09/08/10 1

Cryptography and Cryptography and

Network SecurityNetwork Security

Overview & Chapter 1Overview & Chapter 1

Fifth EditionFifth Edition

by William Stallingsby William Stallings

Lecture slides by Lawrie BrownLecture slides by Lawrie Brown

09/08/10 2

Chapter 0 � Reader�s GuideChapter 0 � Reader�s Guide

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

09/08/10 3

RoadmapRoadmap

� Cryptographic algorithmsCryptographic algorithms� symmetric cipherssymmetric ciphers

� asymmetric encryptionasymmetric encryption

� hash functionshash functions

� Mutual TrustMutual Trust

� Network SecurityNetwork Security

� Computer SecurityComputer Security

09/08/10 4

Standards OrganizationsStandards Organizations

� National Institute of Standards & National Institute of Standards &

Technology (NIST)Technology (NIST)

� Internet Society (ISOC)Internet Society (ISOC)

� International Telecommunication Union International Telecommunication Union

Telecommunication Standardization Telecommunication Standardization

Sector (ITU-T)Sector (ITU-T)

� International Organization for International Organization for

Standardization (ISO)Standardization (ISO)

09/08/10 5

Chapter 1 � IntroductionChapter 1 � Introduction

� The combination of space, time, and The combination of space, time, and

strength that must be considered as the strength that must be considered as the

basic elements of this theory of defense basic elements of this theory of defense

makes this a fairly complicated matter. makes this a fairly complicated matter.

Consequently, it is not easy to find a fixed Consequently, it is not easy to find a fixed

point of departure.point of departure.. .

� � On War, Carl Von ClausewitzOn War, Carl Von Clausewitz

09/08/10 6

Computer SecurityComputer 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 information/data, and

telecommunications)telecommunications)

09/08/10 7

Key Security ConceptsKey Security Concepts

09/08/10 8

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

09/08/10 9

Examples of Security Examples of Security

RequirementsRequirements� confidentiality � student gradesconfidentiality � student grades

� integrity � patient informationintegrity � patient information

� availability � authentication serviceavailability � authentication service

09/08/10 10

Computer Security ChallengesComputer Security Challenges

1.1. not simplenot simple

2.2. must consider potential attacksmust consider potential attacks

3.3. procedures used counter-intuitiveprocedures used counter-intuitive

4.4. involve algorithms and secret infoinvolve algorithms and secret info

5.5. must decide where to deploy mechanismsmust decide where to deploy mechanisms

6.6. battle of wits between attacker / adminbattle of wits between attacker / admin

7.7. not perceived on benefit until failsnot perceived on benefit until fails

8.8. requires regular monitoringrequires regular monitoring

9.9. too often an after-thoughttoo often an after-thought

10.10. regarded as impediment to using systemregarded as impediment to using system

09/08/10 11

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 requirementsproviding 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

09/08/10 12

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

09/08/10 13

Passive AttacksPassive Attacks

09/08/10 14

Active AttacksActive Attacks

09/08/10 15

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

09/08/10 16

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�

09/08/10 17

Security Services (X.800)Security Services (X.800)

� AuthenticationAuthentication - - assurance that assurance that communicating entity is the one claimedcommunicating entity is the one claimed� have both peer-entity & data origin authenticationhave both peer-entity & data 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

� Data IntegrityData Integrity - - assurance that data received is assurance that data received is as sent by an authorized entityas sent by an authorized entity

� Non-RepudiationNon-Repudiation - - protection against denial by protection against denial by one of the parties in a communicationone of the parties in a communication

� AvailabilityAvailability � resource accessible/usable � resource accessible/usable

09/08/10 18

Security MechanismSecurity Mechanism

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

� no single mechanism that will support all no single mechanism that will support all services requiredservices required

� however however one particular element underlies one particular element underlies many of the security mechanisms in use:many of the security mechanisms in use:� cryptographic techniquescryptographic techniques

� hence our focus on this topichence our focus on this topic

09/08/10 19

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

� specific security mechanisms:specific security mechanisms:� encipherment, digital signatures, access encipherment, digital signatures, access

controls, data integrity, authentication controls, data integrity, authentication exchange, traffic padding, routing control, exchange, traffic padding, routing control, notarizationnotarization

� 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

09/08/10 21

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

09/08/10 22

Model for Network Access SecurityModel for Network Access Security

09/08/10 23

Model for Network Access SecurityModel for Network Access Security

� 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

09/08/10 24

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