Cryptography and Network Security Chapter 1. Roadmap Cryptographic algorithms and protocols Symmetric ciphers Symmetric ciphers Asymmetric encryption.

Cryptography and Cryptography and Network SecurityNetwork Security

Chapter 1Chapter 1

RoadmapRoadmap

Cryptographic algorithms and protocolsCryptographic algorithms and protocols Symmetric ciphersSymmetric ciphers Asymmetric encryptionAsymmetric encryption Data integrity: hash functionsData integrity: hash functions Authentication Authentication

Mutual TrustMutual Trust Computer SecurityComputer Security Network SecurityNetwork Security

Computer SecurityComputer Security Need for SecurityNeed for Security NIST definition of Computer SecurityNIST definition of Computer Security

The protection afforded to an automated The protection afforded to an automated information system in order to attain the information system in order to attain the applicable objectives of preserving the applicable objectives of preserving the integrity, availability and confidentiality of integrity, availability and confidentiality of information system resources (includes information system resources (includes hardware, software, firmware, hardware, software, firmware, information/data, and telecommunications)information/data, and telecommunications)

This definition introduces 3 This definition introduces 3 key objectives:key objectives:

Confidentiality: Confidentiality:

Data confidentiality, Privacy.Data confidentiality, Privacy.

Integrity:Integrity:

Data Integrity, System Integrity.Data Integrity, System Integrity.

AvailabilityAvailability

Key Security ConceptsKey Security Concepts

Additional Concepts: Authenticity, Accountability

Examples of Security Examples of Security ViolationsViolations

Capturing a file(by C) during transmission Capturing a file(by C) during transmission from A to Bfrom A to B

Message InterceptionMessage Interception Faking source identityFaking source identity Delaying the messageDelaying the message Deny having sent the messageDeny having sent the message

Levels of ImpactLevels of Impact

can define 3 levels of impact from a can define 3 levels of impact from a security breachsecurity breach

LowLow ModerateModerate HighHigh

Examples of Security Examples of Security RequirementsRequirements

confidentiality – student gradesconfidentiality – student grades integrity – patient informationintegrity – patient information availability – authentication serviceavailability – authentication service

Computer Security ChallengesComputer Security Challenges

1.1. not simplenot simple2.2. must consider potential attacksmust consider potential attacks3.3. procedures used counter-intuitiveprocedures used counter-intuitive4.4. involve algorithms and secret infoinvolve algorithms and secret info5.5. must decide where to deploy mechanismsmust decide where to deploy mechanisms6.6. battle of wits between attacker / adminbattle of wits between attacker / admin7.7. not perceived on benefit until failsnot perceived on benefit until fails8.8. requires regular monitoringrequires regular monitoring9.9. too often an after-thoughttoo often an after-thought10.10. regarded as impediment to using systemregarded as impediment to using system

OSI Security ArchitectureOSI Security Architecture ITU-T X.800 “Security Architecture for OSI”ITU-T X.800 “Security Architecture for OSI”

defines a systematic way of defining and defines a systematic way of defining and providing security requirements.providing security requirements.

For us it provides a useful, if abstract, For us it provides a useful, if abstract, overview of concepts we will studyoverview of concepts we will study

Aspects of SecurityAspects of Security

consider 3 aspects of information security:consider 3 aspects of information security: security attacksecurity attack security mechanismsecurity mechanism security servicesecurity service

note termsnote terms threat threat –– a a potential for violation of securitypotential for violation of security attack attack –– an an assault on system security, a assault on system security, a

deliberate attempt to evade security servicesdeliberate attempt to evade security services

Passive AttacksPassive Attacks

Release of Message Contents

Active AttacksActive Attacks

Active AttacksActive Attacks

(b)Replay

Security ServiceSecurity Service

enhance security of data processing systems enhance security of data processing systems and information transfers of an organizationand information transfers of an organization

intended to counter security attacksintended to counter security attacks using one or more security mechanisms using one or more security mechanisms often replicates functions normally associated often replicates functions normally associated

with physical documentswith physical documents• which, for example, have signatures, dates; need which, for example, have signatures, dates; need

protection from disclosure, tampering, or protection from disclosure, tampering, or destruction; be notarized or witnessed; be destruction; be notarized or witnessed; be recorded or licensedrecorded or licensed

Security ServicesSecurity Services

X.800:X.800:““a service provided by a protocol layer of a service provided by a protocol layer of

communicating open systems, which ensures communicating open systems, which ensures adequate security of the systems or of data adequate security of the systems or of data transfers”transfers”

RFC 2828:RFC 2828:““a processing or communication service a processing or communication service

provided by a system to give a specific kind of provided by a system to give a specific kind of protection to system resources”protection to system resources”

Security Services (X.800)Security Services (X.800) AuthenticationAuthentication - - assurance that communicating assurance that communicating

entity is the one claimedentity is the one claimed peer-entity peer-entity data origin authenticationdata origin authentication

Access ControlAccess Control - - prevention of the prevention of the unauthorized use of a resourceunauthorized use of a resource

Data ConfidentialityData Confidentiality – –protection of data from protection of data from unauthorized disclosureunauthorized disclosure

• Connection Confidentiality• Connectionless Confidentiality• Selective-Field Confidentiality• Traffic-Flow Confidentiality

Data IntegrityData Integrity::

• Connection Integrity with Recovery• Connection Integrity without Recovery• Selective-Field Connection Integrity• Connectionless Integrity• Selective-Field Connectionless Integrity

Non-RepudiationNon-Repudiation - - protection against protection against denial by one of the parties in a denial by one of the parties in a communicationcommunication

• Nnrepudiation, Origin• Nonrepudiation, Destination

Security MechanismSecurity Mechanism

Method or technique used to provide Method or technique used to provide security.security.

