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1、CreatedbyNeeviaDocumentConvertertrialversionChapter7:NetworksecurityFoundations:whatissecurity?cryptographyauthenticationmessageintegritykeydistributionandcertificationSecurityinpractice:http://www.neevia.comapplicationlayer:securee-mailtransportlayer:Internetcommerce,SSL,SETnetworklayer
2、:IPsecurityShaowenYao,SchoolOfSoftware,YNU1CreatedbyNeeviaDocumentConvertertrialversionFriendsandenemies:Alice,Bob,TrudyFigure7.1goesherehttp://www.neevia.comwell-knowninnetworksecurityworldBob,Alice(lovers!)wanttocommunicate“securely”Trudy,the“intruder”mayintercept,delete,addmessagesShaowenY
3、ao,SchoolOfSoftware,YNU2CreatedbyNeeviaDocumentConvertertrialversionWhatisnetworksecurity?Secrecy:onlysender,intendedreceivershould“understand”msgcontentssenderencryptsmsgreceiverdecryptsmsgAuthentication:sender,receiverwanttoconfirmidentityofeachotherhttp://www.neevia.comMessageIntegrity:send
4、er,receiverwanttoensuremessagenotaltered(intransit,orafterwards)withoutdetectionShaowenYao,SchoolOfSoftware,YNU3CreatedbyNeeviaDocumentConvertertrialversionhttp://www.neevia.comShaowenYao,SchoolOfSoftware,YNU4CreatedbyNeeviaDocumentConvertertrialversionhttp://www.neevia.comShaowenYao,SchoolOfSof
5、tware,YNU5CreatedbyNeeviaDocumentConvertertrialversionhttp://www.neevia.comShaowenYao,SchoolOfSoftware,YNU6CreatedbyNeeviaDocumentConvertertrialversionThelanguageofcryptographyplaintextKKplaintextABciphertextFigure7.3goesherehttp://www.neevia.comsymmetrickeycrypto:sender,receiverkeysidenticalpub
6、lic-keycrypto:encryptkeypublic,decryptkeysecretShaowenYao,SchoolOfSoftware,YNU7CreatedbyNeeviaDocumentConvertertrialversionSymmetrickeycryptographysubstitutioncipher:substitutingonethingforanothermonoalphabeticcipher:substituteoneletterforanotherplaintext:abcdefghijklmnopqrstuvwxyzciphertext:mn
7、bvcxzasdfghjklpoiuytrewqE.g.:Plaintext:bob.iloveyou.alicehttp://www.neevia.comciphertext:nkn.sgktcwky.mgsbcQ:Howhardtobreakthissimplecipher?:•bruteforce(howhard?)•other?ShaowenYao,SchoolOfSoftware,YNU8CreatedbyNeeviaDocument
