Atlantic, the Kaiserliche Marine employed them to deprive the British Isles of vital supplies. The deaths of British merchant sailors and the seeming invulnerability of U-boats led to the development of depth charges (1916), hydrophones (passive sonar, 1917), blimps, hunter-killer submarines (HMS R-1 , 1917), forward-throwing anti-submarine weapons, and dipping hydrophones (the latter two both abandoned in 1918).[80] To extend their operations, the Germans proposed supply submarines (1916). Most of these would be forgotten in the interwar period until World War II revived the need.

Aviation

Main article: Aviation in World War I

RAF Sopwith Camel. In April 1917, the average life expectancy of a British pilot on the Western Front was 93 flying hours.[241]

Fixed-wing aircraft were first used militarily by the Italiansin Libya on 23 October 1911 during the Italo-Turkish War for reconnaissance, soon followed by the dropping of grenades and aerial photography the next year. By 1914, their military utility was obvious. They were initially used for reconnaissance and ground attack. To shoot down enemy planes, anti-aircraft guns and fighter aircraft were developed. Strategic bombers were created, principally by the Germans andBritish, though the former used Zeppelins as well.[242] Towards the end of the conflict, aircraft carriers were used for the first time, with HMS   Furious launching Sopwith Camels in a raid to destroy the Zeppelin hangars at Tondern in 1918.[243]

Manned observation balloons, floating high above the trenches,were used as stationary reconnaissance platforms, reporting enemy movements and directing artillery. Balloons commonly hada crew of two, equipped with parachutes,[244] so that if there was an enemy air attack the crew could parachute to safety. Atthe time, parachutes were too heavy to be used by pilots of aircraft (with their marginal power output), and smaller versions were not developed until the end of the war; they were also opposed by the British leadership, who feared they might promote cowardice.[245]

Recognised for their value as observation platforms, balloons were important targets for enemy aircraft. To defend them against air attack, they were heavily protected by antiaircraft guns and patrolled by friendly aircraft; to attack them, unusual weapons such as air-to-air rockets were even tried. Thus, the reconnaissance value of blimps and balloons contributed to the development of air-to-air combat between all types of aircraft, and to the trench stalemate, because it was impossible to move large numbers of troops undetected. The Germans conducted air raids on England during 1915 and 1916 with airships, hoping to damage British morale and cause aircraft to be diverted from the front lines, and indeed the resulting panic led to the diversion of several squadrons of fighters from France.[242][245]

War crimesBaralong incidents

Main article: Baralong incidents

On 19 August 1915, the German submarine U-27 was sunk by the British Q-ship HMS Baralong . All German survivors were summarily executed by Baralong's crew on the orders of Lieutenant Godfrey Herbert, the captain of the ship. The shooting was reported to the media by American citizens who were on board the Nicosia, a British freighter loaded with war supplies, which was stopped by U-27 just minutes before the incident.[246]

On 24 September, Baralong destroyed U-41, which was in the process of sinking the cargo ship Urbino. According to Karl Goetz, the submarine's commander, Baralong continued to fly theUS flag after firing on U-41 and then rammed the lifeboat – carrying the German survivors – sinking it.[247]

HMHS Llandovery Castle

The Canadian hospital ship HMHS Llandovery Castle was torpedoed by the German submarine SM U-86 on 27 June 1918 in violation of international law. Only 24 of the 258 medical personnel, patients, and crew survived. Survivors reported that the U-boat surfaced and ran down the lifeboats, machine-gunning survivors in the water. The U-boat captain, Helmut Patzig, was charged with war crimes in Germany following the war, but escaped prosecution by going to the Free City of Danzig, beyond the jurisdiction of German courts.[248]

Chemical weapons in warfare

Main article: Chemical weapons in World War IFrench soldiers making a gas and flame attack on German trenches in Flanders

The first successful use of poison gas as a weapon of warfare occurred during the Second Battle of Ypres (April 22-May 25, 1915).[249] Gas was soon used by all major belligerents throughout the war. It is estimated that the use of chemical weapons employed by both sides throughout the war had inflicted 1.3 million casualties. For example, the British hadover 180,000 chemical weapons casualties during the war, and up to one-third of American casualties were caused by them. The Russian Army reportedly suffered roughly 500,000 chemical weapon casualties in World War I.[250] The use of chemical weapons in warfare was in direct violation of the 1899 Hague Declaration Concerning Asphyxiating Gases and the 1907 Hague Convention on Land Warfare, which prohibited their use.[251][252]

Poison gas was not only limited to combatants but also civilians as civilian towns were at risk from winds blowing the poison gases through. Civilians rarely had a warning system put into place to alert their neighbors of the danger. In addition to poor warning systems, civilians often did not

have access to effective gas masks. An estimated 100,000–260,000 civilian casualties were caused by chemical weapons during the conflict and tens of thousands of more (along with military personnel) died from scarring of the lungs, skin damage, and cerebral damage in the years after the conflict ended. Many commanders on both sides knew that such weapons would cause major harm to civilians as wind would blow poison gases into nearby civilian towns but nonetheless continued to use them throughout the war. British Field Marshal Sir DouglasHaig wrote in his diary: "My officers and I were aware that such weapons would cause harm to women and children living in nearby towns, as strong winds were common in the battlefront. However, because the weapon was to be directed against the enemy, none of us were overly concerned at all."[253][254][255][256]

Genocide and ethnic cleansing

Austro-Hungarian soldiers executing men and women in Serbia, 1916.[257]

Armenians killed during the Armenian Genocide. Image taken from Ambassador Morgenthau's Story, written by Henry Morgenthau, Sr. and published in 1918.[258]

Main article: Ottoman casualties of World War ISee also: Armenian Genocide, Assyrian Genocide, Greek genocideand Genocide denial

The ethnic cleansing of the Ottoman Empire's Armenian population, including mass deportations and executions, duringthe final years of the Ottoman Empire is considered genocide.

[259] The Ottomans saw the entire Armenian population as an enemy [260] that had chosen to side with Russia at the beginning of the war.[261] In early 1915, a number of Armenians joined theRussian forces, and the Ottoman government used this as a pretext to issue the Tehcir Law (Law on Deportation). This authorized the deportation of Armenians from the Empire's eastern provinces to Syria between 1915 and 1917. The exact number of deaths is unknown, however the International Association of Genocide Scholars estimates over 1 million.[259]

[262] The government of Turkey has consistently rejected chargesof genocide, arguing that those who died were victims of inter-ethnic fighting, famine, or disease during World War I.[263] Other ethnic groups were similarly attacked by the OttomanEmpire during this period, including Assyrians and Greeks, andsome scholars consider those events to be part of the same policy of extermination.[264][265][266]

Russian Empire

Main article: Anti-Jewish pogroms in the Russian EmpireSee also: Russian occupation of Eastern Galicia, 1914–1915, Volhynia and Volga Germans

Many pogroms accompanied the Russian Revolution of 1917 and the ensuing Russian Civil War. 60,000–200,000 civilian Jews were killed in the atrocities throughout the former Russian Empire (mostly within the Pale of Settlement in present-day Ukraine).[267]

Rape of Belgium

Main article: Rape of Belgium

The German invaders treated any resistance—such as sabotaging rail lines—as illegal and immoral, and shot the offenders and burned buildings in retaliation. In addition, they tended to suspect that most civilians were potential franc-tireurs (guerrillas) and, accordingly, took and sometimes killed hostages from among the civilian population. The German army executed over 6,500 French and Belgian civilians between August and November 1914, usually in near-random large-scale shootings of civilians ordered by junior German officers. The German Army destroyed 15,000–20,000 buildings—most famously

the university library at Louvain—and generated a wave of refugees of over a million people. Over half the German regiments in Belgium were involved in major incidents.[268] Thousands of workers were shipped to Germany to work in factories. British propaganda dramatizing the Rape of Belgium attracted much attention in the United States, while Berlin said it was both lawful and necessary because of the threat offranc-tireurs like those in France in 1870.[269] The British andFrench magnified the reports and disseminated them at home andin the United States, where they played a major role in dissolving support for Germany.[270][271]

Soldiers' experiencesMain articles: List of last surviving World War I veterans by country, World War I casualties, Commonwealth War Graves Commission and American Battle Monuments Commission

The First Contingent of the Bermuda Volunteer Rifle Corps to the 1 Lincolns, training in Bermuda for the Western Front, winter 1914–1915. The two BVRC contingents suffered 75% casualties.

The British soldiers of the war were initially volunteers but increasingly were conscripted into service. Surviving veterans, returning home, often found that they could only discuss their experiences amongst themselves. Grouping together, they formed "veterans' associations" or "Legions".

Prisoners of war

Main article: World War I prisoners of war in GermanyGerman prisoners in a French prison camp, during the later part of the war.

About eight million men surrendered and were held in POW campsduring the war. All nations pledged to follow the Hague Conventions on fair treatment of prisoners of war, and the survival rate for POWs was generally much higher than that of

their peers at the front.[272] Individual surrenders were uncommon; large units usually surrendered en masse. At the siege of Maubeuge about 40,000 French soldiers surrendered, atthe battle of Galicia Russians took about 100,000 to 120,000 Austrian captives, at the Brusilov Offensive about 325,000 to 417,000 Germans and Austrians surrendered to Russians, at the Battle of Tannenberg 92,000 Russians surrendered. When the besieged garrison of Kaunas surrendered in 1915, some 20,000 Russians became prisoners, at the battle near Przasnysz (February–March 1915) 14,000 Germans surrendered to Russians, at the First Battle of the Marne about 12,000 Germans surrendered to the Allies. 25–31% of Russian losses (as a proportion of those captured, wounded, or killed) were to prisoner status; for Austria-Hungary 32%, for Italy 26%, for France 12%, for Germany 9%; for Britain 7%. Prisoners from theAllied armies totalled about 1.4 million (not including Russia, which lost 2.5–3.5 million men as prisoners). From theCentral Powers about 3.3 million men became prisoners; most ofthem surrendered to Russians.[273] Germany held 2.5 million prisoners; Russia held 2.2–2.9 million; while Britain and France held about 720,000. Most were captured just before the Armistice. The United States held 48,000. The most dangerous moment was the act of surrender, when helpless soldiers were sometimes gunned down.[274][275] Once prisoners reached a camp, conditions were, in general, satisfactory (and much better than in World War II), thanks in part to the efforts of the International Red Cross and inspections by neutral nations. However, conditions were terrible in Russia: starvation was common for prisoners and civilians alike; about 15–20% of the prisoners in Russia died and in Central Powers imprisonment—8%of Russians.[276] In Germany, food was scarce, but only 5% died.[277][278][279]

Emaciated Indian Army soldier who survived the Siege of Kut.

The Ottoman Empire often treated POWs poorly.[280] Some 11,800 British Empire soldiers, most of them Indians, became prisoners after the Siege of Kut in Mesopotamia in April 1916;4,250 died in captivity.[281] Although many were in a poor condition when captured, Ottoman officers forced them to march1,100 kilometres (684 mi) to Anatolia. A survivor said: "We were driven along like beasts; to drop out was to die."[282] Thesurvivors were then forced to build a railway through the Taurus Mountains.

In Russia, when the prisoners from the Czech Legion of the Austro-Hungarian army were released in 1917, they re-armed themselves and briefly became a military and diplomatic force during the Russian Civil War.

While the Allied prisoners of the Central Powers were quickly sent home at the end of active hostilities, the same treatmentwas not granted to Central Power prisoners of the Allies and Russia, many of whom served as forced labor, e.g., in France until 1920. They were released only after many approaches by the Red Cross to the Allied Supreme Council.[283] German prisoners were still being held in Russia as late as 1924.[284]

Military attachés and war correspondents

Main article: Military attachés and war correspondents in the First World War

Military and civilian observers from every major power closelyfollowed the course of the war. Many were able to report on

events from a perspective somewhat akin to modern "embedded" positions within the opposing land and naval forces.

Support and opposition to the warSupport

Poster urging women to join the British war effort, published by the Young Women's Christian Association

In the Balkans, Yugoslav nationalists such as the leader, AnteTrumbić, strongly supported the war, desiring the freedom of Yugoslavs from Austria-Hungary and other foreign powers and the creation of an independent Yugoslavia.[285] The Yugoslav Committee was formed in Paris on 30 April 1915 but shortly moved its office to London; Trumbić led the Committee.[285] In April 1918, the Rome Congress of Oppressed Nationalities met, including Czechoslovak, Italian, Polish, Transylvanian, and Yugoslav representatives who urged the Allies to support national self-determination for the peoples residing within Austria-Hungary.[286]

In the Middle East, Arab nationalism soared in Ottoman territories in response to the rise of Turkish nationalism during the war, with Arab nationalist leaders advocating the creation of a pan-Arab state.[287] In 1916, the Arab Revolt

began in Ottoman-controlled territories of the Middle East in an effort to achieve independence.[287]

A number of socialist parties initially supported the war whenit began in August 1914.[286] But European socialists split on national lines, with the concept of class conflict held by radical socialists such as Marxists and syndicalists being overborne by their patriotic support for war.[288] Once the war began, Austrian, British, French, German, and Russian socialists followed the rising nationalist current by supporting their countries' intervention in the war.[289]

Italian nationalism was stirred by the outbreak of the war andwas initially strongly supported by a variety of political factions. One of the most prominent and popular Italian nationalist supporters of the war was Gabriele d'Annunzio, whopromoted Italian irredentism and helped sway the Italian public to support intervention in the war.[290] The Italian Liberal Party, under the leadership of Paolo Boselli, promotedintervention in the war on the side of the Allies and utilisedthe Dante Alighieri Society to promote Italian nationalism.[291]

Italian socialists were divided on whether to support the war or oppose it; some were militant supporters of the war, including Benito Mussolini and Leonida Bissolati.[292] However, the Italian Socialist Party decided to oppose the war after anti-militarist protestors were killed, resulting in a generalstrike called Red Week.[293] The Italian Socialist Party purged itself of pro-war nationalist members, including Mussolini.[293]

Mussolini, a syndicalist who supported the war on grounds of irredentist claims on Italian-populated regions of Austria-Hungary, formed the pro-interventionist Il Popolo d'Italia and the Fasci Rivoluzionario d'Azione Internazionalista ("Revolutionary Fasci for International Action") in October 1914 that later developed into the Fasci di Combattimento in 1919, the origin of fascism.[294] Mussolini's nationalism enabled him to raise funds from Ansaldo (an armaments firm) and other companies to create Il Popolo d'Italia to convince socialists and revolutionaries to support the war.[295]

Opposition

Main articles: Opposition to World War I and French Army Mutinies

Sackville Street (now O'Connell Street) after the 1916 Easter Rising in Dublin.

Once war was declared, many socialists and trade unions backedtheir governments. Among the exceptions were the Bolsheviks, the Socialist Party of America, and the Italian Socialist Party, and individuals such as Karl Liebknecht, Rosa Luxemburg, and their followers in Germany.

Benedict XV, elected to the papacy less than three months intoWorld War I, made the war and its consequences the main focus of his early pontificate. In stark contrast to his predecessor,[296] five days after his election he spoke of his determination to do what he could to bring peace. His first encyclical, Ad beatissimi Apostolorum, given 1 November 1914, was concerned with this subject. Benedict XV found his abilities and unique position as a religious emissary of peaceignored by the belligerent powers. The 1915 Treaty of London between Italy and the Triple Entente included secret provisions whereby the Allies agreed with Italy to ignore papal peace moves towards the Central Powers. Consequently, the publication of Benedict's proposed seven-point Peace Note of August 1917 was roundly ignored by all parties except Austria-Hungary.[297]

The Deserter, 1916. Anti-war cartoon depicting Jesus facing a firing squad with soldiers from five European countries.

In Britain, in 1914, the Public Schools Officers' Training Corps annual camp was held at Tidworth Pennings, near

Salisbury Plain. Head of the British Army, Lord Kitchener, wasto review the cadets, but the imminence of the war prevented him. General Horace Smith-Dorrien was sent instead. He surprised the two-or-three thousand cadets by declaring (in the words of Donald Christopher Smith, a Bermudian cadet who was present), "that war should be avoided at almost any cost, that war would solve nothing, that the whole of Europe and more besides would be reduced to ruin, and that the loss of life would be so large that whole populations would be decimated. In our ignorance I, and many of us, felt almost ashamed of a British General who uttered such depressing and unpatriotic sentiments, but during the next four years, those of us who survived the holocaust—probably not more than one-quarter of us—learned how right the General's prognosis was and how courageous he had been to utter it."[298] Voicing these sentiments did not hinder Smith-Dorien's career, or prevent him from doing his duty in World War I to the best of his abilities.

Execution at Verdun at the time of the mutinies in 1917.

German Revolution, Kiel, 1918.

Many countries jailed those who spoke out against the conflict. These included Eugene Debs in the United States and Bertrand Russell in Britain. In the US, the Espionage Act of 1917 and Sedition Act of 1918 made it a federal crime to oppose military recruitment or make any statements deemed "disloyal". Publications at all critical of the government were removed from circulation by postal censors,[142] and many

served long prison sentences for statements of fact deemed unpatriotic.

A number of nationalists opposed intervention, particularly within states that the nationalists were hostile to. Although the vast majority of Irish people consented to participate in the war in 1914 and 1915, a minority of advanced Irish nationalists staunchly opposed taking part.[299] The war began amid the Home Rule crisis in Ireland that had resurfaced in 1912 and, by July 1914, there was a serious possibility of an outbreak of civil war in Ireland.[300] Irish nationalists and Marxists attempted to pursue Irish independence, culminating in the Easter Rising of 1916, with Germany sending 20,000 rifles to Ireland to stir unrest in Britain.[300] The UK government placed Ireland under martial law in response to theEaster Rising; although, once the immediate threat of revolution had dissipated, the authorities did try to make concessions to nationalist feeling.[301]

Other opposition came from conscientious objectors—some socialist, some religious—who refused to fight. In Britain, 16,000 people asked for conscientious objector status.[302] Someof them, most notably prominent peace activist Stephen Henry Hobhouse, refused both military and alternative service.[303] Many suffered years of prison, including solitary confinement and bread and water diets. Even after the war, in Britain manyjob advertisements were marked "No conscientious objectors need apply".

The Central Asian Revolt started in the summer of 1916, when the Russian Empire government ended its exemption of Muslims from military service.[304]

In 1917, a series of French Army Mutinies led to dozens of soldiers being executed and many more imprisoned.

In Milan, in May 1917, Bolshevik revolutionaries organised andengaged in rioting calling for an end to the war, and managed to close down factories and stop public transportation.[305] TheItalian army was forced to enter Milan with tanks and machine guns to face Bolsheviks and anarchists, who fought violently until 23 May when the army gained control of the city. Almost

50 people (including three Italian soldiers) were killed and over 800 people arrested.[305]

In September 1917, Russian soldiers in France began questioning why they were fighting for the French at all and mutinied.[306] In Russia, opposition to the war led to soldiers also establishing their own revolutionary committees, which helped foment the October Revolution of 1917, with the call going up for "bread, land, and peace". The Bolsheviks agreed to a peace treaty with Germany, the peace of Brest-Litovsk, despite its harsh conditions.

In northern Germany, the end of October 1918 saw the beginningof the German Revolution of 1918–1919. Units of the German Navy refused to set sail for a last, large-scale operation in a war which they saw as good as lost; this initiated the uprising. The sailors' revolt which then ensued in the naval ports of Wilhelmshaven and Kiel spread across the whole country within days and led to the proclamation of a republic on 9 November 1918 and shortly thereafter to the abdication ofKaiser Wilhelm II.

Conscription

Young men registering for conscription, New York City, June 5,1917.

Conscription was common in most European countries. However itwas controversial in English speaking countries. It was especially unpopular among minority ethnic groups—especially the Irish Catholics in Ireland[307] and Australia, and the French Catholics in Canada. In Canada the issue produced a major political crisis that permanently alienated the Francophiles. It opened a political gap between French Canadians, who believed their true loyalty was to Canada and

not to the British Empire, and members of the Anglophone majority, who saw the war as a duty to their British heritage.[308] In Australia, a sustained pro-conscription campaign by Billy Hughes, the Prime Minister, caused a split in the Australian Labor Party, so Hughes formed the Nationalist Partyof Australia in 1917 to pursue the matter. Farmers, the labourmovement, the Catholic Church, and the Irish Catholics successfully opposed Hughes' push, which was rejected in two plebiscites.[309]

In Britain, conscription resulted in the calling up of nearly every physically fit man in Britain—six of ten million eligible. Of these, about 750,000 lost their lives; Most deaths were to young unmarried men; however, 160,000 wives lost husbands and 300,000 children lost fathers.[310] In the United States, conscription began in 1917 and was generally well received, with a few pockets of opposition in isolated rural areas.[311]

Legacy and memoryMain article: World War I in popular culture

... "Strange, friend," I said, "Here is no cause to mourn.""None," said the other, "Save the undone years"... 

—Wilfred Owen, Strange Meeting, 1918[237]

The first tentative efforts to comprehend the meaning and consequences of modern warfare began during the initial phasesof the war, and this process continued throughout and after the end of hostilities, and still is underway, more than a century later.

Historiography

Historian Heather Jones argues that the historiography has been reinvigorated by the cultural turn in recent years. Scholars have raised entirely new questions regarding militaryoccupation, radicalizion of politics, race, and the male body.Furthermore, new research has revised our understanding of five major topics that historians have long debated. These are: Why did the war begin? Why did the Allies win? Were the

generals to blame for the high casualty rates? How did the soldiers endure the horrors of trench warfare? To what extent did the civilian homefront accept and endorse the war effort?[312]

Memorials

A typical village war memorial to soldiers killed in World WarIMain article: World War I memorials

Memorials were erected in thousands of villages and towns. Close to battlefields, those buried in improvised burial grounds were gradually moved to formal graveyards under the care of organisations such as the Commonwealth War Graves Commission, the American Battle Monuments Commission, the German War Graves Commission, and Le Souvenir français. Many of these graveyards also have central monuments to the missingor unidentified dead, such as the Menin Gate memorial and the Thiepval Memorial to the Missing of the Somme.

On 3 May 1915, during the Second Battle of Ypres, Lieutenant Alexis Helmer was killed. At his graveside, his friend John McCrae, M.D., of Guelph, Ontario, Canada, wrote the memorable poem In Flanders Fields as a salute to those who perished in the Great War. Published in Punch on 8 December 1915, it is still recited today, especially on Remembrance Day and Memorial Day.[313][314]

National WWI Museum and Memorial in Kansas City, Missouri, is a United States memorial dedicated to all Americans who servedin World War I. The Liberty Memorial was dedicated on 1 November 1921, when the supreme Allied commanders spoke to a crowd of more than 100,000 people.[315] It was the only time in history these leaders were together in one place—Lieutenant

General Baron Jacques of Belgium; General Armando Diaz of Italy; Marshal Ferdinand Foch of France; General Pershing of the United States; and Admiral D. R. Beatty of Britain.[316] After three years of construction, the Liberty Memorial was completed and President Calvin Coolidge delivered the dedication speech to a crowd of 150,000 people in 1926. Liberty Memorial is also home to the National World War I Museum, the only museum in the United States dedicated solely to World War I.[315]

The UK Government has budgeted substantial resources to the commemoration of the war during the period 2014 to 2018. The lead body is the Imperial War Museum.[317] On 3 August 2014, French President Francois Hollande and German President Joachim Gauck together marked the centenary of Germany's declaration of war on France by laying the first stone of a memorial in Vieil Armand, known in German as Hartmannswillerkopf, for French and German soldiers killed in the war.[318]

Cultural memory

Left: John McCrae, author of In Flanders Fields.Right: Siegfried Sassoon.

World War I had a lasting impact on social memory. It was seenby many in Britain as signalling the end of an era of stability stretching back to the Victorian period, and across Europe many regarded it as a watershed.[319] Historian Samuel Hynes explained:

A generation of innocent young men, their heads full of high abstractions like Honour, Glory and England, went off to war to make the world safe for democracy. They were slaughtered instupid battles planned by stupid generals. Those who survived were shocked, disillusioned and embittered by their war experiences, and saw that their real enemies were not the Germans, but the old men at home who had lied to them. They rejected the values of the society that had sent them to war, and in doing so separated their own generation from the past and from their cultural inheritance.[320]

This has become the most common perception of World War I, perpetuated by the art, cinema, poems, and stories published subsequently. Films such as All Quiet on the Western Front, Paths of Gloryand King & Country have perpetuated the idea, while war-time films including Camrades, Poppies of Flanders, and Shoulder Arms indicate that the most contemporary views of the war were overall far more positive.[321] Likewise, the art of Paul Nash, John Nash, Christopher Nevinson, and Henry Tonks in Britain painted a negative view of the conflict in keeping with the growing perception, while popular war-time artists such as Muirhead Bone painted more serene and pleasant interpretationssubsequently rejected as inaccurate.[320] Several historians like John Terraine, Niall Ferguson and Gary Sheffield have challenged these interpretations as partial and polemical views:

These beliefs did not become widely shared because they offered the only accurate interpretation of wartime events. Inevery respect, the war was much more complicated than they suggest. In recent years, historians have argued persuasively against almost every popular cliché of World War I. It has been pointed out that, although the losses were devastating, their greatest impact was socially and geographically limited.

The many emotions other than horror experienced by soldiers inand out of the front line, including comradeship, boredom, andeven enjoyment, have been recognised. The war is not now seen as a 'fight about nothing', but as a war of ideals, a strugglebetween aggressive militarism and more or less liberal democracy. It has been acknowledged that British generals wereoften capable men facing difficult challenges, and that it wasunder their command that the British army played a major part in the defeat of the Germans in 1918: a great forgotten victory.[321]

Though these views have been discounted as "myths",[320][322] theyare common.[321] They have dynamically changed according to contemporary influences, reflecting in the 1950s perceptions of the war as "aimless" following the contrasting Second WorldWar and emphasising conflict within the ranks during times of class conflict in the 1960s.[321] The majority of additions to the contrary are often rejected.[321]

Social trauma

A 1919 book for veterans, from the US War Department.

The social trauma caused by unprecedented rates of casualties manifested itself in different ways, which have been the subject of subsequent historical debate.[323]

The optimism of la belle époque was destroyed, and those who had fought in the war were referred to as the Lost Generation.[324] For years afterwards, people mourned the dead, the missing,

and the many disabled.[325] Many soldiers returned with severe trauma, suffering from shell shock (also called neurasthenia, a condition related to posttraumatic stress disorder).[326] Manymore returned home with few after-effects; however, their silence about the war contributed to the conflict's growing mythological status.[323] Though many participants did not sharein the experiences of combat or spend any significant time at the front, or had positive memories of their service, the images of suffering and trauma became the widely shared perception.[323] Such historians as Dan Todman, Paul Fussell, and Samuel Heyns have all published works since the 1990s arguing that these common perceptions of the war are factuallyincorrect.[323]

Discontent in Germany

The rise of Nazism and Fascism included a revival of the nationalist spirit and a rejection of many post-war changes. Similarly, the popularity of the stab-in-the-back legend (German: Dolchstoßlegende) was a testament to the psychological state of defeated Germany and was a rejection of responsibility for the conflict. This conspiracy theory of betrayal became common, and the German populace came to see themselves as victims. The widespread acceptance of the "stab-in-the-back" theory delegitimized the Weimar government and destabilized the system, opening it to extremes of right and left.

Communist and fascist movements around Europe drew strength from this theory and enjoyed a new level of popularity. These feelings were most pronounced in areas directly or harshly affected by the war. Adolf Hitler was able to gain popularity by utilising German discontent with the still controversial Treaty of Versailles.[327] World War II was in part a continuation of the power struggle never fully resolved by World War I. Furthermore, it was common for Germans in the 1930s to justify acts of aggression due to perceived injustices imposed by the victors of World War I.[328][329][330] American historian William Rubinstein wrote that:

The 'Age of Totalitarianism' included nearly all of the infamous examples of genocide in modern history, headed by theJewish Holocaust, but also comprising the mass murders and

purges of the Communist world, other mass killings carried outby Nazi Germany and its allies, and also the Armenian genocideof 1915. All these slaughters, it is argued here, had a commonorigin, the collapse of the elite structure and normal modes of government of much of central, eastern and southern Europe as a result of World War I, without which surely neither Communism nor Fascism would have existed except in the minds of unknown agitators and crackpots.[331]

Economic effects

See also: Economic history of World War I

Poster showing women workers, 1915.

One of the most dramatic effects of the war was the expansion of governmental powers and responsibilities in Britain, France, the United States, and the Dominions of the British Empire. To harness all the power of their societies, governments created new ministries and powers. New taxes were levied and laws enacted, all designed to bolster the war effort; many have lasted to this day. Similarly, the war strained the abilities of some formerly large and bureaucratised governments, such as in Austria-Hungary and Germany.

Gross domestic product (GDP) increased for three Allies (Britain, Italy, and US), but decreased in France and Russia, in neutral Netherlands, and in the three main Central Powers.

The shrinkage in GDP in Austria, Russia, France, and the Ottoman Empire ranged between 30% to 40%. In Austria, for example, most pigs were slaughtered, so at war's end there wasno meat.

In all nations, the government's share of GDP increased, surpassing 50% in both Germany and France and nearly reaching that level in Britain. To pay for purchases in the United States, Britain cashed in its extensive investments in American railroads and then began borrowing heavily on Wall Street. President Wilson was on the verge of cutting off the loans in late 1916, but allowed a great increase in US government lending to the Allies. After 1919, the US demanded repayment of these loans. The repayments were, in part, fundedby German reparations which, in turn, were supported by American loans to Germany. This circular system collapsed in 1931 and the loans were never repaid. Britain still owed the United States $4.4 billion [332] of World War I debt in 1934, andthis money was never repaid.[333]

Macro- and micro-economic consequences devolved from the war. Families were altered by the departure of many men. With the death or absence of the primary wage earner, women were forcedinto the workforce in unprecedented numbers. At the same time,industry needed to replace the lost labourers sent to war. This aided the struggle for voting rights for women.[334]

Hyperinflation reduced German banknotes' value so much that they could be used as wallpaper. Many savers were ruined.[335]

World War I further compounded the gender imbalance, adding tothe phenomenon of surplus women. The deaths of nearly one million men during the war in Britain increased the gender gapby almost a million; from 670,000 to 1,700,000. The number of unmarried women seeking economic means grew dramatically. In addition, demobilisation and economic decline following the war caused high unemployment. The war increased female employment; however, the return of demoblised men displaced many from the workforce, as did the closure of many of the wartime factories.

In Britain, rationing was finally imposed in early 1918, limited to meat, sugar, and fats (butter and margarine), but not bread. The new system worked smoothly. From 1914 to 1918, trade union membership doubled, from a little over four million to a little over eight million.

Britain turned to her colonies for help in obtaining essentialwar materials whose supply had become difficult from traditional sources. Geologists such as Albert Ernest Kitson were called on to find new resources of precious minerals in the African colonies. Kitson discovered important new depositsof manganese, used in munitions production, in the Gold Coast.[336]

Article 231 of the Treaty of Versailles (the so-called "war guilt" clause) stated Germany accepted responsibility for "allthe loss and damage to which the Allied and Associated Governments and their nationals have been subjected as a consequence of the war imposed upon them by the aggression of Germany and her allies."[337] It was worded as such to lay a legal basis for reparations, and the same clause was inserted,mutatis mutandis "in the treaties with Austria and Hungary, neither of whom interpreted it as declaration of war guilt."[338] In 1921, the total reparation sum was placed at 132billion gold marks. However, "Allied experts knew that Germanycould not pay" this sum. The total sum was divided into three categories, with the third being "deliberately designed to be chimerical" and its "primary function was to mislead public opinion ... into believing the "total sum was being maintained."[339] Thus, 50 billion gold marks (12.5 billion dollars) "represented the actual Allied assessment of German

capacity to pay" and "therefore ... represented the total German reparations" figure that had to be paid.[339]

This figure could be paid in cash or in kind (coal, timber, chemical dyes, etc.). In addition, some of the territory lost—via the treaty of Versailles—was credited towards the reparation figure as were other acts such as helping to restore the Library of Louvain.[340] By 1929, the Great Depression arrived, causing political chaos throughout the world.[341] In 1932 the payment of reparations was suspended by the international community, by which point Germany had only paid the equivalent of 20.598 billon gold marks in reparations.[342] With the rise of Adolf Hitler, all bonds and loans that had been issued and taken out during the 1920s and early 1930s were cancelled. David Andelman notes "refusing to pay doesn't make an agreement null and void. The bonds, the agreement, still exist." Thus, following the Second World War,at the London Conference in 1953, Germany agreed to resume payment on the money borrowed. On 3 October 2010, Germany madethe final payment on these bonds.[343]

Computational hardness assumptionFrom Wikipedia, the free encyclopedia

In cryptography, a major goal is to create cryptographic primitives with provable security. In some cases, cryptographic protocols are found to have information theoretic security; the one-time pad is a common example. However, information theoretic security cannot always be achieved; in such cases, cryptographers fall back to computational security. Roughly speaking, this means that these systems are secure assuming that any adversaries are computationally limited, as all adversaries are in practice. Becausehardness of a problem is difficult to prove, in practice certain problems are "assumed" to be difficult.

Common cryptographic hardness assumptions

There are many common cryptographic hardness assumptions. While the difficulty of solving any of the underlying problemsis unproven, some assumptions on the computational hardness are stronger than others. Note that if assumption A is stronger than assumption B, that means solving the problem underlying assumption B is polytime reducible to solving the problem underlying assumption A – which means that if B is solvable in poly time,A definitely is, but the reverse doesn't follow. When devisingcryptographic protocols, one hopes to be able to prove security using the weakest possible assumptions.

This is a list of some of the most common cryptographic hardness assumptions, and some cryptographic protocols that use them.

Integer factorization o Rabin cryptosystem o Blum Blum Shub generator o Okamoto–Uchiyama cryptosystem o Hofheinz–Kiltz–Shoup cryptosystem

RSA problem (weaker than factorization) o RSA cryptosystem

Quadratic residuosity problem (stronger than factorization)

o Goldwasser–Micali cryptosystem Decisional composite residuosity assumption (stronger

than factorization) o Paillier cryptosystem

Higher residuosity problem (stronger than factorization) o Benaloh cryptosystem o Naccache–Stern cryptosystem

Phi-hiding assumption (stronger than factorization) o Cachin–Micali–Stadler PIR

Discrete log problem (DLP) Computational Diffie–Hellman assumption (CDH; stronger

than DLP) o Diffie–Hellman key exchange

Decisional Diffie–Hellman assumption (DDH; stronger than CDH)

o ElGamal encryption Shortest Vector Problem

o NTRUEncrypt

o NTRUSign

Non-cryptographic hardness assumptionsAs well as their cryptographic applications, hardness assumptions are used in computational complexity theory to provide evidence for mathematical statements that are difficult to prove unconditionally. In these applications, oneproves that the hardness assumption implies some desired complexity-theoretic statement, instead of proving that the statement is itself true. The best-known assumption of this type is the assumption that P ≠ NP,[1] but others include the exponential time hypothesis [2] and the unique games conjecture.[3]

Integer factorization

From Wikipedia, the free encyclopedia

"Prime decomposition" redirects here. For the prime decomposition theorem for 3-manifolds, see Prime decomposition(3-manifold).

List of unsolved problems in computer science

Can integer factorization be done in polynomial time?

In number theory, integer factorization is the decomposition of a composite number into a product of smaller integers. If these integers are further restricted to prime numbers, the process is called prime factorization.

When the numbers are very large, no efficient, non-quantum integer factorization algorithm is known; an effort by severalresearchers concluded in 2009, factoring a 232-digit number (RSA-768), utilizing hundreds of machines over a span of two years.[1] However, it has not been proven that no efficient algorithm exists. The presumed difficulty of this problem is at the heart of widely used algorithms in cryptography such as

RSA. Many areas of mathematics and computer science have been brought to bear on the problem, including elliptic curves, algebraic number theory, and quantum computing.

Not all numbers of a given length are equally hard to factor. The hardest instances of these problems (for currently known techniques) are semiprimes, the product of two prime numbers. When they are both large, for instance more than two thousand bits long, randomly chosen, and about the same size (but not too close, e.g., to avoid efficient factorization by Fermat's factorization method), even the fastest prime factorization algorithms on the fastest computers can take enough time to make the search impractical; that is, as the number of digits of the primes being factored increases, the number of operations required to perform the factorization on any computer increases drastically.

Many cryptographic protocols are based on the difficulty of factoring large composite integers or a related problem—for example, the RSA problem. An algorithm that efficiently factors an arbitrary integer would render RSA-based public-keycryptography insecure.

Contents

1 Prime decomposition

2 Current state of the art

2.1 Difficulty and complexity

3 Factoring algorithms

3.1 Special-purpose

3.2 General-purpose

3.3 Other notable algorithms

4 Heuristic running time

5 Rigorous running time

5.1 Schnorr-Seysen-Lenstra Algorithm

5.2 Expected running time

6 Applications

6.1 Fast Fourier Transforms

7 See also

8 Notes

9 References

10 External links

Prime decomposition

This image demonstrates the prime decomposition of 864. A shorthand way of writing the resulting prime factors is 25 × 33

By the fundamental theorem of arithmetic, every positive integer greater than one has a unique prime factorization. A special case for one can be avoided using an appropriate notion of the empty product. However, the fundamental theorem of arithmetic gives no insight into how to obtain an integer'sprime factorization; it only guarantees its existence.

Given a general algorithm for integer factorization, one can factor any integer down to its constituent prime factors by repeated application of this algorithm. However, this is not the case with a special-purpose factorization algorithm, since

it may not apply to the smaller factors that occur during decomposition, or may execute very slowly on these values. Forexample, if N is the number (2521 − 1) × (2607 − 1), then trial division will quickly factor 10 × N as 2 × 5 × N, but will not quickly factor N into its factors.

Current state of the art

See also: integer factorization records

Among the b-bit numbers, the most difficult to factor in practice using existing algorithms are those that are productsof two primes of similar size. For this reason, these are the integers used in cryptographic applications. The largest such semiprime yet factored was RSA-768, a 768-bit number with 232 decimal digits, on December 12, 2009.[1] This factorization was a collaboration of several research institutions, spanningtwo years and taking the equivalent of almost 2000 years of computing on a single-core 2.2 GHz AMD Opteron. Like all recent factorization records, this factorization was completedwith a highly optimized implementation of the general number field sieve run on hundreds of machines.

Difficulty and complexity

No algorithm has been published that can factor all integers in polynomial time, i.e., that can factor b-bit numbers in time O(bk) for some constant k. There are published algorithmsthat are faster than O((1+ε)b) for all positive ε, i.e., sub-exponential.

