8/3/2019 Crypt Final Ppt
1/19
UDITA SHAH
ECE-B
8TH SEMESTER
8/3/2019 Crypt Final Ppt
2/19
WHAT IS CRYPTOGRAPHY?y Cryptography is the practice and study of hiding information.
Modern cryptography intersects the disciplines of mathematics,
computer science and electrical engineering.
y Cryptanalysis -term used for the study of methods for obtaining
the meaning of encrypted information without access to the key
normally required to do so; i.e., it is the study of how to crack
encryption algorithms or their implementations.
y A basic task in cryptography is to enable users to communicate
securely over an insecure channel in a way that guarantees their
transmissions' privacy and authenticity.
8/3/2019 Crypt Final Ppt
3/19
8/3/2019 Crypt Final Ppt
4/19
TYPES OF CRYPTOGRAPHY
8/3/2019 Crypt Final Ppt
5/19
SECRET KEY CRYPTOGRAPHY
y Also known as symmetric key cryptography.
y Single key used to encrypt and decrypt.
y Key must be known to both the parties.
y Method works well only for limited number of people.
8/3/2019 Crypt Final Ppt
6/19
Plaintext encryption Cipher text decryption plaintext
8/3/2019 Crypt Final Ppt
7/19
PUBLIC KEY CRYPTOGRAPHY
y Also calledasymmetric encryption.
y Uses a pair of keys for encryption anddecryption.
y Has 2 keys-
1. private key (a secret)
2. public key (well known)
8/3/2019 Crypt Final Ppt
8/19
plaintext encryption Cipher text decryption Plaintext
Public key Private key
8/3/2019 Crypt Final Ppt
9/19
DIGITAL SIGNAL ALGORITHM Public key cryptography is also used to provide digitalPublic key cryptography is also used to provide digital
signatures.signatures.
signingsigningPlaintextPlaintext------------------------------ signed messagesigned message
private keyprivate key
verificationverificationsigned messagesigned message -------------------------------------- plaintextplaintext
public keypublic key
8/3/2019 Crypt Final Ppt
10/19
TYPES OF ATTACK
y Passive Attack:
Carried out by a PassiveAttacker who can only
readthe secret information being exchanged.
yActive Attack:
Carried
out
by anA
ctiv
eIn
tru
der who can r
ea
dand modifythe secret information.
8/3/2019 Crypt Final Ppt
11/19
Passive Attacks
8/3/2019 Crypt Final Ppt
12/19
Active Attacks
8/3/2019 Crypt Final Ppt
13/19
WHY DO WE NEED CRYPTOGRAPHY?
Computers are used by millions of people for manypurposes-
BankingShopping
Tax return
Military
Student records
8/3/2019 Crypt Final Ppt
14/19
y Privacy is very important in all these applications. Itis a service usedto keep the content of informationfrom all butthose authorizedto posses it.
y Data integrity is a service which addresses the
unauthorized alteration ofdata.yAuthentication is a service relatedto identification.
Two parties entering into a communication shouldidentifyeach other.
y Non- repudiation is a service which prevents anentity from denying previous commitments or actions.
8/3/2019 Crypt Final Ppt
15/19
ADVANTAGES AND DISADVANTAGES
ADVANTAGES:
y The biggest advantage of public key cryptographyis the secure nature ofthe private key. In fact, itnever needs to betransmitted or revealedtoanyone.
y Itenables the use ofdigital signatures, which is avery securetechnique of signature authorization.
8/3/2019 Crypt Final Ppt
16/19
DISADVANTAGES:
y Transmission time for documents encrypted usingpublic key cryptography are significantly slowerthen symmetric cryptography.
y Public key cryptography is susceptibletoimpersonation attacks.
y public-key cryptography is usually not necessary ina single-user environment. For example, if youwantto keep your personal files encrypted, youcan do so with any secret- keyencryptionalgorithm using, say, your personal password asthe secret key.
8/3/2019 Crypt Final Ppt
17/19
HOW CRYPTO SYSTEM
FAIL??y Crypto system fails by falling into either ofthetwo
categories, in the cipher itself or in the operatingenvironment.
The cipher is the mechanism by which wetransferplain textto cipher text.
The operating environment in which code is usedincludes the rules of handling plaintext,distribution
of keys, roles of people involve and physical protectiongiven to various elements.
Cracking a code involves either an attack on code itselfor on way it is used.
8/3/2019 Crypt Final Ppt
18/19
CONCLUSION
Cryptography has undergonetremendous development
sincethedays it had comeinto existence some 4000years ago.Developments arealso taking place in the areaofdigital Steganography,
quantum cryptography,etc.
8/3/2019 Crypt Final Ppt
19/19
THANKYOU !