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1、CHAPTER14SecurityPrintingandSealsAsealisonlyasgoodasthemaninwhosebriefcaseit’scarried.—KarenSparckJones¨Youcan’tmakesomethingsecureifyoudon’tknowhowtobreakit.—MarcWeberTobias14.1IntroductionManycomputersystemsrelytosomeextentonsecureprinting,packagingandsealstogu
2、aranteeimportantaspectsoftheirprotection.Mostsecurityproductscanbedefeatedifabadmancangetatthemwhethertopatchthem,damagethem,orsubstitutethembeforeyouinstallthem.Seals,andtamper-evidentpackaginggenerally,canhelpwithtrusteddistribution,thatis,assuringtheuserthatth
3、eproducthasntbeentamperedwithsinceleavingthefactory.Manysoftwareproductsgetsomeprotectionagainstforgeryusingsealsandpackaging.Theycanatleastraisethecostsoflarge-scaleforgerysomewhat.Wesawhowmonitoringsystems,suchastaximeters,oftenusesealstomakeitharderforuserstot
4、amperwithinput.Nomatterhowsophis-ticatedthecryptography,adefeatforthesealscanbeadefeatforthesystem.Ialsodiscussedhowcontactlesssystemssuchasthoseusedinthechipsinpassportsandidentitycardscanbevulnerabletoman-in-the-middle433434Chapter14■SecurityPrintingandSealsatt
5、acks.IfyourescrutinisingtheIDofanengineerfromoneofyoursuppliersbeforeyoulethimintoyourhostingcentre,itcanbeagoodideatoeyeballtheIDaswellasreadingitelectronically.Ifallyoudoisthelatter,hemightberelayingthetransactiontosomewhereelse.SoevenwithelectronicIDcards,thes
6、ecurityprintingcanstillmatter.Manysecuritytokens,suchassmartcards,aredif?culttomaketrulytamperproof.Itmaybefeasiblefortheopponenttodismantlethedeviceandprobeoutthecontent.Amorerealisticgoalmaybetamperevidenceratherthantamperproofness:ifsomeonedismantlestheirsmart
7、cardandgetsthekeysout,theyshouldnotbeabletoreassembleitintosomethingthatwillpasscloseexamination.Securityprintingcanhelphere.Ifabanksmartcardreallyistamper-evident,thenthebankmighttellitscus-tomersthatdisputeswillonlybeentertainediftheycanproducethecardintact.(Ba
8、nksmightnotgetawaywiththisthough,becauseconsumerprotectionlawyerswilldemandthattheydealfairlywithhonestcus-tomerswholosetheircardsorhavethemstolen).Quiteapartf