The best published asymptotic running time is for the general number field sieve (GNFS) algorithm, which, for a b-bit numbern, is:

O\left(\exp\left(\left(\begin{matrix}\frac{64}{9}\end{matrix} b\right)^{1\over3} (\log b)^{2\over3}\right)\right).

For current computers, GNFS is the best published algorithm for large n (more than about 100 digits). For a quantum computer, however, Peter Shor discovered an algorithm in 1994 that solves it in polynomial time. This will have significant implications for cryptography if quantum computation is possible. Shor's algorithm takes only O(b3) time and O(b) space on b-bit number inputs. In 2001, the first seven-qubit quantum computer became the first to run Shor's algorithm. It factored the number 15.[2]

When discussing what complexity classes the integer factorization problem falls into, it's necessary to distinguish two slightly different versions of the problem:

The function problem version: given an integer N, find an integer d with 1 < d < N that divides N (or conclude that N isprime). This problem is trivially in FNP and it's not known whether it lies in FP or not. This is the version solved by practical implementations.

The decision problem version: given an integer N and an integer M with 1 < M < N, does N have a factor d with 1 < d ≤ M? This version is useful because most well-studied complexityclasses are defined as classes of decision problems, not function problems.

For M=\sqrt{N}, the decision problem is equivalent to asking if N is prime.

An algorithm for either version provides one for the other. Repeated application of the function problem (applied to d andN/d, and their factors, if needed) will eventually provide either a factor of N no larger than M or a factorization into primes all greater than M. All known algorithms for the decision problem work in this way. Hence it is only of theoretical interest that, with at most \log{N} queries using an algorithm for the decision problem, one would isolate a factor of N (or prove it prime) by binary search.

It is not known exactly which complexity classes contain the decision version of the integer factorization problem. It is known to be in both NP and co-NP. This is because both YES andNO answers can be verified in polynomial time. An answer of YES can be certified by exhibiting a factorization N = d(N/d) with d ≤ M. An answer of NO can be certified by exhibiting thefactorization of N into distinct primes, all larger than M. Wecan verify their primality using the AKS primality test, and that their product is N by multiplication. The fundamental theorem of arithmetic guarantees that there is only one possible string that will be accepted (providing the factors are required to be listed in order), which shows that the problem is in both UP and co-UP.[3] It is known to be in BQP because of Shor's algorithm. It is suspected to be outside of all three of the complexity classes P, NP-complete, and co-NP-complete. It is therefore a candidate for the NP-intermediate complexity class. If it could be proved that it is in either NP-Complete or co-NP-Complete, that would imply NP = co-NP. That would be a very surprising result, and therefore integer factorization is widely suspected to be outside both of those classes. Many people have tried to find classical polynomial-time algorithms for it and failed, and therefore it is widely suspected to be outside P.

In contrast, the decision problem "is N a composite number?" (or equivalently: "is N a prime number?") appears to be much easier than the problem of actually finding the factors of N.

Specifically, the former can be solved in polynomial time (in the number n of digits of N) with the AKS primality test. In addition, there are a number of probabilistic algorithms that can test primality very quickly in practice if one is willing to accept the vanishingly small possibility of error. The easeof primality testing is a crucial part of the RSA algorithm, as it is necessary to find large prime numbers to start with.

Factoring algorithms

Special-purpose

A special-purpose factoring algorithm's running time depends on the properties of the number to be factored or on one of its unknown factors: size, special form, etc. Exactly what therunning time depends on varies between algorithms.

An important subclass of special-purpose factoring algorithms is the Category 1 or First Category algorithms, whose running time depends on the size of smallest prime factor. Given an integer of unknown form, these methods are usually applied before general-purpose methods to remove small factors.[4] Forexample, trial division is a Category 1 algorithm.

Trial division

Wheel factorization

Pollard's rho algorithm

Algebraic-group factorisation algorithms, among which are Pollard's p − 1 algorithm, Williams' p + 1 algorithm, and Lenstra elliptic curve factorization

Fermat's factorization method

Euler's factorization method

Special number field sieve

General-purpose

A general-purpose factoring algorithm, also known as a Category 2, Second Category, or Kraitchik family algorithm (after Maurice Kraitchik),[4] has a running time which dependssolely on the size of the integer to be factored. This is the type of algorithm used to factor RSA numbers. Most general-purpose factoring algorithms are based on the congruence of squares method.

Dixon's algorithm

Continued fraction factorization (CFRAC)

Quadratic sieve

Rational sieve

General number field sieve

Shanks' square forms factorization (SQUFOF)

Other notable algorithms

Shor's algorithm, for quantum computers

Heuristic running time

In number theory, there are many integer factoring algorithms that heuristically have expected running time

L_n\left[1/2,1+o(1)\right]=e^{(1+o(1))(\log n)^{\frac{1}{2}}(\log \log n)^{\frac{1}{2}}}

in o and L-notation. Some examples of those algorithms are theelliptic curve method and the quadratic sieve. Another such algorithm is the class group relations method proposed by Schnorr,[5] Seysen,[6] and Lenstra,[7] that is proved under the assumption of the Generalized Riemann Hypothesis (GRH).

Rigorous running time

The Schnorr-Seysen-Lenstra probabilistic algorithm has been rigorously proven by Lenstra and Pomerance[8] to have expectedrunning time L_n\left[1/2,1+o(1)\right] by replacing the GRH assumption with the use of multipliers. The algorithm uses theclass group of positive binary quadratic forms of discriminantΔ denoted by GΔ. GΔ is the set of triples of integers (a, b, c) in which those integers are relative prime.

Schnorr-Seysen-Lenstra Algorithm

Given is an integer n that will be factored, where n is an oddpositive integer greater than a certain constant. In this factoring algorithm the discriminant Δ is chosen as a multipleof n, Δ= -dn, where d is some positive multiplier. The algorithm expects that for one d there exist enough smooth forms in GΔ. Lenstra and Pomerance show that the choice of d can be restricted to a small set to guarantee the smoothness result.

Denote by PΔ the set of all primes q with Kronecker symbol \left(\tfrac{\Delta}{q}\right)=1. By constructing a set of generators of GΔ and prime forms fq of GΔ with q in PΔ a sequence of relations between the set of generators and fq areproduced. The size of q can be bounded by c_0(\log|\Delta|)^2 for some constant c_0.

The relation that will be used is a relation between the product of powers that is equal to the neutral element of GΔ. These relations will be used to construct a so-called ambiguous form of GΔ, which is an element of GΔ of order dividing 2. By calculating the corresponding factorization of Δ and by taking a gcd, this ambiguous form provides the complete prime factorization of n. This algorithm has these main steps:

Let n be the number to be factored.

Let Δ be a negative integer with Δ = -dn, where d is a multiplier and Δ is the negative discriminant of some quadratic form.

Take the t first primes p_1=2,p_2=3,p_3=5, \dots ,p_t, forsome t\in{\mathbb N}.

Let f_q be a random prime form of GΔ with \left(\tfrac{\Delta}{q}\right)=1.

Find a generating set X of GΔ

Collect a sequence of relations between set X and {fq : q ∈ PΔ} satisfying: \left(\prod_{x \in X_{}} x^{r(x)}\right).\left(\prod_{q \in P_\Delta} f^{t(q)}_{q}\right) = 1

Construct an ambiguous form (a, b, c) that is an element f∈ GΔ of order dividing 2 to obtain a coprime factorization of the largest odd divisor of Δ in which Δ = -4a.c or a(a - 4c) or (b - 2a).(b + 2a)

If the ambiguous form provides a factorization of n then stop, otherwise find another ambiguous form until the factorization of n is found. In order to prevent useless ambiguous forms from generating, build up the 2-Sylow group S2(Δ) of G(Δ).

To obtain an algorithm for factoring any positive integer, it is necessary to add a few steps to this algorithm such as trial division, and the Jacobi sum test.

Expected running time

The algorithm as stated is a probabilistic algorithm as it makes random choices. Its expected running time is at most L_n\left[1/2,1+o(1)\right].[8]

Information-theoretic security

From Wikipedia, the free encyclopedia

(Redirected from Information theoretic security)

A cryptosystem is information-theoretically secure if its security derives purely from information theory. That is, it cannot be broken even when the adversary has unlimited computing power. Theadversary simply does not have enough information to break the encryption, so these cryptosystems are considered cryptanalytically unbreakable.

An encryption protocol that has information-theoretic securitydoes not depend for its effectiveness on unproven assumptions about computational hardness, and such an algorithm is not vulnerable to future developments in computer power such as quantum computing. An example of an information-theoretically secure cryptosystem is the one-time pad. The concept of information-theoretically secure

communication was introduced in 1949 by American mathematician Claude Shannon, the inventor of information theory, who used it to prove that the one-time pad system was secure.[1] Information-theoretically secure cryptosystems have been used for the most sensitive governmental communications, such as diplomatic cables andhigh-level military communications, because of the great efforts enemy governments expend toward breaking them.

An interesting special case is perfect security: an encryptionalgorithm is perfectly secure if a ciphertext produced using it provides no information about the plaintext without knowledge of thekey. If E is a perfectly secure encryption function, for any fixed message m there must exist for each ciphertext c at least one key k such that c = E_k(m). It has been proved that any cipher with the perfect secrecy property must use keys with effectively the same requirements as one-time pad keys.[1]

It is common for a cryptosystem to leak some information but nevertheless maintain its security properties even against an adversary that has unlimited computational resources. Such a cryptosystem would have information theoretic but not perfect security. The exact definition of security would depend on the cryptosystem in question.

There are a variety of cryptographic tasks for which information-theoretic security is a meaningful and useful requirement. A few of these are:

Secret sharing schemes such as Shamir's are information-theoretically secure (and also perfectly secure) in that less than the requisite number of shares of the secret provide no information about the secret.

More generally, secure multiparty computation protocols often, but not always, have information-theoretic security.

Private information retrieval with multiple databases can be achieved with information-theoretic privacy for the user's query.

Reductions between cryptographic primitives or tasks can often be achieved information-theoretically. Such reductions are important from a theoretical perspective, because they establish that primitive \Pi can be realized if primitive \Pi' can be realized.

Symmetric encryption can be constructed under an information-theoretic notion of security called entropic security, which assumes that the adversary knows almost nothing about the message being sent. The goal here is to hide all functions of the plaintext rather than all information about it.

Quantum cryptography is largely part of information-theoretic cryptography.

Besides the conventional methods of secrecy that just hides the message, there are scenarios that we need a stronger type of secrecy which not only hides the message by encryption, but also hides the existence of communication that is called covert communication. [2]

Contents

1 Physical layer encryption

2 Unconditional security

3 See also

4 References

Physical layer encryption

A weaker notion of security defined by Aaron D. Wyner established a now flourishing area of research known as physical layer encryption.[3] This exploits the physical wireless channel forits security by communications, signal processing, and coding techniques. The security is provable, unbreakable, and quantifiable (in bits/second/hertz).

Wyner's initial physical layer encryption work in the 1970s posed the Alice – Bob – Eve problem in which Alice wants to send a message to Bob without Eve decoding it. It was shown that if the channel from Alice to Bob is statistically better than the channel from Alice to Eve, secure communication is possible.[4] This is intuitive, but Wyner measured the secrecy in information theoretic terms defining secrecy capacity, which essentially is the rate at which Alice can transmit secret information to Bob. Shortly after, Imre Csiszár and Körner showed that secret communication was possible even when Eve had a statistically better channel to Alice than did Bob.[5] More recent theoretical results are concerned with determining the secrecy capacity and optimal power allocation in broadcast fading channels.[6][7] There are caveats, as many capacities are not computable unless the assumption is made that Alice knows the channel to Eve. If this were known, Alice could simply place a null in Eve's direction. Secrecy capacity for MIMO and multiple colluding eavesdroppers is more recent and ongoing work,[8][9] and these results still make the non-useful assumption about eavesdropper channel state information knowledge.

Still other work is less theoretical and attempts to compare implementable schemes. One physical layer encryption scheme is to broadcast artificial noise in all directions except that of Bob's channel, basically jamming Eve. One paper by Negi and Goel details the implementation, and Khisti and Wornell computed the secrecy capacity when only statistics about Eve's channel are known.[10][11]

Parallel to this work in the information theory community is work in the antenna community that has been termed near-field directantenna modulation or directional modulation.[12] It was shown that

by using a parasitic array, the transmitted modulation in different directions could be controlled independently.[13] Secrecy could be realized by making the modulations in undesired directions difficultto decode. Directional modulation data transmission was experimentally demonstrated using a phased array.[14] Others have demonstrated directional modulation with switched arrays and phase-conjugating lenses.[15][16][17]

This type of directional modulation is really a subset of Negiand Goel's additive artificial noise encryption scheme. Another scheme using pattern-reconfigurable transmit antennas for Alice called reconfigurable multiplicative noise (RMN) complements additive artificial noise.[18] The two work well together in channelsimulations in which nothing is assumed known to Alice or Bob about the eavesdroppers.

Unconditional security

Information-theoretic security is often used interchangeably with unconditional security. However, the latter term can also referto systems that don't rely on unproven computational hardness assumptions. Today these systems are essentially the same as those that are information-theoretically secure. Nevertheless, it does notalways have to be that way. One day RSA might be proved secure (it relies on the assertion that factoring large numbers is hard), thus becoming unconditionally secure, but it will never be information-theoretically secure (because even though no efficient algorithms for factoring large primes may exist, in principle it can still be done given unlimited computational power).

One-time pad

From Wikipedia, the free encyclopedia

Excerpt from a one-time pad

In cryptography, the one-time pad (OTP) is an encryption technique that cannot be cracked if used correctly. In this

technique, a plaintext is paired with a random secret key (also referred to as a one-time pad). Then, each bit or character of the plaintext is encrypted by combining it with the corresponding bit orcharacter from the pad using modular addition. If the key is truly random, is at least as long as the plaintext, is never reused in whole or in part, and is kept completely secret, then the resulting ciphertext will be impossible to decrypt or break.[1][2][3] It has also been proven that any cipher with the perfect secrecy property must use keys with effectively the same requirements as OTP keys.[4]However, practical problems have prevented one-time pads from being widely used.

First described by Frank Miller in 1882,[5][6] the one-time pad was re-invented in 1917. On July 22, 1919, U.S. Patent 1,310,719was issued to Gilbert S. Vernam for the XOR operation used for the encryption of a one-time pad.[7] It is derived from the Vernam cipher, named after Gilbert Vernam, one of its inventors. Vernam's system was a cipher that combined a message with a key read from a punched tape. In its original form, Vernam's system was vulnerable because the key tape was a loop, which was reused whenever the loop made a full cycle. One-time use came later, when Joseph Mauborgne recognized that if the key tape were totally random, then cryptanalysis would be impossible.[8]

The "pad" part of the name comes from early implementations where the key material was distributed as a pad of paper, so that the top sheet could be easily torn off and destroyed after use. For ease of concealment, the pad was sometimes reduced to such a small size that a powerful magnifying glass was required to use it. The KGB used pads of such size that they could fit in the palm of one's hand,[9] or in a walnut shell.[10] To increase security, one-time pads were sometimes printed onto sheets of highly flammable nitrocellulose, so that they could be quickly burned after use.

There is some ambiguity to the term because some authors[who?]use the terms "Vernam cipher" and "one-time pad" synonymously, whileothers refer to any additive stream cipher as a "Vernam cipher",

including those based on a cryptographically secure pseudorandom number generator (CSPRNG).[11]

Contents

1 History of invention

2 Example

2.1 Attempt at cryptanalysis

3 Perfect secrecy

4 Problems

4.1 Key distribution

4.2 Authentication

4.3 True randomness

5 Uses

5.1 Applicability

5.2 Historical uses

5.3 Exploits

6 See also

7 References

8 Further reading

9 External links

History of invention

Frank Miller in 1882 was the first to describe the one-time pad system for securing telegraphy.[6][12]

The next one-time pad system was electrical. In 1917, Gilbert Vernam (of AT&T Corporation) invented and later patented in 1919 (U.S. Patent 1,310,719) a cipher based on teleprinter technology. Each character in a message was electrically combined with a character on a paper tape key. Joseph Mauborgne (then a captain in the U.S. Army and later chief of the Signal Corps) recognized that the character sequence on the key tape could be completely random and that, if so, cryptanalysis would be more difficult. Together they invented the first one-time tape system.[11]

The next development was the paper pad system. Diplomats had long used codes and ciphers for confidentiality and to minimize telegraph costs. For the codes, words and phrases were converted to groups of numbers (typically 4 or 5 digits) using a dictionary-like codebook. For added security, secret numbers could be combined with (usually modular addition) each code group before transmission, withthe secret numbers being changed periodically (this was called superencryption). In the early 1920s, three German cryptographers (Werner Kunze, Rudolf Schauffler and Erich Langlotz), who were involved in breaking such systems, realized that they could never bebroken if a separate randomly chosen additive number was used for every code group. They had duplicate paper pads printed with lines of random number groups. Each page had a serial number and eight lines. Each line had six 5-digit numbers. A page would be used as a work sheet to encode a message and then destroyed. The serial numberof the page would be sent with the encoded message. The recipient would reverse the procedure and then destroy his copy of the page. The German foreign office put this system into operation by 1923.[11]

A separate notion was the use of a one-time pad of letters to encode plaintext directly as in the example below. Leo Marks describes inventing such a system for the British Special OperationsExecutive during World War II, though he suspected at the time that it was already known in the highly compartmentalized world of cryptography, as for instance at Bletchley Park.[13]

The final discovery was by Claude Shannon in the 1940s who recognized and proved the theoretical significance of the one-time pad system. Shannon delivered his results in a classified report in 1945, and published them openly in 1949.[4] At the same time, Vladimir Kotelnikov had independently proven absolute security of the one-time pad; his results were delivered in 1941 in a report that apparently remains classified.[14]

Example

Suppose Alice wishes to send the message "HELLO" to Bob. Assume two pads of paper containing identical random sequences of letters were somehow previously produced and securely issued to both. Alice chooses the appropriate unused page from the pad. The way to do this is normally arranged for in advance, as for instance 'use the 12th sheet on 1 May', or 'use the next available sheet for the next message'.

The material on the selected sheet is the key for this message. Each letter from the pad will be combined in a predetermined way with one letter of the message. (It is common, butnot required, to assign each letter a numerical value, e.g., "A" is 0, "B" is 1, and so on.)

In this example, the technique is to combine the key and the message using modular addition. The numerical values of corresponding message and key letters are added together, modulo 26.So, if key material begins with "XMCKL" and the message is "HELLO", then the coding would be done as follows:

H E L L O message

7 (H) 4 (E) 11 (L) 11 (L) 14 (O) message

+ 23 (X) 12 (M) 2 (C) 10 (K) 11 (L) key

= 30 16 13 21 25 message + key

= 4 (E) 16 (Q) 13 (N) 21 (V) 25 (Z) message + key (mod 26)

E Q N V Z → ciphertext

If a number is larger than 26, then the remainder after subtraction of 26 is taken in modular arithmetic fashion. This simply means that if the computations "go past" Z, the sequence starts again at A.

The ciphertext to be sent to Bob is thus "EQNVZ". Bob uses thematching key page and the same process, but in reverse, to obtain the plaintext. Here the key is subtracted from the ciphertext, againusing modular arithmetic:

E Q N V Z ciphertext

4 (E) 16 (Q) 13 (N) 21 (V) 25 (Z) ciphertext

- 23 (X) 12 (M) 2 (C) 10 (K) 11 (L) key

= -19 4 11 11 14 ciphertext – key

= 7 (H) 4 (E) 11 (L) 11 (L) 14 (O) ciphertext – key (mod 26)

H E L L O → message

Similar to the above, if a number is negative then 26 is addedto make the number zero or higher.

Thus Bob recovers Alice's plaintext, the message "HELLO". BothAlice and Bob destroy the key sheet immediately after use, thus preventing reuse and an attack against the cipher. The KGB often issued its agents one-time pads printed on tiny sheets of "flash

paper"—paper chemically converted to nitrocellulose, which burns almost instantly and leaves no ash.[15]

The classical one-time pad of espionage used actual pads of minuscule, easily concealed paper, a sharp pencil, and some mental arithmetic. The method can be implemented now as a software program,using data files as input (plaintext), output (ciphertext) and key material (the required random sequence). The XOR operation is often used to combine the plaintext and the key elements, and is especially attractive on computers since it is usually a native machine instruction and is therefore very fast. However, it is difficult to ensure that the key material is actually random, is used only once, never becomes known to the opposition, and is completely destroyed after use. The auxiliary parts of a software one-time pad implementation present real challenges: secure handling/transmission of plaintext, truly random keys, and one-time-only use of the key.

Attempt at cryptanalysis

To continue the example from above, suppose Eve intercepts Alice's ciphertext: "EQNVZ". If Eve had infinite time, she would find that the key "XMCKL" would produce the plaintext "HELLO", but she would also find that the key "TQURI" would produce the plaintext"LATER", an equally plausible message:

4 (E) 16 (Q) 13 (N) 21 (V) 25 (Z) ciphertext

− 19 (T) 16 (Q) 20 (U) 17 (R) 8 (I) possible key

= −15 0 −7 4 17 ciphertext-key

= 11 (L) 0 (A) 19 (T) 4 (E) 17 (R) ciphertext-key (mod 26)

In fact, it is possible to "decrypt" out of the ciphertext anymessage whatsoever with the same number of characters, simply by

using a different key, and there is no information in the ciphertextwhich will allow Eve to choose among the various possible readings of the ciphertext.

Perfect secrecy

One-time pads are "information-theoretically secure" in that the encrypted message (i.e., the ciphertext) provides no informationabout the original message to a cryptanalyst (except the maximum possible length[16] of the message). This is a very strong notion ofsecurity first developed during WWII by Claude Shannon and proved, mathematically, to be true for the one-time pad by Shannon about thesame time. His result was published in the Bell Labs Technical Journal in 1949.[17] Properly used one-time pads are secure in this sense even against adversaries with infinite computational power.

Claude Shannon proved, using information theory considerations, that the one-time pad has a property he termed perfect secrecy; that is, the ciphertext C gives absolutely no additional information about the plaintext. This is because, given atruly random key which is used only once, a ciphertext can be translated into any plaintext of the same length, and all are equally likely. Thus, the a priori probability of a plaintext message M is the same as the a posteriori probability of a plaintextmessage M given the corresponding ciphertext. Mathematically, this is expressed as H(M)=H(M|C), where H(M) is the entropy of the plaintext and H(M|C) is the conditional entropy of the plaintext given the ciphertext C. Perfect secrecy is a strong notion of cryptanalytic difficulty.[4]

Conventional symmetric encryption algorithms use complex patterns of substitution and transpositions. For the best of these currently in use, it is not known whether there can be a cryptanalytic procedure which can reverse (or, usefully, partially reverse) these transformations without knowing the key used during encryption. Asymmetric encryption algorithms depend on mathematical problems that are thought to be difficult to solve, such as integer

factorization and discrete logarithms. However there is no proof that these problems are hard, and a mathematical breakthrough could make existing systems vulnerable to attack.

Given perfect secrecy, in contrast to conventional symmetric encryption, OTP is immune even to brute-force attacks. Trying all keys simply yields all plaintexts, all equally likely to be the actual plaintext. Even with known plaintext, like part of the message being known, brute-force attacks cannot be used, since an attacker is unable to gain any information about the parts of the key needed to decrypt the rest of the message.

Problems

Despite Shannon's proof of its security, the one-time pad has serious drawbacks in practice because it requires:

Truly random (as opposed to pseudorandom) one-time pad values, which is a non-trivial requirement. See Pseudorandom number generator.

Secure generation and exchange of the one-time pad values,which must be at least as long as the message. (The security of the one-time pad is only as secure as the security of the one-time pad exchange).

Careful treatment to make sure that it continues to remainsecret, and is disposed of correctly preventing any reuse in whole or part—hence "one time". See data remanence for a discussion of difficulties in completely erasing computer media.

The theoretical perfect security of the one-time-pad applies only in a theoretically perfect setting; no real-world implementation of any cryptosystem can provide perfect security because practical considerations introduce potential vulnerabilities.

One-time pads solve few current practical problems in cryptography. High quality ciphers are widely available and their security is not considered a major worry at present.[when?][citationneeded] Such ciphers are almost always easier to employ than one-time pads; the amount of key material which must be properly generated and securely distributed is far smaller, and public key cryptography overcomes this problem.[18]

Key distribution

Further information: Key distribution

Because the pad, like all shared secrets, must be passed and kept secure, and the pad has to be at least as long as the message, there is often no point in using one-time padding, as one can simplysend the plain text instead of the pad (as both can be the same sizeand have to be sent securely). However, once a very long pad has been securely sent (e.g., a computer disk full of random data), it can be used for numerous future messages, until the sum of their sizes equals the size of the pad. Quantum key distribution also proposes a solution to this problem.

Distributing very long one-time pad keys is inconvenient and usually poses a significant security risk.[1] The pad is essentiallythe encryption key, but unlike keys for modern ciphers, it must be extremely long and is much too difficult for humans to remember. Storage media such as thumb drives, DVD-Rs or personal digital audioplayers can be used to carry a very large one-time-pad from place toplace in a non-suspicious way, but even so the need to transport thepad physically is a burden compared to the key negotiation protocolsof a modern public-key cryptosystem, and such media cannot reliably be erased securely by any means short of physical destruction (e.g.,incineration). A 4.7 GB DVD-R full of one-time-pad data, if shreddedinto particles 1 mm² in size, leaves over 4 megabits of (admittedly hard to recover, but not impossibly so) data on each particle.[citation needed] In addition, the risk of compromise during transit(for example, a pickpocket swiping, copying and replacing the pad)

is likely much greater in practice than the likelihood of compromisefor a cipher such as AES. Finally, the effort needed to manage one-time pad key material scales very badly for large networks of communicants—the number of pads required goes up as the square of the number of users freely exchanging messages. For communication between only two persons, or a star network topology, this is less of a problem.

The key material must be securely disposed of after use, to ensure the key material is never reused and to protect the messages sent.[1] Because the key material must be transported from one endpoint to another, and persist until the message is sent or received, it can be more vulnerable to forensic recovery than the transient plaintext it protects (see data remanence).

Authentication

As traditionally used, one-time pads provide no message authentication, the lack of which can pose a security threat in real-world systems. The straightforward XORing with the keystream, or the use of any invertible function known to the attacker, such asmod 26 addition, creates a potential vulnerability in message integrity. For example, an attacker who knows that the message contains "meet jane and me tomorrow at three thirty pm" at a particular point can replace that content by any other content of exactly the same length, such as "three thirty meeting is cancelled,stay home", without having access to the one-time pad, a property ofall stream ciphers known as malleability.[19] See also stream cipherattack.

Standard techniques to prevent this, such as the use of a message authentication code can be used along with a one-time pad system to prevent such attacks, as can classical methods such as variable length padding and Russian copulation, but they all lack the perfect security the OTP itself has. Universal hashing provides a way to authenticate messages up to an arbitrary security bound (i.e., for any p>0, a large enough hash ensures that even a

computationally unbounded attacker's likelihood of successful forgery is less than p), but this uses additional random data from the pad, and removes the possibility of implementing the system without a computer.

True randomness

High-quality random numbers are difficult to generate. The random number generation functions in most programming language libraries are not suitable for cryptographic use. Even those generators that are suitable for normal cryptographic use, including/dev/random and many hardware random number generators, make some use of cryptographic functions whose security is unproven.

In particular, one-time use is absolutely necessary. If a one-time pad is used just twice, simple mathematical operations can reduce it to a running key cipher. If both plaintexts are in a natural language (e.g., English or Russian or Irish) then, even though both are secret, each stands a very high chance of being recovered by heuristic cryptanalysis, with possibly a few ambiguities. Of course the longer message can only be broken for theportion that overlaps the shorter message, plus perhaps a little more by completing a word or phrase. The most famous exploit of thisvulnerability occurred with the Venona project.[20]

Uses

Applicability

Any digital data storage device can be used to transport one-time pad data.

Despite its problems, the one-time-pad retains some practical interest. In some hypothetical espionage situations, the one-time pad might be useful because it can be computed by hand with only pencil and paper. Indeed, nearly all other high quality ciphers are entirely impractical without computers. Spies can receive their padsin person from their "handlers." In the modern world, however,

computers (such as those embedded in personal electronic devices such as mobile phones) are so ubiquitous that possessing a computer suitable for performing conventional encryption (for example, a phone which can run concealed cryptographic software) will usually not attract suspicion.

The one-time-pad is the most optimal cryptosystem with theoretically perfect secrecy.

The one-time-pad is one of the most practical methods of encryption where one or both parties must do all work by hand, without the aid of a computer. This made it important in the pre-computer era, and it could conceivably still be useful in situationswhere possession of a computer is illegal or incriminating or where trustworthy computers are not available.

One-time pads are practical in situations where two parties in a secure environment must be able to depart from one another and communicate from two separate secure environments with perfect secrecy.

The one-time-pad can be used in superencryption.[21]

The algorithm most commonly associated with quantum key distribution is the one-time pad.

The one-time pad is mimicked by stream ciphers.

The one-time pad can be a part of an introduction to cryptography.[22]

Historical uses

One-time pads have been used in special circumstances since the early 1900s. In 1923, it was employed for diplomatic communications by the German diplomatic establishment.[23] The Weimar Republic Diplomatic Service began using the method in about 1920. The breaking of poor Soviet cryptography by the British, with messages made public for political reasons in two instances in the 1920s, appear to have induced the U.S.S.R. to adopt one-time pads for some purposes by around 1930. KGB spies are also known to have used pencil and paper one-time pads more recently. Examples include Colonel Rudolf Abel, who was arrested and convicted in New York Cityin the 1950s, and the 'Krogers' (i.e., Morris and Lona Cohen), who were arrested and convicted of espionage in the United Kingdom in the early 1960s. Both were found with physical one-time pads in their possession.

A number of nations have used one-time pad systems for their sensitive traffic. Leo Marks reports that the British Special Operations Executive used one-time pads in World War II to encode traffic between its offices. One-time pads for use with its overseasagents were introduced late in the war.[13] A few British one-time tape cipher machines include the Rockex and Noreen. The German StasiSprach Machine was also capable of using one time tape which East Germany, Russia, and even Cuba used to send encrypted messages to their agents.[24]

The World War II voice scrambler SIGSALY was also a form of one-time system. It added noise to the signal at one end and removedit at the other end. The noise was distributed to the channel ends in the form of large shellac records which were manufactured in unique pairs. There were both starting synchronization and longer-term phase drift problems which arose and were solved before the system could be used.

The NSA describes one-time tape systems like SIGTOT and 5-UCO as being used for intelligence traffic until the introduction of theelectronic cipher based KW-26 in 1957.[25]

The hotline between Moscow and Washington D.C., established in1963 after the Cuban missile crisis, used teleprinters protected by a commercial one-time tape system. Each country prepared the keying tapes used to encode its messages and delivered them via their embassy in the other country. A unique advantage of the OTP in this case was that neither country had to reveal more sensitive encryption methods to the other.[26]

During the 1983 Invasion of Grenada, U.S. forces found a supply of pairs of one-time pad books in a Cuban warehouse.[27]

Starting in 1988, the African National Congress (ANC) used disk-based one-time pads as part of a secure communication system between ANC leaders outside South Africa and in-country operatives as part of Operation Vula, a successful effort to build a resistancenetwork inside South Africa. Random numbers on the disk were erased after use. A Belgian airline stewardess acted as courier to bring inthe pad disks. A regular resupply of new disks was needed as they were used up fairly quickly. One problem with the system was that itcould not be used for secure data storage. Later Vula added a streamcipher keyed by book codes to solve this problem.[28]

A related notion is the one-time code—a signal, used only once, e.g., "Alpha" for "mission completed", "Bravo" for "mission failed" or even "Torch" for "Allied invasion of French Northern Africa" [29] cannot be "decrypted" in any reasonable sense of the word. Understanding the message will require additional information,often 'depth' of repetition, or some traffic analysis. However, suchstrategies (though often used by real operatives, and baseball coaches) are not a cryptographic one-time pad in any significant sense.

Exploits

While one-time pads provide perfect secrecy if generated and used properly, small mistakes can lead to successful cryptanalysis:

In 1944–1945, the U.S. Army's Signals Intelligence Servicewas able to solve a one-time pad system used by the German Foreign Office for its high-level traffic, codenamed GEE.[30] GEE was insecure because the pads were not completely random—the machine used to generate the pads produced predictable output.

In 1945, the US discovered that Canberra-Moscow messages were being encrypted first using a code-book and then using a one-time pad. However, the one-time pad used was the same one used by Moscow for Washington, DC-Moscow messages. Combined with the fact that some of the Canberra-Moscow messages included known British government documents, this allowed some of the encrypted messages tobe broken.

One-time pads were employed by Soviet espionage agencies for covert communications with agents and agent controllers. Analysis has shown that these padswere generated by typists using actual typewriters. This method is of course not truly random, as it makes certain convenient key sequences more likely than others, yet it proved to be generally effective because while a person will not produce truly random sequences they equally do not follow the same kind ofstructured mathematical rules that a machine would either, and each person generates ciphers in a different way making attacking any message challenging. Without copies of the key material used,only some defect in the generation method or

reEspionageFrom Wikipedia, the free encyclopedia"Spy" and "Secret agent" redirect here. For other uses, see Spy (disambiguation) and Secret agent (disambiguation).For other uses, see Espionage (disambiguation).

Espionage or, casually, spying involves a spy ring, governmentand company/firm or individual obtaining information considered secret or confidential without the permission of the holder of the information.[1] Espionage is inherently clandestine, as it is taken for granted that it is unwelcome and in many cases illegal and punishable by law. It is a subset of "intelligence gathering", which otherwise may be conducted from public sources and using perfectly legal and ethical means. It is crucial to distinguish espionage from "intelligence" gathering, as the latter does not necessarily involve espionage, but often collates open-source information.

Espionage is often part of an institutional effort by a government or commercial concern. However, the term is generally associated with state spying on potential or actual

enemies primarily for military purposes. Spying involving corporations is known as industrial espionage.

One of the most effective ways to gather data and information about the enemy (or potential enemy) is by infiltrating the enemy's ranks. This is the job of the spy (espionage agent). Spies can bring back all sorts of information concerning the size and strength of enemy forces. They can also find dissidents within the enemy's forces and influence them to defect. In times of crisis, spies can also be used to steal technology and to sabotage the enemy in various ways. Counterintelligence operatives can feed false information to enemy spies, protecting important domestic secrets, and preventing attempts at subversion. Nearly every country has very strict laws concerning espionage, and the penalty for being caught is often severe. However, the benefits that can be gained through espionage are generally great enough that most governments and many large corporations make use of it tovarying degrees.

Further information on clandestine HUMINT (human intelligence)information collection techniques is available, including discussions of operational techniques, asset recruiting, and the tradecraft used to collect this information.

Contents 1 History

o 1.1 Early historyo 1.2 Modern development

1.2.1 Military Intelligence 1.2.2 Naval Intelligence 1.2.3 Civil intelligence agencies 1.2.4 Counter-intelligence

o 1.3 First World War 1.3.1 Codebreaking

o 1.4 Russian Revolutiono 1.5 Today

2 Targets of espionage 3 Methods and terminology

o 3.1 Technology and techniques 4 Organization

5 Industrial espionage 6 Agents in espionage 7 Law 8 Use against non-spies 9 Espionage laws in the UK

o 9.1 Government intelligence laws and its distinctionfrom espionage

10 Military conflicts 11 List of famous spies

o 11.1 World War Io 11.2 World War IIo 11.3 Post World War II

12 Spy fiction o 12.1 World War II: 1939–1945o 12.2 Cold War era: 1945–1991

13 See also 14 References 15 Further reading 16 External links

HistoryEarly history

A bamboo version of The Art of War, written by Sun-Tzu and containing advice on espionage tactics.

Events involving espionage are well documented throughout history. The ancient writings of Chinese and Indian military strategists such as Sun-Tzu and Chanakya contain information on deception and subversion. Chanakya's student Chandragupta Maurya, founder of the Maurya Empire in India, made use of assassinations, spies and secret agents, which are described

in Chanakya's Arthasastra. The ancient Egyptians had a thoroughlydeveloped system for the acquisition of intelligence, and the Hebrews used spies as well, as in the story of Rahab. Spies were also prevalent in the Greek and Roman empires.[2] During the 13th and 14th centuries, the Mongols relied heavily on espionage in their conquests in Asia and Europe. Feudal Japan often used ninja to gather intelligence.

Aztecs used Pochtecas, people in charge of commerce, as spies and diplomats, and had diplomatic immunity. Along with the pochteca, before a battle or war, secret agents, quimitchin, were sent to spy amongst enemies usually wearing the local costume and speaking the local language, techniques similar tomodern secret agents.[3]

Many modern espionage methods were established by Francis Walsingham in Elizabethan England.[4] Walsingham's staff in England included the cryptographer Thomas Phelippes, who was an expert in deciphering letters and forgery, and Arthur Gregory, who was skilled at breaking and repairing seals without detection.[5]

In 1585, Mary, Queen of Scots was placed in the custody of SirAmias Paulet, who was instructed to open and read all of Mary's clandestine correspondence.[5] In a successful attempt to entrap her, Walsingham arranged a single exception: a covert means for Mary's letters to be smuggled in and out of Chartley in a beer keg. Mary was misled into thinking these secret letters were secure, while in reality they were deciphered and read by Walsingham's agents.[5] He succeeded in intercepting letters that indicated a conspiracy to displace Elizabeth I with Mary, Queen of Scots.

In foreign intelligence, Walsingham's extensive network of "intelligencers", who passed on general news as well as secrets, spanned Europe and the Mediterranean.[5] While foreignintelligence was a normal part of the principal secretary's activities, Walsingham brought to it flair and ambition, and large sums of his own money.[6] He cast his net more widely than others had done previously: expanding and exploiting links across the continent as well as in Constantinople and Algiers, and building and inserting contacts among Catholic exiles.[5]

Modern development

Political cartoon depicting the Afghan Emir Sher Ali with his "friends" the Russian Bear and British Lion (1878). The Great Game saw the rise of systematic espionage and surveillance throughout the region by both powers.

Modern tactics of espionage and dedicated government intelligence agencies were developed over the course of the late 19th century. A key background to this development was the Great Game, a period denoting the strategic rivalry and conflict that existed between the British Empire and the Russian Empire throughout Central Asia. To counter Russian ambitions in the region and the potential threat it posed to the British position in India, a system of surveillance, intelligence and counterintelligence was built up in the Indian Civil Service. The existence of this shadowy conflict was popularised in Rudyard Kipling's famous spy book, Kim, where he portrayed the Great Game (a phrase he popularised) asan espionage and intelligence conflict that 'never ceases, dayor night'.

