资源描述：
《Chapter 3 Protocols》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。
1、CHAPTER3ProtocolsItisimpossibletoforeseetheconsequencesofbeingclever.ChristopherStracheyEverythingsecretdegenerates,eventheadministrationofjustice;nothingissafethatdoesnotshowhowitcanbeardiscussionandpublicity.LordActon3.1IntroductionIfsecurityengineeringhasadeepunify
2、ingtheme,itisthestudyofsecurityprotocols.WevecomeacrossafewprotocolsinformallyalreadyIvemen-tionedchallenge-responseauthenticationandKerberos.Inthischapter,Illdigdownintothedetails.Ratherthanstartingoffwithaformaldefinitionofasecurityprotocol,Iwillgivearoughindicationa
3、ndthenrefineitusinganumberofexamples.Asthisisanengineeringbook,Iwillalsogivemanyexamplesofhowprotocolsfail.Atypicalsecuritysystemconsistsofanumberofprincipalssuchaspeople,companies,computersandmagneticcardreaders,whichcommunicateusingavarietyofchannelsincludingphones,e
4、mail,radio,infrared,andbycarryingdataonphysicaldevicessuchasbankcardsandtransporttickets.Thesecurityprotocolsaretherulesthatgovernthesecommunications.Theyaretypicallydesignedsothatthesystemwillsurvivemaliciousactssuchaspeopletellingliesonthephone,hostilegovernmentsjam
5、mingradio,orforgersalteringthedataontraintickets.Protectionagainstallpossibleattacksisoftentooexpensive,soprotocolsaretypicallydesignedundercertainassumptionsaboutthethreats.Forexample,thelogonprotocolthatconsistsofauser6364Chapter3■Protocolsenteringapasswordintoamach
6、ineassumesthatshecanenteritintotherightmachine.Intheolddaysofhard-wiredterminalsintheworkplace,thiswasreasonable;nowthatpeoplelogontowebsitesovertheInternet,itismuchlessso.Evaluatingaprotocolthusinvolvesansweringtwoquestions:first,isthethreatmodelrealistic?Second,doest
7、heprotocoldealwithit?Protocolsmaybeextremelysimple,suchasswipingabadgethroughareaderinordertoenterabuilding.Theyofteninvolveinteraction,anddonotnecessarilyinvolvetechnicalmeasureslikecryptography.Forexample,whenweorderabottleoffinewineinarestaurant,thestandardwine-wait
8、erprotocolprovidessomeprivacy(theotherdinersatourtabledontlearntheprice),someintegrity(wecanbesurewegottherightbottleandthat