Feature designed to detect, prevent, or Feature designed to detect, prevent, or recover from a security attackrecover from a security attack

No single mechanism will support all No single mechanism will support all security services requiredsecurity services required

Security Mechanisms (X.800)Security Mechanisms (X.800)

specific security mechanisms:specific security mechanisms: Encipherment (reversible, irreversible), digital Encipherment (reversible, irreversible), digital

signatures, access controls, data integrity, signatures, access controls, data integrity, authentication exchange, traffic padding, authentication exchange, traffic padding, routing control, notarizationrouting control, notarization

pervasive security mechanisms:pervasive security mechanisms: trusted functionality, security labels, event trusted functionality, security labels, event

detection, security audit trails, security detection, security audit trails, security recoveryrecovery

        Mechanism      

    Digital Access Data Authentication Traffic Routing  

Service Encipherment Signature Control Integrity Exchange Padding ControlNotariza

tion

Peer Entity Authentication

Data Origin Authentication

Access Control

Confidentiality

Traffic Flow Confidentiality

Data Integrity

Nonrepudiation

Availability

        Mechanism      

    Digital Access Data Authentication Traffic Routing  

Service Encipherment Signature Control Integrity Exchange Padding ControlNotariza

tion

Peer Entity Authentication Y Y     Y      

Data Origin Authentication Y Y            

Access Control     Y          

Confidentiality Y           Y  

Traffic Flow Confidentiality Y         Y Y  

Data Integrity Y Y   Y        

Nonrepudiation   Y   Y       Y

Availability       Y Y      

       Attack  

              Release of Traffic Masquerade Replay Modification of Denial of

Service Message Contents Analysis Messages Service

Peer Entity Authentication

Y

Data Origin Authentication

Y

Access ControlY

Confidentiality YTraffic Flow Confidentiality

Y

Data Integrity

Nonrepudiation Y

Availability

Attack   Release of Traffic Masquerade Replay Modification of Denial of

Mechanism Message Contents Analysis Messages Service

Encipherment

Digital SignatureAccess ControlData IntegrityAuthentication

ExchangeTraffic PaddingRouting Control

Notarization

Exercises

1. An organization wants protection against passive attacks. As a security manager of the organization which security services would you recommend for your organization? Justify your answer.

 2. Consider a database management system used by a departmental store. Give examples of confidentiality, integrity, availability, and authenticity requirements associated with the system. In each case indicate the degree of importance of the requirement.

3. An organization has a server in which some manual are kept. It also provides some applications. The organization wants the manuals to be viewed by all the employees whenever required by them. However project managers can modify the contents of the manuals. For this they must first request the admin. If the admin is confirmed that it is only the concerned project manager making a request he grants permission to make changes to the concerned manual. What type of security services must be present to enable these activities in the organization?

4. Consider an implanted medical device that monitors and records data about a patient’s health and stores the information locally. To access the data, authorized personnel must transmit a PIN to the implanted device, and once authorized, electronically request specific portions of the data. Give examples of confidentiality, integrity and availability requirements associated with the system, and in each indicate the degree of importance of the requirement.

Model for Network SecurityModel for Network Security

Model for Network SecurityModel for Network Security

using this model requires us to: using this model requires us to: 1.1. design a suitable algorithm for the security design a suitable algorithm for the security

transformation transformation 2.2. generate the secret information (keys) used generate the secret information (keys) used

by the algorithm by the algorithm 3.3. develop methods to distribute and share the develop methods to distribute and share the

secret information secret information 4.4. specify a protocol enabling the principals to specify a protocol enabling the principals to

use the transformation and secret use the transformation and secret information for a security service information for a security service

Model for Network Access Model for Network Access SecuritySecurity

Model for Network Access Model for Network Access SecuritySecurity

using this model requires us to: using this model requires us to: 1.1. select appropriate gatekeeper functions to select appropriate gatekeeper functions to

identify users identify users 2.2. implement security controls to ensure only implement security controls to ensure only

authorised users access designated authorised users access designated information or resources information or resources

SummarySummary

topic roadmap & standards organizationstopic roadmap & standards organizations security concepts:security concepts:

confidentiality, integrity, availabilityconfidentiality, integrity, availability X.800 security architectureX.800 security architecture security attacks, services, mechanismssecurity attacks, services, mechanisms models for network (access) securitymodels for network (access) security

The art of war teaches us to rely not on the The art of war teaches us to rely not on the likelihood of the enemy's not coming, but likelihood of the enemy's not coming, but on our own readiness to receive him; not on our own readiness to receive him; not on the chance of his not attacking, but on the chance of his not attacking, but rather on the fact that we have made our rather on the fact that we have made our position unassailable. position unassailable. ——The Art of War, The Art of War, Sun TzuSun Tzu

Text Book:

1. William Stallings - Cryptography and Network Security: Principles and Practice, Prentice Hall, 5th edition, 2010.

  Reference Book:

1. Behrouz A. Forouzan and Debdeep Mukhopadhyay - Cryptography and Network Security, McGraw Hill, 2nd Edition, 2008.