Although the techniques originally used were distinctly amateurish - British agents would often pose unconvincingly asbotanists or archaeologists - more professional tactics and systems were slowly put in place. In many respects, it was here that a modern intelligence apparatus with permanent bureaucracies for internal and foreign infiltration and espionage, was first developed. A pioneering cryptographic unit was established as early as 1844 in India, which achievedsome important successes in decrypting Russian communications in the area.[7]

The establishment of dedicated intelligence organizations was directly linked to the colonial rivalries between the major European powers and the accelerating development of military technology.

An early source of military intelligence was the diplomatic system of military attachés (an officer attached to the diplomatic service operating through the embassy in a foreign country), that became widespread in Europe after the Crimean War. Although officially restricted to a role of transmitting openly received information, they were soon being used to clandestinely gather confidential information and in some cases even to recruit spies and to operate de facto spy rings.

Military Intelligence

Seal of the Evidenzbureau, military intelligence service of the Austrian Empire.

Shaken by the revolutionary years 1848-1849, the Austrian Empire founded the Evidenzbureau in 1850 as the first permanent military intelligence service. It was first used in the 1859 Austro-Sardinian war and the 1866 campaign against Prussia, albeit with little success. The bureau collected intelligence of military relevance from various sources into daily reports to the Chief of Staff (Generalstabschef) and weekly reports to Emperor Franz Joseph. Sections of the Evidenzbureauwere assigned different regions, the most important one was aimed against Russia.

During the Crimean War, the Topographical & Statistic Department T&SD was established within the British War Office as an embryonic military intelligence organization. The department initially focused on the accurate mapmaking of strategically sensitive locations and the collation of militarily relevant statistics. After the deficiencies in the British army's performance during the war became known a

large-scale reform of army institutions was overseen by the Edward Cardwell. As part of this, the T&SD was reorganized as the Intelligence Branch of the War Office in 1873 with the mission to "collect and classify all possible information relating to the strength, organization etc. of foreign armies... to keep themselves acquainted with the progress madeby foreign countries in military art and science..."[8]

The French Ministry of War authorized the creation of the Deuxième Bureau on June 8, 1871, a service charged with performing "research on enemy plans and operations."[9] This was followed a year later by the creation of a military counter-espionage service. It was this latter service that wasdiscredited through its actions over the notorious Dreyfus Affair, where a French Jewish officer was falsely accused of handing over military secrets to the Germans. As a result of the political division that ensued, responsibility for counter-espionage was moved to the civilian control of the Ministry of the Interior.

Field Marshal Helmuth von Moltke established a military intelligence unit, Abteilung (Section) IIIb, to the German General Staff in 1889 which steadily expanded its operations into France and Russia. The Italian Ufficio Informazioni del Commando Supremo was put on a permanent footing in 1900. AfterRussia's defeat in the Russo-Japanese War of 1904-05, Russian military intelligence was reorganized under the 7th Section ofthe 2nd Executive Board of the great imperial headquarters.[10]

Naval Intelligence

It was not just the army that felt a need for military intelligence. Soon, naval establishments were demanding similar capabilities from their national governments to allow them to keep abreast of technological and strategic developments in rival countries.

The Naval Intelligence Division was set up as the independent intelligence arm of the British Admiralty in 1882 (initially as the Foreign Intelligence Committee) and was headed by Captain William Henry Hall.[11] The division was initially responsible for fleet mobilization and war plans as well as foreign intelligence collection; in the 1900s two further

responsibilities - issues of strategy and defence and the protection of merchant shipping - were added.

Naval intelligence originated in the same year in the US and was founded by the Secretary of the Navy, William H. Hunt "...for the purpose of collecting and recording such naval information as may be useful to the Department in time of war,as well as in peace." This was followed in October 1885 by theMilitary Information Division, the first standing military intelligence agency of the United States with the duty of collecting military data on foreign nations.[12]

In 1900, the Imperial German Navy established the Nachrichten-Abteilung, which was devoted to gathering intelligence on Britain. The navies of Italy, Russia and Austria-Hungary set up similar services as well.

Civil intelligence agencies

William Melville helped establish the first independent intelligence agency, the British Secret Service, and was appointed as its first chief.

Integrated intelligence agencies run directly by governments were also established. The British Secret Service Bureau was founded in 1909 as the first independent and interdepartmentalagency fully in control over all government espionage activities.

At a time of widespread and growing anti-German feeling and fear, plans were drawn up for an extensive offensive intelligence system to be used an instrument in the event of a

European war. Due to intense lobbying from William Melville and after he obtained German mobilization plans and proof of their financial support to the Boers, the government authorized the creation of a new intelligence section in the War Office, MO3 (subsequently redesignated M05) headed by Melville, in 1903. Working under cover from a flat in London, Melville ran both counterintelligence and foreign intelligenceoperations, capitalizing on the knowledge and foreign contactshe had accumulated during his years running Special Branch.

Due to its success, the Government Committee on Intelligence, with support from Richard Haldane and Winston Churchill, established the Secret Service Bureau in 1909. It consisted ofnineteen military intelligence departments - MI1 to MI19, but MI5 and MI6 came to be the most recognized as they are the only ones to have remained active to this day.

The Bureau was a joint initiative of the Admiralty, the War Office and the Foreign Office to control secret intelligence operations in the UK and overseas, particularly concentrating on the activities of the Imperial German Government. Its firstdirector was Captain Sir George Mansfield Smith-Cumming alias "C".[13] In 1910, the bureau was split into naval and army sections which, over time, specialised in foreign espionage and internal counter-espionage activities respectively. The Secret Service initially focused its resources on gathering intelligence on German shipbuilding plans and operations. Espionage activity in France was consciously refrained from, so as not to jeopardize the burgeoning alliance between the two nations.

For the first time, the government had access to a peace-time,centralized independent intelligence bureaucracy with indexed registries and defined procedures, as opposed to the more ad hoc methods used previously. Instead of a system whereby rivaldepartments and military services would work on their own priorities with little to no consultation or cooperation with each other, the newly established Secret Intelligence Service was interdepartmental, and submitted its intelligence reports to all relevant government departments.[14]

Counter-intelligence

The Okhrana was founded in 1880 and was tasked with counteringenemy espionage. St. Petersburg Okhrana group photo, 1905.

As espionage became more widely used, it became imperative to expand the role of existing police and internal security forces into a role of detecting and countering foreign spies. The Austro-Hungarian Evidenzbureau was entrusted with the rolefrom the late 19th century to counter the actions of the Pan-Slavist movement operating out of Serbia.

As mentioned above, after the fallout from the Dreyfus Affair in France, responsibility for military counter-espionage was passed in 1899 to the Sûreté générale - an agency originally responsible for order enforcement and public safety - and overseen by the Ministry of the Interior.[9]

The Okhrana [15] was initially formed in 1880 to combat politicalterrorism and left-wing revolutionary activity throughout the Russian Empire, but was also tasked with countering enemy espionage.[16] Its main concern was the activities of revolutionaries, who often worked and plotted subversive actions from abroad. It created an antenna in Paris run by Pyotr Rachkovsky to monitor their activities. The agency used many methods to achieve its goals, including covert operations, undercover agents, and "perlustration" — the interception and reading of private correspondence. The Okhrana became notorious for its use of agents provocateurs who often succeeded in penetrating the activities of revolutionary groups including the Bolsheviks.[17]

In Britain, the Secret Service Bureau was split into a foreignand counter intelligence domestic service in 1910. The latter

was headed by Sir Vernon Kell and was originally aimed at calming public fears of large scale German espionage.[18] As theService was not authorized with police powers, Kell liased extensively with the Special Branch of Scotland Yard (headed by Basil Thomson), and succeeded in disrupting the work of Indian revolutionaries collaborating with the Germans during the war.

First World War

Cover of the Petit Journal of 20 January 1895, covering the arrestof Captain Alfred Dreyfus for espionage and treason. The case convulsed France and raised public awareness of the rapidly developing world of espionage.

By the outbreak of the First World War all the major powers had highly sophisticated structures in place for the training and handling of spies and for the processing of the intelligence information obtained through espionage. The figure and mystique of the spy had also developed considerablyin the public eye. The Dreyfus Affair, which involved international espionage and treason, contributed much to public interest in espionage.[19][20]

The spy novel emerged as a distinct genre in the late 19th century, and dealt with themes such as colonial rivalry, the growing threat of conflict in Europe and the revolutionary andanarchist domestic threat. The "spy novel" was defined by The

Riddle of the Sands (1903) by British author Robert Erskine Childers, which played on public fears of a German plan to invade Britain (the nefarious plot is uncovered by an amateur spy). Its success was followed by a flood of imitators, including William Le Queux and E. Phillips Oppenheim.

It was during the War that modern espionage techniques were honed and refined, as all belligerent powers utilized their intelligence services to obtain military intelligence, commit acts of sabotage and carry out propaganda. As the progress of the war became static and armies dug down in trenches the utility of cavaly reconnaissance became of very limited effectiveness.[21]

Information gathered at the battlefront from the interrogationof prisoners-of-war was only capable of giving insight into local enemy actions of limited duration. To obtain high-level information on the enemy's strategic intentions, its military capabilities and deployment required undercover spy rings operating deep in enemy territory. On the Western Front the advantage lay with the Western Allies, as throughout most of the war German armies occupied Belgium and parts of northern France, thereby providing a large and dissaffected population that could be organized into collecting and transmitting vitalintelligence.[21]

British and French intelligence services recruited Belgian or French refugees and infiltrated these agents behind enemy lines via the Netherlands - a neutral country. Many collaborators were then recruited from the local population, who were mainly driven by patriotism and hatred of the harsh German occupation. By the end of the war, over 250 networks had been created, comprising more than 6,400 Belgian and French citizens. These rings concentrated on infiltrating the German railway network so that the allies could receive advance warning of strategic troop and ammunition movements.[21]

Mata Hari was a famous Dutch dancer who was executed on charges of espionage for Germany. Pictured at her arrest.

The most effective such ring in German-occupied Belgium, was the Dame Blanche ("White Lady") network, founded in 1916 by Walthère Dewé as an underground intelligence network. It supplied as much as 75% of the intelligence collected from occupied Belgium and northern France to the Allies. By the endof the war, its 1,300 agents covered all of occupied Belgium, northern France and, through a collaboration with Louise de Bettignies' network, occupied Luxembourg. The network was ableto provide a crucial few days warning before the launch of theGerman 1918 Spring Offensive.[22]

German intelligence was only ever able to recruit a very smallnumber of spies. These were trained at an academy run by the Kriegsnachrichtenstelle in Antwerp and headed by Elsbeth Schragmüller, known as "Fräulein Doktor". These agents were generally isolated and unable to rely on a large support network for the relaying of information. The most famous German spy was Margaretha Geertruida Zelle, an exotic Dutch dancer with the stage name Mata Hari. As a Dutch subject, she was able to cross national borders freely. In 1916, she was arrested and brought to London where she was interrogated at length by Sir Basil Thomson, Assistant Commissioner at New Scotland Yard. She eventually claimed to be working for Frenchintelligence. In fact, she had entered German service from 1915, and sent her reports to the mission in the German embassy in Madrid.[23] In January 1917, the German military

attaché in Madrid transmitted radio messages to Berlin describing the helpful activities of a German spy code-named H-21. French intelligence agents intercepted the messages and,from the information it contained, identified H-21 as Mata Hari. She was executed by firing squad on 15 October 1917.

German spies in Britain did not meet with much success - the German spy ring operating in Britain was successfully disrupted by MI5 under Vernon Kell on the day after the declaration of the war. Home Secretary, Reginald McKenna, announced that "within the last twenty-four hours no fewer than twenty-one spies, or suspected spies, have been arrested in various places all over the country, chiefly in important military or naval centres, some of them long known to the authorities to be spies",[24][25]

One exception was Jules C. Silber, who evaded MI5 investigations and obtained a position at the censor's office in 1914. Using mailed window envelopes that had already been stamped and cleared he was able to forward microfilm to Germany that contained increasingly important information. Silber was regularly promoted and ended up in the position of chief censor, which enabled him to analyze all suspect documents.[26]

The British economic blockade of Germany was made effective through the support of spy networks operating out of neutral Netherlands. Points of weakness in the naval blockade were determined by agents on the ground and relayed back to the Royal Navy. The blockade led to severe food deprivation in Germany and was a major cause in the collapse of the Central Powers war effort in 1918.[27]

Codebreaking

The interception and decryption of the Zimmermann telegram by Room 40 at the Admiralty was of pivotal importance for the outcome of the war.

Two new methods for intelligence collection were developed over the course of the war - aerial reconnaissance and photography and the interception and decryption of radio signals.[27] The British rapidly built up great expertise in thenewly emerging field of signals intelligence and codebreaking.

In 1911, a committee of the Committee of Imperial Defence on cable communications concluded that in the event of war with Germany, German-owned submarine cables should be destroyed. Onthe night of 3 August 1914, the cable ship Alert located and cutGermany's five trans-Atlantic cables, which ran down the English Channel. Soon after, the six cables running between Britain and Germany were cut.[28] As an immediate consequence, there was a significant increase in cable messages sent via cables belonging to other countries, and cables sent by wireless. These could now be intercepted, but codes and ciphers were naturally used to hide the meaning of the

messages, and neither Britain nor Germany had any established organisations to decode and interpret the messages. At the start of the war, the navy had only one wireless station for intercepting messages, at Stockton. However, installations belonging to the Post Office and the Marconi Company, as well as private individuals who had access to radio equipment, began recording messages from Germany.[29]

Room 40, under Director of Naval Education Alfred Ewing and formed in October 1914, was the section in the British Admiralty most identified with the British cryptoanalysis effort during the First World War. The basis of Room 40 operations evolved around a German naval codebook, the Signalbuch der Kaiserlichen Marine (SKM), and around maps (containing coded squares), which were obtained from three different sources in the early months of the war. Alfred Ewing directed Room 40 until May 1917, when direct control passed to Captain (later Admiral) Reginald 'Blinker' Hall, assisted by William Milbourne James.[30]

A similar organisation began in the Military Intelligence department of the War Office, which become known as MI1b, and Colonel Macdonagh proposed that the two organisations should work together, decoding messages concerning the Western Front.A sophisticated interception system (known as 'Y' service), together with the post office and Marconi stationsgrew rapidlyto the point it could intercept almost all official German messages.[29]

As the number of intercepted messages increased it became necessary to decide which were unimportant and should just be logged, and which should be passed on outside Room 40. The German fleet was in the habit each day of wirelessing the exact position of each ship and giving regular position reports when at sea. It was possible to build up a precise picture of the normal operation of the High Seas Fleet, indeedto infer from the routes they chose where defensive minefieldshad been place and where it was safe for ships to operate. Whenever a change to the normal pattern was seen, it immediately signalled that some operation was about to take place and a warning could be given. Detailed information aboutsubmarine movements was available.[31]

Both the British and German interception services began to experiment with direction finding radio equipment in the startof 1915. Captain H. J. Round working for Marconi had been carrying out experiments for the army in France and Hall instructed him to build a direction finding system for the navy. Stations were built along the coast, and by May 1915 theAdmiralty was able to track German submarines crossing the North Sea. Some of these stations also acted as 'Y' stations to collect German messages, but a new section was created within Room 40 to plot the positions of ships from the directional reports. No attempts were made by the German fleetto restrict its use of wireless until 1917, and then only in response to perceived British use of direction finding, not because it believed messages were being decoded.[32]

Room 40 played an important role in several naval engagements during the war, notably in detecting major German sorties intothe North Sea that led to the battles of Dogger Bank and Jutland as the British fleet was sent out to intercept them. However its most important contribution was probably in decrypting the Zimmermann Telegram, a telegram from the GermanForeign Office sent via Washington to its ambassador Heinrich von Eckardt in Mexico.

In the telegram's plaintext, Nigel de Grey and William Montgomery learned of the German Foreign Minister Arthur Zimmermann's offer to Mexico of United States' territories of Arizona, New Mexico, and Texas as an enticement to join the war as a German ally. The telegram was passed to the U.S. by Captain Hall, and a scheme was devised (involving a still unknown agent in Mexico and a burglary) to conceal how its plaintext had become available and also how the U.S. had gained possession of a copy. The telegram was made public by the United States, which declared war on Germany on 6 April 1917, entering the war on the Allied side.[33] This effectively demonstrated how the course of a war could be changed by effective intelligence operations.

Russian Revolution

From the London Evening Standard's Master Spy serial: Reilly, disguised as a member of the Cheka, bluffs his way through a Red Army checkpoint.

The outbreak of revolution in Russia and the subsequent seizure of power by the Bolsheviks, a party deeply hostile towards the capitalist powers, was an important catalyst for the development of modern international espionage techniques. A key figure was Sidney Reilly, a Russian-born adventurer and secret agent employed by Scotland Yard and the Secret Intelligence Service. He set the standard for modern espionage, turning it from a gentleman's amateurish game to a ruthless and professional methodology for the achievement of military and political ends.

Reilly's remarkable and varied career culminated in an audiacious attempt to depose the Bolshevik Government and assassinate Vladimir Ilyich Lenin.[34]

In May 1918, Robert Bruce Lockhart,[35] an agent of the British Secret Intelligence Service, and Reilly repeatedly met Boris Savinkov, head of the counter-revolutionary Union for the Defence of the Motherland and Freedom (UDMF). Lockhart and Reilly then contacted anti-Bolshevik groups linked to Savinkovand supported these factions with SIS funds.[36] In June, disillusioned members of the Latvian Riflemen began appearing in anti-Bolshevik circles in Petrograd and were eventually directed to Captain Cromie, a British naval attaché, and Mr. Constantine, a Turkish merchant who was actually Reilly. Reilly believed their participation in the pending coup to be vital and arranged their meeting with Lockhart at the British mission in Moscow. At this stage, Reilly planned a coup

against the Bolshevik government and drew up a list of Soviet military leaders ready to assume responsibilities on the fall of the Bolshevik government.[36]

Paul Dukes was knighted for his achievements in the Secret Intelligence Service.

On 17 August, Reilly conducted meetings between Latvian regimental leaders and liaised with Captain George Hill, another British agent operating in Russia. Hill had managed toestablish a network of 10 secure houses around Moscow, and a professional courier network that reached across northern Russia and that allowed him to smuggle top secret documents from Moscow to Stockholm to London in days. They agreed the coup would occur the first week of September during a meeting of the Council of People's Commissars and the Moscow Soviet atthe Bolshoi Theatre. However, on the eve of the coup, unexpected events thwarted the operation. Fanya Kaplan shot and wounded Lenin triggering the "Red Terror" - the Cheka implicated all malcontents in a grand conspiracy that warranted a full-scale campaign. Using lists supplied by undercover agents, the Cheka arrested those involved in Reilly's pending coup, raided the British Embassy in Petrogradand killed Francis Cromie and arrested Lockhart.[36]

Another pivotal figure was Sir Paul Dukes, arguably the first professional spy of the modern age.[37] Recruited personally by

Mansfield Smith-Cumming to act as a secret agent in Imperial Russia, he set up elaborate plans to help prominent White Russians escape from Soviet prisons after the Revolution and smuggled hundreds of them into Finland. Known as the "Man of aHundred Faces," Dukes continued his use of disguises, which aided him in assuming a number of identities and gained him access to numerous Bolshevik organizations. He successfully infiltrated the Communist Party of the Soviet Union, the Comintern, and the political police, or CHEKA. Dukes also learned of the inner workings of the Politburo, and passed theinformation to British intelligence.

In the course of a few months, Dukes, Hill and Reilly succeeded in infiltrating Lenin’s inner circle, and gaining access to the activities of the Cheka and the Communist International at the highest level. This helped to convince the government of the importance of a well-funded secret intelligence service in peace time as a key component in formulating foreign policy.[37] Winston Churchill argued that intercepted communications were more useful "as a means of forming a true judgement of public policy than any other source of knowledge at the disposal of the State."[38]

Today

Today, espionage agencies target the illegal drug trade and terrorists as well as state actors. Since 2008 the United States has charged at least 57 defendants for attempting to spy for China.[39]

Different intelligence services value certain intelligence collection techniques over others. The former Soviet Union, for example, preferred human sources over research in open sources, while the United States has tended to emphasize technological methods such as SIGINT and IMINT. Both Soviet political (KGB) and military intelligence (GRU [40] ) officers were judged by the number of agents they recruited.

Targets of espionageEspionage agents are usually trained experts in a specific targeted field so they can differentiate mundane information

from targets of intrinsic value to their own organisational development. Correct identification of the target at its execution is the sole purpose of the espionage operation.[41]

Broad areas of espionage targeting expertise include:[42]

Natural resources : strategic production identification and assessment (food, energy, materials). Agents are usually found among bureaucrats who administer these resources in their own countries

Popular sentiment towards domestic and foreign policies (popular, middle class, elites). Agents often recruited from field journalistic crews, exchange postgraduate students and sociology researchers

Strategic economic strengths (production, research, manufacture, infrastructure). Agents recruited from science and technology academia, commercial enterprises, and more rarely from among military technologists

Military capability intelligence (offensive, defensive, maneuver, naval, air, space). Agents are trained by special military espionage education facilities, and posted to an area of operation with covert identities to minimize prosecution

Counterintelligence operations specifically targeting opponents' intelligence services themselves, such as breaching confidentiality of communications, and recruiting defectors or moles

Methods and terminologyAlthough the news media may speak of "spy satellites" and the like, espionage is not a synonym for all intelligence-gathering disciplines. It is a specific form of human source intelligence (HUMINT). Codebreaking (cryptanalysis or COMINT),aircraft or satellite photography, (IMINT) and research in open publications (OSINT) are all intelligence gathering disciplines, but none of them are considered espionage. Many HUMINT activities, such as prisoner interrogation, reports from military reconnaissance patrols and from diplomats, etc.,are not considered espionage. Espionage is the disclosure of sensitive information (classified) to people who are not

cleared for that information or access to that sensitive information.

Unlike other forms of intelligence collection disciplines, espionage usually involves accessing the place where the desired information is stored or accessing the people who knowthe information and will divulge it through some kind of subterfuge. There are exceptions to physical meetings, such asthe Oslo Report, or the insistence of Robert Hanssen in never meeting the people who bought his information.

The US defines espionage towards itself as "The act of obtaining, delivering, transmitting, communicating, or receiving information about the national defense with an intent, or reason to believe, that the information may be usedto the injury of the United States or to the advantage of any foreign nation". Black's Law Dictionary (1990) defines espionage as:"... gathering, transmitting, or losing ... information related to the national defense". Espionage is a violation of United States law, 18 U.S.C. §§   792 –798 and Article 106a of the Uniform Code of Military Justice".[43] The United States, like most nations, conducts espionage against other nations, under the control of the National Clandestine Service. Britain's espionage activities are controlled by the Secret Intelligence Service.

Technology and techniques

See also: Tradecraft and List of intelligence gathering disciplines

Agent handling Concealment device Covert agent Covert listening device Cut-out Cyber spying Dead drop False flag operations Honeypot Interrogation Non-official cover Numbers messaging

Official cover One-way voice link Safe house Side channel attack Steganography Surveillance Surveillance aircraft

[44]

Organization

An intelligence officer's clothing, accessories, and behavior must be as unremarkable as possible — their lives (and others') may depend on it.

A spy is a person employed to seek out top secret information from a source. Within the United States Intelligence Community, "asset" is a more common usage. A case officer, whomay have diplomatic status (i.e., official cover or non-official cover), supports and directs the human collector. Cutouts are couriers who do not know the agent or case officerbut transfer messages. A safe house is a refuge for spies. Spies often seek to obtain secret information from another source.

In larger networks the organization can be complex with many methods to avoid detection, including clandestine cell systems. Often the players have never met. Case officers are stationed in foreign countries to recruit and to supervise intelligence agents, who in turn spy on targets in their

countries where they are assigned. A spy need not be a citizenof the target country—hence does not automatically commit treason when operating within it. While the more common practice is to recruit a person already trusted with access tosensitive information, sometimes a person with a well-preparedsynthetic identity (cover background), called a legend in tradecraft,[citation needed] may attempt to infiltrate a target organization.

These agents can be moles (who are recruited before they get access to secrets), defectors (who are recruited after they get access to secrets and leave their country) or defectors inplace (who get access but do not leave).

A legend is also employed for an individual who is not an illegalagent, but is an ordinary citizen who is "relocated", for example, a "protected witness". Nevertheless, such a non-agentvery likely will also have a case officer who will act as controller. As in most, if not all synthetic identity schemes,for whatever purpose (illegal or legal), the assistance of a controller is required.

Spies may also be used to spread disinformation in the organization in which they are planted, such as giving false reports about their country's military movements, or about a competing company's ability to bring a product to market. Spies may be given other roles that also require infiltration,such as sabotage.

Many governments routinely spy on their allies as well as their enemies, although they typically maintain a policy of not commenting on this. Governments also employ private companies to collect information on their behalf such as SCG International Risk, International Intelligence Limited and others.

Many organizations, both national and non-national, conduct espionage operations. It should not be assumed that espionage is always directed at the most secret operations of a target country. National and terrorist organizations and other groupsare also targets.[45] This is because governments want to retrieve information that they can use to be proactive in protecting their nation from potential terrorist attacks.

Communications both are necessary to espionage and clandestineoperations, and also a great vulnerability when the adversary has sophisticated SIGINT detection and interception capability. Agents must also transfer money securely.[45]

Industrial espionageMain article: Industrial espionage

Reportedly Canada is losing $12 billion[46] and German companiesare estimated to be losing about €50 billion ($87 billion) and30,000 jobs[47] to industrial espionage every year.

Agents in espionageIn espionage jargon, an "agent" is the person who does the spying; a citizen of one country who is recruited by a second country to spy on or work against his own country or a third country. In popular usage, this term is often erroneously applied to a member of an intelligence service who recruits and handles agents; in espionage such a person is referred to as an intelligence officer, intelligence operative or case officer. There are several types of agent in use today.

Double agent , "is a person who engages in clandestine activity for two intelligence or security services (or more in joint operations), who provides information aboutone or about each to the other, and who wittingly withholds significant information from one on the instructions of the other or is unwittingly manipulated by one so that significant facts are withheld from the adversary. Peddlers, fabricators, and others who work forthemselves rather than a service are not double agents because they are not agents. The fact that doubles have an agent relationship with both sides distinguishes them from penetrations, who normally are placed with the target service in a staff or officer capacity."[48]

o Re-doubled agent , an agent who gets caught as a double agent and is forced to mislead the foreign intelligence service.

Unwitting double agent, an agent who offers or is forced to recruit as a double or re-doubled

agent and in the process is recruited by eithera third party intelligence service or his own government without the knowledge of the intended target intelligence service or the agent. This can be useful in capturing important information from an agent that is attempting to seek allegiance with another country. The double agent usually has knowledgeof both intelligence services and can identify operational techniques of both, thus making third party recruitment difficult or impossible. The knowledge of operational techniques can also affect the relationship between the Operations Officer (or case officer) and the agent if the case is transferred by an Operational Targeting Officerto a new Operations Officer, leaving the new officer vulnerable to attack. This type of transfer may occur when an officer has completed his term of service or when his cover is blown.

Triple agent , an agent that is working forthree intelligence services.

Intelligence agent: Provides access to sensitive information through the use of special privileges. If used in corporate intelligence gathering, this may include gathering information of a corporate business venture or stock portfolio. In economic intelligence, "Economic Analysts may use their specialized skills to analyze and interpreteconomic trends and developments, assess and track foreign financial activities, and develop new econometricand modeling methodologies."[49] This may also include information of trade or tariff.

Access agent: Provides access to other potential agents by providing profiling information that can help lead to recruitment into an intelligence service.

Agent of influence: Someone who may provide political influence in an area of interest or may even provide publications needed to further an intelligence service agenda. The use of the media to print a story to mislead a foreign service into action, exposing their operations while under surveillance.

Agent provocateur : This type of agent instigates trouble,or may provide information to gather as many people as possible into one location for an arrest.

Facilities agent: A facilities agent may provide access to buildings such as garages or offices used for staging operations, resupply, etc.

Principal agent: This agent functions as a handler for anestablished network of agents usually "Blue Chip".

Confusion agent : May provide misleading information to anenemy intelligence service or attempt to discredit the operations of the target in an operation.

Sleeper agent : A sleeper agent is a person who is recruited to an intelligence service to wake up and perform a specific set of tasks or functions while livingunder cover in an area of interest. This type of agent isnot the same as a deep cover operative, who continually contacts a case officer to file intelligence reports. A sleeper agent is not in contact with anyone until activated.

Illegal agent: This is a person who is living in another country under false credentials that does not report to alocal station. A non official cover operative is a type of cover used by an intelligence operative and can be dubbed an "Illegal"[50] when working in another country without diplomatic protection.

LawEspionage is a crime under the legal code of many nations. In the United States it is covered by the Espionage Act of 1917. The risks of espionage vary. A spy breaking the host country'slaws may be deported, imprisoned, or even executed. A spy breaking his/her own country's laws can be imprisoned for espionage or/and treason (which in the USA and some other jurisdictions can only occur if he or she take ups arms or aids the enemy against his or her own country during wartime),or even executed, as the Rosenbergs were. For example, when Aldrich Ames handed a stack of dossiers of U.S. Central Intelligence Agency (CIA) agents in the Eastern Bloc to his KGB-officer "handler", the KGB "rolled up" several networks, and at least ten people were secretly shot. When Ames was arrested by the U.S. Federal Bureau of Investigation (FBI), he

faced life in prison; his contact, who had diplomatic immunity, was declared persona non grata and taken to the airport. Ames's wife was threatened with life imprisonment if her husband did not cooperate; he did, and she was given a five-year sentence. Hugh Francis Redmond, a CIA officer in China, spent nineteen years in a Chinese prison for espionage—and died there—as he was operating without diplomatic cover and immunity.[51]

In United States law, treason,[52] espionage,[53] and spying[54] are separate crimes. Treason and espionage have graduated punishment levels.

The United States in World War I passed the Espionage Act of 1917. Over the years, many spies, such as the Soble spy ring, Robert Lee Johnson, the Rosenberg ring, Aldrich Hazen Ames,[55] Robert Philip Hanssen,[56] Jonathan Pollard, John Anthony Walker, James Hall III, and others have been prosecuted under this law.

Use against non-spiesHowever, espionage laws are also used to prosecute non-spies. In the United States, the Espionage Act of 1917 was used against socialist politician Eugene V. Debs (at that time the act had much stricter guidelines and amongst other things banned speech against military recruiting). The law was later used to suppress publication of periodicals, for example of Father Coughlin in World War II. In the early 21st century, the act was used to prosecute whistleblowers such as Thomas Andrews Drake, John Kiriakou, and Edward Snowden, as well as officials who communicated with journalists for innocuous reasons, such as Stephen Jin-Woo Kim.[57][58]

As of 2012, India and Pakistan were holding several hundred prisoners of each other's country for minor violations like trespass or visa overstay, often with accusations of espionageattached. Some of these include cases where Pakistan and Indiaboth deny citizenship to these people, leaving them stateless.The BBC reported in 2012 on one such case, that of Mohammed Idrees, who was held under Indian police control for approximately 13 years for overstaying his 15-day visa by 2–3

days after seeing his ill parents in 1999. Much of the 13 years was spent in prison waiting for a hearing, and more timewas spent homeless or living with generous families. The Indian People's Union for Civil Liberties and Human Rights LawNetwork both decried his treatment. The BBC attributed some ofthe problems to tensions caused by the Kashmir conflict.[59]

Espionage laws in the UKEspionage is illegal in the UK under the Official Secrets Actsof 1911 and 1920. The UK law under this legislation considers espionage as actions "intend to help an enemy and deliberatelyharm the security of the nation". According to MI5, a person will be charged with the crime of espionage if they, "for any purpose prejudicial to the safety or interests of the State": approaches, enters or inspects a prohibited area; makes documents such as plans that are intended, calculated, or could directly or indirectly be of use to an enemy; or "obtains, collects, records, or publishes, or communicates to any other person any secret official code word, or pass word, or any sketch, plan, model, article, or note, or other document which is calculated to be or might be or is intended to be directly or indirectly useful to an enemy". The illegality of espionage also includes any action which may be considered 'preparatory to' spying, or encouraging or aiding another to spy.[60]

An individual convicted of espionage can be imprisoned for up to 14 years in the UK, although multiple sentences can be issued.

Government intelligence laws and its distinction from espionage

Government intelligence is very much distinct from espionage, and is not illegal in the UK, providing that the organisationsof individuals are registered, often with the ICO, and are acting within the restrictions of the Regulation of Investigatory Powers Act (RIPA). 'Intelligence' is considered legally as "information of all sorts gathered by a government or organisation to guide its decisions. It includes information that may be both public and private, obtained from

many different public or secret sources. It could consist entirely of information from either publicly available or secret sources, or be a combination of the two."[61]

However, espionage and intelligence can be linked. According to the MI5 website, "foreign intelligence officers acting in the UK under diplomatic cover may enjoy immunity from prosecution. Such persons can only be tried for spying (or, indeed, any criminal offence) if diplomatic immunity is waivedbeforehand. Those officers operating without diplomatic cover have no such immunity from prosecution".

There are also laws surrounding government and organisational intelligence and surveillance. Generally, the body involved should be issued with some form of warrant or permission from the government, and should be enacting their procedures in theinterest of protecting national security or the safety of public citizens. Those carrying out intelligence missions should act within not only RIPA, but also the Data Protection Act and Human Rights Act. However, there are specific spy equipment laws and legal requirements around intelligence methods that vary for each form of intelligence enacted.

Military conflicts

French spy captured during the Franco-Prussian War.

In military conflicts, espionage is considered permissible as many nations recognizes the inevitability of opposing sides seeking intelligence each about the dispositions of the other.To make the mission easier and successful, soldiers or agents wear disguises to conceal their true identity from the enemy while penetrating enemy lines for intelligence gathering. However, if they are caught behind enemy lines in disguises, they are not entitled to prisoner-of-war status and subject toprosecution and punishment—including execution.

The Hague Convention of 1907 addresses the status of wartime spies, specifically within "Laws and Customs of War on Land" (Hague IV); October 18, 1907: CHAPTER II Spies".[62] Article 29 states that a person is considered a spy who, acts clandestinely or on false pretenses, infiltrates enemy lines with the intention of acquiring intelligence about the enemy and communicate it to the belligerent during times of war. Soldiers who penetrates enemy lines in proper uniforms for thepurpose of acquiring intelligence are not considered spies butare lawful combatants entitled to be treated as prisoners of war upon capture by the enemy. Article 30 states that a spy captured behind enemy lines may only be punished following a trial. However, Article 31 provides that if a spy successfullyrejoined his own military and is then captured by the enemy asa lawful combatant, he cannot be punished for his previous acts of espionage and must be treated as a prisoner of war. Note that this provision does not apply to citizens who committed treason against their own country or co-belligerentsof that country and may be captured and prosecuted at any place or any time regardless whether he rejoined the military to which he belongs or not or during or after the war.[63][64]

The ones that are excluded from being treated as spies while behind enemy lines are escaping prisoners of war and downed airmen as international law distinguishes between a disguised spy and a disguised escaper.[44] It is permissible for these groups to wear enemy uniforms or civilian clothes in order to facilitate their escape back to friendly lines so long as theydo not attack enemy forces, collect military intelligence, or engage in similar military operations while so disguised.[65][66] Soldiers who are wearing enemy uniforms or civilian clothes simply for the sake of warmth along with other purposes ratherthan engaging in espionage or similar military operations while so attired is also excluded from being treated as unlawful combatants.[44]

Saboteurs are treated as spies as they too wear disguises behind enemy lines for the purpose of waging destruction on enemy's vital targets in addition to intelligence gathering.[67]

[68] For example, during World War II, eight German agents entered the U.S. in June 1942 as part of Operation Pastorius, a sabotage mission against U.S. economic targets. Two weeks

later, all were arrested in civilian clothes by the FBI thanksto two German agents betraying the mission to the U.S. Under the Hague Convention of 1907, these Germans were classified asspies and tried by a military tribunal in Washington D.C. [69] OnAugust 3, 1942, all eight were found guilty and sentenced to death. Five days later, six were executed by electric chair atthe District of Columbia jail. Two who had given evidence against the others had their sentences reduced by President Franklin D. Roosevelt to prison terms. In 1948, they were released by President Harry S. Truman and deported to the American Zone of occupied Germany.

The U.S. codification of enemy spies is Article 106 of the Uniform Code of Military Justice. This provides a mandatory death sentence if a person captured in the act is proven to be"lurking as a spy or acting as a spy in or about any place, vessel, or aircraft, within the control or jurisdiction of anyof the armed forces, or in or about any shipyard, any manufacturing or industrial plant, or any other place or institution engaged in work in aid of the prosecution of the war by the United States, or elsewhere".[70]

List of famous spiesThis article is in a list format that may be better presented using prose. You can help by converting this article to prose, if appropriate. Editing help is available. (March 2010)

See also: Intelligence agency, Special Operations Executive and United States government security breaches

Howard Burnham (1915)

FBI file photo of the leader of the Duquesne Spy Ring (1941)

Reign of Elizabeth I of England

Sir Francis WalsinghamChristopher Marlowe

American Revolution

Thomas Knowlton, The First American SpyNathan HaleJohn AndreJames ArmisteadBenjamin Tallmadge, Case agent who organized of the Culper SpyRing in New York City

Napoleonic Wars

Charles-Louis SchulmeisterWilliam Wickham

American Civil War

One of the innovations in the American Civil War was the use of proprietary companies for intelligence collection by the Union; see Allan Pinkerton.Confederate Secret ServiceBelle Boyd [71]

Aceh War

Dutch professor Snouck Hurgronje world leading authority on Islam was a proponent of espionage to quell Muslim resistance in Aceh in the Dutch East Indies. In his role as Colonial Advisor on Oriental Affairs, he gathered intelligence under the name "Haji Abdul Ghaffar".He used his knowledge of Islamic and Aceh culture to devise strategies that significantly helped crush the resistance of

the Aceh inhabitants and impose Dutch colonial rule, ending the 40 year Aceh War. Casualty estimates ranged between 50,000and 100,000 inhabitants dead and about a million wounded.Christiaan Snouck Hurgronje

Second Boer War

Fritz Joubert DuquesneSidney Reilly

Russo-Japanese War

Sidney ReillyHo Liang-ShungAkashi Motojiro

World War I

See also: Espionage in Norway during World War I

Fritz Joubert Duquesne Jules C. Silber Mata Hari Howard Burnham T.E. Lawrence Sidney Reilly Maria de Victorica

11 German spies were executed in the Tower of London during WW1.[72]

Executed :- Carl Hans Lody on 6 November 1914, in the Miniature Rifle Range.

