密码编码学与网络安全第五版答案.docx

密码编码学与网络安全第五版答案.docx

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密码编码学与网络安全第五版答案

Chapter1:

Introduction5

Chapter2:

ClassicalEncryptionTechniques7

Chapter3:

BlockCiphersandtheDateEncryptionStandard13

Chapter4:

FiniteFields21

Chapter5:

AdvancedEncryptionStandard28

Chapter6:

MoreonSymmetricCiphers33

Chapter7:

ConfidentialityUsingSymmetricEncryption38

Chapter8:

IntroductiontoNumberTheory42

Chapter9:

Public-KeyCryptographyandRSA46

Chapter10:

KeyManagement;OtherPublic-KeyCryptosystems55

Chapter11:

MessageAuthenticationandHashFunctions59

Chapter12:

HashandMACAlgorithms62

Chapter13:

DigitalSignaturesandAuthenticationProtocols66

Chapter14:

AuthenticationApplications71

Chapter15:

ElectronicMailSecurity73

Chapter16:

IPSecurity76

Chapter17:

WebSecurity80

Chapter18:

Intruders83

Chapter19:

MaliciousSoftware87

Chapter20:

Firewalls89

AnswerstoQuestions

1.1TheOSISecurityArchitectureisaframeworkthatprovidesasystematicwayofdefiningtherequirementsforsecurityandcharacterizingtheapproachestosatisfyingthoserequirements.Thedocumentdefinessecurityattacks,mechanisms,andservices,andtherelationshipsamongthesecategories.

1.2Passiveattackshavetodowitheavesdroppingon,ormonitoring,transmissions.Electronicmail,filetransfers,andclient/serverexchangesareexamplesoftransmissionsthatcanbemonitored.Activeattacksincludethemodificationoftransmitteddataandattemptstogainunauthorizedaccesstocomputersystems.

1.3Passiveattacks:

releaseofmessagecontentsandtrafficanalysis.Activeattacks:

masquerade,replay,modificationofmessages,anddenialofservice.

1.4Authentication:

Theassurancethatthecommunicatingentityistheonethatitclaimstobe.

Accesscontrol:

Thepreventionofunauthorizeduseofaresource（i.e.,thisservicecontrolswhocanhaveaccesstoaresource,underwhatconditionsaccesscanoccur,andwhatthoseaccessingtheresourceareallowedtodo）.

Dataconfidentiality:

Theprotectionofdatafromunauthorizeddisclosure.

Dataintegrity:

Theassurancethatdatareceivedareexactlyassentbyanauthorizedentity（i.e.,containnomodification,insertion,deletion,orreplay）.

Nonrepudiation:

Providesprotectionagainstdenialbyoneoftheentitiesinvolvedinacommunicationofhavingparticipatedinallorpartofthecommunication.

Availabilityservice:

Thepropertyofasystemorasystemresourcebeingaccessibleandusableupondemandbyanauthorizedsystementity,accordingtoperformancespecificationsforthesystem（i.e.,asystemisavailableifitprovidesservicesaccordingtothesystemdesignwheneverusersrequestthem）.

1.5SeeTable1.3.

AnswerstoProblems

1.1

Releaseofmessagecontents

Trafficanalysis

Masquerade

Replay

Modificationofmessages

Denialofservice

Peerentityauthentication

Y

Dataoriginauthentication

Y

Accesscontrol

Y

Confidentiality

Y

Trafficflowconfidentiality

Y

Dataintegrity

Y

Y

Non-repudiation

Y

Availability

Y

1.2

Releaseofmessagecontents

Trafficanalysis

Masquerade

Replay

Modificationofmessages

Denialofservice

Encipherment

Y

Digitalsignature

Y

Y

Y

Accesscontrol

Y

Y

Y

Y

Y

Dataintegrity

Y

Y

Authenticationexchange

Y

Y

Y

Y

Trafficpadding

Y

Routingcontrol

Y

Y

Y

Notarization

Y

Y

Y

Chapter2

ClassicalEncryptionTechniquesr

AnswerstoQuestions

2.1Plaintext,encryptionalgorithm,secretkey,ciphertext,decryptionalgorithm.

2.2Permutationandsubstitution.

2.3Onekeyforsymmetricciphers,twokeysforasymmetricciphers.

2.4Astreamcipherisonethatencryptsadigitaldatastreamonebitoronebyteatatime.Ablockcipherisoneinwhichablockofplaintextistreatedasawholeandusedtoproduceaciphertextblockofequallength.

2.5Cryptanalysisandbruteforce.

2.6Ciphertextonly.Onepossibleattackunderthesecircumstancesisthebrute-forceapproachoftryingallpossiblekeys.Ifthekeyspaceisverylarge,thisbecomesimpractical.Thus,theopponentmustrelyonananalysisoftheciphertextitself,generallyapplyingvariousstatisticalteststoit.Knownplaintext.Theanalystmaybeabletocaptureoneormoreplaintextmessagesaswellastheirencryptions.Withthisknowledge,theanalystmaybeabletodeducethekeyonthebasisofthewayinwhichtheknownplaintextistransformed.Chosenplaintext.Iftheanalystisabletochoosethemessagestoencrypt,theanalystmaydeliberatelypickpatternsthatcanbeexpectedtorevealthestructureofthekey.

2.7Anencryptionschemeisunconditionallysecureiftheciphertextgeneratedbytheschemedoesnotcontainenoughinformationtodetermineuniquelythecorrespondingplaintext,nomatterhowmuchciphertextisavailable.An