computer science cryptography cryptography and data security ppt slides (2001 gutmann)外语英文电子书

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1、CryptographyandDataSecurityPeterGutmannUniversityofAucklandhttp://www.cs.auckland.ac.nz/~pgut001SecurityRequirementsConfidentiality•ProtectionfromdisclosuretounauthorisedpersonsIntegrity•MaintainingdataconsistencyAuthentication•AssuranceofidentityofpersonororiginatorofdataNon-repudiation•

2、Originatorofcommunicationscan’tdenyitlaterSecurityRequirements(ctd)Availability•LegitimateusershaveaccesswhentheyneeditAccesscontrol•UnauthorisedusersarekeptoutTheseareoftencombined•Userauthenticationusedforaccesscontrolpurposes•Non-repudiationcombinedwithauthenticationSecurityThreatsInfo

3、rmationdisclosure/informationleakageIntegrityviolationMasqueradingDenialofserviceIllegitimateuseGenericthreat:Backdoors,trojanhorses,insiderattacksMostInternetsecurityproblemsareaccesscontrolorauthenticationones•Denialofserviceisalsopopular,butmostlyanannoyanceAttackTypesPassiveattackcano

4、nlyobservecommunicationsordataActiveattackcanactivelymodifycommunicationsordata•Oftendifficulttoperform,butverypowerful–Mailforgery/modification–TCP/IPspoofing/sessionhijackingSecurityServicesFromtheOSIdefinition:•Accesscontrol:Protectsagainstunauthoriseduse•Authentication:Providesassuran

5、ceofsomeone'sidentity•Confidentiality:Protectsagainstdisclosuretounauthorisedidentities•Integrity:Protectsfromunauthoriseddataalteration•Non-repudiation:ProtectsagainstoriginatorofcommunicationslaterdenyingitSecurityMechanismsThreebasicbuildingblocksareused:•Encryptionisusedtoprovideconfi

6、dentiality,canprovideauthenticationandintegrityprotection•Digitalsignaturesareusedtoprovideauthentication,integrityprotection,andnon-repudiation•Checksums/hashalgorithmsareusedtoprovideintegrityprotection,canprovideauthenticationOneormoresecuritymechanismsarecombinedtoprovideasecurityserv

7、iceServices,Mechanisms,AlgorithmsAtypicalsecurityprotocolprovidesoneormoreservices•Servicesarebuiltfrommechanisms•MechanismsareimplementedusingalgorithmsConventionalEncryptionUsesasharedkeyProblemofcommunicatingalargemessageinsecretreducedtocommunicatingasmallkeyins