Executed :- Carl Frederick Muller on 23 June 1915, in Miniature Rifle Range. Prepared bullets were used by the execution party.

Executed :- Haicke Marinus Janssen & Willem Johannes Roosboth executed on 30 July 1915, both in the Tower ditch.

Executed :- Ernst Waldemar Melin on 10 September 1915, Miniature Rifle Range.

Executed :- Augusto Alfredo Roggen on 17 September 1915, in Miniature Rifle Range.

Executed :- Fernando Buschman on 19 October 1915, in Miniature Rifle Range.

Executed :- George Traugott Breeckow, otherwise known as Reginald Rowland or George T. Parker on 26 October 1915, in Miniature Rifle Range. Worked with a lady called Lizzie Louise Wertheim who was sentenced to ten years penal servitude. Later on 17 January 1918 was certified as insane and died in Broadmoor criminal lunatic asylum on 29 July 1920.

Executed :- Irving Guy Ries on 27 October 1915, in Miniature Rifle Range.

Executed :- Albert Mayer on 2 December 1915, in MiniatureRifle Range.

Executed :- Ludovico Hurwitz-y-Zender on 11 April 1916 inMiniature Rifle Range.

Carl Hans Lody has his own grave and black headstone in the East London Cemetery, Plaistow. The others are buried about 150 yards away under a small memorial stone alongside a pathway.

World War II

Imagined German Intelligence Officer thanks British Forces forgiving away details of operations, (Graham & Gillies Advertising)

Informants were common in World War II. In November 1939, the German Hans Ferdinand Mayer sent what is called the Oslo Report to inform the British of German technology and projectsin an effort to undermine the Nazi regime. The Réseau AGIR wasa French network developed after the fall of France that reported the start of construction of V-weapon installations in Occupied France to the British.

Counterespionage included the use of turned Double Cross agents to misinform Nazi Germany of impact points during the Blitz and internment of Japanese in the US against "Japan's wartime spy program". Additional WWII espionage examples include Soviet spying on the US Manhattan project, the German Duquesne Spy Ring convicted in the US, and the Soviet Red Orchestra spying on Nazi Germany. The US lacked a specific agency at the start of the war, but quickly formed the Office of Strategic Services (OSS).

Spying has sometimes been considered a gentlemanly pursuit, with recruiting focused on military officers, or at least on persons of the class from whom officers are recruited. However, the demand for male soldiers, an increase in women's rights, and the tactical advantages of female spies led the British Special Operations Executive (SOE) to set aside any lingering Victorian Era prejudices and begin employing them inApril 1942.[73] Their task was to transmit information from Nazioccupied France back to Allied Forces. The main strategic reason was that men in France faced a high risk of being interrogated by Nazi troops but women were less likely to arouse suspicion. In this way they made good couriers and proved equal to, if not more effective than, their male counterparts. Their participation in Organization and Radio Operation was also vital to the success of many operations, including the main network between Paris and London.

See also: Clandestine HUMINT asset recruiting § Love, honeypots and recruitment

Post World War II

Further information: Cold War espionage

In the United States, there are seventeen[74] federal agencies that form the United States Intelligence Community. The Central Intelligence Agency operates the National Clandestine Service (NCS)[75] to collect human intelligence and perform Covert operations.[76] The National Security Agency collects Signals Intelligence. Originally the CIA spearheaded the US-IC. Pursuant to the September 11 attacks the Office of the Director of National Intelligence (ODNI) was created to promulgate information-sharing.

Kim Philby Ray Mawby

Spy fictionMain article: Spy fiction

This section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (July 2011)

An early example of espionage literature is Kim by the Englishnovelist Rudyard Kipling, with a description of the training of an intelligence agent in the Great Game between the UK and Russia in 19th century Central Asia. An even earlier work was James Fenimore Cooper's classic novel, The Spy, written in 1821,about an American spy in New York during the Revolutionary War.

During the many 20th century spy scandals, much information became publicly known about national spy agencies and dozens of real-life secret agents. These sensational stories piqued public interest in a profession largely off-limits to human interest news reporting, a natural consequence of the secrecy inherent to their work. To fill in the blanks, the popular conception of the secret agent has been formed largely by 20thand 21st century literature and cinema. Attractive and sociable real-life agents such as Valerie Plame find little employment in serious fiction, however. The fictional secret agent is more often a loner, sometimes amoral—an existential hero operating outside the everyday constraints of society. Loner spy personalities may have been a stereotype of

convenience for authors who already knew how to write loner private investigator characters that sold well from the 1920s to the present.

Johnny Fedora achieved popularity as a fictional agent of early Cold War espionage, but James Bond is the most commercially successful of the many spy characters created by intelligence insiders during that struggle. His less fantasticrivals include Le Carre's George Smiley and Harry Palmer as played by Michael Caine. Most post-Vietnam era characters weremodeled after the American, C.C. Taylor, reportedly the last sanctioned "asset" of the U.S. government. Taylor, a true "Double 0 agent", worked alone and would travel as an Americanor Canadian tourist or businessman throughout Europe and Asia,he was used extensively in the Middle East toward the end of his career. Taylor received his weapons training from Carlos Hathcock, holder of a record 93 confirmed kills from WWII through the Viet Nam conflict. According to documents made available through the Freedom of Information Act, his operations were classified as "NOC" or Non-Official Cover.

Jumping on the spy bandwagon, other writers also started writing about spy fiction featuring female spies as protagonists, such as The Baroness, which has more graphic action and sex, as compared to other novels featuring male protagonists.

It also made its way into the videogame world, hence the famous creation of Hideo Kojima, the Metal Gear Solid Series.

Espionage has also made its way into comedy depictions. The 1960s TV series Get Smart portrays an inept spy, while the 1985 movie Spies Like Us depicts a pair of none-too-bright men sent to the Soviet Union to investigate a missile.

World War II: 1939–1945

Author(s) Title Publisher

Date Notes

Babington-Smith, Constance

Air Spy: The Story of Photo Intelligence in World War II — 195

7 —

Bryden, John Best-Kept Secret: Canadian Secret Lester 199 —

Intelligence in the Second World War 3

Hinsley, F. H. and Alan Stripp

Codebreakers: The Inside Story ofBletchley Park — 200

1 —

Hinsley, F. H.

British Intelligence in the Second World War — 199

6

Abridged version of multivolume official history.

Hohne, Heinz Canaris: Hitler's Master Spy — 1979 —

Jones, R. V. The Wizard War: British Scientific Intelligence 1939–1945 — 197

8 —

Kahn, David Hitler's Spies: German Military Intelligence in World War II' — 197

8 —

Kahn, DavidSeizing the Enigma: The Race to Break the German U-Boat Codes, 1939–1943

— 1991 FACE

Kitson, Simon

The Hunt for Nazi Spies: Fighting Espionage in Vichy France - 200

8Lewin, Ronald

The American Magic: Codes, Ciphers and the Defeat of Japan — 198

2 —

Masterman, J. C.

The Double Cross System in the War of 1935 to 1945 Yale 197

2 —

Persico, Joseph

Roosevelt's Secret War: FDR and World War II Espionage — 200

1 —

Persico, Joseph

Casey: The Lives and Secrets of William J. Casey-From the OSS to the CIA

— 1991 —

Ronnie, Art Counterfeit Hero: Fritz Duquesne,Adventurer and Spy — 199

5ISBN 1-55750-733-3

Sayers, Michael & Albert E. Kahn

Sabotage! The Secret War Against America — 194

2 —

Smith, Richard Harris

OSS: The Secret History of America's First Central Intelligence Agency

— 2005 —

Stanley, RoyM. World War II Photo Intelligence — 198

1 —

Wark, WesleyThe Ultimate Enemy: British Intelligence and Nazi Germany, 1933–1939

— 1985 —

Wark, Wesley

"Cryptographic Innocence: The Origins of Signals Intelligence in Canada in the Second World War" in Journal of Contemporary History 22

— 1987 —

West, NigelSecret War: The Story of SOE, Britain's Wartime Sabotage Organization

— 1992 —

Winterbotham, F. W. The Ultra Secret Harper &

Row1974 —

Winterbotham, F. W. The Nazi Connection Harper &

Row1978 —

Cowburn, B. No Cloak No DaggerBrown, Watson, Ltd.

1960 —

Wohlstetter,Roberta.

Pearl Harbor: Warning and Decision — 196

2 —

Cold War era: 1945–1991

Author(s) Title Publisher Date NotesAmbrose, Stephen E.

Ike's Spies: Eisenhower and the Intelligence Establishment — 1981

- —

Andrew, Christopher and Vasili Mitrokhin

The Sword and the Shield: The Mitrokhin Archive and the Secret History of the KGB

Basic Books1991, 2005

ISBN 0-465-00311-7

Andrew, Christopher, and Oleg Gordievsky

KGB: The Inside Story of Its Foreign Operations from Leninto Gorbachev

— 1990 —

Aronoff, MyronJ.

The Spy Novels of John Le Carré: Balancing Ethics and Politics

— 1999 —

Bissell, Richard

Reflections of a Cold Warrior: From Yalta to the Bay of Pigs' — 1996 —

Bogle, Lori, Cold War Espionage and — 2001 essays

ed. Spying -Christopher Andrew and Vasili Mitrokhin

The World Was Going Our Way: The KGB and the Battle for the Third World

— — —

Christopher Andrew and Vasili Mitrokhin

The Mitrokhin Archive: The KGB in Europe and the West

Gardners Books 2000

ISBN 978-0-14-028487-4

Colella, Jim My Life as an Italian Mafioso Spy — 2000 —

Craig, R. Bruce

Treasonable Doubt: The Harry Dexter Spy Case

University Press of Kansas

2004

ISBN 978-0-7006-1311-3

Dorril, Stephen

MI6: Inside the Covert World of Her Majesty's Secret Intelligence Service

— 2000 —

Dziak, John J. Chekisty: A History of the KGB — 1988 —

Gates, Robert M.

From The Shadows: The Ultimate Insider's Story Of FivePresidents And How They Won The Cold War'

— 1997 —

Frost, Mike and Michel Gratton

Spyworld: Inside the Canadianand American Intelligence Establishments

Doubleday Canada 1994 —

Haynes, John Earl, and Harvey Klehr

Venona: Decoding Soviet Espionage in America — 1999 —

Helms, RichardA Look over My Shoulder: A Life in the Central Intelligence Agency

— 2003 —

Koehler, John O.

Stasi: The Untold Story of the East German Secret Police' — 1999 —

Persico, Joseph

Casey: The Lives and Secrets ofWilliam J. Casey-From the OSS to the CIA

— 1991 —

Murphy, David E., Sergei A. Kondrashev,

Battleground Berlin: CIA vs. KGB in the Cold War

— 1997 —

and George Bailey

Prados, JohnPresidents' Secret Wars: CIA and Pentagon Covert Operations Since World War II

— 1996 —

Rositzke, Harry.

The CIA's Secret Operations: Espionage, Counterespionage,and Covert Action

— 1988 —

Srodes, James Allen Dulles: Master of Spies Regnery 2000CIA head to1961

Sontag Sherry,and Christopher Drew

Blind Man's Bluff: The Untold Story of American Submarine Espinonage

Harper 1998 —

Encyclopedia of Cold War Espionage, Spies and Secret Operations

Greenwood Press/Questia[77]

2004 —

use of keys offered much hope of cryptanalysis. Beginning in the late 1940s, US and UK intelligence agencies were able to break some of the Soviet one-time pad traffic to Moscow during WWII as a result of errors made in generating and distributing the key material. One suggestion is that Moscow Centre personnel were somewhat rushed by the presence of German troops just outside Moscowin late 1941 and early 1942, and they produced more than one copy ofthe same key material during that period. This decades-long effort was finally codenamed VENONA (BRIDE had been an earlier name); it produced a considerable amount of information, including more than alittle about some of the Soviet atom spies. Even so, only a small percentage of the intercepted messages were either fully or partially decrypted (a few thousand out of several hundred thousand).[31]

Sedition

From Wikipedia, the free encyclopedia

This article is about the legal term. For other uses, see Sedition (disambiguation).

Not to be confused with sedation or seduction.

Part of a series on

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Pakistan

Paraguay

Poland

Portugal

Romania

Russia

Samoa

Saudi Arabia

Singapore

Somalia

South Korea

Soviet Union

Sri Lanka

Sweden

Taiwan (ROC)

Thailand

Tunisia

Turkey

United Kingdom

United States

Uzbekistan

Venezuela

Zimbabwe

See also

Freedom of speech by country

Internet censorship by country

v

t

e

In law, sedition is overt conduct, such as speech and organization, that tends toward insurrection against the establishedorder. Sedition often includes subversion of a constitution and incitement of discontent (or resistance) to lawful authority. Sedition may include any commotion, though not aimed at direct and open violence against the laws. Seditious words in writing are seditious libel. A seditionist is one who engages in or promotes theinterests of sedition.

Typically, sedition is considered a subversive act, and the overt acts that may be prosecutable under sedition laws vary from one legal code to another. Where the history of these legal codes has been traced, there is also a record of the change in the definition of the elements constituting sedition at certain points in history. This overview has served to develop a sociological definition of sedition as well, within the study of state persecution.

Contents

1 History in common law jurisdictions

1.1 Australia

1.2 Canada

1.3 Hong Kong

1.4 India

1.5 Malaysia

1.6 New Zealand

1.7 Singapore

1.8 United Kingdom

1.9 United States

1.9.1 Civilian

1.9.2 Military

2 Civil law jurisdictions

2.1 Germany

3 See also

4 Notes

5 References

6 External links

7 Further reading

History in common law jurisdictions

The term sedition in its modern meaning first appeared in the Elizabethan Era (c. 1590) as the "notion of inciting by words or writings disaffection towards the state or constituted authority".[citation needed] "Sedition complements treason and martial law: while treason controls primarily the privileged, ecclesiastical opponents, priests, and Jesuits, as well as certain commoners; and martial law frightens commoners, sedition frightens intellectuals."[citation needed]

Australia

Main article: Australian sedition law

Australia's sedition laws were amended in anti-terrorism legislation passed on 6 December 2005, updating definitions and increasing penalties.

In late 2006, the Commonwealth Government, under the Prime-Ministership of John Howard proposed plans to amend Australia's Crimes Act 1914, introducing laws that mean artists and writers may be jailed for up to seven years if their work was considered seditious or inspired sedition either deliberately or accidentally.[1] Opponents of these laws have suggested that they could be used against legitimate dissent.

In 2006, the then Australian attorney-general Philip Ruddock had rejected calls by two reports — from a Senate committee and the Australian Law Reform Commission — to limit the sedition provisions in the Anti-Terrorism Act 2005 by requiring proof of intention to cause disaffection or violence. He had also brushed

aside recommendations to curtail new clauses outlawing “urging conduct” that “assists” an “organisation or country engaged in armedhostilities” against the Australian military.

The new laws, inserted into the legislation December 2005,allow for the criminalization of basic expressions of political opposition, including supporting resistance to Australian military interventions, such as those in Afghanistan, Iraq and the Asia-Pacific region.[2]

These laws were amended in Australia on September 19, 2011. The ‘sedition’ clauses were repealed and replaced with ‘urging violence’. [1]

Canada

During World War II former Mayor of Montreal Camillien Houde campaigned against conscription in Canada. On August 2, 1940, Houde publicly urged the men of Quebec to ignore the National RegistrationAct. Three days later, he was placed under arrest by the Royal Canadian Mounted Police on charges of sedition. After being found guilty, he was confined in internment camps in Petawawa, Ontario, and Gagetown, New Brunswick, until 1944. Upon his release on August 18, 1944, he was greeted by a cheering crowd of 50,000 Montrealers and won back his position as the Mayor of Montreal in the election in 1944.[citation needed]

Hong Kong

A Sedition Ordinance had existed in the territory since 1970, which was subsequently consolidated into the Crime Ordinance in 1972.[3] According to the Crime Ordinance, a seditious intention is an intention to bring into hatred or contempt or to excite disaffection against the person of government, to excite inhabitantsof Hong Kong to attempt to procure the alteration, otherwise than bylawful means, of any other matter in Hong Kong as by law

established, to bring into hatred or contempt or to excite disaffection against the administration of justice in Hong Kong, to raise discontent or disaffection amongst inhabitants of Hong Kong, to promote feelings of ill-will and enmity between different classesof the population of Hong Kong, to incite persons to violence, or tocounsel disobedience to law or to any lawful order.[4][5]

Article 23 of the Basic Law requires the special administrative region to enact laws prohibiting any act of treason, secession, sedition, subversion against the Central People's Government of the People's Republic of China.[6] The National Security (Legislative Provisions) Bill was tabled in early 2003 to replace the existing laws regarding treason and sedition, and to introduce new laws to prohibit secessionist and subversive acts and theft of state secrets, and to prohibit political organisations fromestablishing overseas ties. The bill was shelved following massive opposition from the public.

India

Sedition is defined by Section 124A of the Indian Penal code. The section had been inserted into the IPC by Imperial Legislative Council Act No. 27 of 1870. The original section was substituted with a new one by Act 4 of 1898. The section currently reads:

124A. Sedition Whoever, by words, either spoken or written, or by signs, or by visible representation, or otherwise, brings or attempts to bring into hatred or contempt, or excites or attempts to excite disaffection towards,[a] the Government established by law in[b] India,[c] shall be punished with imprisonment for life,[d] to which fine may be added, or with imprisonment which may extend to three years, to which fine may be added, or with fine.

Explanation 1. — The expression “disaffection” includes disloyalty and all feelings of enmity.

Explanation 2. — Comments expressing disapprobation ofthe measures of the Government with a view to obtain their alteration by lawful means, without exciting or attempting to excitehatred, contempt or disaffection, do not constitute an offence underthis section.

Explanation 3. — Comments expressing disapprobation ofthe administrative or other action of the Government without exciting or attempting to excite hatred, contempt or disaffection, do not constitute an offence under this section.[8]

Mahatma Gandhi, then serving as editor of Young India, and printer and publisher Shankarlal Ghelabhai Banker, were arrested andtried under charges of sedition on 18 March 1922. During his trial Gandhi stated, "Section 124 A, under which I am happily charged, is perhaps the prince among the political sections of the Indian Penal Code designed to suppress the liberty of the citizen. Affection cannot be manufactured or regulated by law. If one has no affection for a person or system, one should be free to give the fullest expression to his disaffection, so long as he does not contemplate, promote, or incite to violence. But the section under which mere promotion of disaffection is a crime. I have studied some of the cases tried under it; I know that some of the most loved of India’s patriots have been convicted under it. I consider it a privilege, therefore, to be charged under that section. I have endeavored to give in their briefest outline the reasons for my disaffection. I have no personal ill-will against any single administrator, much less can I have any disaffection towards the King's person. But I hold it to be a virtue to be disaffected towards a Government which in its totality has done more harm to India than any previous system. India is less manly under the British rule than she ever wasbefore. Holding such a belief, I consider it to be a sin to have affection for the system."[9][10]

Dr Manohar Garg MBBS MOB NO 8968694599 Was Charged Three TimesU/S 124- A IPC ON 29 /7 / 1999, 2000, 2004, Address Dr M.G, House NO2200, Sandhu Nagar, LUDHIANA

In 2010, writer Arundhati Roy was sought to be charged with sedition for her comments on Kashmir and Maoists.[11] Two individuals have been charged with sedition since 2007.[12] Binayak Sen, an Indian pediatrician, public health specialist and activist, was found guilty of sedition.[13] He is national Vice-President of the People's Union for Civil Liberties (PUCL). On 24 December 2010, the Additional Sessions and District Court Judge B.P Varma Raipur found Binayak Sen, Naxal ideologue Narayan Sanyal and Kolkata businessman Piyush Guha, guilty of sedition for helping the Maoists in their fight against the state. They were sentenced to life imprisonment, but he got bail in Supreme Court on 16 April 2011.[14]

On 10 September 2012, Aseem Trivedi, a political cartoonist, was sent to judicial custody till 24 September 2012 on charges of sedition over a series of cartoons against corruption. Trivedi was accused of uploading "ugly and obscene" content to his website, alsoaccused of insulting the Constitution during an anti-corruption protest in Mumbai in 2011. Trivedi's arrest under sedition has been heavily criticized in India. The Press Council of India (PCI) termedit a "stupid" move.[15]

Malaysia

See also: Sedition Act (Malaysia)

New Zealand

Sedition charges were not uncommon in New Zealand early in the20th Century. For instance, the future Prime Minister Peter Fraser had been convicted of sedition in his youth for arguing against conscription during World War I, and was imprisoned for a year. Perhaps ironically, Fraser re-introduced the conscription of troops as the Prime Minister during World War II.[16]

In New Zealand's first sedition trial in decades, Tim Selwyn was convicted of sedition (section 83 of the Crimes Act 1961) on 8 June 2006. Shortly after, in September 2006, the New Zealand Police laid a sedition charge against a Rotorua youth, Christopher Russell,17, who was also charged with threatening to kill.[17] The Police withdrew the sedition charge when Russell agreed to plead guilty on the other charge.[18]

In March 2007, Mark Paul Deason, the manager of a tavern near the University of Otago, was charged with seditious intent[19] although he was later granted diversion when he pleaded guilty to publishing a document which encourages public disorder[20] Deason ran a promotion for his tavern that offered one litre of beer for one litre of petrol. At the end of the promotion, the prize would have been a couch soaked in the petrol. It is presumed the intent was for the couch to be burned — a popular university student prank.Police also applied for Deason's liquor license to be revoked.

Following a recommendation from the New Zealand Law Commission,[21] the New Zealand government announced on 7 May 2007 that the sedition law would be repealed.[22] The Crimes (Repeal of Seditious Offences) Amendment Act 2007 was passed on 24 October 2007, and entered into force on 1 January 2008.[23]

Russell Campbell made a documentary regarding conscientious objectors in New Zealand called Sedition.

Singapore

See also: Sedition Act (Singapore)

United Kingdom

See also: Sedition Act 1661

Sedition was a common law offence in the UK. James Fitzjames Stephen's "Digest of the Criminal Law" stated that "a seditious intention is an intention to bring into hatred or contempt, or to exite disaffection against the person of His Majesty, his heirs or successors, or the government and constitution of the United Kingdom, as by law established, or either House of Parliament, or the administration of justice, or to excite His Majesty's subjects to attempt otherwise than by lawful means, the alteration of any matter in Church or State by law established, or to incite any person to commit any crime in disturbance of the peace, or to raise discontent or disaffection amongst His Majesty's subjects, or to promote feelings of ill-will and hostility between different classesof such subjects.

An intention to show that His Majesty has been misled or mistaken in his measures, or to point out errors or defects in the government or constitution as by law established, with a view to their reformation, or to excite His Majesty's subjects to attempt bylawful means the alteration of any matter in Church or State by law established, or to point out, in order to secure their removal, matters which are producing, or have a tendency to produce, feelingsof hatred and ill-will between classes of His Majesty's subjects, isnot a seditious intention."

Stephen in his "History of the Criminal Law of England" accepted the view that a seditious libel was nothing short of a direct incitement to disorder and violence. He stated that the modern view of the law was plainly and fully set out by Littledale J. in Collins. In that case the jury were instructed that they couldconvict of seditious libel only if they were satisfied that the defendant "meant that the people should make use of physical force as their own resource to obtain justice, and meant to excite the people to take the power in to their own hands, and meant to excite them to tumult and disorder."

The last prosecution for sedition in the United Kingdom was in1972, when three people were charged with seditious conspiracy and

uttering seditious words for attempting to recruit people to travel to Northern Ireland to fight in support of Republicans. The seditious conspiracy charge was dropped, but the men received suspended sentences for uttering seditious words and for offences against the Public Order Act.[24]

In 1977, a Law Commission working paper recommended that the common law offence of sedition in England and Wales be abolished. They said that they thought that this offence was redundant and thatit was not necessary to have any offence of sedition.[24] However this proposal was not implemented until 2009, when sedition and seditious libel (as common law offences) were abolished by section 73 of the Coroners and Justice Act 2009 (with effect on 12 January 2010).[25] Sedition by an alien is still an offence under section 3 of the Aliens Restriction (Amendment) Act 1919.[26]

In Scotland, section 51 of the Criminal Justice and Licensing (Scotland) Act 2010 abolished the common law offences of sedition and leasing-making[27] with effect from 28 March 2011.[28]

United States

See also: Seditious conspiracy

Civilian

In 1798, President John Adams signed into law the Alien and Sedition Acts, the fourth of which, the Sedition Act or "An Act for the Punishment of Certain Crimes against the United States" set out punishments of up to two years of imprisonment for "opposing or resisting any law of the United States" or writing or publishing "false, scandalous, and malicious writing" about the President or the U.S. Congress (though not the office of the Vice-President, thenoccupied by Adams' political opponent Thomas Jefferson). This Act ofCongress was allowed to expire in 1801 after Jefferson's election tothe Presidency.[citation needed]

Political cartoon by Art Young, The Masses, 1917.

In the Espionage Act of 1917, Section 3 made it a federal crime, punishable by up to 20 years of imprisonment and a fine of upto $10,000, to willfully spread false news of the American army and navy with an intent to disrupt their operations, to foment mutiny intheir ranks, or to obstruct recruiting. This Act of Congress was amended Sedition Act of 1918, which expanded the scope of the Espionage Act to any statement criticizing the Government of the United States. These Acts were upheld in 1919 in the case of Schenckv. United States, but they were largely repealed in 1921, leaving laws forbidding foreign espionage in the United States and allowing military censorship of sensitive material.

In 1940, the Alien Registration Act, or "Smith Act", was passed, which made it a federal crime to advocate or to teach the desirability of overthrowing the United States Government, or to be a member of any organization which does the same. It was often used against Communist Party organizations. This Act was invoked in threemajor cases, one of which against the Socialist Worker's Party in Minneapolis in 1941, resulting in 23 convictions, and again in what became known as the Great Sedition Trial of 1944 in which a number of pro-Nazi figures were indicted but released when the prosecution ended in a mistrial. Also, a series of trials of 140 leaders of the Communist Party USA also relied upon the terms of the "Smith Act"—beginning in 1949—and lasting until 1957. Although the U.S. Supreme Court upheld the convictions of 11 CPUSA leaders in 1951 in Dennis v. United States, that same Court reversed itself in 1957 in the case of Yates v. United States, by ruling that teaching an ideal, nomatter how harmful it may seem, does not equal advocating or planning its implementation. Although unused since at least 1961, the "Smith Act" remains a Federal law.

There was, however, a brief attempt to use the sedition laws against protesters of the Vietnam War. On October 17, 1967, two demonstrators, including then Marin County resident Al Wasserman, while engaged in a 'sit in' at the Army Induction Center in Oakland,Ca., were arrested and charged with sedition by deputy US. Marshall

Richard St. Germain. U.S. Attorney Cecil Poole changed the charge totrespassing. Poole said, "three guys (according to Mr. Wasserman there were only 2) reaching up and touching the leg of an inductee, and that's conspiracy to commit sedition? That's ridiculous!" The inductees were in the process of physically stepping on the demonstrators as they attempted to enter the building, and the demonstrators were trying to protect themselves from the inductees' feet. Attorney Poole later added, "We'll decide what to prosecute, not marshals."[29]

In 1981, Oscar López Rivera, a Puerto Rican Nationalist and Vietnam war veteran, was convicted and sentenced to 70 years in prison for seditious conspiracy and various other offenses. He was among the 16 Puerto Rican nationalists offered conditional clemency by U.S. President Bill Clinton in 1999, but he rejected the offer. His sister, Zenaida López, said he refused the offer because on parole, he would be in "prison outside prison." He has been jailed for 34 years, 3 months and 2 days.[30] The clemency agreement required him to renounce the use of terrorism, including use or advocacy of the use of violence, to achieve their aim of independence for Puerto Rico, by that means refraining from the for any purpose.[31] Congressman Pedro Pierluisi, has stated that "the primary reason that López Rivera did not accept the clemency offer extended to him in 1999 was because it had not also been extended tocertain fellow [ independence ] prisoner, including Mr. Torres", andwho was subsequently released from prison in July 2010."[32]

In 1987, fourteen white supremacists were indicted by a federal grand jury on charges filed by the U.S. Department of Justice against a seditious conspiracy between July 1983 and March 1985. Some alleged conspirators were serving time for overt acts, such as the crimes committed by The Order. Others such as Louis Beamand Richard Butler were charged for their speech seen as spurring onthe overt acts by the others. In April 1988, a federal jury in Arkansas acquitted all the accused of charges of seditious conspiracy.[33]

On October 1, 1995, Omar Abdel-Rahman and nine others were convicted of seditious conspiracy.[34]

Laura Berg, a nurse at a U.S. Department of Veterans Affairs hospital in New Mexico was investigated for sedition in September 2005[35] after writing a letter[36][37] to the editor of a local newspaper, accusing several national leaders of criminal negligence.Though their action was later deemed unwarranted by the director of Veteran Affairs, local human resources personnel took it upon themselves to request an FBI investigation. Ms. Berg was representedby the ACLU.[38] Charges were dropped in 2006.[39]

On March 28, 2010, nine members of the Hutaree militia were arrested and charged with crimes including seditious conspiracy.[40]

Military

Sedition is a punishable offense under Article 94 of the Uniform Code of Military Justice.[41]

Civil law jurisdictions

Germany

Volksverhetzung ("incitement of the people") is a legal concept in Germany and some Nordic countries. It is sometimes loosely translated as sedition,[42] although the law bans the incitement of hatred against a segment of the population. Segment ofthe population meaning, for example, a race or religion.

Key disclosure law

From Wikipedia, the free encyclopedia

This article includes inline citations, but they are not properly formatted. Please improve this article by correcting them. (June 2014)

Key disclosure laws, also known as mandatory key disclosure, is legislation that requires individuals to surrender cryptographic keys to law enforcement. The purpose is to allow access to material for confiscation or digital forensics purposes and use it either as evidence in a court of law or to enforce national security interests. Similarly, mandatory decryption laws force owners of encrypted data to supply decrypted data to law enforcement.

Nations vary widely in the specifics of how they implement keydisclosure laws. Some, such as Australia, give law enforcement wide-ranging power to compel assistance in decrypting data from any party. Some, such as Belgium, concerned with self-incrimination, only allow law enforcement to compel assistance from non-suspects. Some require only specific third parties such as telecommunications carriers, certification providers, or maintainers of encryption services to provide assistance with decryption. In all cases, a warrant is generally required.

Contents

1 Theory and countermeasures

2 Criticism and alternatives

3 Legislation by nation

3.1 Antigua and Barbuda

3.2 Australia

3.3 Belgium

3.4 Canada

3.5 Finland

3.6 France

3.7 India

3.8 New Zealand

3.9 Poland

3.10 South Africa

3.11 Sweden

3.12 The Netherlands

3.13 United Kingdom

3.14 United States

4 See also

5 References

6 Further reading

Theory and countermeasures

Mandatory decryption is technically a weaker requirement than key disclosure, since it is possible in some cryptosystems to prove thata message has been decrypted correctly without revealing the key. For example, using RSA public-key encryption, one can verify given the message (plaintext), the encrypted message (ciphertext), and thepublic key of the recipient that the message is correct by merely re-encrypting it and comparing the result to the encrypted message. Such a scheme is called undeniable, since once the government has validated the message they cannot deny that it is the correct decrypted message.[1]

As a countermeasure to key disclosure laws, some personal privacy products such as BestCrypt, FreeOTFE, and TrueCrypt have begun incorporating deniable encryption technology, which enable a single piece of encrypted data to be decrypted in two or more different ways, creating plausible deniability.[2][3] Another alternative is steganography, which hides encrypted data inside of benign data so that it is more difficult to identify in the first place.

A problematic aspect of key disclosure is that it leads to a total compromise of all data encrypted using that key in the past or future; time-limited encryption schemes such as those of Desmedt et al.[1] allow decryption only for a limited time period.

Criticism and alternatives

Critics of key disclosure laws view them as compromising informationprivacy, by revealing personal information that may not be pertinentto the crime under investigation, as well as violating the right against self-incrimination and more generally the right to silence, in nations which respect these rights. In some cases, it may be impossible to decrypt the data because the key has been lost, forgotten or revoked, or because the data is actually random data which cannot be effectively distinguished from encrypted data.

A proactive alternative to key disclosure law is key escrow law, where the government holds in escrow a copy of all cryptographic keys in use, but is only permitted to use them if an appropriate warrant is issued. Key escrow systems face difficult technical issues and are subject to many of the same criticisms as key disclosure law; they avoid some issues like lost keys, while introducing new issues such as the risk of accidental disclosure of large numbers of keys, theft of the keys by hackers or abuse of power by government employees with access to the keys. It would alsobe nearly impossible to prevent the government from secretly using the key database to aid mass surveillance efforts such as those exposed by Edward Snowden. The ambiguous term key recovery is applied to both types of systems.

Legislation by nation

Antigua and Barbuda

The Computer Misuse Bill, 2006, Article 21(5)(c), if enacted, would allow police with a warrant to demand and use decryption keys.

Failure to comply may incur "a fine of fifteen thousand [East Caribbean] dollars" and/or "imprisonment for two years."[4]

Australia

The Cybercrime Act 2001 No. 161, Items 12 and 28 grant police with amagistrate's order the wide-ranging power to require "a specified person to provide any information or assistance that is reasonable and necessary to allow the officer to" access computer data that is "evidential material"; this is understood to include mandatory decryption. Failing to comply carries a penalty of 6 months imprisonment. Electronic Frontiers Australia calls the provision "alarming" and "contrary to the common law privilege against self-incrimination."[5]

The Crimes Act 1914, 3LA(5) A person commits an offence if the person fails to comply with the order. Penalty for contravention of this subsection: Imprisonment for 2 years [6]

Belgium

The Loi du 28 novembre 2000 relative à la criminalité informatique (Law on computer crime of 28 November 2000), Article 9 allows a judge to order both operators of computer systems and telecommunications providers to provide assistance to law enforcement, including mandatory decryption, and to keep their assistance secret; but this action cannot be taken against suspects or their families.[7][8] Failure to comply is punishable by 6 monthsto 1 year in jail and/or a fine of 130 to 100,000 Euros.

Canada

Canada implements key disclosure by broad interpretation of "existing interception, search and seizure and assistance procedures";[9] in a 1998 statement, Cabinet Minister John Manley explained, "warrants and assistance orders also apply to situations

where encryption is encountered — to obtain the decrypted material or decryption keys."[10]

Finland

The Coercive Measures Act (Pakkokeinolaki) 2011/806 section 8 paragraph 23[11] requires the system owner, its administrator, or a specified person to surrender the necessary "passwords and other such information" in order to provide access to information stored on an information system. The suspect and some other persons specified in section 7 paragraph 3 that cannot otherwise be called as witnesses are exempt of this requirement.

France

Loi no 2001-1062 du 15 novembre 2001 relative à la sécurité quotidienne, article 30 (Law #2001-1062 of 15 November 2001 on Community Safety) allows a judge or prosecutor to compel any qualified person to decrypt or surrender keys to make available any information encountered in the course of an investigation. Failure to comply incurs three years of jail time and a fine of €45,000; if the compliance would have prevented or mitigated a crime, the penalty increases to five years of jail time and €75,000.[12]

India

Section 69 of the Information Technology Act, as amended by the Information Technology (Amendment) Act, 2008, empowers the central and state governments to compel assistance from any "subscriber or intermediary or any person in charge of the computer resource" in decrypting information.[13][14] Failure to comply is punishable by up to seven years imprisonment and/or a fine.

New Zealand

New Zealand Customs is seeking Power to compel Key disclosure.[15]

Poland

In relatively few known cases in which police or prosecutor requested cryptographic keys from those formally accused and these requests were not fulfilled, no further consequences were imposed onthe accused. There's no specific law in this matter, as e.g. in the UK. It is generally assumed that the Polish Criminal Procedure Code (Kodeks Postępowania Karnego Dz.U. 1997 nr 89 poz. 555.) provides means of protecting against self-incrimination, including lack of penalization for refusing to answer any question which would enable law enforcement agencies to obtain access to potential evidence, which could be used against testifying person.[16]

South Africa

Under the RICA Act of 2002, refusal to disclose a cryptographic key in your possession could result in a fine up to ZAR 2 Million or up to 10 years imprisonment. This requires a judge to issue a decryption direction to a person believed to hold the key.[citation needed]

Sweden

There are currently no laws that force the disclosure of cryptographic keys. However, there is legislation proposed on the basis that the Council of Europe has already adopted a convention oncyber-crime related to this issue. The proposed legislation would allow police to require an individual to disclose information, such as passwords and cryptographic keys, during searches. The proposal has been introduced to make it easier for police and prosecutors. The proposal has been criticized by The Swedish Data Inspection Board.[17][18]

The Netherlands

Article 125k of the Wetboek van Strafvordering allows investigators with a warrant to access information carriers and networked systems.The same article allows the district attorney and similar officers

of the court to order persons who know how to access those systems to share their knowledge in the investigation, including any knowledge of encryption of data on information carriers. However, such an order may not be given to the suspect under investigation.[19]

United Kingdom

The Regulation of Investigatory Powers Act 2000 (RIPA), Part III, activated by ministerial order in October 2007,[20] requires personsto supply decrypted information and/or keys to government representatives with a court order. Failure to disclose carries a maximum penalty of two years in jail. The provision was first used against animal rights activists in November 2007,[21] and at least three people have been prosecuted and convicted for refusing to surrender their encryption keys,[22] one of whom was sentenced to 13months' imprisonment.[23]

United States

The Fifth Amendment to the United States Constitution protects witnesses from being forced to incriminate themselves, and there is currently no law regarding key disclosure in the United States.[24] However, the federal case In re Boucher may be influential as case law. In this case, a man's laptop was inspected by customs agents and child pornography was discovered. The device was seized and powered-down, at which point disk encryption technology made the evidence unavailable. The judge held that it was a foregone conclusion that the content exists since it had already been seen bythe customs agents, Boucher's encryption password "adds little or nothing to the sum total of the Government's information about the existence and location of files that may contain incriminating information."[25][26]

In another case, a district court judge ordered a Colorado woman to decrypt her laptop so prosecutors can use the files against her in acriminal case: "I conclude that the Fifth Amendment is not

implicated by requiring production of the unencrypted contents of the Toshiba Satellite M305 laptop computer," Colorado U.S. District Judge Robert Blackburn ruled on January 23, 2012.[27] In Commonwealth v. Gelfgatt,[28] the court ordered a suspect to decrypthis computer, citing exception to Fifth Amendment can be invoked because "an act of production does not involve testimonial communication where the facts conveyed already are known to the government...".[29]

However, in United States v. Doe, the United States Court of Appealsfor the Eleventh Circuit ruled on 24 February 2012 that forcing the decryption of one's laptop violates the Fifth Amendment.[30][31]

The Federal Bureau of Investigation may also issue national securityletters that require the disclosure of keys for investigative purposes.[32] One company, Lavabit, chose to shut down rather than surrender its master private keys.

