密码编码学与网络安全-原理与实践-ch01.ppt

Cryptography and Network SecurityOverview&Chapter 1Fifth Editionby William StallingsLecture slides by Lawrie Brown.Chapter 0 Readers GuideThe art of war teaches us to rely not on the likelihood of the enemys not coming,but on our own readiness to receive him;not on the chance of his not attacking,but rather on the fact that we have made our position unassailable.The Art of War,Sun Tzu.RoadmapCryptographic algorithmsl lsymmetric cipherssymmetric ciphersl lasymmetric encryptionasymmetric encryptionl lhash functionshash functionsMutual TrustNetwork SecurityComputer Security.Standards OrganizationsNational Institute of Standards&Technology(NIST)Internet Society(ISOC)International Telecommunication Union Telecommunication Standardization Sector(ITU-T)International Organization for Standardization(ISO).Chapter 1 IntroductionThe combination of space,time,and strength that must be considered as the basic elements of this theory of defense makes this a fairly complicated matter.Consequently,it is not easy to find a fixed point of departure.On War,Carl Von Clausewitz.Computer Securitythe protection afforded to an automated information system in order to attain the applicable objectives of preserving the integrity,availability and confidentiality of information system resources(includes hardware,software,firmware,information/data,and telecommunications).Key Security Concepts.Levels of Impactcan define 3 levels of impact from a security breachl lLowLowl lModerateModeratel lHighHigh.Examples of Security Requirementsconfidentiality student gradesintegrity patient informationavailability authentication service.Computer Security Challenges1.1.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 ArchitectureITU-T X.800“Security Architecture for OSI”defines a systematic way of defining and providing security requirementsfor us it provides a useful,if abstract,overview of concepts we will study.Aspects of Securityconsider 3 aspects of information security:l lsecurity attacksecurity attackl lsecurity mechanismsecurity mechanisml lsecurity servicesecurity servicenote termsl lthreat threat a potential for violation of security a potential for violation of securityl lattack attack an assault on system security,a an assault on system security,a deliberate attempt to evade security servicesdeliberate attempt to evade security services.Passive Attacks.Active Attacks.Security Servicel lenhance security of data processing systems enhance security of data processing systems and information transfers of an organizationand information transfers of an organizationl lintended to counter security attacksintended to counter security attacksl lusing one or more security mechanisms using one or more security mechanisms l loften 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 ServicesX.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:“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)AuthenticationAuthentication-assurance that communicating -assurance that communicating entity is the one claimedentity is the one claimedl lhave both peer-entity&data origin authenticationhave both peer-entity&data origin authenticationAccess ControlAccess Control-prevention of the -prevention of the unauthorized use of a resourceunauthorized use of a resourceData ConfidentialityData Confidentiality protection of data from protection of data from unauthorized disclosureunauthorized disclosureData IntegrityData Integrity-assurance that data received is -assurance that data received is as sent by an authorized entityas sent by an authorized entityNon-RepudiationNon-Repudiation-protection against denial by -protection against denial by one of the parties in a communicationone of the parties in a communicationAvailabilityAvailability resource accessible/usable resource accessible/usable.Security Mechanismfeature designed to detect,prevent,or recover from a security attackno single mechanism that will support all services requiredhowever one particular element underlies many of the security mechanisms in use:l lcryptographic techniquescryptographic techniqueshence our focus on this topic.Security Mechanisms(X.800)specific security mechanisms:l lencipherment,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,notarizationnotarizationpervasive security mechanisms:l ltrusted functionality,security labels,event trusted functionality,security labels,event detection,security audit trails,security detection,security audit trails,security recoveryrecovery.Model for Network Security.Model for Network Securityusing 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 Security.Model for Network Access Securityusing 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 resourcesinformation or resources .Summarytopic roadmap&standards organizationssecurity concepts:l lconfidentiality,integrity,availabilityconfidentiality,integrity,availabilityX.800 security architecturesecurity attacks,services,mechanismsmodels for network(access)security.