Digital rights management

From Wikipedia, the free encyclopedia

Digital rights management (DRM) is a term referring to various access control technologies that are used by software and hardware manufacturers, publishers, copyright holders, and individuals with the intent to control the use of digital content and devices.[1] Digital rights management includes technologies that control the use, modification, and distribution of works, as well as systems within devices that enforce these policies. The term is also sometimes referred to as "copy protection", copy prevention, and copy control, although the correctness of doing so is disputed.[2]

The use of digital rights management is not universally accepted. Proponents of DRM argue that it is necessary to prevent intellectualproperty from being copied freely, just as physical locks are neededto prevent personal property from being stolen,[3] that it can help

the copyright holder maintain artistic control,[4] and that it can ensure continued revenue streams.[5] Those opposed to DRM contend there is no evidence that DRM helps prevent copyright infringement, arguing instead that it serves only to inconvenience legitimate customers, and that DRM helps big business stifle innovation and competition.[6] Furthermore, works can become permanently inaccessible if the DRM scheme changes or if the service is discontinued.[7] DRM can also restrict users from exercising their legal rights under copyright law, such as backing up copies of CDs or DVDs, lending materials out through a library, accessing works inthe public domain, or using copyrighted materials for research and education under the the fair use doctrine,[3] and under French law.[8] The Electronic Frontier Foundation (EFF) and the Free Software Foundation (FSF) consider the use of DRM systems to be an anti-competitive practice.[9][10]

Worldwide, many laws have been created which criminalize the circumvention of DRM, communication about such circumvention, and the creation and distribution of tools used for such circumvention. Such laws are part of the Copyright Directive,[11] the Digital Millennium Copyright Act,[12] and DADVSI.[13]

Contents

1 Introduction

1.1 Common DRM techniques

2 Technologies

2.1 DRM and computer games

2.1.1 Limited install activations

2.1.2 Persistent online authentication

2.1.3 Software tampering

2.1.4 CD Keys

2.2 DRM and documents

2.3 DRM and e-books

2.4 DRM and film

2.5 DRM and music

2.5.1 Audio CDs

2.5.2 Internet music

2.5.2.1 Mobile ring tones

2.6 DRM and television

2.7 Metadata

2.8 Watermarks

2.9 Streaming media services

3 Laws regarding DRM

3.1 Digital Millennium Copyright Act

3.2 European Union

3.3 International issues

3.4 Israel

4 Opposition to DRM

4.1 DRM-free works

5 Shortcomings

5.1 DRM server and Internet outages

5.2 Methods to bypass DRM

5.2.1 DRM bypass methods for audio and video content

5.3 Analog hole

5.4 DRM on general computing platforms

5.5 DRM on purpose-built hardware

5.6 Watermarks

5.7 Undecrypted copying failure

5.8 Obsolescence

5.9 Environmental issues

5.10 Moral and legitimacy implications

5.11 Relaxing some forms of DRM can be beneficial

5.12 Can increase piracy

6 Alternatives to DRM

6.1 "Easy and cheap"

6.2 Crowdfunding or pre-order model

6.3 Digital content as promotion for traditional products

6.4 Artistic Freedom Voucher

7 Historical note

8 See also

8.1 Related concepts

8.2 Lawsuits

8.3 Organizations

9 References

10 Further reading

11 External links

Introduction

The advent of digital media and analog-to-digital conversion technologies (especially those that are usable on mass-market general-purpose personal computers) has vastly increased the concerns of copyright-owning individuals and organizations. These concerns are particularly prevalent within the music and movie

industries, because these sectors are partly or wholly dependent on the revenue generated from such works. While analog media inevitablyloses quality with each copy generation, and in some cases even during normal use, digital media files may be duplicated an unlimited number of times with no degradation in the quality of subsequent copies.

The advent of personal computers as household appliances has made itconvenient for consumers to convert media (which may or may not be copyrighted) originally in a physical, analog or broadcast form intoa universal, digital form (this process is called ripping) for portability or viewing later. This, combined with the Internet and popular file-sharing tools, has made unauthorized distribution of copies of copyrighted digital media (also called digital piracy) much easier.

DRM technologies enable content publishers to enforce their own access policies on content, such as restrictions on copying or viewing. In cases where copying or some other use of the content is prohibited, regardless of whether such copying or other use is legally considered a "fair use", DRM technologies have come under fire. DRM is in common use by the entertainment industry (e.g., audio and video publishers).[14] Many online music stores, such as Apple's iTunes Store, and e-book publishers also use DRM, as do cable and satellite service operators, to prevent unauthorized use of content or services. However, Apple quietly dropped DRM from all iTunes music files in about 2009.[15]

In recent years the industry expanded the usage of DRM to even traditional hardware products, examples are Keurig's coffeemakers[16][17] and John Deere's tractors.[18] For instance, tractor companies try to prevent the DIY repairing by the owning farmers under usage of DRM-laws as DMCA.[19]

Common DRM techniques

Digital Rights Management Techniques include:

Restrictive Licensing Agreements: The access to digital materials, copyright and public domain is controlled. Some restrictive licenses are imposed on consumers as a condition of entering a website or when downloading software.[20]

Encryption, Scrambling of expressive material and embedding of atag: This technology is designed to control access and reproduction of information. This includes backup copies for personal use.[21]

Technologies

DRM and computer games

Limited install activations

Computer games sometimes use DRM technologies to limit the number ofsystems the game can be installed on by requiring authentication with an online server. Most games with this restriction allow three or five installs, although some allow an installation to be 'recovered' when the game is uninstalled. This not only limits userswho have more than three or five computers in their homes (seeing asthe rights of the software developers allow them to limit the numberof installations), but can also prove to be a problem if the user has to unexpectedly perform certain tasks like upgrading operating systems or reformatting the computer's hard drive, tasks which, depending on how the DRM is implemented, count a game's subsequent reinstall as a new installation, making the game potentially unusable after a certain period even if it is only used on a single computer.

In mid-2008, the publication of Mass Effect marked the start of a wave of titles primarily making use of SecuROM for DRM and requiringauthentication with a server. The use of the DRM scheme in 2008's Spore backfired and there were protests, resulting in a considerablenumber of users seeking a pirated version instead. This backlash

against the 3× activation limit was a significant factor in Spore becoming the most pirated game in 2008, with TorrentFreak compiling a "top 10" list with Spore topping the list.[22][23] However, Tweakguides concluded that the presence of intrusive DRM does not appear to increase piracy of a game, noting that other games on the list such as Call of Duty 4, Assassin's Creed and Crysis use SafeDisc DRM, which has no install limits and no online activation. Additionally, other video games that do use intrusive DRM such as BioShock, Crysis Warhead, and Mass Effect, do not appear on the list.[24]

Persistent online authentication

Main article: Always-on DRM

Many mainstream publishers continued to rely on online DRM throughout the later half of 2008 and early 2009, including Electronic Arts, Ubisoft, Valve, and Atari, The Sims 3 being a notable exception in the case of Electronic Arts.[25] Ubisoft broke with the tendency to use online DRM in late 2008, with the release of Prince of Persia as an experiment to "see how truthful people really are" regarding the claim that DRM was inciting people to use pirated copies.[26] Although Ubisoft has not commented on the results of the "experiment", Tweakguides noted that two torrents on Mininova had over 23,000 people downloading the game within 24 hoursof its release.[27]

Ubisoft formally announced a return to online authentication on 9 February 2010, through its Uplay online gaming platform, starting with Silent Hunter 5, The Settlers 7, and Assassin's Creed II.[28] Silent Hunter 5 was first reported to have been compromised within 24 hours of release,[29] but users of the cracked version soon foundout that only early parts of the game were playable.[30] The Uplay system works by having the installed game on the local PCs incomplete and then continuously downloading parts of the game-code from Ubisoft's servers as the game progresses.[31] It was more than a month after the PC release in the first week of April that software was released that could bypass Ubisoft's DRM in Assassin's Creed II. The software did this by emulating a Ubisoft server for

the game. Later that month, a real crack was released that was able to remove the connection requirement altogether.[32][33]

In early March 2010, Uplay servers suffered a period of inaccessibility due to a large-scale DDoS attack, causing around 5% of game owners to become locked out of playing their game.[34] The company later credited owners of the affected games with a free download, and there has been no further downtime.[35]

Other developers, such as Blizzard Entertainment are also shifting to a strategy where most of the game logic is on the "side" or takencare of by the servers of the game maker. Blizzard uses this strategy for its game Diablo III and Electronic Arts used this same strategy with their reboot of SimCity, the necessity of which has been questioned.[36]

Software tampering

Bohemia Interactive have used a form of technology since Operation Flashpoint: Cold War Crisis, wherein if the game is suspected of being pirated, annoyances like guns losing their accuracy or the players being turned into a bird are introduced.[37]

Croteam, the company that released Serious Sam 3: BFE in November 2011, implemented a different form of DRM wherein, instead of displaying error messages that stop the pirated version of the game from running, it causes a special invincible foe in the game to appear and constantly attack the player until they are killed.[38][39]

CD Keys

One of the oldest and least complicated DRM protection method for the computer games is a CD Key. CD Keys are a series of numbers and letters included with copies of the game, usually printed somewhere

on the CD or the software package. During installation the program will request that the user enter CD Key to authenticate the product.Without the CD Key, installation is impossible. There are sizable disadvantages to this protection method for both consumers and producers. For example, if a consumer loses his CD Key, he is unableto install and legitimize his purchased product without contacting customer service. CD Keys were made notable by Microsoft Windows, anoperating system which, if not provided as an OEM copy, will requirea 25 digit key code. For the producers and developers piracy is a significant issue. Many websites are offering “cd key cracks” and “cd key generators” for several games and products. This will generate a series of characters that the software interprets as a valid CD Key and bypasses this form of DRM protection.[40][41]

DRM and documents

Enterprise digital rights management (E-DRM or ERM) is the application of DRM technology to the control of access to corporate documents such as Microsoft Word, PDF, and AutoCAD files, emails, and intranet web pages rather than to the control of consumer media.[42] E-DRM, now more commonly referenced as IRM (Information Rights Management), is generally intended to prevent the unauthorized use (such as industrial or corporate espionage or inadvertent release) of proprietary documents. IRM typically integrates with content management system software but corporations such as Samsung Electronics also develop their own custom DRM systems.[43]

DRM has been used by organizations such as the British Library in its secure electronic delivery service to permit worldwide access tosubstantial numbers of rare (and in many cases unique) documents which, for legal reasons, were previously only available to authorized individuals actually visiting the Library's document centre at Boston Spa in England.[citation needed]

DRM and e-books

Electronic books read on a personal computer, or an e-book reader ore-reader app typically use DRM technology to limit copying, printing, and sharing of e-books. E-books (alternatively spelled "ebooks") are usually limited to be used on a limited number of reading devices, and some e-publishers prevent any copying or printing. Some commentors believe DRM makes e-book publishing complex.[44]

As of August 2012, there are five main ebook formats: EPUB, KF8, Mobipocket, PDF, and Topaz,.[45] The Amazon Kindle uses KF8, Mobipocket, and Topaz; it also supports native PDF format ebooks andnative PDF files. Other ebook readers mostly use EPUB format ebooks,but with differing DRM schemes.[citation needed]

There are four main ebook DRM schemes in common use today, one each from Adobe, Amazon, Apple, and the Marlin Trust Management Organization (MTMO).

Adobe's ADEPT DRM is applied to EPUBs and PDFs, and can be read by several third-party ebook readers, as well as Adobe Digital Editions (ADE) software. Barnes & Noble uses a DRM technology provided by Adobe, applied to EPUBs and the older PDB (Palm OS) format ebooks. In 2014, Adobe announced a new DRM scheme to replace the old one, to become available as soon as March 2014.[citation needed]

Amazon's DRM is an adaption of the original Mobipocket encryption and is applied to Amazon's .azw4, KF8, and Mobipocket format ebooks. Topaz format ebooks have their own encryption system.[citation needed]

Apple's FairPlay DRM is applied to EPUBs and can currently only be read by Apple's iBooks app on iOS devices.

The Marlin DRM was developed and is maintained in an open industry group known as the Marlin Developer Community (MDC) and is licensed by MTMO. (Marlin was founded by five companies, Intertrust,Panasonic, Philips, Samsung, and Sony.) The Kno online textbook

publisher uses Marlin to protect ebooks it sells in the EPUB format.These books can be read on the Kno App for iOS and Android.

In one instance of DRM that caused a rift with consumers, Amazon.comin July 2009, remotely deleted purchased copies of George Orwell's Animal Farm (1945) and Nineteen Eighty-Four (1949) from customers' Amazon Kindles after providing them a refund for the purchased products.[46] Commentors have widely described these actions as Orwellian, and have alluded to Big Brother from Orwell's Nineteen Eighty-Four.[47][48][49][50] After Amazon CEO Jeff Bezos issued a public apology, the Free Software Foundation wrote that this was just one more example of the excessive power Amazon has to remotely censor what people read through its software, and called upon Amazonto free its e-book reader and drop DRM.[51] Amazon then revealed thereason behind its deletion: the ebooks in question were unauthorizedreproductions of Orwell's works, which were not within the public domain and to which the company that published and sold them on Amazon's service had no rights.[52]

Websites - including library.nu (shut down by court order on February 15, 2012), BookFinder, and Library Genesis - have emerged which allow downloading ebooks by violating copyright.[53]

DRM and film

An early example of a DRM system is the Content Scrambling System (CSS) employed by the DVD Forum on film DVDs c. 1996. CSS uses an encryption algorithm to encrypt content on the DVD disc. Manufacturers of DVD players must license this technology and implement it in their devices so that they can decrypt the encryptedcontent to play it. The CSS license agreement includes restrictions on how the DVD content is played, including what outputs are permitted and how such permitted outputs are made available. This keeps the encryption intact as the video material is played out to aTV.

In 1999, Jon Lech Johansen released an application called DeCSS which allowed a CSS-encrypted DVD to play on a computer running the Linux operating system, at a time when no licensed DVD player application for Linux had yet been created. The legality of DeCSS isquestionable, one of the authors has been the subject to a lawsuit and reproduction of the keys themselves are subject to restrictions as illegal numbers.[54]

Also in 1999, Windows came out with Windows Media DRM, which read instructions from media files in a rights management language that stated what the user may do with the media.[55] The language can define how many times the media file can be played, if it can be burned to a CD, if it can be printed, forwarded, or saved to the local disk.[56] Later versions of Windows Media DRM also allow producers to declare whether the user may transfer the media file toother devices,[57] to implement music subscription services that make downloaded files unplayable after canceled subscription, and implement regional lockout.[58]

Microsoft's Windows Vista contains a DRM system called the ProtectedMedia Path, which contains the Protected Video Path (PVP). PVP triesto stop DRM-restricted content from playing while unsigned software is running in order to prevent the unsigned software from accessing the content. Additionally, PVP can encrypt information during transmission to the monitor or the graphics card, which makes it more difficult to make unauthorized recordings.

Advanced Access Content System (AACS) is a DRM system for HD DVD andBlu-ray Discs developed by the AACS Licensing Administrator, LLC (AACS LA), a consortium that includes Disney, Intel, Microsoft, Matsushita (Panasonic), Warner Brothers, IBM, Toshiba and Sony. In December 2006, a process key was published on the internet by hackers, enabling unrestricted access to AACS-protected HD DVD content.[59] After the cracked keys were revoked, further cracked keys were released.[60]

Marlin (DRM) is a technology that is developed and maintained in an open industry group known as the Marlin Developer Community (MDC) and licensed by the Marlin Trust Management Organization (MTMO). Founded in 2005, by five companies: Intertrust, Panasonic, Philips, Samsung, and Sony, Marlin DRM has been deployed in multiple places around the world. In Japan the acTVila IPTV service uses Marlin to encrypt video streams, which are permitted to be recorded on a DVR in the home. In Europe, Philips NetTVs implement Marlin DRM. Also inEurope, Marlin DRM is required in such industry groups as the Open IPTV Forum and national initiatives such as YouView in the UK, Tivu in Italy, and HDForum in France, which are starting to see broad deployments.

OMA DRM is a system invented by the Open Mobile Alliance, whose members represent mobile phone manufacturers (e.g. LG, Motorola, Samsung, Sony), mobile system manufacturers (e.g. Ericsson, Openwave), mobile phone network operators (e.g. Vodafone, O2, Cingular, Deutsche Telekom, Orange), and information technology companies (e.g. Microsoft, IBM).

DRM and music

Audio CDs

Discs with DRM schemes are not standards-compliant Compact Discs (CDs) but are rather CD-ROM media. Therefore, they all lack the CD logotype found on discs which follow the standard (known as Red Book). These CDs cannot be played on all CD players or personal computers. Personal computers running Microsoft Windows sometimes even crash when attempting to play the CDs.[61]

In 2005, Sony BMG introduced new DRM technology which installed DRM software on users' computers without clearly notifying the user or requiring confirmation. Among other things, the installed software included a rootkit, which created a severe security vulnerability others could exploit. When the nature of the DRM involved was made public much later, Sony BMG initially minimized the significance of

the vulnerabilities its software had created, but was eventually compelled to recall millions of CDs, and released several attempts to patch the surreptitiously included software to at least remove the rootkit. Several class action lawsuits were filed, which were ultimately settled by agreements to provide affected consumers with a cash payout or album downloads free of DRM.[62]

Sony BMG's DRM software actually had only a limited ability to prevent copying, as it affected only playback on Windows computers, not on other equipment. Even on the Windows platform, users regularly bypassed the restrictions. And, while the Sony BMG DRM technology created fundamental vulnerabilities in customers' computers, parts of it could be trivially bypassed by holding down the "shift" key while inserting the CD, or by disabling the autorun feature. In addition, audio tracks could simply be played and re-recorded, thus completely bypassing all the DRM (this is known as the analog hole). Sony BMG's first two attempts at releasing a patchwhich would remove the DRM software from users' computers failed.

In January 2007, EMI stopped publishing audio CDs with DRM, stating that "the costs of DRM do not measure up to the results."[63] Following EMI, Sony BMG was the last publisher to abolish DRM completely, and audio CDs containing DRM are no longer released by the four largest commercial record label companies.[64]

Internet music

Many internet music stores employ DRM to restrict usage of music purchased and downloaded.

Prior to 2009, Apple's iTunes Store utilized the FairPlay DRM system for music. Apple did not license its DRM to other companies, so only Apple devices and Apple’s QuickTime media player could play iTunes music.[7][58] In May 2007, EMI tracks became available in iTunes Plus format at a higher price point. These tracks were higherquality (256 kbit/s) and DRM free. In October 2007, the cost of

iTunes Plus tracks was lowered to US$0.99.[65] In April 2009, all iTunes music became available completely DRM-free. (Videos sold and rented through iTunes, as well as iOS Apps, however, were to continue using Apple's FairPlay DRM.)

Napster music store offers a subscription-based approach to DRM alongside permanent purchases. Users of the subscription service candownload and stream an unlimited amount of music transcoded to Windows Media Audio (WMA) while subscribed to the service. But when the subscription period lapses, all the downloaded music is unplayable until the user renews his or her subscription. Napster also charges users who wish to use the music on their portable device an additional $5 per month. In addition, Napster gives users the option of paying an additional $0.99 per track to burn it to CD or for the song to never expire. Music bought through Napster can beplayed on players carrying the Microsoft PlaysForSure logo (which, notably, do not include iPods or even Microsoft's own Zune). As of June 2009, Napster is offering DRM free MP3 music, which can be played on iPhones and iPods.

Wal-Mart Music Downloads, another music download store, charges $0.94 per track for all non-sale downloads. All Wal-Mart downloads are able to be played on any Windows PlaysForSure marked product. The music does play on the SanDisk's Sansa mp3 player, for example, but must be copied to the player's internal memory. It cannot be played through the player's microSD card slot, which is a problem that many users of the mp3 player experience.

Sony operated a music download service called "Connect" which used Sony's proprietary OpenMG DRM technology. Music downloaded fromthis store (usually via Sony's SonicStage software) was only playable on computers running Microsoft Windows and Sony hardware (including the PSP and some Sony Ericsson phones).

Kazaa is one of a few services offering a subscription-based pricing model. However, music downloads from the Kazaa website are DRM-protected, and can only be played on computers or portable devices running Windows Media Player, and only as long as the customer remains subscribed to Kazaa.

The various services are currently not interoperable, though those that use the same DRM system (for instance the several Windows MediaDRM format stores, including Napster, Kazaa and Yahoo Music) all provide songs that can be played side-by-side through the same player program. Almost all stores require client software of some sort to be downloaded, and some also need plug-ins. Several collegesand universities, such as Rensselaer Polytechnic Institute, have made arrangements with assorted Internet music suppliers to provide access (typically DRM-restricted) to music files for their students,to less than universal popularity, sometimes making payments from student activity fee funds.[66] One of the problems is that the music becomes unplayable after leaving school unless the student continues to pay individually. Another is that few of these vendors are compatible with the most common portable music player, the AppleiPod. The Gowers Review of Intellectual Property (to HMG in the UK; 141 pages, 40+ specific recommendations) has taken note of the incompatibilities, and suggests (Recommendations 8—12) that there beexplicit fair dealing exceptions to copyright allowing libraries to copy and format-shift between DRM schemes, and further allowing end users to do the same privately. If adopted, some acrimony may decrease.

Although DRM is prevalent for Internet music, some online music stores such as eMusic, Dogmazic, Amazon, and Beatport, do not use DRM despite encouraging users to avoid sharing music. Major labels have begun releasing more music without DRM. Eric Bangeman suggests in Ars Technica that this is because the record labels are "slowly beginning to realize that they can't have DRMed music and complete control over the online music market at the same time... One way to break the cycle is to sell music that is playable on any digital audio player. eMusic does exactly that, and their surprisingly extensive catalog of non-DRMed music has vaulted it into the number two online music store position behind the iTunes Store."[67] Apple's Steve Jobs called on the music industry to eliminate DRM in an open letter titled Thoughts on Music.[68] Apple's iTunes Store will start to sell DRM-free 256 kbit/s (up from 128 kbit/s) AAC encoded music from EMI for a premium price (this has since reverted to the standard price).

In March 2007, Musicload.de, one of Europe's largest internet music retailers, announced their position strongly against DRM. In an openletter, Musicload stated that three out of every four calls to theircustomer support phone service are as a result of consumer frustration with DRM.[69]

Mobile ring tones

The Open Mobile Alliance created a standard for interoperable DRM onmobile devices. The first version of OMA DRM consisted of a simple rights management language and was widely used to protect mobile phone ringtones from being copied from the phone to other devices. Later versions expanded the rights management language to similar expressiveness as Fairplay, but did not become widely used.[58]

DRM and television

The CableCard standard is used by cable television providers in the United States to restrict content to services to which the customer has subscribed.

The broadcast flag concept was developed by Fox Broadcasting in 2001, and was supported by the MPAA and the U.S. Federal Communications Commission (FCC). A ruling in May 2005, by a United States courts of appeals held that the FCC lacked authority to impose it on the TV industry in the US. It required that all HDTVs obey a stream specification determining whether a stream can be recorded. This could block instances of fair use, such as time-shifting. It achieved more success elsewhere when it was adopted by the Digital Video Broadcasting Project (DVB), a consortium of about 250 broadcasters, manufacturers, network operators, software developers, and regulatory bodies from about 35 countries involved in attempting to develop new digital TV standards.

An updated variant of the broadcast flag has been developed in the Content Protection and Copy Management group under DVB (DVB-CPCM). Upon publication by DVB, the technical specification was submitted to European governments in March 2007. As with much DRM, the CPCM system is intended to control use of copyrighted material by the end-user, at the direction of the copyright holder. According to RenBucholz of the EFF, which paid to be a member of the consortium, "You won't even know ahead of time whether and how you will be able to record and make use of particular programs or devices".[70] The DVB claims that the system will harmonize copyright holders' controlacross different technologies, thereby making things easier for end users.[citation needed] The normative sections have now all been approved for publication by the DVB Steering Board, and will be published by ETSI as a formal European Standard as ETSI TS 102 825-Xwhere X refers to the Part number of specification. Nobody has yet stepped forward to provide a Compliance and Robustness regime for the standard (though several are rumoured to be in development), so it is not presently possible to fully implement a system, as there is nowhere to obtain the necessary device certificates.

Copyright infringement

From Wikipedia, the free encyclopedia

For information on handling copyright concerns in Wikipedia, see Wikipedia:Copyright violations.

"Illegal Music" redirects here. For the record label, see Illegal Musik.

"Pirated" and "Internet piracy" redirect here. For other uses, see Piracy (disambiguation).

An advertisement for copyright and patent preparation services from 1906, when copyright registration formalities were still required inthe US.

Copyright infringement is the use of works protected by copyright law without permission, infringing certain exclusive rights granted to the copyright holder, such as the right to reproduce, distribute,display or perform the protected work, or to make derivative works.

The copyright holder is typically the work's creator, or a publisheror other business to whom copyright has been assigned. Copyright holders routinely invoke legal and technological measures to preventand penalize copyright infringement.

Copyright infringement disputes are usually resolved through direct negotiation, a notice and take down process, or litigation in civil court. Egregious or large-scale commercial infringement, especially when it involves counterfeiting, is sometimes prosecuted via the criminal justice system. Shifting public expectations, advances in digital technology, and the increasing reach of the Internet have led to such widespread, anonymous infringement that copyright-dependent industries now focus less on pursuing individuals who seekand share copyright-protected content online, and more on expanding copyright law to recognize and penalize—as "indirect" infringers—theservice providers and software distributors which are said to facilitate and encourage individual acts of infringement by others.

Estimates of the actual economic impact of copyright infringement vary widely and depend on many factors. Nevertheless, copyright holders, industry representatives, and legislators have long characterized copyright infringement as piracy or theft—language which some U.S. courts now regard as pejorative or otherwise contentious.[1][2][3]

Contents

1 Terminology

1.1 "Piracy"

1.2 "Theft"

2 Motivation

2.1 Developing world

2.2 Motivations due to censorship

3 Existing and proposed laws

3.1 Civil law

3.2 Criminal law

3.3 Noncommercial file sharing

3.3.1 Legality of downloading

3.3.2 Legality of uploading

3.3.3 Relaxed penalties

3.4 The DMCA and anti-circumvention laws

3.5 Online intermediary liability

3.5.1 Definition of intermediary

3.5.2 Litigation and legislation concerning intermediaries

3.5.3 Peer-to-peer issues

4 Limitations

4.1 Non-infringing uses

4.2 Non-infringing types of works

5 Preventative measures

5.1 Legal

5.2 Protected distribution

6 Economic impact of copyright infringement

6.1 Motion picture industry estimates

6.2 Software industry estimates

6.3 Music industry estimates

6.4 Criticism of industry estimates

6.5 Economic impact of infringement in emerging markets

7 Pro-open culture organizations

8 Anti-copyright infringement organizations

9 See also

10 References

11 Further reading

Terminology

The terms piracy and theft are often associated with copyright infringement.[4][5] The original meaning of piracy is "robbery or illegal violence at sea",[6] but the term has been in use for centuries as a synonym for acts of copyright infringement.[7][8] Theft, meanwhile, emphasizes the potential commercial harm of infringement to copyright holders. However, copyright is a type of intellectual property, an area of law distinct from that which covers robbery or theft, offenses related only to tangible property.Not all copyright infringement results in commercial loss, and the U.S. Supreme Court ruled in 1985 that infringement does not easily equate with theft.[1]

In the case MPAA v. Hotfile, Judge Kathleen Williams granted a motion to deny the prosecution the usage of pejorative words in the copyright infringement case.[3] This list included the words "piracy," "theft," "stealing," and their derivatives—the use of which, even if the defendants had been found to have directly infringed on the Plaintiffs’ copyrights, the defense asserted, wouldserve no purpose but to misguide and inflame the jury.[2] The plaintiff argued the common use of the terms when referring to copyright infringement should invalidate the motion, but the judge did not concur.[3] (The case was settled shortly before it reached the jury phase of the trial.[9])

"Piracy"

Pirated edition of German philosopher Alfred Schmidt (Amsterdam, ca.1970).

The practice of labelling the infringement of exclusive rights in creative works as "piracy" predates statutory copyright law. Prior to the Statute of Anne in 1710, the Stationers' Company of London in1557 received a Royal Charter giving the company a monopoly on publication and tasking it with enforcing the charter. Those who violated the charter were labelled pirates as early as 1603.[7] The term "piracy" has been used to refer to the unauthorized copying, distribution and selling of works in copyright.[8] Article 12 of the1886 Berne Convention for the Protection of Literary and Artistic Works uses the term "piracy" in relation to copyright infringement, stating "Pirated works may be seized on importation into those countries of the Union where the original work enjoys legal protection."[8] Article 61 of the 1994 Agreement on Trade-Related Aspects of Intellectual Property Rights (TRIPs) requires criminal procedures and penalties in cases of "willful trademark counterfeiting or copyright piracy on a commercial scale."[10] Piracy traditionally refers to acts of copyright infringement intentionally committed for financial gain, though more recently, copyright holders have described online copyright infringement, particularly in relation to peer-to-peer file sharing networks, as "piracy."[8]

Richard Stallman and the GNU Project have criticized the use of the word "piracy" in these situations, saying that publishers use the word to refer to "copying they don't approve of" and that "they [publishers] imply that it is ethically equivalent to attacking ships on the high seas, kidnapping and murdering the people on them."[11]

"Theft"

Copyright holders frequently refer to copyright infringement as theft. In copyright law, infringement does not refer to theft of physical objects that take away the owner's possession, but an instance where a person exercises one of the exclusive rights of thecopyright holder without authorization.[12] Courts have distinguished between copyright infringement and theft. For

instance, the United States Supreme Court held in Dowling v. United States (1985) that bootleg phonorecords did not constitute stolen property. Instead, "interference with copyright does not easily equate with theft, conversion, or fraud. The Copyright Act even employs a separate term of art to define one who misappropriates a copyright: '[...] an infringer of the copyright.'" The court said that in the case of copyright infringement, the province guaranteed to the copyright holder by copyright law—certain exclusive rights—isinvaded, but no control, physical or otherwise, is taken over the copyright, nor is the copyright holder wholly deprived of using the copyrighted work or exercising the exclusive rights held.[1]

Motivation

Some of the motives for engaging in copyright infringement are the following:[13]

Pricing – unwillingness or inability to pay the price requested by the legitimate sellers

Unavailability – no legitimate sellers providing the product in the country of the end-user: not yet launched there, already withdrawn from sales, never to be sold there, geographical restrictions on online distribution and international shipping

Usefulness – the legitimate product comes with various means (DRM, region lock, DVD region code, Blu-ray region code) of restricting legitimate use (backups, usage on devices of different vendors, offline usage) or comes with annoying non-skippable advertisements and anti-piracy disclaimers, which are removed in thepirated product making it more desirable for the end-user

Shopping experience – no legitimate sellers providing the product with the required quality through online distribution and through a shopping system with the required level of user-friendliness

Anonymity – Downloading works does not require identification whereas downloads directly from the website of the copyright owner often require a valid email address and/ or other credentials

Sometimes only partial compliance with license agreements is the cause. For example, in 2013 the US Army settled a lawsuit with Texas-based company Apptricity, which makes software that allows thearmy to track their soldiers in real time. In 2004, the US Army paidUS$4.5 million for a license of 500 users, while allegedly installing the software for more than 9000 users; the case was settled for US$50 million.[14][15] Major anti-piracy organizations, like the BSA, conduct software licensing audits regularly to ensure full compliance.[16]

Cara Cusumano, director of the Tribeca Film Festival, stated in April 2014: "Piracy is less about people not wanting to pay and moreabout just wanting the immediacy — people saying, 'I want to watch Spiderman right now' and downloading it". The statement occurred during the third year that the festival used the Internet to presentits content, while it was the first year that it featured a showcaseof content producers who work exclusively online. Cusumano further explained that downloading behavior is not merely conducted by people who merely want to obtain content for free:

I think that if companies were willing to put that material out there, moving forward, consumers will follow. It's just that they [consumers] want to consume films online and they're ready to consume films that way and we're not necessarily offering them in that way. So it's the distribution models that need to catch up. People will pay for the content.[4]

In response to Cusumano's perspective, Screen Producers Australia executive director Matt Deaner clarified the motivation of the film industry: "Distributors are usually wanting to encourage cinema-going as part of this process [monetizing through returns] and restrict the immediate access to online so as to encourage the maximum number of people to go to the cinema." Deaner further explained the matter in terms of the Australian film industry, stating: "there are currently restrictions on quantities of tax

support that a film can receive unless the film has a traditional cinema release."[4]

In a study published in the Journal of Behavioural and Experimental Economics, and reported on in early May 2014, researchers from the University of Portsmouth in the UK discussed findings from examiningthe illegal downloading behavior of 6,000 Finnish people, aged sevento 84. The list of reasons for downloading given by the study respondents included money saving; the ability to access material not on general release, or before it was released; and assisting artists to avoid involvement with record companies and movie studios.[17]

In a public talk between Bill Gates, Warren Buffett, and Brent Schlender at the University of Washington in 1998, Bill Gates commented on piracy as a means to an end, whereby people who use Microsoft software illegally will eventually pay for it, out of familiarity, as a country's economy develops and legitimate productsbecome more affordable to businesses and consumers:

Although about three million computers get sold every year in China, people don't pay for the software. Someday they will, though.And as long as they're going to steal it, we want them to steal ours. They'll get sort of addicted, and then we'll somehow figure out how to collect sometime in the next decade.[18]

Developing world

In Media Piracy in Emerging Economies, the first independent international comparative study of media piracy with center on Brazil, India, Russia, South Africa, Mexico, Turkey and Bolivia, “high prices for media goods, low incomes, and cheap digital technologies” are the chief factors that lead to the global spread of media piracy, especially in emerging markets.[19]

According to the same study, even though digital piracy inflicts additional costs on the production side of media, it also offers themain access to media goods in developing countries. The strong tradeoffs that favor using digital piracy in developing economies dictate the current neglected law enforcements toward digital piracy.[20] In China, the issue of digital piracy is not merely legal, but social – originating from the high demand for cheap and affordable pirated goods as well as the governmental connections of the businesses which produce such goods.[21]

Motivations due to censorship

There have been instances where a country's government bans a movie,resulting in the spread of pirated videos and DVDs. Romanian-born documentary maker Ilinca Calugareanu wrote a New York Times article telling the story of Irina Margareta Nistor, a narrator for state TVunder Nicolae Ceauşescu's regime. A visitor from the west gave her bootlegged copies of American movies, which she dubbed for secret viewings through Romania. According to the article, she dubbed more than 3,000 movies and became the country's second-most famous voice after Ceauşescu, even though no one knew her name until many years later.[22]

Existing and proposed laws

Main articles: History of copyright law, Digital Millennium Copyright Act, Protect IP Act, Stop Online Piracy Act and Software copyright

Demonstration in Sweden in support of file sharing, 2006.

The Pirate Bay logo, a retaliation to the stereotypical image of piracy

Most countries extend copyright protections to authors of works. In countries with copyright legislation, enforcement of copyright is generally the responsibility of the copyright holder.[23] However,

in several jurisdictions there are also criminal penalties for copyright infringement.[24]

Civil law

In the U.S., copyright infringement is sometimes confronted via lawsuits in civil court, against alleged infringers directly, or against providers of services and software that support unauthorizedcopying. For example, major motion-picture corporation MGM Studios filed suit against P2P file-sharing services Grokster and Streamcastfor their contributory role in copyright infringement.[25] In 2005, the Supreme Court ruled in favor of MGM, holding that such services could be held liable for copyright infringement since they functioned and, indeed, willfully marketed themselves as venues for acquiring copyrighted movies. The MGM v. Grokster case did not overturn the earlier Sony decision, but rather clouded the legal waters; future designers of software capable of being used for copyright infringement were warned.[26]

In the United States, copyright term has been extended many times over[27] from the original term of 14 years with a single renewal allowance of 14 years, to the current term of the life of the authorplus 70 years. If the work was produced under corporate authorship it may last 120 years after creation or 95 years after publication, whichever is less.

Article 50 of the Agreement on Trade-Related Aspects of IntellectualProperty Rights (TRIPs) requires that signatory countries enable courts to remedy copyright infringement with injunctions and the destruction of infringing products, and award damages.[10] Some jurisdictions only allow actual, provable damages, and some, like the U.S., allow for large statutory damage awards intended to deter would-be infringers and allow for compensation in situations where actual damages are difficult to prove.

In some jurisdictions, copyright or the right to enforce it can be contractually assigned to a third party which did not have a role inproducing the work. When this outsourced litigator appears to have no intention of taking any copyright infringement cases to trial, but rather only takes them just far enough through the legal system to identify and exact settlements from suspected infringers, criticscommonly refer to the party as a "copyright troll." Such practices have had mixed results in the U.S.[28]

Criminal law

Main article: Criminal Copyright Law in the United States

Punishment of copyright infringement varies case-by-case across countries. Convictions may include jail time and/or severe fines foreach instance of copyright infringement. In the United States, willful copyright infringement carries a maximum penalty of $150,000per instance.[29]

Article 61 of the Agreement on Trade-Related Aspects of IntellectualProperty Rights (TRIPs) requires that signatory countries establish criminal procedures and penalties in cases of "willful trademark counterfeiting or copyright piracy on a commercial scale".[10] Copyright holders have demanded that states provide criminal sanctions for all types of copyright infringement.[23]

The first criminal provision in U.S. copyright law was added in 1897, which established a misdemeanor penalty for “unlawful performances and representations of copyrighted dramatic and musicalcompositions” if the violation had been “willful and for profit.”[30] Criminal copyright infringement requires that the infringer acted “for the purpose of commercial advantage or private financial gain." 17 U.S.C. § 506(a). To establish criminal liability, the prosecutor must first show the basic elements of copyright infringement: ownership of a valid copyright, and the violation of one or more of the copyright holder’s exclusive rights.

The government must then establish that defendant willfully infringed or, in other words, possessed the necessary mens rea. Misdemeanor infringement has a very low threshold in terms of numberof copies and the value of the infringed works.

The ACTA trade agreement, signed in May 2011 by the United States, Japan, Switzerland, and the EU, requires that its parties add criminal penalties, including incarceration and fines, for copyrightand trademark infringement, and obligated the parties to actively police for infringement.[23][31][32]

United States v. LaMacchia 871 F.Supp. 535 (1994) was a case decidedby the United States District Court for the District of Massachusetts which ruled that, under the copyright and cybercrime laws effective at the time, committing copyright infringement for non-commercial motives could not be prosecuted under criminal copyright law. The ruling gave rise to what became known as the "LaMacchia Loophole," wherein criminal charges of fraud or copyrightinfringement would be dismissed under current legal standards, so long as there was no profit motive involved.[33]

The United States No Electronic Theft Act (NET Act), a federal law passed in 1997 in response to LaMacchia, provides for criminal prosecution of individuals who engage in copyright infringement under certain circumstances, even when there is no monetary profit or commercial benefit from the infringement. Maximum penalties can be five years in prison and up to $250,000 in fines. The NET Act also raised statutory damages by 50%. The court's ruling explicitly drew attention to the shortcomings of current law that allowed people to facilitate mass copyright infringement while being immune to prosecution under the Copyright Act.

Proposed laws such as the Stop Online Piracy Act broaden the definition of "willful infringement", and introduce felony charges for unauthorized media streaming. These bills are aimed towards

defeating websites that carry or contain links to infringing content, but have raised concerns about domestic abuse and internet censorship.

Noncommercial file sharing

Legality of downloading

To an extent, copyright law in some countries permits downloading copyright-protected content for personal, noncommercial use. Examples include Canada[34] and European Union (EU) member states like Poland,[35] The Netherlands,[36] and Spain.[37]

The personal copying exemption in the copyright law of EU member states stems from the EU Copyright Directive of 2001, which is generally devised to allow EU members to enact laws sanctioning making copies without authorization, as long as they are for personal, noncommerical use. The Copyright Directive was not intended to legitimize file-sharing, but rather the common practice of space shifting copyright-protected content from a legally purchased CD (for example) to certain kinds of devices and media, provided rights holders are compensated and no copy protection measures are circumvented. Rights-holder compensation takes various forms, depending on the country, but is generally either a levy on "recording" devices and media, or a tax on the content itself. In some countries, such as Canada, the applicability of such laws to copying onto general-purpose storage devices like computer hard drives, portable media players, and phones, for which no levies are collected, has been the subject of debate and further efforts to reform copyright law.

In some countries, the personal copying exemption explicitly requires that the content being copied was obtained legitimately—i.e., from authorized sources, not file-sharing networks. Other countries, such as the Netherlands, make no such distinction; the exemption there had been assumed, even by the government, to apply to any such copying, even from file-sharing networks. However, in

April 2014, the Court of Justice of the European Union ruled that "national legislation which makes no distinction between private copies made from lawful sources and those made from counterfeited orpirated sources cannot be tolerated."[38] Thus, in the Netherlands, for example, downloading from file-sharing networks is no longer legal.

Legality of uploading

Although downloading or other private copying is sometimes permitted, public distribution—by uploading or otherwise offering toshare copyright-protected content—remains illegal in most, if not all countries. For example, in Canada, even though it is legal to download any copyrighted file as long as it is for noncommercial use, it is illegal to distribute the copyrighted files (e.g. by uploading them to a P2P network).[39]

Relaxed penalties

Some countries, like Canada and Germany, have limited the penalties for non-commercial copyright infringement. For example, statutory damages in Canada for non-commercial copyright infringement is capped at $5,000.[40] Germany has even passed a bill to limit the fine for individuals accused of sharing music and movies to $200.[41]

On September 20, 2013, the Spanish government approved new laws thatwill take effect at the beginning of 2014. The approved legislation will mean that website owners who are earning “direct or indirect profit,” such as via advertising links, from pirated content can be imprisoned for up to six years. However, peer-to-peer file-sharing platforms and search engines are exempt from the laws.[42]

The DMCA and anti-circumvention laws

Title I of the U.S. DMCA, the WIPO Copyright and Performances and Phonograms Treaties Implementation Act has provisions that prevent

persons from "circumvent[ing] a technological measure that effectively controls access to a work". Thus if a distributor of copyrighted works has some kind of software, dongle or password access device installed in instances of the work, any attempt to bypass such a copy protection scheme may be actionable — though the US Copyright Office is currently reviewing anticircumvention rulemaking under DMCA — anticircumvention exemptions that have been in place under the DMCA include those in software designed to filterwebsites that are generally seen to be inefficient (child safety andpublic library website filtering software) and the circumvention of copy protection mechanisms that have malfunctioned, have caused the instance of the work to become inoperable or which are no longer supported by their manufacturers.[43]

Online intermediary liability

Whether Internet intermediaries are liable for copyright infringement by their users is a subject of debate and court cases in a number of countries.[44]

Definition of intermediary

Internet intermediaries were formerly understood to be internet service providers (ISPs). However, questions of liability have also emerged in relation to other Internet infrastructure intermediaries,including Internet backbone providers, cable companies and mobile communications providers.[45]

In addition, intermediaries are now also generally understood to include Internet portals, software and games providers, those providing virtual information such as interactive forums and commentfacilities with or without a moderation system, aggregators of various kinds, such as news aggregators, universities, libraries andarchives, web search engines, chat rooms, web blogs, mailing lists, and any website which provides access to third party content through, for example, hyperlinks, a crucial element of the World Wide Web.

Litigation and legislation concerning intermediaries

Early court cases focused on the liability of Internet service providers (ISPs) for hosting, transmitting or publishing user-supplied content that could be actioned under civil or criminal law,such as libel, defamation, or pornography.[46] As different content was considered in different legal systems, and in the absence of common definitions for "ISPs," "bulletin boards" or "online publishers," early law on online intermediaries' liability varied widely from country to country. The first laws on online intermediaries' liability were passed from the mid-1990s onwards.[citation needed]

The debate has shifted away from questions about liability for specific content, including that which may infringe copyright, towards whether online intermediaries should be generally responsible for content accessible through their services or infrastructure.[47]

The U.S. Digital Millennium Copyright Act (1998) and the European E-Commerce Directive (2000) provide online intermediaries with limitedstatutory immunity from liability for copyright infringement. Onlineintermediaries hosting content that infringes copyright are not liable, so long as they do not know about it and take actions once the infringing content is brought to their attention. In U.S. law this is characterized as "safe harbor" provisions. Under European law, the governing principles for Internet Service Providers are "mere conduit", meaning that they are neutral 'pipes' with no knowledge of what they are carrying; and 'no obligation to monitor' meaning that they cannot be given a general mandate by governments to monitor content. These two principles are a barrier for certain forms of online copyright enforcement and they were the reason behind an attempt to amend the European Telecoms Package in 2009 to support new measures against copyright infringement.[48]

Peer-to-peer issues

Peer-to-peer file sharing intermediaries have been denied access to safe harbor provisions in relation to copyright infringement. Legal action against such intermediaries, such as Napster, are generally brought in relation to principles of secondary liability for copyright infringement, such as contributory liability and vicariousliability.[49]

Animation showing 7 remote computers exchanging data with an 8th (local) computer over a network.

The BitTorrent protocol: In this animation, the colored bars beneathall of the 7 clients in the upper region above represent the file, with each color representing an individual piece of the file. After the initial pieces transfer from the seed (large system at the bottom), the pieces are individually transferred from client to client. The original seeder only needs to send out one copy of the file for all the clients to receive a copy.

These types of intermediaries do not host or transmit infringing content, themselves, but may be regarded in some courts as encouraging, enabling or facilitating infringement by users. These intermediaries may include the author, publishers and marketers of peer-to-peer networking software, and the websites that allow users to download such software. In the case of the BitTorrent protocol, intermediaries may include the torrent tracker and any websites or search engines which facilitate access to torrent files. Torrent files don't contain copyrighted content, but they may make referenceto files that do, and they may point to trackers which coordinate the sharing of those files. Some torrent indexing and search sites, such as The Pirate Bay, now encourage the use of magnet links, instead of direct links to torrent files, creating another layer of indirection; using such links, torrent files are obtained from otherpeers, rather than from a particular website.

Since the late 1990s, copyright holders have taken legal actions against a number of peer-to-peer intermediaries, such as pir, Grokster, eMule, SoulSeek, BitTorrent and Limewire, and case law on

the liability of Internet service providers (ISPs) in relation to copyright infringement has emerged primarily in relation to these cases.[50]

Nevertheless, whether and to what degree any of these types of intermediaries have secondary liability is the subject of ongoing litigation. The decentralised structure of peer-to-peer networks, inparticular, does not sit easily with existing laws on online intermediaries' liability. The BitTorrent protocol established an entirely decentralised network architecture in order to distribute large files effectively. Recent developments in peer-to-peer technology towards more complex network configurations are said to have been driven by a desire to avoid liability as intermediaries under existing laws.[51]

Limitations

Copyright law does not grant authors and publishers absolute controlover the use of their work. Only certain types of works and certain kinds of uses are protected;[52] only unauthorized uses of protectedworks can be said to be infringing.

Non-infringing uses

Article 10 of the Berne Convention mandates that national laws provide for limitations to copyright, so that copyright protection does not extend to certain kinds of uses that fall under what the treaty calls "fair practice," including but not limited to minimal quotations used in journalism and education.[53] The laws implementing these limitations and exceptions for uses that would otherwise be infringing broadly fall into the categories of either fair use or fair dealing. In common law systems, these fair practicestatutes typically enshrine principles underlying many earlier judicial precedents, and are considered essential to freedom of speech.[54]

Another example is the practice of compulsory licensing, which is where the law forbids copyright owners from denying a license for certain uses of certain kinds of works, such as compilations and live performances of music. Compulsory licensing laws generally say that for certain uses of certain works, no infringement occurs as long as a royalty, at a rate determined by law rather than private negotiation, is paid to the copyright owner or representative copyright collective. Some fair dealing laws, such as Canada's, include similar royalty requirements.[55]

In Europe, the copyright infringement case Public Relations Consultants Association Ltd v Newspaper Licensing Agency Ltd had twoprongs; one concerned whether a news aggregator service infringed the copyright of the news generators; the other concerned whether the temporary web cache created by the web browser of a consumer of the aggregator's service, also infringed the copyright of the news generators.[56] The first prong was decided in favor of the news generators; in June 2014 the second prong was decided by the Court of Justice of the European Union (CJEU), which ruled that the temporary web cache of consumers of the aggregator did not infringe the copyright of the news generators.[56][57][58]

Non-infringing types of works

In order to qualify for protection, a work must be an expression with a degree of originality, and it must be in a fixed medium, suchas written down on paper or recorded digitally.[59][60] The idea itself is not protected. That is, a copy of someone else's original idea is not infringing unless it copies that person's unique, tangible expression of the idea. Some of these limitations, especially regarding what qualifies as original, are embodied only in case law (judicial precedent), rather than in statutes.

In the U.S., for example, copyright case law contains a substantial similarity requirement to determine whether the work falls under thefair use clause. Likewise, courts may require computer software to pass an Abstraction-Filtration-Comparison test (AFC Test)[61][62] to

determine if it is too abstract to qualify for protection, or too dissimilar to an original work to be considered infringing. Software-related case law has also clarified that the amount of R&D,effort and expense put into a work's creation doesn't affect copyright protection.[63]

Evaluation of alleged copyright infringement in a court of law may be substantial; the time and costs required to apply these tests vary based on the size and complexity of the copyrighted material. Furthermore, there is no standard or universally accepted test; somecourts have rejected the AFC Test, for example, in favor of narrowercriteria.

The POSAR test,[64] a recently devised forensic procedure for establishing software copyright infringement cases, is an extension or an enhancement of the AFC test. POSAR, with its added features and additional facilities, offers something more to the legal and the judicial domain than what the AFC test offers. These additional features and facilities make the test more sensitive to the technical and legal requirements of software copyright infringement.

Preventative measures

The BSA outlined four strategies that governments can adopt to reduce software piracy rates in its 2011 piracy study results:

"Increase public education and raise awareness about software piracy and IP rights in cooperation with industry and law enforcement."

"Modernize protections for software and other copyrighted materials to keep pace with new innovations such as cloud computing and the proliferation of networked mobile devices."

"Strengthen enforcement of IP laws with dedicated resources, including specialized enforcement units, training for law enforcement and judiciary officials, improved cross-border

cooperation among law enforcement agencies, and fulfillment of obligations under the World Trade Organization’s Agreement on Trade-Related Aspects of Intellectual Property Rights (TRIPS)."

"Lead by example by using only fully licensed software, implementing software asset management (SAM) programs, and promotingthe use of legal software in state-owned enterprises, and among all contractors and suppliers."[65]

Legal

Corporations and legislatures take different types of preventative measures to deter copyright infringement, with much of the focus since the early 1990s being on preventing or reducing digital methods of infringement. Strategies include education, civil & criminal legislation, and international agreements,[66] as well as publicizing anti-piracy litigation successes and imposing forms of digital media copy protection, such as controversial digital rights management (DRM) technology and anti-circumvention laws, which limitthe amount of control consumers have over the use of products and content they have purchased.

Legislatures have reduced infringement by narrowing the scope of what is considered infringing. Aside from upholding international copyright treaty obligations to provide general limitations and exceptions,[53] nations have enacted compulsory licensing laws applying specifically to digital works and uses. For example, in theU.S., the DMCA, an implementation of the 1996 WIPO Copyright Treaty,considers digital transmissions of audio recordings to be licensed as long as a designated copyright collective's royalty and reportingrequirements are met.[67] The DMCA also provides safe harbor for digital service providers whose users are suspected of copyright infringement, thus reducing the likelihood that the providers themselves will be considered directly infringing.[68]

Some copyright owners voluntarily reduce the scope of what is considered infringement by employing relatively permissive, "open" licensing strategies: rather than privately negotiating license terms with individual users who must first seek out the copyright owner and ask for permission, the copyright owner publishes and distributes the work with a prepared license that anyone can use, aslong as they adhere to certain conditions. This has the effect of reducing infringement—and the burden on courts—by simply permitting certain types of uses under terms that the copyright owner considersreasonable. Examples include free software licenses, like the GNU General Public License (GPL), and the Creative Commons licenses, which are predominantly applied to visual and literary works.[69]

Protected distribution

To prevent piracy of films, the standard drill of film distribution is to have a movie first released through movie theaters (theatricalwindow), on average approximately 16 and a half weeks,[70] before having it released to Blu-Ray and DVD (entering its video window). During the theatrical window, digital versions of films are often transported in data storage devices by couriers rather than by data transmission.[71] The data can be encrypted, with the key being madeto work only at specific times in order to prevent leakage between screens.[71] Coded Anti-Piracy marks can be added to films to identify the source of illegal copies and shut them down. As a result of these measures, the only versions of films available for piracy during the theatrical window are usually "cams" made by videorecordings of the movie screens, which are of inferior quality compared to the original film version.

Economic impact of copyright infringement

Organizations disagree on the scope and magnitude of copyright infringement's economic effects and public support for the copyrightregime.

In relation to computer software, the Business Software Alliance (BSA) claimed in its 2011 piracy study: "Public opinion continues tosupport intellectual property (IP) rights: Seven PC users in 10 support paying innovators to promote more technological advances."[65]

Following consultation with experts on copyright infringement, the United States Government Accountability Office (GAO) clarified in 2010 that "estimating the economic impact of IP [intellectual property] infringements is extremely difficult, and assumptions mustbe used due to the absence of data," while "it is difficult, if not impossible, to quantify the net effect of counterfeiting and piracy on the economy as a whole."[72]

The U.S. GAO's 2010 findings regarding the great difficulty of accurately gauging the economic impact of copyright infringement wasreinforced within the same report by the body's research into three commonly cited estimates that had previously been provided to U.S. agencies. The GAO report explained that the sources—a Federal Bureauof Investigation (FBI) estimate, a Customs and Border Protection (CBP) press release and a Motor and Equipment Manufacturers Association estimate—"cannot be substantiated or traced back to an underlying data source or methodology."[72]

Deaner explained the importance of rewarding the "investment risk" taken by motion picture studios in 2014:

Usually movies are hot because a distributor has spent hundreds of thousands of dollars promoting the product in print and TV and other forms of advertising. The major Hollywood studios spend millions on this process with marketing costs rivalling the costs ofproduction. They are attempting then to monetise through returns that can justify the investment in both the costs of promotion and production.[4]

Motion picture industry estimates

In 2008 the Motion Picture Association of America (MPAA) reported that its six major member companies lost US$6.1 billion to piracy.[73] A 2009 Los Angeles Daily News article then cited a loss figure of "roughly $20 billion a year" for Hollywood studios.[74]

In an early May 2014 Guardian article, an annual loss figure of US$20.5 billion was cited for the movie industry. The article's basis is the results of a University of Portsmouth study that only involved Finnish participants, aged between seven and 84. The researchers, who worked with 6,000 participants, stated: "Movie pirates are also more likely to cut down their piracy if they feel they are harming the industry compared with people who illegally download music".[17]

Software industry estimates

According to a 2007 BSA and International Data Corporation (IDC) study, the five countries with the highest rates of software piracy were: 1. Armenia (93%); 2. Bangladesh (92%); 3. Azerbaijan (92%); 4.Moldova (92%); and 5. Zimbabwe (91%). According to the study's results, the five countries with the lowest piracy rates were: 1. U.S. (20%); 2. Luxembourg (21%); 3. New Zealand (22%); 4. Japan (23%); and 5. Austria (25%). The 2007 report showed that the Asia-Pacific region was associated with the highest amount of loss, in terms of U.S. dollars, with $14,090,000, followed by the European Union, with a loss of $12,383,000; the lowest amount of U.S. dollarswas lost in the Middle East/Africa region, where $2,446,000 was documented.[75]

In its 2011 report, conducted in partnership with IDC and Ipsos Public Affairs, the BSA stated: "Over half of the world’s personal computer users—57 percent—admit to pirating software." The ninth annual "BSA Global Software Piracy Study" claims that the "commercial value of this shadow market of pirated software" was

worth US$63.4 billion in 2011, with the highest commercial value of pirated PC software existent in the U.S. during that time period (US$9,773,000). According to the 2011 study, Zimbabwe was the nationwith the highest piracy rate, at 92%, while the lowest piracy rate was present in the U.S., at 19%.[65]

The GAO noted in 2010 that the BSA's research up until that year defined "piracy as the difference between total installed software and legitimate software sold, and its scope involved only packaged physical software."[72]

Music industry estimates

[icon] This section requires expansion. (May 2014)

In 2007, the Institute for Policy Innovation (IPI) reported that music piracy took $12.5 billion from the U.S. economy. According to the study, musicians and those involved in the recording industry are not the only ones who experience losses attributed to music piracy. Retailers have lost over a billion dollars, while piracy hasresulted in 46,000 less production-level jobs and almost 25,000 retail jobs. The U.S. government was also reported to suffer from music piracy, losing $422 million in tax revenue.[76]

A recent report from 2013 released by the European Commission Joint Research Centre suggests that illegal music downloads have almost noeffect on the amount of legal music downloads. The study analyzed the behavior of 16,000 European music consumers and found that although music piracy negatively affects offline music sales, illegal music downloads had a positive affect on legal music purchases. Without illegal downloading, legal purchases were about two percent lower.[77]

The study has received criticism, particularly from The International Federation of the Phonographic Industry, who believes the study is flawed and misleading. One argument against the

research is that many music consumers only download music illegally.The IFPI also points out that music piracy does not only affect online music sales but multiple facets of the music industry, which is not addressed in the study.[78]

Criticism of industry estimates

The methodology of studies utilized by industry spokespeople has been heavily criticized. Inflated claims for damages and allegationsof economic harm are common in copyright disputes.[79][80] Some studies and figures, including those cited by the MPAA and RIAA withregards to the economic effects of film and music downloads, have been widely disputed as based on questionable assumptions which resulted in statistically unsound numbers.[81][82]

In one extreme example, the RIAA claimed damages against LimeWire totaling $75 trillion – more than the global GDP – and "respectfully" disagreed with the judges ruling that such claims were "absurd".[83]

However, this $75 trillion figure is obtained through one specific interpretation of copyright law that would count each song downloaded as an infringement of copyright. After the conclusion of the case, LimeWire agreed to pay $105 million to RIAA.[84]

Economic impact of infringement in emerging markets

The 2011 Business Software Alliance Piracy Study Standard estimates the total commercial value of pirated software to be at $59 billion in 2010, with emerging markets accounting for $31.9 billion, over half of the total. Furthermore, mature markets for the first time received less PC shipments than emerging economies in 2010, making emerging markets now responsible for more than half of all computersin use worldwide. In addition with software piracy rates of 68 percent comparing to 24 percent of mature markets, emerging markets thus possess the majority of the global increase in the commercial

value of pirated software. China continues to have the highest commercial value of pirated software at $8.9 billion among developing countries and second in the world behind the US at $9.7 billion in 2011.[85][86] In 2011, the Business Software Alliance announced that 83 percent of software deployed on PCs in Africa has been pirated (excluding South Africa).[87]

Some countries distinguish corporate piracy from private use, which is tolerated as a welfare service.[citation needed] This is the leading reason developing countries refuse to accept or respect copyright laws. Traian Băsescu, the president of Romania, stated that "piracy helped the young generation discover computers. It set off the development of the IT industry in Romania."[88]

Plaintext

From Wikipedia, the free encyclopedia

This article is about cryptography. For the computing term meaning the storage of textual material that is (largely) unformatted, see plain text.

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (June 2011)

In cryptography, plaintext is information a sender wishes to transmit to a receiver. Cleartext is often used as a synonym. Plaintext has reference to the operation of cryptographic algorithms, usually encryption algorithms, and is the input upon which they operate. Cleartext, by contrast, refers to data that is transmitted or stored unencrypted (that is, 'in the clear').

Contents

1 Overview

2 Secure handling of plaintext

2.1 Web browser saved password security controversy

3 See also

4 References

Overview

Before the computer era, plaintext most commonly meant message text in the language of the communicating parties. Since computers becamecommonly available, the definition has expanded to include:

messages (for example, email messages)

document content such as word processor and spreadsheet files

audio and video files, digital photographs and any other multimedia

files containing other files such as Zip files or ISO images

ATM, credit card and other banking information

sensor data

any other data that a person wishes to keep private

Much of this data is not directly meaningful to humans, being already transformed into computer manipulable forms. While the original definition implied that the message could be read by a human being, the modern definition emphasizes that a person using a computer could easily interpret the data.

Any information which the communicating parties wish to conceal fromothers can now be treated, and referred to, as plaintext. Thus, in asignificant sense, plaintext is the 'normal' representation of data

before any action has been taken to conceal, compress, or 'digest' it. It need not represent text, and even if it does, the text may not be "plain".

Plaintext is used as input to an encryption algorithm; the output isusually termed ciphertext particularly when the algorithm is a cipher. Codetext is less often used, and almost always only when thealgorithm involved is actually a code. In some systems, however, multiple layers of encryption are used, in which case the output of one encryption algorithm becomes plaintext input for the next.

Secure handling of plaintext

In a cryptosystem, weaknesses can be introduced through insecure handling of plaintext, allowing an attacker to bypass the cryptography altogether. Plaintext is vulnerable in use and in storage, whether in electronic or paper format. Physical security deals with methods of securing information and its storage media from local, physical, attacks. For instance, an attacker might entera poorly secured building and attempt to open locked desk drawers orsafes. An attacker can also engage in dumpster diving, and may be able to reconstruct shredded information if it is sufficiently valuable to be worth the effort. One countermeasure is to burn or thoroughly crosscut shred discarded printed plaintexts or storage media; NSA is infamous for its disposal security precautions.

If plaintext is stored in a computer file (and the situation of automatically made backup files generated during program execution must be included here, even if invisible to the user), the storage media along with the entire computer and its components must be secure. Sensitive data is sometimes processed on computers whose mass storage is removable, in which case physical security of the removed disk is separately vital. In the case of securing a computer, useful (as opposed to handwaving) security must be physical (e.g., against burglary, brazen removal under cover of supposed repair, installation of covert monitoring devices, etc.), as well as virtual (e.g., operating system modification, illicit

network access, Trojan programs, ...). The wide availability of keydrives, which can plug into most modern computers and store largequantities of data, poses another severe security headache. A spy (perhaps posing as a cleaning person) could easily conceal one and even swallow it, if necessary.

Discarded computers, disk drives and media are also a potential source of plaintexts. Most operating systems do not actually erase anything — they simply mark the disk space occupied by a deleted file as 'available for use', and remove its entry from the file system directory. The information in a file deleted in this way remains fully present until overwritten at some later time when the operating system reuses the disk space. With even low-end computers commonly sold with many gigabytes of disk space and rising monthly, this 'later time' may be months later, or never. Even overwriting the portion of a disk surface occupied by a deleted file is insufficient in many cases. Peter Gutmann of the University of Auckland wrote a celebrated 1996 paper on the recovery of overwritten information from magnetic disks; areal storage densitieshave gotten much higher since then, so this sort of recovery is likely to be more difficult than it was when Gutmann wrote.

Also, independently, modern hard drives automatically remap sectors that are starting to fail; those sectors no longer in use will contain information that is entirely invisible to the file system (and all software which uses it for access to disk data), but is nonetheless still present on the physical drive platter. It may, of course, be sensitive plaintext. Some government agencies (e.g., NSA)require that all disk drives be physically pulverized when they are discarded, and in some cases, chemically treated with corrosives before or after. This practice is not widespread outside of the government, however. For example, Garfinkel and Shelat (2003) analyzed 158 second-hand hard drives acquired at garage sales and the like and found that less than 10% had been sufficiently sanitized. A wide variety of personal and confidential information was found readable from the others. See data remanence.

Laptop computers are a special problem. The US State Department, theBritish Secret Service, and the US Department of Defense have all had laptops containing secret information,some perhaps in plaintext form, 'vanish' in recent years. Announcements of similar losses are becoming a common item in news reports. Disk encryption techniques can provide protection against such loss or theft — if properly chosen and used.

On occasion, even when the data on the host systems is itself encrypted, the media used to transfer data between such systems is nevertheless plaintext due to poorly designed data policy. An incident in October 2007 in which HM Revenue and Customs lost CDs containing no less than the records of 25 million child benefit recipients in the United Kingdom — the data apparently being entirely unencrypted — is a case in point.

Modern cryptographic systems are designed to resist known plaintext or even chosen plaintext attacks and so may not be entirely compromised when plaintext is lost or stolen. Older systems used techniques such as padding and Russian copulation to obscure information in plaintext that could be easily guessed, and to resistthe effects of loss of plaintext on the security of the cryptosystem.

Web browser saved password security controversy

Several popular web browsers which offer to store a user's passwordsdo so in plaintext form. Even though most of them initially hide thesaved passwords, it is possible for anyone to view all passwords in cleartext with a few clicks of the mouse, by going into the browsers' security settings options menus. In 2010, it emerged that this is the case with Firefox (still the case as of end-2014), and in Aug 2013 it emerged that Google Chrome does so as well.[1] When asoftware developer raised the issue with the Chrome security team,[2] a company representative responded that Google would not change the feature, and justified the refusal by saying that hiding the

passwords would "provide users with a false sense of security" and "that's just not how we approach security on Chrome".[3]

Cipher

From Wikipedia, the free encyclopedia

For other uses, see Cipher (disambiguation).

Edward Larsson's rune cipher resembling that found on the KensingtonRunestone. Also includes runically unrelated blackletter writing style and pigpen cipher.

In cryptography, a cipher (or cypher) is an algorithm for performingencryption or decryption—a series of well-defined steps that can be followed as a procedure. An alternative, less common term is encipherment. To encipher or encode is to convert information into cipher or code. In non-technical usage, a 'cipher' is the same thingas a 'code'; however, the concepts are distinct in cryptography. In classical cryptography, ciphers were distinguished from codes.

Codes generally substitute different length strings of characters inthe output, while ciphers generally substitute the same number of characters as are input. There are exceptions and some cipher systems may use slightly more, or fewer, characters when output versus the number that were input.

Codes operated by substituting according to a large codebook which linked a random string of characters or numbers to a word or phrase.For example, "UQJHSE" could be the code for "Proceed to the following coordinates." When using a cipher the original informationis known as plaintext, and the encrypted form as ciphertext. The ciphertext message contains all the information of the plaintext message, but is not in a format readable by a human or computer without the proper mechanism to decrypt it.

The operation of a cipher usually depends on a piece of auxiliary information, called a key (or, in traditional NSA parlance, a cryptovariable). The encrypting procedure is varied depending on thekey, which changes the detailed operation of the algorithm. A key must be selected before using a cipher to encrypt a message. Withoutknowledge of the key, it should be extremely difficult, if not impossible, to decrypt the resulting ciphertext into readable plaintext.

Most modern ciphers can be categorized in several ways

By whether they work on blocks of symbols usually of a fixed size (block ciphers), or on a continuous stream of symbols (stream ciphers).

By whether the same key is used for both encryption and decryption (symmetric key algorithms), or if a different key is usedfor each (asymmetric key algorithms). If the algorithm is symmetric,the key must be known to the recipient and sender and to no one else. If the algorithm is an asymmetric one, the enciphering key is different from, but closely related to, the deciphering key. If one key cannot be deduced from the other, the asymmetric key algorithm has the public/private key property and one of the keys may be made public without loss of confidentiality.

Contents

1 Etymology

2 Versus codes

3 Types

3.1 Historical

3.2 Modern

4 Key size and vulnerability

5 See also

6 Notes

7 References

8 External links

Etymology

"Cipher" is alternatively spelled "cypher"; similarly "ciphertext" and "cyphertext", and so forth.

The word "cipher" in former times meant "zero" and had the same origin: Middle French as cifre and Medieval Latin as cifra, from the

Arabic ص�ف�ر ṣifr = zero (see Zero—Etymology). "Cipher" was later used for any decimal digit, even any number. There are many theories about how the word "cipher" may have come to mean "encoding":It was firstly introduced by Abū ʿAbdallāh Muḥammad ibn Mūsā al-Khwārizmī.

Encoding often involved numbers.

The Roman number system was very cumbersome because there was noconcept of zero (or empty space). The concept of zero (which was also called "cipher"), which is now common knowledge, was alien to medieval Europe, so confusing and ambiguous to common Europeans thatin arguments people would say "talk clearly and not so far fetched as a cipher". Cipher came to mean concealment of clear messages or encryption.

The French formed the word "chiffre" and adopted the Italianword "zero".

The English used "zero" for "0", and "cipher" from the word "ciphering" as a means of computing.

The Germans used the words "Ziffer" (digit) and "Chiffre".

The Dutch still use the word "cijfer" to refer to a numerical digit.

The Serbians use the word "cifra", which refers to a digit, or in some cases, any number. Besides "cifra", they use word "broj" for a number.

The Italians and the Spanish also use the word "cifra" to refer to a number.

The Swedes use the word "siffra" which refers to a digit and"nummer" to refer to a combination of "siffror".

Ibrahim Al-Kadi concluded that the Arabic word sifr, for the digit zero, developed into the European technical term for encryption.[1]

As the decimal zero and its new mathematics spread from the Arabic world to Europe in the Middle Ages, words derived from ṣifr and zephyrus came to refer to calculation, as well as to privileged knowledge and secret codes. According to Ifrah, "in thirteenth-century Paris, a 'worthless fellow' was called a '... cifre en algorisme', i.e., an 'arithmetical nothing'."[2] Cipher was the European pronunciation of sifr, and cipher came to mean a message orcommunication not easily understood.[3]

Versus codes

Main article: Code (cryptography)

In non-technical usage, a "(secret) code" typically means a "cipher". Within technical discussions, however, the words "code" and "cipher" refer to two different concepts. Codes work at the level of meaning—that is, words or phrases are converted into something else and this chunking generally shortens the message.

An example of this is the Telegraph Code which was used to shorten long telegraph messages which resulted from entering into commercialcontracts using exchanges of Telegrams.

Another example is given by whole words cipher s, which allow the user to replace an entire word with a symbol or character, much likethe way Japanese utilize Kanji (Chinese) characters to supplement their language. ex "The quick brown fox jumps over the lazy dog" becomes "The quick brown 狐 jumps 狐 the lazy 狐".

Ciphers, on the other hand, work at a lower level: the level of individual letters, small groups of letters, or, in modern schemes, individual bits and blocks of bits. Some systems used both codes andciphers in one system, using superencipherment to increase the security. In some cases the terms codes and ciphers are also used synonymously to substitution and transposition.

Historically, cryptography was split into a dichotomy of codes and ciphers; and coding had its own terminology, analogous to that for ciphers: "encoding, codetext, decoding" and so on.

However, codes have a variety of drawbacks, including susceptibilityto cryptanalysis and the difficulty of managing a cumbersome codebook. Because of this, codes have fallen into disuse in modern cryptography, and ciphers are the dominant technique.

Types

There are a variety of different types of encryption. Algorithms used earlier in the history of cryptography are substantially different from modern methods, and modern ciphers can be classified according to how they operate and whether they use one or two keys.

Historical

Historical pen and paper ciphers used in the past are sometimes known as classical ciphers. They include simple substitution ciphers(such as Rot 13) and transposition ciphers (such as a Rail Fence

Cipher). For example, "GOOD DOG" can be encrypted as "PLLX XLP" where "L" substitutes for "O", "P" for "G", and "X" for "D" in the message. Transposition of the letters "GOOD DOG" can result in "DGOGDOO". These simple ciphers and examples are easy to crack, evenwithout plaintext-ciphertext pairs.

Simple ciphers were replaced by polyalphabetic substitution ciphers (such as the Vigenère) which changed the substitution alphabet for every letter. For example, "GOOD DOG" can be encrypted as "PLSX TWF"where "L", "S", and "W" substitute for "O". With even a small amountof known or estimated plaintext, simple polyalphabetic substitution ciphers and letter transposition ciphers designed for pen and paper encryption are easy to crack.[4] It is possible to create a secure pen and paper cipher based on a one-time pad though, but the usual disadvantages of one-time pads apply.

During the early twentieth century, electro-mechanical machines wereinvented to do encryption and decryption using transposition, polyalphabetic substitution, and a kind of "additive" substitution. In rotor machines, several rotor disks provided polyalphabetic substitution, while plug boards provided another substitution. Keys were easily changed by changing the rotor disks and the plugboard wires. Although these encryption methods were more complex than previous schemes and required machines to encrypt and decrypt, othermachines such as the British Bombe were invented to crack these encryption methods.

Modern

Modern encryption methods can be divided by two criteria: by type ofkey used, and by type of input data.

By type of key used ciphers are divided into:

symmetric key algorithms (Private-key cryptography), where the same key is used for encryption and decryption, and

asymmetric key algorithms (Public-key cryptography), where two different keys are used for encryption and decryption.

In a symmetric key algorithm (e.g., DES and AES), the sender and receiver must have a shared key set up in advance and kept secret from all other parties; the sender uses this key for encryption, andthe receiver uses the same key for decryption. The Feistel cipher uses a combination of substitution and transposition techniques. Most block cipher algorithms are based on this structure. In an asymmetric key algorithm (e.g., RSA), there are two separate keys: apublic key is published and enables any sender to perform encryption, while a private key is kept secret by the receiver and enables only him to perform correct decryption.

Ciphers can be distinguished into two types by the type of input data:

block ciphers, which encrypt block of data of fixed size, and

stream ciphers, which encrypt continuous streams of data

Key size and vulnerability

In a pure mathematical attack, (i.e., lacking any other information to help break a cipher) two factors above all count:

Computational power available, i.e., the computing power which can be brought to bear on the problem. It is important to note that average performance/capacity of a single computer is not the only factor to consider. An adversary can use multiple computers at once,

for instance, to increase the speed of exhaustive search for a key (i.e., "brute force" attack) substantially.

Key size, i.e., the size of key used to encrypt a message. As the key size increases, so does the complexity of exhaustive search to the point where it becomes impracticable to crack encryption directly.

Since the desired effect is computational difficulty, in theory one would choose an algorithm and desired difficulty level, thus decide the key length accordingly.

An example of this process can be found at Key Length which uses multiple reports to suggest that a symmetric cipher with 128 bits, an asymmetric cipher with 3072 bit keys, and an elliptic curve cipher with 512 bits, all have similar difficulty at present.

Claude Shannon proved, using information theory considerations, thatany theoretically unbreakable cipher must have keys which are at least as long as the plaintext, and used only once: one-time pad.

Algorithm

From Wikipedia, the free encyclopedia

"Algorithms" redirects here. For the journal, see Algorithms (journal).

"Rule set" redirects here. For other uses, see Rule.

"Algorhythm" redirects here. For the album, see Boxcar (band).

For the French musical project, see The Algorithm.

Flow chart of an algorithm (Euclid's algorithm) for calculating the greatest common divisor (g.c.d.) of two numbers a and b in locationsnamed A and B. The algorithm proceeds by successive subtractions in two loops: IF the test B ≥ A yields "yes" (or true) (more accuratelythe number b in location B is greater than or equal to the number a in location A) THEN, the algorithm specifies B ← B − A (meaning the

number b − a replaces the old b). Similarly, IF A > B, THEN A ← A − B. The process terminates when (the contents of) B is 0, yielding the g.c.d. in A. (Algorithm derived from Scott 2009:13; symbols and drawing style from Tausworthe 1977).

In mathematics and computer science, an algorithm (Listeni/ˈælɡərɪðəm/ AL-gə-ri-dhəm) is a self-contained step-by-stepset of operations to be performed. Algorithms exist that perform calculation, data processing, and automated reasoning.

An algorithm is an effective method that can be expressed within a finite amount of space and time[1] and in a well-defined formal language[2] for calculating a function.[3] Starting from an initial state and initial input (perhaps empty),[4] the instructions describe a computation that, when executed, proceeds through a finite[5] number of well-defined successive states, eventually producing "output"[6] and terminating at a final ending state. The transition from one state to the next is not necessarily deterministic; some algorithms, known as randomized algorithms, incorporate random input.[7]

The concept of algorithm has existed for centuries, however a partial formalization of what would become the modern algorithm began with attempts to solve the Entscheidungsproblem (the "decisionproblem") posed by David Hilbert in 1928. Subsequent formalizations were framed as attempts to define "effective calculability"[8] or "effective method";[9] those formalizations included the Gödel–Herbrand–Kleene recursive functions of 1930, 1934 and 1935, Alonzo Church's lambda calculus of 1936, Emil Post's "Formulation 1" of 1936, and Alan Turing's Turing machines of 1936–7 and 1939. Giving aformal definition of algorithms, corresponding to the intuitive notion, remains a challenging problem.[10]

Contents

1 Word origin

2 Informal definition

3 Formalization

3.1 Expressing algorithms

4 Implementation

5 Computer algorithms

6 Examples

6.1 Algorithm example

6.2 Euclid’s algorithm

6.2.1 Computer language for Euclid's algorithm

6.2.2 An inelegant program for Euclid's algorithm

6.2.3 An elegant program for Euclid's algorithm

6.3 Testing the Euclid algorithms

6.4 Measuring and improving the Euclid algorithms

7 Algorithmic analysis

7.1 Formal versus empirical

7.2 Execution efficiency

8 Classification

8.1 By implementation

8.2 By design paradigm

8.3 Optimization problems

8.4 By field of study

8.5 By complexity

9 Continuous algorithms

10 Legal issues

11 Etymology

12 History: Development of the notion of "algorithm"

12.1 Ancient Greece

12.2 Origin

12.3 Discrete and distinguishable symbols

12.4 Manipulation of symbols as "place holders" for numbers:algebra

12.5 Mechanical contrivances with discrete states

12.6 Mathematics during the 19th century up to the mid-20th century

12.7 Emil Post (1936) and Alan Turing (1936–37, 1939)

12.8 J. B. Rosser (1939) and S. C. Kleene (1943)

12.9 History after 1950

13 See also

14 Notes

15 References

15.1 Secondary references

16 Further reading

17 External links

Word origin

'Algorithm' stems from the name of a Latin translation of a book written by al-Khwārizmī, a Persian[11][12] mathematician, astronomerand geographer. Al-Khwarizmi wrote a book titled On the Calculation with Hindu Numerals in about 825 AD, and was principally responsiblefor spreading the Indian system of numeration throughout the Middle East and Europe. It was translated into Latin as Algoritmi de numeroIndorum (in English, "Al-Khwarizmi on the Hindu Art of Reckoning").

The term "Algoritmi" in the title of the book led to the term "algorithm".[13]

Informal definition

For a detailed presentation of the various points of view on the definition of "algorithm", see Algorithm characterizations.

An informal definition could be "a set of rules that precisely defines a sequence of operations."[14] which would include all computer programs, including programs that do not perform numeric calculations. Generally, a program is only an algorithm if it stops eventually.[15]

A prototypical example of an algorithm is Euclid's algorithm to determine the maximum common divisor of two integers; an example (there are others) is described by the flow chart above and as an example in a later section.

Boolos & Jeffrey (1974, 1999) offer an informal meaning of the word in the following quotation:

No human being can write fast enough, or long enough, or small enough† ( †"smaller and smaller without limit ...you'd be trying to write on molecules, on atoms, on electrons") to list all members of an enumerably infinite set by writing out their names, one after another, in some notation. But humans can do something equally useful, in the case of certain enumerably infinite sets: They can give explicit instructions for determining the nth member of the set, for arbitrary finite n. Such instructions are to be given quiteexplicitly, in a form in which they could be followed by a computingmachine, or by a human who is capable of carrying out only very elementary operations on symbols.[16]

An "enumerably infinite set" is one whose elements can be put into one-to-one correspondence with the integers. Thus, Boolos and Jeffrey are saying that an algorithm implies instructions for a process that "creates" output integers from an arbitrary "input" integer or integers that, in theory, can be arbitrarily large. Thus an algorithm can be an algebraic equation such as y = m + n—two arbitrary "input variables" m and n that produce an output y. But various authors' attempts to define the notion indicate that the word implies much more than this, something on the order of (for theaddition example):

Precise instructions (in language understood by "the computer")[17] for a fast, efficient, "good"[18] process that specifies the "moves" of "the computer" (machine or human, equipped with the necessary internally contained information and capabilities)[19] to find, decode, and then process arbitrary input integers/symbols m and n, symbols + and = ... and "effectively"[20] produce, in a "reasonable" time,[21] output-integer y at a specified place and in a specified format.

The concept of algorithm is also used to define the notion of decidability. That notion is central for explaining how formal systems come into being starting from a small set of axioms and rules. In logic, the time that an algorithm requires to complete cannot be measured, as it is not apparently related with our customary physical dimension. From such uncertainties, that characterize ongoing work, stems the unavailability of a definition of algorithm that suits both concrete (in some sense) and abstract usage of the term.

Formalization

Algorithms are essential to the way computers process data. Many computer programs contain algorithms that detail the specific instructions a computer should perform (in a specific order) to carry out a specified task, such as calculating employees' paychecksor printing students' report cards. Thus, an algorithm can be

considered to be any sequence of operations that can be simulated bya Turing-complete system. Authors who assert this thesis include Minsky (1967), Savage (1987) and Gurevich (2000):

Minsky: "But we will also maintain, with Turing . . . that any procedure which could "naturally" be called effective, can in fact be realized by a (simple) machine. Although this may seem extreme, the arguments . . . in its favor are hard to refute".[22]

Gurevich: "...Turing's informal argument in favor of his thesis justifies a stronger thesis: every algorithm can be simulated by a Turing machine ... according to Savage [1987], an algorithm is a computational process defined by a Turing machine".[23]

Typically, when an algorithm is associated with processing information, data is read from an input source, written to an outputdevice, and/or stored for further processing. Stored data is regarded as part of the internal state of the entity performing the algorithm. In practice, the state is stored in one or more data structures.

For some such computational process, the algorithm must be rigorously defined: specified in the way it applies in all possible circumstances that could arise. That is, any conditional steps must be systematically dealt with, case-by-case; the criteria for each case must be clear (and computable).

Because an algorithm is a precise list of precise steps, the order of computation is always critical to the functioning of the algorithm. Instructions are usually assumed to be listed explicitly,and are described as starting "from the top" and going "down to the bottom", an idea that is described more formally by flow of control.

So far, this discussion of the formalization of an algorithm has assumed the premises of imperative programming. This is the most common conception, and it attempts to describe a task in discrete, "mechanical" means. Unique to this conception of formalized algorithms is the assignment operation, setting the value of a variable. It derives from the intuition of "memory" as a scratchpad.There is an example below of such an assignment.

For some alternate conceptions of what constitutes an algorithm see functional programming and logic programming.

Expressing algorithms

Algorithms can be expressed in many kinds of notation, including natural languages, pseudocode, flowcharts, drakon-charts, programming languages or control tables (processed by interpreters).Natural language expressions of algorithms tend to be verbose and ambiguous, and are rarely used for complex or technical algorithms. Pseudocode, flowcharts, drakon-charts and control tables are structured ways to express algorithms that avoid many of the ambiguities common in natural language statements. Programming languages are primarily intended for expressing algorithms in a formthat can be executed by a computer, but are often used as a way to define or document algorithms.

There is a wide variety of representations possible and one can express a given Turing machine program as a sequence of machine tables (see more at finite state machine, state transition table andcontrol table), as flowcharts and drakon-charts (see more at state diagram), or as a form of rudimentary machine code or assembly code called "sets of quadruples" (see more at Turing machine).

Representations of algorithms can be classed into three accepted levels of Turing machine description:[24]

1 High-level description

"...prose to describe an algorithm, ignoring the implementation details. At this level we do not need to mention how the machine manages its tape or head."

2 Implementation description

"...prose used to define the way the Turing machine uses its head and the way that it stores data on its tape. At this level we do not give details of states or transition function."

3 Formal description

Most detailed, "lowest level", gives the Turing machine's "statetable".

For an example of the simple algorithm "Add m+n" described in all three levels, see Algorithm#Examples.

Implementation

Logical NAND algorithm implemented electronically in 7400 chip

Most algorithms are intended to be implemented as computer programs.However, algorithms are also implemented by other means, such as in a biological neural network (for example, the human brain implementing arithmetic or an insect looking for food), in an electrical circuit, or in a mechanical device.

Computer algorithms

Flowchart examples of the canonical Böhm-Jacopini structures: the SEQUENCE (rectangles descending the page), the WHILE-DO and the IF-THEN-ELSE. The three structures are made of the primitive conditional GOTO (IF test=true THEN GOTO step xxx) (a diamond), the unconditional GOTO (rectangle), various assignment operators (rectangle), and HALT (rectangle). Nesting of these structures inside assignment-blocks result in complex diagrams (cf Tausworthe 1977:100,114).

In computer systems, an algorithm is basically an instance of logic written in software by software developers to be effective for the intended "target" computer(s) to produce output from given input (perhaps null). An optimal algorithm, even running in old hardware, would produce faster results than a non optimal (higher time complexity) algorithm for the same purpose, running in more efficient hardware; that is why the algorithms, like computer hardware, are considered technology.

"Elegant" (compact) programs, "good" (fast) programs : The notion of"simplicity and elegance" appears informally in Knuth and precisely in Chaitin:

Knuth: ". . .we want good algorithms in some loosely defined aesthetic sense. One criterion . . . is the length of time taken to perform the algorithm . . .. Other criteria are adaptability of the algorithm to computers, its simplicity and elegance, etc"[25]

Chaitin: " . . . a program is 'elegant,' by which I mean that it's the smallest possible program for producing the output that it does"[26]

Chaitin prefaces his definition with: "I'll show you can't prove that a program is 'elegant'"—such a proof would solve the Halting problem (ibid).

Algorithm versus function computable by an algorithm: For a given function multiple algorithms may exist. This is true, even without expanding the available instruction set available to the programmer.Rogers observes that "It is . . . important to distinguish between the notion of algorithm, i.e. procedure and the notion of function computable by algorithm, i.e. mapping yielded by procedure. The samefunction may have several different algorithms".[27]

Unfortunately there may be a tradeoff between goodness (speed) and elegance (compactness)—an elegant program may take more steps to complete a computation than one less elegant. An example that uses Euclid's algorithm appears below.

Computers (and computors), models of computation: A computer (or human "computor"[28]) is a restricted type of machine, a "discrete deterministic mechanical device"[29] that blindly follows its instructions.[30] Melzak's and Lambek's primitive models[31] reducedthis notion to four elements: (i) discrete, distinguishable locations, (ii) discrete, indistinguishable counters[32] (iii) an agent, and (iv) a list of instructions that are effective relative to the capability of the agent.[33]

Minsky describes a more congenial variation of Lambek's "abacus" model in his "Very Simple Bases for Computability".[34] Minsky's machine proceeds sequentially through its five (or six depending on how one counts) instructions unless either a conditional IF–THEN GOTO or an unconditional GOTO changes program flow out of sequence. Besides HALT, Minsky's machine includes three assignment (replacement, substitution)[35] operations: ZERO (e.g. the contents of location replaced by 0: L ← 0), SUCCESSOR (e.g. L ← L+1), and DECREMENT (e.g. L ← L − 1).[36] Rarely must a programmer write "code" with such a limited instruction set. But Minsky shows (as do Melzak and Lambek) that his machine is Turing complete with only four general types of instructions: conditional GOTO, unconditional GOTO, assignment/replacement/substitution, and HALT.[37]

Simulation of an algorithm: computer (computor) language: Knuth advises the reader that "the best way to learn an algorithm is to try it . . . immediately take pen and paper and work through an example".[38] But what about a simulation or execution of the real thing? The programmer must translate the algorithm into a language that the simulator/computer/computor can effectively execute. Stone gives an example of this: when computing the roots of a quadratic equation the computor must know how to take a square root. If they

don't then for the algorithm to be effective it must provide a set of rules for extracting a square root.[39]

This means that the programmer must know a "language" that is effective relative to the target computing agent (computer/computor).

But what model should be used for the simulation? Van Emde Boas observes "even if we base complexity theory on abstract instead of concrete machines, arbitrariness of the choice of a model remains. It is at this point that the notion of simulation enters".[40] When speed is being measured, the instruction set matters. For example, the subprogram in Euclid's algorithm to compute the remainder would execute much faster if the programmer had a "modulus" (division) instruction available rather than just subtraction (or worse: just Minsky's "decrement").

Structured programming, canonical structures: Per the Church–Turing thesis any algorithm can be computed by a model known to be Turing complete, and per Minsky's demonstrations Turing completeness requires only four instruction types—conditional GOTO, unconditionalGOTO, assignment, HALT. Kemeny and Kurtz observe that while "undisciplined" use of unconditional GOTOs and conditional IF-THEN GOTOs can result in "spaghetti code" a programmer can write structured programs using these instructions; on the other hand "it is also possible, and not too hard, to write badly structured programs in a structured language".[41] Tausworthe augments the three Böhm-Jacopini canonical structures:[42] SEQUENCE, IF-THEN-ELSE, and WHILE-DO, with two more: DO-WHILE and CASE.[43] An additional benefit of a structured program is that it lends itself to proofs of correctness using mathematical induction.[44]

Canonical flowchart symbols[45]: The graphical aide called a flowchart offers a way to describe and document an algorithm (and a computer program of one). Like program flow of a Minsky machine, a

flowchart always starts at the top of a page and proceeds down. Its primary symbols are only 4: the directed arrow showing program flow,the rectangle (SEQUENCE, GOTO), the diamond (IF-THEN-ELSE), and the dot (OR-tie). The Böhm-Jacopini canonical structures are made of these primitive shapes. Sub-structures can "nest" in rectangles but only if a single exit occurs from the superstructure. The symbols and their use to build the canonical structures are shown in the diagram.

Examples

Further information: List of algorithms

Algorithm example

An animation of the quicksort algorithm sorting an array of randomized values. The red bars mark the pivot element; at the startof the animation, the element farthest to the right hand side is chosen as the pivot.

One of the simplest algorithms is to find the largest number in a list of numbers of random order. Finding solution requires looking at every number in the list. From this follows a simple algorithm, which can be stated in a high-level description English prose, as:

High-level description:

If there are no numbers in the set then there is no highest number.

Assume the first number in the set is the largest number in the set.

For each remaining number in the set: if this number is larger than the current largest number, consider this number to be the largest number in the set.

When there are no numbers left in the set to iterate over, consider the current largest number to be the largest number of the set.

(Quasi-)formal description: Written in prose but much closer to the high-level language of a computer program, the following is the moreformal coding of the algorithm in pseudocode or pidgin code:

Algorithm LargestNumber

Input: A list of numbers L.

Output: The largest number in the list L.

if L.size = 0 return null

largest ← L[0]

for each item in L, do

if item > largest, then

largest ← item

return largest

"←" is a shorthand for "changes to". For instance, "largest ← item" means that the value of largest changes to the value of item.

"return" terminates the algorithm and outputs the value that follows.

Euclid’s algorithm

Further information: Euclid algorithm

The example-diagram of Euclid's algorithm from T.L. Heath 1908 with more detail added. Euclid does not go beyond a third measuring and gives no numerical examples. Nicomachus gives the example of 49 and 21: "I subtract the less from the greater; 28 is left; then again I subtract from this the same 21 (for this is possible); 7 is left; I subtract this from 21, 14 is left; from which I again subtract 7

(for this is possible); 7 is left, but 7 cannot be subtracted from 7." Heath comments that, "The last phrase is curious, but the meaning of it is obvious enough, as also the meaning of the phrase about ending 'at one and the same number'."(Heath 1908:300).

Euclid’s algorithm appears as Proposition II in Book VII ("Elementary Number Theory") of his Elements.[46] Euclid poses the problem: "Given two numbers not prime to one another, to find their greatest common measure". He defines "A number [to be] a multitude composed of units": a counting number, a positive integer not including 0. And to "measure" is to place a shorter measuring lengths successively (q times) along longer length l until the remaining portion r is less than the shorter length s.[47] In modern words, remainder r = l − q*s, q being the quotient, or remainder r is the "modulus", the integer-fractional part left over after the division.[48]

For Euclid’s method to succeed, the starting lengths must satisfy two requirements: (i) the lengths must not be 0, AND (ii) the subtraction must be “proper”, a test must guarantee that the smallerof the two numbers is subtracted from the larger (alternately, the two can be equal so their subtraction yields 0).

Euclid's original proof adds a third: the two lengths are not prime to one another. Euclid stipulated this so that he could construct a reductio ad absurdum proof that the two numbers' common measure is in fact the greatest.[49] While Nicomachus' algorithm is the same asEuclid's, when the numbers are prime to one another it yields the number "1" for their common measure. So to be precise the following is really Nicomachus' algorithm.

A graphical expression on Euclid's algorithm using example with 1599and 650.

1599 = 650*2 + 299

650 = 299*2 + 52

299 = 52*5 + 39

52 = 39*1 + 13

39 = 13*3 + 0

Computer language for Euclid's algorithm

Only a few instruction types are required to execute Euclid's algorithm—some logical tests (conditional GOTO), unconditional GOTO,assignment (replacement), and subtraction.

A location is symbolized by upper case letter(s), e.g. S, A, etc.

The varying quantity (number) in a location is written in lower case letter(s) and (usually) associated with the location's name. For example, location L at the start might contain the number l = 3009.

An inelegant program for Euclid's algorithm

"Inelegant" is a translation of Knuth's version of the algorithm with a subtraction-based remainder-loop replacing his use of division (or a "modulus" instruction). Derived from Knuth 1973:2–4. Depending on the two numbers "Inelegant" may compute the g.c.d. in fewer steps than "Elegant".

The following algorithm is framed as Knuth's 4-step version of Euclid's and Nichomachus', but rather than using division to find the remainder it uses successive subtractions of the shorter length s from the remaining length r until r is less than s. The high-leveldescription, shown in boldface, is adapted from Knuth 1973:2–4:

INPUT:

1 [Into two locations L and S put the numbers l and s that representthe two lengths]:

INPUT L, S

2 [Initialize R: make the remaining length r equal to the starting/initial/input length l]:

R ← L

E0: [Ensure r ≥ s.]

3 [Ensure the smaller of the two numbers is in S and the larger in R]:

IF R > S THEN

the contents of L is the larger number so skip over the exchange-steps 4, 5 and 6:

GOTO step 6

ELSE

swap the contents of R and S.

4 L ← R (this first step is redundant, but is useful for later discussion).

5 R ← S

6 S ← L

E1: [Find remainder]: Until the remaining length r in R is less thanthe shorter length s in S, repeatedly subtract the measuring number s in S from the remaining length r in R.

7 IF S > R THEN

done measuring so

GOTO 10

ELSE

measure again,

8 R ← R − S

9 [Remainder-loop]:

GOTO 7.

E2: [Is the remainder 0?]: EITHER (i) the last measure was exact andthe remainder in R is 0 program can halt, OR (ii) the algorithm mustcontinue: the last measure left a remainder in R less than measuringnumber in S.

10 IF R = 0 THEN

done so

GOTO step 15

ELSE

CONTINUE TO step 11,

E3: [Interchange s and r]: The nut of Euclid's algorithm. Use remainder r to measure what was previously smaller number s:; L serves as a temporary location.

11 L ← R

12 R ← S

13 S ← L

14 [Repeat the measuring process]:

GOTO 7

OUTPUT:

15 [Done. S contains the greatest common divisor]:

PRINT S

DONE:

16 HALT, END, STOP.

An elegant program for Euclid's algorithm

The following version of Euclid's algorithm requires only 6 core instructions to do what 13 are required to do by "Inelegant"; worse,"Inelegant" requires more types of instructions. The flowchart of "Elegant" can be found at the top of this article. In the (unstructured) Basic language the steps are numbered, and the instruction LET [] = [] is the assignment instruction symbolized by ←.

5 REM Euclid's algorithm for greatest common divisor

6 PRINT "Type two integers greater than 0"

10 INPUT A,B

20 IF B=0 THEN GOTO 80

30 IF A > B THEN GOTO 60

40 LET B=B-A

50 GOTO 20

60 LET A=A-B

70 GOTO 20

80 PRINT A

90 END

How "Elegant" works: In place of an outer "Euclid loop", "Elegant" shifts back and forth between two "co-loops", an A > B loop that computes A ← A − B, and a B ≤ A loop that computes B ← B − A. This works because, when at last the minuend M is less than or equal to the subtrahend S ( Difference = Minuend − Subtrahend), the minuend can become s (the new measuring length) and the subtrahend can become the new r (the length to be measured); in other words the "sense" of the subtraction reverses.

Testing the Euclid algorithms

Does an algorithm do what its author wants it to do? A few test cases usually suffice to confirm core functionality. One source[50] uses 3009 and 884. Knuth suggested 40902, 24140. Another interestingcase is the two relatively prime numbers 14157 and 5950.

But exceptional cases must be identified and tested. Will "Inelegant" perform properly when R > S, S > R, R = S? Ditto for "Elegant": B > A, A > B, A = B? (Yes to all). What happens when one number is zero, both numbers are zero? ("Inelegant" computes foreverin all cases; "Elegant" computes forever when A = 0.) What happens if negative numbers are entered? Fractional numbers? If the input numbers, i.e. the domain of the function computed by the algorithm/program, is to include only positive integers including zero, then the failures at zero indicate that the algorithm (and theprogram that instantiates it) is a partial function rather than a total function. A notable failure due to exceptions is the Ariane V rocket failure.

Proof of program correctness by use of mathematical induction: Knuthdemonstrates the application of mathematical induction to an "extended" version of Euclid's algorithm, and he proposes "a generalmethod applicable to proving the validity of any algorithm".[51] Tausworthe proposes that a measure of the complexity of a program bethe length of its correctness proof.[52]

Measuring and improving the Euclid algorithms

Elegance (compactness) versus goodness (speed): With only 6 core instructions, "Elegant" is the clear winner compared to "Inelegant" at 13 instructions. However, "Inelegant" is faster (it arrives at HALT in fewer steps). Algorithm analysis[53] indicates why this is the case: "Elegant" does two conditional tests in every subtraction loop, whereas "Inelegant" only does one. As the algorithm (usually) requires many loop-throughs, on average much time is wasted doing a "B = 0?" test that is needed only after the remainder is computed.

Can the algorithms be improved?: Once the programmer judges a program "fit" and "effective"—that is, it computes the function intended by its author—then the question becomes, can it be improved?

The compactness of "Inelegant" can be improved by the elimination of5 steps. But Chaitin proved that compacting an algorithm cannot be automated by a generalized algorithm;[54] rather, it can only be done heuristically, i.e. by exhaustive search (examples to be found at Busy beaver), trial and error, cleverness, insight, application of inductive reasoning, etc. Observe that steps 4, 5 and 6 are repeated in steps 11, 12 and 13. Comparison with "Elegant" provides a hint that these steps together with steps 2 and 3 can be eliminated. This reduces the number of core instructions from 13 to 8, which makes it "more elegant" than "Elegant" at 9 steps.

The speed of "Elegant" can be improved by moving the B=0? test outside of the two subtraction loops. This change calls for the addition of 3 instructions (B=0?, A=0?, GOTO). Now "Elegant" computes the example-numbers faster; whether for any given A, B and R, S this is always the case would require a detailed analysis.

Algorithmic analysis

Main article: Analysis of algorithms

It is frequently important to know how much of a particular resource(such as time or storage) is theoretically required for a given algorithm. Methods have been developed for the analysis of algorithms to obtain such quantitative answers (estimates); for example, the sorting algorithm above has a time requirement of O(n),using the big O notation with n as the length of the list. At all times the algorithm only needs to remember two values: the largest number found so far, and its current position in the input list. Therefore, it is said to have a space requirement of O(1), if the space required to store the input numbers is not counted, or O(n) ifit is counted.

Different algorithms may complete the same task with a different setof instructions in less or more time, space, or 'effort' than others. For example, a binary search algorithm usually outperforms abrute force sequential search when used for table lookups on sorted lists.

Formal versus empirical

Main articles: Empirical algorithmics, Profiling (computer programming) and Program optimization

The analysis and study of algorithms is a discipline of computer science, and is often practiced abstractly without the use of a specific programming language or implementation. In this sense, algorithm analysis resembles other mathematical disciplines in that it focuses on the underlying properties of the algorithm and not on

the specifics of any particular implementation. Usually pseudocode is used for analysis as it is the simplest and most general representation. However, ultimately, most algorithms are usually implemented on particular hardware / software platforms and their algorithmic efficiency is eventually put to the test using real code. For the solution of a "one off" problem, the efficiency of a particular algorithm may not have significant consequences (unless nis extremely large) but for algorithms designed for fast interactive, commercial or long life scientific usage it may be critical. Scaling from small n to large n frequently exposes inefficient algorithms that are otherwise benign.

Empirical testing is useful because it may uncover unexpected interactions that affect performance. Benchmarks may be used to compare before/after potential improvements to an algorithm after program optimization.

Execution efficiency

Main article: Algorithmic efficiency

To illustrate the potential improvements possible even in well established algorithms, a recent significant innovation, relating toFFT algorithms (used heavily in the field of image processing), can decrease processing time up to 1,000 times for applications like medical imaging.[55] In general, speed improvements depend on special properties of the problem, which are very common in practical applications.[56] Speedups of this magnitude enable computing devices that make extensive use of image processing (like digital cameras and medical equipment) to consume less power.

Classification

There are various ways to classify algorithms, each with its own merits.

By implementation

One way to classify algorithms is by implementation means.

Recursion or iteration

A recursive algorithm is one that invokes (makes reference to) itself repeatedly until a certain condition (also known as termination condition) matches, which is a method common to functional programming. Iterative algorithms use repetitive constructs like loops and sometimes additional data structures like stacks to solve the given problems. Some problems are naturally suited for one implementation or the other. For example, towers of Hanoi is well understood using recursive implementation. Every recursive version has an equivalent (but possibly more or less complex) iterative version, and vice versa.

Logical

An algorithm may be viewed as controlled logical deduction. Thisnotion may be expressed as: Algorithm = logic + control.[57] The logic component expresses the axioms that may be used in the computation and the control component determines the way in which deduction is applied to the axioms. This is the basis for the logic programming paradigm. In pure logic programming languages the control component is fixed and algorithms are specified by supplyingonly the logic component. The appeal of this approach is the elegantsemantics: a change in the axioms has a well-defined change in the algorithm.

Serial, parallel or distributed

Algorithms are usually discussed with the assumption that computers execute one instruction of an algorithm at a time. Those computers are sometimes called serial computers. An algorithm designed for such an environment is called a serial algorithm, as opposed to parallel algorithms or distributed algorithms. Parallel algorithms take advantage of computer architectures where several processors can work on a problem at the same time, whereas distributed algorithms utilize multiple machines connected with a network. Parallel or distributed algorithms divide the problem into more symmetrical or asymmetrical subproblems and collect the resultsback together. The resource consumption in such algorithms is not

only processor cycles on each processor but also the communication overhead between the processors. Some sorting algorithms can be parallelized efficiently, but their communication overhead is expensive. Iterative algorithms are generally parallelizable. Some problems have no parallel algorithms, and are called inherently serial problems.

Deterministic or non-deterministic

Deterministic algorithms solve the problem with exact decision at every step of the algorithm whereas non-deterministic algorithms solve problems via guessing although typical guesses are made more accurate through the use of heuristics.

Exact or approximate

While many algorithms reach an exact solution, approximation algorithms seek an approximation that is close to the true solution.Approximation may use either a deterministic or a random strategy. Such algorithms have practical value for many hard problems.

Quantum algorithm

They run on a realistic model of quantum computation. The term is usually used for those algorithms which seem inherently quantum, or use some essential feature of quantum computation such as quantumsuperposition or quantum entanglement.

By design paradigm

Another way of classifying algorithms is by their design methodologyor paradigm. There is a certain number of paradigms, each different from the other. Furthermore, each of these categories include many different types of algorithms. Some common paradigms are:

Brute-force or exhaustive search

This is the naive method of trying every possible solution to see which is best.[58]

Divide and conquer

A divide and conquer algorithm repeatedly reduces an instance ofa problem to one or more smaller instances of the same problem (usually recursively) until the instances are small enough to solve easily. One such example of divide and conquer is merge sorting. Sorting can be done on each segment of data after dividing data intosegments and sorting of entire data can be obtained in the conquer phase by merging the segments. A simpler variant of divide and conquer is called a decrease and conquer algorithm, that solves an identical subproblem and uses the solution of this subproblem to solve the bigger problem. Divide and conquer divides the problem into multiple subproblems and so the conquer stage is more complex than decrease and conquer algorithms. An example of decrease and conquer algorithm is the binary search algorithm.

Search and enumeration

Many problems (such as playing chess) can be modeled as problemson graphs. A graph exploration algorithm specifies rules for moving around a graph and is useful for such problems. This category also includes search algorithms, branch and bound enumeration and backtracking.

Randomized algorithm

Such algorithms make some choices randomly (or pseudo-randomly).They can be very useful in finding approximate solutions for problems where finding exact solutions can be impractical (see heuristic method below). For some of these problems, it is known that the fastest approximations must involve some randomness.[59] Whether randomized algorithms with polynomial time complexity can bethe fastest algorithms for some problems is an open question known as the P versus NP problem. There are two large classes of such algorithms:

Monte Carlo algorithms return a correct answer with high-probability. E.g. RP is the subclass of these that run in polynomialtime.

Las Vegas algorithms always return the correct answer, but theirrunning time is only probabilistically bound, e.g. ZPP.

Reduction of complexity

This technique involves solving a difficult problem by transforming it into a better known problem for which we have (hopefully) asymptotically optimal algorithms. The goal is to find areducing algorithm whose complexity is not dominated by the resulting reduced algorithm's. For example, one selection algorithm for finding the median in an unsorted list involves first sorting the list (the expensive portion) and then pulling out the middle element in the sorted list (the cheap portion). This technique is also known as transform and conquer.

Optimization problems

For optimization problems there is a more specific classification ofalgorithms; an algorithm for such problems may fall into one or moreof the general categories described above as well as into one of thefollowing:

Linear programming

When searching for optimal solutions to a linear function bound to linear equality and inequality constrains, the constrains of the problem can be used directly in producing the optimal solutions. There are algorithms that can solve any problem in this category, such as the popular simplex algorithm.[60] Problems that can be solved with linear programming include the maximum flow problem for directed graphs. If a problem additionally requires that one or moreof the unknowns must be an integer then it is classified in integer programming. A linear programming algorithm can solve such a problemif it can be proved that all restrictions for integer values are superficial, i.e. the solutions satisfy these restrictions anyway. In the general case, a specialized algorithm or an algorithm that

finds approximate solutions is used, depending on the difficulty of the problem.

Dynamic programming

When a problem shows optimal substructures — meaning the optimalsolution to a problem can be constructed from optimal solutions to subproblems — and overlapping subproblems, meaning the same subproblems are used to solve many different problem instances, a quicker approach called dynamic programming avoids recomputing solutions that have already been computed. For example, Floyd–Warshall algorithm, the shortest path to a goal from a vertex in a weighted graph can be found by using the shortest path to the goal from all adjacent vertices. Dynamic programming and memoization go together. The main difference between dynamic programming and divideand conquer is that subproblems are more or less independent in divide and conquer, whereas subproblems overlap in dynamic programming. The difference between dynamic programming and straightforward recursion is in caching or memoization of recursive calls. When subproblems are independent and there is no repetition, memoization does not help; hence dynamic programming is not a solution for all complex problems. By using memoization or maintaining a table of subproblems already solved, dynamic programming reduces the exponential nature of many problems to polynomial complexity.

The greedy method

A greedy algorithm is similar to a dynamic programming algorithmin that it works by examining substructures, in this case not of theproblem but of a given solution. Such algorithms start with some solution, which may be given or have been constructed in some way, and improve it by making small modifications. For some problems theycan find the optimal solution while for others they stop at local optima, that is at solutions that cannot be improved by the algorithm but are not optimum. The most popular use of greedy algorithms is for finding the minimal spanning tree where finding the optimal solution is possible with this method. Huffman Tree, Kruskal, Prim, Sollin are greedy algorithms that can solve this optimization problem.

The heuristic method

In optimization problems, heuristic algorithms can be used to find a solution close to the optimal solution in cases where findingthe optimal solution is impractical. These algorithms work by getting closer and closer to the optimal solution as they progress. In principle, if run for an infinite amount of time, they will find the optimal solution. Their merit is that they can find a solution very close to the optimal solution in a relatively short time. Such algorithms include local search, tabu search, simulated annealing, and genetic algorithms. Some of them, like simulated annealing, are non-deterministic algorithms while others, like tabu search, are deterministic. When a bound on the error of the non-optimal solutionis known, the algorithm is further categorized as an approximation algorithm.

By field of study

See also: List of algorithms

Every field of science has its own problems and needs efficient algorithms. Related problems in one field are often studied together. Some example classes are search algorithms, sorting algorithms, merge algorithms, numerical algorithms, graph algorithms, string algorithms, computational geometric algorithms, combinatorial algorithms, medical algorithms, machine learning, cryptography, data compression algorithms and parsing techniques.

Fields tend to overlap with each other, and algorithm advances in one field may improve those of other, sometimes completely unrelated, fields. For example, dynamic programming was invented foroptimization of resource consumption in industry, but is now used insolving a broad range of problems in many fields.

By complexity

See also: Complexity class and Parameterized complexity

Algorithms can be classified by the amount of time they need to complete compared to their input size. There is a wide variety: somealgorithms complete in linear time relative to input size, some do so in an exponential amount of time or even worse, and some never halt. Additionally, some problems may have multiple algorithms of differing complexity, while other problems might have no algorithms or no known efficient algorithms. There are also mappings from some problems to other problems. Owing to this, it was found to be more suitable to classify the problems themselves instead of the algorithms into equivalence classes based on the complexity of the best possible algorithms for them.

Burgin (2005, p. 24) uses a generalized definition of algorithms that relaxes the common requirement that the output of the algorithmthat computes a function must be determined after a finite number ofsteps. He defines a super-recursive class of algorithms as "a class of algorithms in which it is possible to compute functions not computable by any Turing machine" (Burgin 2005, p. 107). This is closely related to the study of methods of hypercomputation.

Continuous algorithms

The adjective "continuous" when applied to the word "algorithm" can mean:

An algorithm operating on data that represents continuous quantities, even though this data is represented by discrete approximations—such algorithms are studied in numerical analysis; or

An algorithm in the form of a differential equation that operates continuously on the data, running on an analog computer.[61]

Legal issues

See also: Software patents for a general overview of the patentability of software, including computer-implemented algorithms.

Algorithms, by themselves, are not usually patentable. In the UnitedStates, a claim consisting solely of simple manipulations of abstract concepts, numbers, or signals does not constitute "processes" (USPTO 2006), and hence algorithms are not patentable (as in Gottschalk v. Benson). However, practical applications of algorithms are sometimes patentable. For example, in Diamond v. Diehr, the application of a simple feedback algorithm to aid in the curing of synthetic rubber was deemed patentable. The patenting of software is highly controversial, and there are highly criticized patents involving algorithms, especially data compression algorithms, such as Unisys' LZW patent.

Additionally, some cryptographic algorithms have export restrictions(see export of cryptography).

Etymology

The word "Algorithm", or "Algorism" in some other writing versions, comes from the name al-Khwārizmī, pronounced in classical Arabic as

Al-Khwarithmi. Al-Khwārizmī (Persian: مي� وازز� c. 780-850) was a ,خ��Persian mathematician, astronomer, geographer and a scholar in the House of Wisdom in Baghdad, whose name means "the native of Khwarezm", a city that was part of the Greater Iran during his era and now is in modern-day Uzbekistan.[11][12] About 825, he wrote a treatise in the Arabic language, which was translated into Latin in the 12th century under the title Algoritmi de numero Indorum. This title means "Algoritmi on the numbers of the Indians", where "Algoritmi" was the translator's Latinization of Al-Khwarizmi's name.[62] Al-Khwarizmi was the most widely read mathematician in Europe in the late Middle Ages, primarily through his other book, the Algebra.[63] In late medieval Latin, algorismus, the corruption of his name, simply meant the "decimal number system" that is still

the meaning of modern English algorism. In 17th-century French the word's form, but not its meaning, changed to algorithme. English adopted the French very soon afterwards, but it wasn't until the late 19th century that "Algorithm" took on the meaning that it has in modern English.[64]

Alternative etymology claims origin from the terms algebra in its late medieval sense of "Arabic arithmetics" and arithmos the Greek term for number (thus literally meaning "Arabic numbers" or "Arabic calculation"). Algorithms of Al-Kharizmi's works are not meant in their modern sense but as a type of repetitive calculus (here is to mention that his fundamental work known as algebra was originally titled "The Compendious Book on Calculation by Completion and Balancing" describing types of repetitive calculation and quadratic equations). In that sense, algorithms were known in Europe long before Al-Kharizmi. The oldest algorithm known today is the Euclidean algorithm (see also Extended Euclidean algorithm). Before the coining of the term algorithm the Greeks were calling them anthyphairesis literally meaning anti-subtraction or reciprocal subtraction (further reading here and here). Algorithms were known to the Greeks centuries before[65] Euclid. Instead of the word algebra the Greeks were using the term arithmetica (ἀριθμητική, i.e.in Diophantus' works the so-called "father of Algebra" - see also Diophantine equation and Eudoxos).

History: Development of the notion of "algorithm"

Ancient Greece

Algorithms were used in ancient Greece. Two examples are the Sieve of Eratosthenes, which was described in Introduction to Arithmetic by Nicomachus,[66][67]:Ch 9.2 and the Euclidean algorithm, which wasfirst described in Euclid's Elements (c. 300 BC).[67]:Ch 9.1

Origin

The word algorithm comes from the name of the 9th century Persian mathematician Abu Abdullah Muhammad ibn Musa Al-Khwarizmi, whose

work built upon that of the 7th-century Indian mathematician Brahmagupta. The word algorism originally referred only to the rulesof performing arithmetic using Hindu–Arabic numerals but evolved viaEuropean Latin translation of Al-Khwarizmi's name into algorithm by the 18th century. The use of the word evolved to include all definite procedures for solving problems or performing tasks.[68]

Discrete and distinguishable symbols

Tally-marks: To keep track of their flocks, their sacks of grain andtheir money the ancients used tallying: accumulating stones or marksscratched on sticks, or making discrete symbols in clay. Through theBabylonian and Egyptian use of marks and symbols, eventually Roman numerals and the abacus evolved (Dilson, p. 16–41). Tally marks appear prominently in unary numeral system arithmetic used in Turingmachine and Post–Turing machine computations.

Manipulation of symbols as "place holders" for numbers: algebra

The work of the ancient Greek geometers (Euclidean algorithm), the Indian mathematician Brahmagupta, and the Persian mathematician Al-Khwarizmi (from whose name the terms "algorism" and "algorithm" are derived), and Western European mathematicians culminated in Leibniz's notion of the calculus ratiocinator (ca 1680):

A good century and a half ahead of his time, Leibniz proposed analgebra of logic, an algebra that would specify the rules for manipulating logical concepts in the manner that ordinary algebra specifies the rules for manipulating numbers.[69]

Mechanical contrivances with discrete states

The clock: Bolter credits the invention of the weight-driven clock as "The key invention [of Europe in the Middle Ages]", in particularthe verge escapement[70] that provides us with the tick and tock of

a mechanical clock. "The accurate automatic machine"[71] led immediately to "mechanical automata" beginning in the 13th century and finally to "computational machines"—the difference engine and analytical engines of Charles Babbage and Countess Ada Lovelace, mid-19th century.[72] Lovelace is credited with the first creation of an algorithm intended for processing on a computer - Babbage's analytical engine, the first device considered a real Turing-complete computer instead of just a calculator - and is sometimes called "history's first programmer" as a result, though a full implementation of Babbage's second device would not be realized until decades after her lifetime.

Logical machines 1870—Stanley Jevons' "logical abacus" and "logical machine": The technical problem was to reduce Boolean equations whenpresented in a form similar to what are now known as Karnaugh maps. Jevons (1880) describes first a simple "abacus" of "slips of wood furnished with pins, contrived so that any part or class of the [logical] combinations can be picked out mechanically . . . More recently however I have reduced the system to a completely mechanical form, and have thus embodied the whole of the indirect process of inference in what may be called a Logical Machine" His machine came equipped with "certain moveable wooden rods" and "at the foot are 21 keys like those of a piano [etc] . . .". With this machine he could analyze a "syllogism or any other simple logical argument".[73]

This machine he displayed in 1870 before the Fellows of the Royal Society.[74] Another logician John Venn, however, in his 1881 Symbolic Logic, turned a jaundiced eye to this effort: "I have no high estimate myself of the interest or importance of what are sometimes called logical machines ... it does not seem to me that any contrivances at present known or likely to be discovered really deserve the name of logical machines"; see more at Algorithm characterizations. But not to be outdone he too presented "a plan somewhat analogous, I apprehend, to Prof. Jevon's abacus ... [And] [a]gain, corresponding to Prof. Jevons's logical machine, the following contrivance may be described. I prefer to call it merely alogical-diagram machine ... but I suppose that it could do very

completely all that can be rationally expected of any logical machine".[75]

Jacquard loom, Hollerith punch cards, telegraphy and telephony—the electromechanical relay: Bell and Newell (1971) indicate that the Jacquard loom (1801), precursor to Hollerith cards (punch cards, 1887), and "telephone switching technologies" were the roots of a tree leading to the development of the first computers.[76] By the mid-19th century the telegraph, the precursor of the telephone, was in use throughout the world, its discrete and distinguishable encoding of letters as "dots and dashes" a common sound. By the late19th century the ticker tape (ca 1870s) was in use, as was the use of Hollerith cards in the 1890 U.S. census. Then came the teleprinter (ca. 1910) with its punched-paper use of Baudot code on tape.

Telephone-switching networks of electromechanical relays (invented 1835) was behind the work of George Stibitz (1937), the inventor of the digital adding device. As he worked in Bell Laboratories, he observed the "burdensome' use of mechanical calculators with gears. "He went home one evening in 1937 intending to test his idea... Whenthe tinkering was over, Stibitz had constructed a binary adding device".[77]

Davis (2000) observes the particular importance of the electromechanical relay (with its two "binary states" open and closed):

It was only with the development, beginning in the 1930s, of electromechanical calculators using electrical relays, that machineswere built having the scope Babbage had envisioned."[78]

Mathematics during the 19th century up to the mid-20th century

Symbols and rules: In rapid succession the mathematics of George Boole (1847, 1854), Gottlob Frege (1879), and Giuseppe Peano (1888–1889) reduced arithmetic to a sequence of symbols manipulated by rules. Peano's The principles of arithmetic, presented by a new method (1888) was "the first attempt at an axiomatization of mathematics in a symbolic language".[79]

But Heijenoort gives Frege (1879) this kudos: Frege's is "perhaps the most important single work ever written in logic. ... in which we see a " 'formula language', that is a lingua characterica, a language written with special symbols, "for pure thought", that is, free from rhetorical embellishments ... constructed from specific symbols that are manipulated according to definite rules".[80] The work of Frege was further simplified and amplified by Alfred North Whitehead and Bertrand Russell in their Principia Mathematica (1910–1913).

The paradoxes: At the same time a number of disturbing paradoxes appeared in the literature, in particular the Burali-Forti paradox (1897), the Russell paradox (1902–03), and the Richard Paradox.[81] The resultant considerations led to Kurt Gödel's paper (1931)—he specifically cites the paradox of the liar—that completely reduces rules of recursion to numbers.

Effective calculability: In an effort to solve the Entscheidungsproblem defined precisely by Hilbert in 1928, mathematicians first set about to define what was meant by an "effective method" or "effective calculation" or "effective calculability" (i.e., a calculation that would succeed). In rapid succession the following appeared: Alonzo Church, Stephen Kleene andJ.B. Rosser's λ-calculus[82] a finely honed definition of "general recursion" from the work of Gödel acting on suggestions of Jacques Herbrand (cf. Gödel's Princeton lectures of 1934) and subsequent simplifications by Kleene.[83] Church's proof[84] that the Entscheidungsproblem was unsolvable, Emil Post's definition of effective calculability as a worker mindlessly following a list of instructions to move left or right through a sequence of rooms and

while there either mark or erase a paper or observe the paper and make a yes-no decision about the next instruction.[85] Alan Turing'sproof of that the Entscheidungsproblem was unsolvable by use of his "a- [automatic-] machine"[86]—in effect almost identical to Post's "formulation", J. Barkley Rosser's definition of "effective method" in terms of "a machine".[87] S. C. Kleene's proposal of a precursor to "Church thesis" that he called "Thesis I",[88] and a few years later Kleene's renaming his Thesis "Church's Thesis"[89] and proposing "Turing's Thesis".[90]

Emil Post (1936) and Alan Turing (1936–37, 1939)

Here is a remarkable coincidence of two men not knowing each other but describing a process of men-as-computers working on computations—and they yield virtually identical definitions.

Emil Post (1936) described the actions of a "computer" (human being)as follows:

"...two concepts are involved: that of a symbol space in which the work leading from problem to answer is to be carried out, and a fixed unalterable set of directions.

His symbol space would be

"a two way infinite sequence of spaces or boxes... The problem solver or worker is to move and work in this symbol space, being capable of being in, and operating in but one box at a time.... a box is to admit of but two possible conditions, i.e., being empty orunmarked, and having a single mark in it, say a vertical stroke.

"One box is to be singled out and called the starting point. ...a specific problem is to be given in symbolic form by a finite number of boxes [i.e., INPUT] being marked with a stroke.

Likewise the answer [i.e., OUTPUT] is to be given in symbolic form by such a configuration of marked boxes....

"A set of directions applicable to a general problem sets up a deterministic process when applied to each specific problem. This process terminates only when it comes to the direction of type (C ) [i.e., STOP]".[91] See more at Post–Turing machine

Alan Turing's statue at Bletchley Park.

Alan Turing's work[92] preceded that of Stibitz (1937); it is unknown whether Stibitz knew of the work of Turing. Turing's biographer believed that Turing's use of a typewriter-like model derived from a youthful interest: "Alan had dreamt of inventing typewriters as a boy; Mrs. Turing had a typewriter; and he could well have begun by asking himself what was meant by calling a typewriter 'mechanical'".[93] Given the prevalence of Morse code andtelegraphy, ticker tape machines, and teletypewriters we might conjecture that all were influences.

Turing—his model of computation is now called a Turing machine—begins, as did Post, with an analysis of a human computer that he whittles down to a simple set of basic motions and "states of mind".But he continues a step further and creates a machine as a model of computation of numbers.[94]

"Computing is normally done by writing certain symbols on paper.We may suppose this paper is divided into squares like a child's arithmetic book....I assume then that the computation is carried outon one-dimensional paper, i.e., on a tape divided into squares. I shall also suppose that the number of symbols which may be printed is finite....

"The behaviour of the computer at any moment is determined by the symbols which he is observing, and his "state of mind" at that moment. We may suppose that there is a bound B to the number of symbols or squares which the computer can observe at one moment. If he wishes to observe more, he must use successive observations. We will also suppose that the number of states of mind which need be taken into account is finite...

"Let us imagine that the operations performed by the computer tobe split up into 'simple operations' which are so elementary that itis not easy to imagine them further divided."[95]

Turing's reduction yields the following:

"The simple operations must therefore include:

"(a) Changes of the symbol on one of the observed squares

"(b) Changes of one of the squares observed to another square within L squares of one of the previously observed squares.

"It may be that some of these change necessarily invoke a change of state of mind. The most general single operation must therefore be taken to be one of the following:

"(A) A possible change (a) of symbol together with a possible change of state of mind.

"(B) A possible change (b) of observed squares, together with a possible change of state of mind"

"We may now construct a machine to do the work of this computer."[95]

A few years later, Turing expanded his analysis (thesis, definition)with this forceful expression of it:

"A function is said to be "effectively calculable" if its valuescan be found by some purely mechanical process. Though it is fairly easy to get an intuitive grasp of this idea, it is nevertheless desirable to have some more definite, mathematical expressible definition . . . [he discusses the history of the definition pretty much as presented above with respect to Gödel, Herbrand, Kleene, Church, Turing and Post] . . . We may take this statement literally,understanding by a purely mechanical process one which could be carried out by a machine. It is possible to give a mathematical description, in a certain normal form, of the structures of these machines. The development of these ideas leads to the author's definition of a computable function, and to an identification of computability † with effective calculability . . . .

"† We shall use the expression "computable function" to meana function calculable by a machine, and we let "effectively calculable" refer to the intuitive idea without particular identification with any one of these definitions".[96]

J. B. Rosser (1939) and S. C. Kleene (1943)

J. Barkley Rosser defined an 'effective [mathematical] method' in the following manner (italicization added):

"'Effective method' is used here in the rather special sense of a method each step of which is precisely determined and which is certain to produce the answer in a finite number of steps. With thisspecial meaning, three different precise definitions have been givento date. [his footnote #5; see discussion immediately below]. The simplest of these to state (due to Post and Turing) says essentially

that an effective method of solving certain sets of problems exists if one can build a machine which will then solve any problem of the set with no human intervention beyond inserting the question and (later) reading the answer. All three definitions are equivalent, soit doesn't matter which one is used. Moreover, the fact that all three are equivalent is a very strong argument for the correctness of any one." (Rosser 1939:225–6)

Rosser's footnote #5 references the work of (1) Church and Kleene and their definition of λ-definability, in particular Church's use of it in his An Unsolvable Problem of Elementary Number Theory (1936); (2) Herbrand and Gödel and their use of recursion in particular Gödel's use in his famous paper On Formally Undecidable Propositions of Principia Mathematica and Related Systems I (1931); and (3) Post (1936) and Turing (1936–7) in their mechanism-models ofcomputation.

Stephen C. Kleene defined as his now-famous "Thesis I" known as the Church–Turing thesis. But he did this in the following context (boldface in original):

"12. Algorithmic theories... In setting up a complete algorithmic theory, what we do is to describe a procedure, performable for each set of values of the independent variables, which procedure necessarily terminates and in such manner that from the outcome we can read a definite answer, "yes" or "no," to the question, "is the predicate value true?"" (Kleene 1943:273)

History after 1950

A number of efforts have been directed toward further refinement of the definition of "algorithm", and activity is on-going because of issues surrounding, in particular, foundations of mathematics (especially the Church–Turing thesis) and philosophy of mind

(especially arguments about artificial intelligence). For more, see Algorithm characterizations.

Key (cryptography)

From Wikipedia, the free encyclopedia

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In cryptography, a key is a piece of information (a parameter) that determines the functional output of a cryptographic algorithm or cipher. Without a key, the algorithm would produce no useful result.In encryption, a key specifies the particular transformation of plaintext into ciphertext, or vice versa during decryption. Keys arealso used in other cryptographic algorithms, such as digital signature schemes and message authentication codes.

Contents

1 Need for secrecy

2 Key scope

3 Ownership and revocation

4 Key sizes

5 Key choice

6 See also

7 References

Need for secrecy

In designing security systems, it is wise to assume that the detailsof the cryptographic algorithm are already available to the attacker. This is known as Kerckhoffs' principle — "only secrecy of the key provides security", or, reformulated as Shannon's maxim, "the enemy knows the system". The history of cryptography provides evidence that it can be difficult to keep the details of a widely used algorithm secret (see security through obscurity). A key is often easier to protect (it's typically a small piece of information) than an encryption algorithm, and easier to change if compromised. Thus, the security of an encryption system in most cases relies on some key being kept secret.

Trying to keep keys secret is one of the most difficult problems in practical cryptography; see key management. An attacker who obtains the key (by, for example, theft, extortion, dumpster diving or social engineering) can recover the original message from the encrypted data, and issue signatures.

Key scope

Keys are generated to be used with a given suite of algorithms, called a cryptosystem. Encryption algorithms which use the same key for both encryption and decryption are known as symmetric key algorithms. A newer class of "public key" cryptographic algorithms was invented in the 1970s. These asymmetric key algorithms use a pair of keys —or keypair— a public key and a private one. Public keys are used for encryption or signature verification; private onesdecrypt and sign. The design is such that finding out the private key is extremely difficult, even if the corresponding public key is known. As that design involves lengthy computations, a keypair is often used to exchange an on-the-fly symmetric key, which will only be used for the current session. RSA and DSA are two popular public-key cryptosystems; DSA keys can only be used for signing and verifying, not for encryption.

Ownership and revocation

Part of the security brought about by cryptography concerns confidence about who signed a given document, or who replies at the other side of a connection. Assuming that keys are not compromised, that question consists of determining the owner of the relevant public key. To be able to tell a key's owner, public keys are often enriched with attributes such as names, addresses, and similar identifiers. The packed collection of a public key and its attributes can be digitally signed by one or more supporters. In thePKI model, the resulting object is called a certificate and is signed by a certificate authority (CA). In the PGP model, it is still called a "key", and is signed by various people who personallyverified that the attributes match the subject.[1]

In both PKI and PGP models, compromised keys can be revoked. Revocation has the side effect of disrupting the relationship between a key's attributes and the subject, which may still be valid. In order to have a possibility to recover from such disruption, signers often use different keys for everyday tasks: Signing with an intermediate certificate (for PKI) or a subkey (for PGP) facilitates keeping the principal private key in an offline safe.

Key sizes

Main article: Key size

For the one-time pad system the key must be at least as long as the message. In encryption systems that use a cipher algorithm, messagescan be much longer than the key. The key must, however, be long enough so that an attacker cannot try all possible combinations.

A key length of 80 bits is generally considered the minimum for strong security with symmetric encryption algorithms. 128-bit keys are commonly used and considered very strong. See the key size article for a more complete discussion.

The keys used in public key cryptography have some mathematical structure. For example, public keys used in the RSA system are the product of two prime numbers. Thus public key systems require longerkey lengths than symmetric systems for an equivalent level of security. 3072 bits is the suggested key length for systems based onfactoring and integer discrete logarithms which aim to have securityequivalent to a 128 bit symmetric cipher. Elliptic curve cryptography may allow smaller-size keys for equivalent security, but these algorithms have only been known for a relatively short time and current estimates of the difficulty of searching for their keys may not survive. As of 2004, a message encrypted using a 109-bit key elliptic curve algorithm had been broken by brute force.[2] The current rule of thumb is to use an ECC key twice as long as the symmetric key security level desired. Except for the random one-timepad, the security of these systems has not (as of 2008) been proven mathematically, so a theoretical breakthrough could make everything one has encrypted an open book. This is another reason to err on theside of choosing longer keys.

Key choice

To prevent a key from being guessed, keys need to be generated trulyrandomly and contain sufficient entropy. The problem of how to safely generate truly random keys is difficult, and has been addressed in many ways by various cryptographic systems. There is a RFC on generating randomness (RFC 4086, Randomness Requirements for Security). Some operating systems include tools for "collecting" entropy from the timing of unpredictable operations such as disk drive head movements. For the production of small amounts of keying material, ordinary dice provide a good source of high quality randomness.

When a password (or passphrase) is used as an encryption key, well-designed cryptosystems first run it through a key derivation function which adds a salt and compresses or expands it to the key length desired, for example by compressing a long phrase into a 128-bit value suitable for use in a block cipher.

Sometimes, metadata is included in purchased media which records information such as the purchaser's name, account information, or email address. Also included may be the file's publisher, author, creation date, download date, and various notes. This information isnot embedded in the played content, like a watermark, but is kept separate, but within the file or stream.

As an example, metadata is used in media purchased from Apple's iTunes Store for DRM-free as well as DRM-restricted versions of their music or videos. This information is included as MPEG standardmetadata.[71][72]

Watermarks

Digital watermarks are features of media that are added during production or distribution. Digital watermarks involve data that is arguably steganographically embedded within the audio or video data.

Watermarks can be used for different purposes that may include:

recording the copyright owner

recording the distributor

recording the distribution chain

identifying the purchaser of the music

Watermarks are not complete DRM mechanisms in their own right, but are used as part of a system for copyright enforcement, such as helping provide prosecution evidence for purely legal avenues of rights management, rather than direct technological restriction. Some programs used to edit video and/or audio may distort, delete, or otherwise interfere with watermarks. Signal/modulator-carrier chromatography may also separate watermarks from original audio or detect them as glitches. Additionally, comparison of two separately

obtained copies of audio using simple, home-grown algorithms can often reveal watermarks. New methods of detection are currently under investigation by both industry and non-industry researchers.

Streaming media services

Since the late-2000s the trend in media consumption has been towardsrenting content using online streaming services, for example Spotifyfor music and Netflix for video content. Copyright holders often require that these services protect the content they licence using DRM mechanisms.

Laws regarding DRM

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The examples and perspective in this section may not represent a worldwide view of the subject. Please improve this article and discuss the issue on the talk page. (November 2012)

Article 11 of the 1996 WIPO Copyright Treaty (WCT), requires nationsparty to the treaties to enact laws against DRM circumvention, and has been implemented in most member states of the World IntellectualProperty Organization. The American implementation is the Digital Millennium Copyright Act (DMCA), while in Europe the treaty has beenimplemented by the 2001 European directive on copyright, which requires member states of the European Union to implement legal protections for technological prevention measures. In 2006, the lower house of the French parliament adopted such legislation as part of the controversial DADVSI law, but added that protected DRM techniques should be made interoperable, a move which caused widespread controversy in the United States. The Tribunal de grande instance de Paris concluded in 2006, that the complete blocking of any possibilities of making private copies was an impermissible behaviour under French copyright law.[8]

Digital Millennium Copyright Act

Main article: Digital Millennium Copyright Act

The Digital Millennium Copyright Act (DMCA) is an amendment to United States copyright law, passed unanimously on May 14, 1998, which criminalizes the production and dissemination of technology that allows users to circumvent technical copy-restriction methods. Under the Act, circumvention of a technological measure that effectively controls access to a work is illegal if done with the primary intent of violating the rights of copyright holders.[verification needed] (For a more detailed analysis of the statute, see WIPO Copyright and Performances and Phonograms Treaties Implementation Act.)

Reverse engineering of existing systems is expressly permitted underthe Act under specific conditions. Under the reverse engineering safe harbor, circumvention necessary to achieve interoperability with other software is specifically authorized. See 17 U.S.C. Sec. 1201(f). Open-source software to decrypt content scrambled with the Content Scrambling System and other encryption techniques presents an intractable problem with the application of the Act. Much dependson the intent of the actor. If the decryption is done for the purpose of achieving interoperability of open source operating systems with proprietary operating systems, the circumvention would be protected by Section 1201(f) the Act. Cf., Universal City Studios, Inc. v. Corley, 273 F.3d 429 (2d Cir. 2001) at notes 5 and 16. However, dissemination of such software for the purpose of violating or encouraging others to violate copyrights has been held illegal. See Universal City Studios, Inc. v. Reimerdes, 111 F. Supp.2d 346 (S.D.N.Y. 2000).

The DMCA has been largely ineffective in protecting DRM systems,[73]as software allowing users to circumvent DRM remains widely available. However, those who wish to preserve the DRM systems have attempted to use the Act to restrict the distribution and development of such software, as in the case of DeCSS.

Although the Act contains an exception for research, the exception is subject to vague qualifiers that do little to reassure researchers. Cf., 17 U.S.C. Sec. 1201(g). The DMCA has had an impacton cryptography, because many[who?] fear that cryptanalytic researchmay violate the DMCA. The arrest of Russian programmer Dmitry Sklyarov in 2001, for alleged infringement of the DMCA, was a highlypublicized example of the law's use to prevent or penalize development of anti-DRM measures. Sklyarov was arrested in the United States after a presentation at DEF CON, and subsequently spent several months in jail. The DMCA has also been cited as chilling to non-criminal inclined users, such as students of cryptanalysis (including, in a well-known instance, Professor Feltenand students at Princeton[74]); security consultants, such as Netherlands based Niels Ferguson, who declined to publish vulnerabilities he discovered in Intel's secure-computing scheme dueto fear of being arrested under the DMCA when he travels to the US; and blind or visually impaired users of screen readers or other assistive technologies.[75]

European Union

On 22 May 2001, the European Union passed the EU Copyright Directive, an implementation of the 1996 WIPO Copyright Treaty, thataddressed many of the same issues as the DMCA.

On 25 April 2007, the European Parliament supported the first directive of EU, which aims to harmonize criminal law in the member states. It adopted a first reading report on harmonizing the national measures for fighting copyright abuse. If the European Parliament and the Council approve the legislation, the submitted directive will oblige the member states to consider a crime a violation of international copyright committed with commercial purposes. The text suggests numerous measures: from fines to imprisonment, depending on the gravity of the offense. The EP members supported the Commission motion, changing some of the texts.They excluded patent rights from the range of the directive and decided that the sanctions should apply only to offenses with

commercial purposes. Copying for personal, non-commercial purposes was also excluded from the range of the directive.

In 2012, the Court of Justice of the European Union ruled in favor of reselling copyrighted games, prohibiting any preventative action that would prevent such transaction.[76] The court said that "The first sale in the EU of a copy of a computer program by the copyright holder or with his consent exhausts the right of distribution of that copy in the EU. A rightholder who has marketed a copy in the territory of a Member State of the EU thus loses the right to rely on his monopoly of exploitation in order to oppose theresale of that copy."[77]

In 2014, the Court of Justice of the European Union ruled that circumventing DRM on game devices may be legal under some circumstances, limiting the legal protection to only cover technological measures intended to prevent or eliminate unauthorisedacts of reproduction, communication, public offer or distribution.[78][79]

International issues

In Europe, there are several ongoing dialog activities that are characterized by their consensus-building intention:

Workshop on Digital Rights Management of the World Wide Web Consortium (W3C), January 2001.[80]

Participative preparation of the European Committee for Standardization/Information Society Standardization System (CEN/ISSS) DRM Report, 2003 (finished).[81]

DRM Workshops of Directorate-General for Information Society andMedia (European Commission) (finished), and the work of the DRM working groups (finished), as well as the work of the High Level Group on DRM (ongoing).[82]

Consultation process of the European Commission, DG Internal Market, on the Communication COM(2004)261 by the European Commissionon "Management of Copyright and Related Rights" (closed).[83]

The INDICARE project is an ongoing dialogue on consumer acceptability of DRM solutions in Europe. It is an open and neutral platform for exchange of facts and opinions, mainly based on articles by authors from science and practice.

The AXMEDIS project is a European Commission Integrated Project of the FP6. The main goal of AXMEDIS is automating the content production, copy protection and distribution, reducing the related costs and supporting DRM at both B2B and B2C areas harmonizing them.

The Gowers Review of Intellectual Property is the result of a commission by the British Government from Andrew Gowers, undertaken in December 2005, and published in 2006, with recommendations regarding copyright term, exceptions, orphaned works, and copyright enforcement.

Israel

Israel is a signatory to, but has not yet ratified, the WIPO Copyright Treaty. Israeli law does not currently expressly prohibit the circumvention of technological measures used to implement digital rights management. The Israeli Ministry of Justice proposed a bill to prohibit such activities in June 2012, but the bill was not passed by the Knesset. In September 2013, the Supreme Court ruled that the current copyright law could not be interpreted to prohibit the circumvention of digital rights management, though the Court left open the possibility that such activities could result inliability under the law of unjust enrichment.[84]

Opposition to DRM

Many organizations, prominent individuals, and computer scientists are opposed to DRM. Two notable DRM critics are John Walker, as expressed for instance, in his article "The Digital Imprimatur: How

Big brother and big media can put the Internet genie back in the bottle",[85] and Richard Stallman in his article The Right to Read[86] and in other public statements: "DRM is an example of a malicious feature – a feature designed to hurt the user of the software, and therefore, it's something for which there can never betoleration".[87] Stallman also believes that using the word "rights"is misleading and suggests that the word "restrictions", as in "Digital Restrictions Management", be used instead.[88][89][90][91][92] This terminology has since been adopted by many other writers and critics unconnected with Stallman.[93][94][95]

Other prominent critics of DRM include Professor Ross Anderson of Cambridge University, who heads a British organization which opposesDRM and similar efforts in the UK and elsewhere, and Cory Doctorow, a writer and technology blogger.[96]

There have been numerous others who see DRM at a more fundamental level. This is similar to some of the ideas in Michael H. Goldhaber's presentation about "The Attention Economy and the Net" at a 1997 conference on the "Economics of Digital Information".[97] (sample quote from the "Advice for the Transition" section of that presentation:[97] "If you can't figure out how to afford it without charging, you may be doing something wrong.")

The EFF and similar organizations such as FreeCulture.org also hold positions which are characterized as opposed to DRM.[citation needed]

The Foundation for a Free Information Infrastructure has criticized DRM's impact as a trade barrier from a free market perspective.[citation needed]

The final version of the GNU General Public License version 3, as released by the Free Software Foundation, has a provision that

'strips' DRM of its legal value, so people can break the DRM on GPL software without breaking laws like the DMCA. Also, in May 2006, theFSF launched a "Defective by Design" campaign against DRM.[98][99]

Creative Commons provides licensing options encouraging the expansion of and building upon creative work without the use of DRM.[100] In addition, the use of DRM by a licensee to restrict the freedoms granted by a Creative Commons license is a breach of the Baseline Rights asserted by each license.[101]

Bill Gates spoke about DRM at CES in 2006. According to him, DRM is not where it should be, and causes problems for legitimate consumerswhile trying to distinguish between legitimate and illegitimate users.[102]

According to Steve Jobs, Apple opposes DRM music after a public letter calling its music labels to stop requiring DRM on its iTunes Store. As of January 6, 2009, the iTunes Store is DRM-free for songs.[103]

Defective by Design member protesting DRM on May 25, 2007.

The Norwegian consumer rights organization "Forbrukerrådet" complained to Apple Inc. in 2007, about the company's use of DRM in,and in conjunction with, its iPod and iTunes products. Apple was accused of restricting users' access to their music and videos in anunlawful way, and of using EULAs which conflict with Norwegian consumer legislation. The complaint was supported by consumers' ombudsmen in Sweden and Denmark, and is currently being reviewed in the EU. Similarly, the United States Federal Trade Commission held hearings in March 2009, to review disclosure of DRM limitations to customers' use of media products.[104]

DRM opponents argue that the presence of DRM violates existing private property rights and restricts a range of heretofore normal

and legal user activities. A DRM component would control a device a user owns (such as a digital audio player) by restricting how it mayact with regards to certain content, overriding some of the user's wishes (for example, preventing the user from burning a copyrighted song to CD as part of a compilation or a review). Doctorow has described this possibility as "the right to make up your own copyright laws".[105]

An example of this restriction to legal user activities may be seen in Microsoft's Windows Vista operating system in which content usinga Protected Media Path is disabled or degraded depending on the DRM scheme's evaluation of whether the hardware and its use are 'secure'.[106] All forms of DRM depend on the DRM enabled device (e.g., computer, DVD player, TV) imposing restrictions that (at least by intent) cannot be disabled or modified by the user. Key issues around DRM such as the right to make personal copies, provisions for persons to lend copies to friends, provisions for service discontinuance, hardware agnosticism, software and operatingsystem agnosticism,[107] contracts for public libraries, and customers' protection against one-side amendments of the contract bythe publisher have not been fully addressed.(see references 80–89) It has also been pointed out that it is entirely unclear whether owners of content with DRM are legally permitted to pass on their property as inheritance to another person.[108]

Tools like FairUse4WM have been created to strip Windows Media of DRM restrictions.[109]

Valve Corporation president Gabe Newell also stated "most DRM strategies are just dumb" because they only decrease the value of a game in the consumer's eyes. Newell suggests that the goal should instead be "[creating] greater value for customers through service value".[110]

At the 2012 Game Developers Conference, the CEO of CD Projekt Red, Marcin Iwinski, announced that the company will not use DRM in any of its future releases. Iwinski stated of DRM, "it's just over-complicating things. We release the game. It's cracked in two hours,it was no time for Witcher 2. What really surprised me is that the pirates didn't use the GOG version, which was not protected. They took the SecuROM retail version, cracked it and said 'we cracked it'– meanwhile there's a non-secure version with a simultaneous release. You'd think the GOG version would be the one floating around." Iwinski added after the presentation, "DRM does not protectyour game. If there are examples that it does, then people maybe should consider it, but then there are complications with legit users."[111]

Bruce Schneier argues that digital copy prevention is futile: "What the entertainment industry is trying to do is to use technology to contradict that natural law. They want a practical way to make copying hard enough to save their existing business. But they are doomed to fail."[112] He has also described trying to make digital files uncopyable as being like "trying to make water not wet".[113] The creators of StarForce also take this stance, stating that "The purpose of copy protection is not making the game uncrackable – it is impossible."[114]

The Association for Computing Machinery and the Institute of Electrical and Electronics Engineers have historically opposed DRM, even going so far as to name AACS as a technology "most likely to fail" in an issue of IEEE Spectrum.[115]

DRM-free works

Label proposed by the Free Software Foundation for DRM-free works

In reaction to opposition to DRM, many publishers and artists label their works as "DRM-free". Major companies that have done so includethe following:

Apple Inc. sold DRM content on their iTunes Store when it started 2003, but made music DRM-free after April 2007[116] and has been labeling all music as "DRM-Free" since January 2009.[117] The music still carries a digital watermark to identify the purchaser. Other works sold on iTunes such as e-books, movies, TV shows, audiobooks and apps continue to be protected by DRM.[118]

All music sold on Google Play is DRM free.

GOG.com, a digital distributor started in 2008, specialized in the distribution of PC video games. While most other digital distribution services allow various forms of DRM (or have them embedded) gog.com has a strict non-DRM policy.[119]

Tor Books, a major publisher of science fiction and fantasy books, started selling DRM-free e-books in July 2012.[120] Smaller e-book publishers such as O'Reilly Media and Baen Books had already forgone DRM previously.

Since 2014, Comixology, which distributes digital comics, allowsrights holders to provide the option of a DRM-free download of purchased comics. Publishers which allow this include Image Comics, Dynamite Entertainment, Zenescope Entertainment, Thrillbent and Top Shelf Productions.[121]

The Free Software Foundation does a DRM-free guide which includes GOG and Vimeo on Demand.[122]

Shortcomings

DRM server and Internet outages

Many DRM systems require authentication with an online server. Whenever the server goes down, or a region or country experiences anInternet outage, it effectively locks out people from registering orusing the material. This is especially true for a product that requires a persistent online authentication, where, for example, a successful DDoS attack on the server would essentially make all copies of the material unusable.

Methods to bypass DRM

There are many methods to bypass DRM control on audio, video, and ebook content.

DRM bypass methods for audio and video content

One simple method to bypass DRM on audio files is to burn the content to an audio CD and then rip it into DRM-free files. Some software products simplify and automate this burn-rip process by allowing the user to burn music to a CD-RW disc or to a Virtual CD-Rdrive, then automatically ripping and encoding the music, and automatically repeating this process until all selected music has been converted, rather than forcing the user to do this one CD (72–80 minutes worth of music) at a time.

Many software programs have been developed that intercept the data stream as it is decrypted out of the DRM-restricted file, and then use this data to construct a DRM-free file. These programs require adecryption key. Programs that do this for DVDs, HD DVDs, and Blu-rayDiscs include universal decryption keys in the software itself. Programs that do this for TiVo ToGo recordings, iTunes audio, and PlaysForSure songs, however, rely on the user's own key — that is, they can only process content that the user has legally acquired under his or her own account.

Another method is to use software to record the signals being sent through the audio or video cards, or to plug analog recording devices into the analog outputs of the media player. These techniques utilize the "analog hole."

Analog hole

Main article: Analog hole

All forms of DRM for audio and visual material (excluding interactive materials, e.g., videogames) are subject to the analog

hole, namely that in order for a viewer to play the material, the digital signal must be turned into an analog signal containing lightand/or sound for the viewer, and so available to be copied as no DRMis capable of controlling content in this form. In other words, a user could play a purchased audio file while using a separate program to record the sound back into the computer into a DRM-free file format.

All DRM to date can therefore be bypassed by recording this signal and digitally storing and distributing it in a non DRM limited form,by anyone who has the technical means of recording the analog stream. Furthermore, the analog hole vulnerability cannot be overcome without the additional protection of externally imposed restrictions, such as legal regulations, because the vulnerability is inherent to all analog means of transmission.[123] However, the conversion from digital to analog and back is likely to force a lossof quality, particularly when using lossy digital formats. HDCP is an attempt to plug the analog hole, although it is largely ineffective.[124][125]

Asus released a soundcard which features a function called "Analog Loopback Transformation" to bypass the restrictions of DRM. This feature allows the user to record DRM-restricted audio via the soundcard's built-in analog I/O connection.[126][127]

In order to prevent this exploit there has been some discussions between copyright holders and manufacturers of electronics capable of playing such content, to no longer include analog connectivity intheir devices. The movement dubbed as "Analog Sunset" has seen a steady decline in analog output options on most Blu-ray devices manufactured after 2010.

DRM on general computing platforms

Many of the DRM systems in use are designed to work on general purpose computing hardware, such as desktop PCs, apparently because

this equipment is felt to be a major contributor to revenue loss from disallowed copying.[citation needed] Large commercial copyrightinfringers ("pirates") avoid consumer equipment,[citation needed] solosses from such infringers will not be covered by such provisions.

Such schemes, especially software based ones, can never be wholly secure since the software must include all the information necessaryto decrypt the content, such as the decryption keys. An attacker will be able to extract this information, directly decrypt and copy the content, which bypasses the restrictions imposed by a DRM system.[96]

DRM on purpose-built hardware

Many DRM schemes use encrypted media which requires purpose-built hardware to hear or see the content. This appears to ensure that only licensed users (those with the hardware) can access the content. It additionally tries to protect a secret decryption key from the users of the system.

While this in principle can work, it is extremely difficult to buildthe hardware to protect the secret key against a sufficiently determined adversary. Many such systems have failed in the field. Once the secret key is known, building a version of the hardware that performs no checks is often relatively straightforward. In addition user verification provisions are frequently subject to attack, pirate decryption being among the most frequented ones.

A common real-world example can be found in commercial direct broadcast satellite television systems such as DirecTV and Malaysia's Astro. The company uses tamper-resistant smart cards to store decryption keys so that they are hidden from the user and the satellite receiver. However, the system has been compromised in the past, and DirecTV has been forced to roll out periodic updates and replacements for its smart cards.

Watermarks

Watermarks can often be removed, although degradation of video or audio can occur.

Undecrypted copying failure

Mass piracy of hard copies does not necessarily need DRM to be decrypted or removed, as it can be achieved by bit-perfect copying of a legally obtained medium without accessing the decrypted content. Additionally, still-encrypted disk images can be distributed over the Internet and played on legitimately licensed players.

Obsolescence

When standards and formats change, it may be difficult to transfer DRM-restricted content to new media. Additionally, any system that requires contact with an authentication server is vulnerable to thatserver becoming unavailable, as happened[128] in 2007, when videos purchased from Major League Baseball (mlb.com) prior to 2006, becameunplayable due to a change to the servers that validate the licenses.

Amazon PDF and LIT ebooks

In August 2006, Amazon stopped selling DRMed PDF and .LIT formatebooks. Customers were unable to download purchased ebooks 30 days after that date, losing access to their purchased content on new devices.[129][130]

Microsoft Zune

When Microsoft introduced their Zune[131] media player in 2006, it did not support content that uses Microsoft's own PlaysForSure DRM scheme they had previously been selling. The EFF calls this "a raw deal".[132]

MSN Music

In April 2008, Microsoft sent an email to former customers of the now-defunct MSN Music store:

As of August 31, 2008, we will no longer be able to support the retrieval of license keys for the songs you purchased from MSN Music or the authorization of additional computers. You will need toobtain a license key for each of your songs downloaded from MSN Music on any new computer, and you must do so before August 31, 2008. If you attempt to transfer your songs to additionalCryptosystem

From Wikipedia, the free encyclopedia

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In cryptography cryptosystem refers to a suite of cryptographic algorithms needed to implement a particular security service, most commonly for achieving confidentiality (encryption).[1]

Typically, a cryptosystem consists of three algorithms: one for key generation, one for encryption, and one for decryption. The term cipher (sometimes cypher) is often used to refer to a pair of algorithms, one for encryption and one for decryption. Therefore, the term "cryptosystem" is most often used when the key generation algorithm is important. For this reason, the term "cryptosystem" is commonly used to refer to public key techniques; however both "cipher" and "cryptosystem" are used for symmetric key techniques.

Formal definition

Mathematically, a cryptosystem or encryption scheme can be defined as a tuple (\mathcal{P},\mathcal{C},\mathcal{K},\mathcal{E},\mathcal{D}) with the following properties.

\mathcal{P} is a set called the "plaintext space". Its elements are called plaintexts.

\mathcal{C} is a set called the "ciphertext space". Its elementsare called ciphertexts.

\mathcal{K} is a set called the "key space". Its elements are called keys.

\mathcal{E} = \{ E_k : k \in \mathcal{K} \} is a set of functions E_k : \mathcal{P} \rightarrow \mathcal{C}. Its elements are called "encryption functions".

\mathcal{D} = \{ D_k : k \in \mathcal{K} \} is a set of functions D_k : \mathcal{C} \rightarrow \mathcal{P}. Its elements are called "decryption functions".

For each e \in \mathcal{K}, there is d \in \mathcal{K} such that D_d(E_e(p)) = p for all p \in \mathcal{P}.[2]

Note; typically this definition is modified in order to distinguish an encryption scheme as being either a symmetric-key or public-key type of cryptosystem. computers after August 31, 2008, those songs will not successfully play.[133]

Authentication

From Wikipedia, the free encyclopedia

Contents

1 Methods

2 Factors and identity

2.1 Two-factor authentication