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ID:40056479
大小:604.15 KB
页数:56页
时间:2019-07-18
《Chapter 5 Cryptography》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、CHAPTER5CryptographyZHQMZMGMZMFMGJuliusCaesarKXJEYUREBEZWEHEWRYTUHEYFSKREHEGOYFIWTTTUOLKSYCAJPOBOTEIZONTXBYBWTGONEYCUZWRGDSONSXBOUYWRHEBAAHYUSEDQJohnFKennedy5.1IntroductionCryptographyiswheresecurityengineeringmeetsmathematics.Itprovidesuswiththetoolsthatunderliemostmodernsecurityprotocol
2、s.Itisprobablythekeyenablingtechnologyforprotectingdistributedsystems,yetitissurprisinglyhardtodoright.AswevealreadyseeninChapter3,Protocols,cryptographyhasoftenbeenusedtoprotectthewrongthings,orusedtoprotecttheminthewrongway.Wellseeplentymoreexampleswhenwestartlookingindetailatrealapplic
3、ations.Unfortunately,thecomputersecurityandcryptologycommunitieshavedriftedapartoverthelast25years.Securitypeopledontalwaysunderstandtheavailablecryptotools,andcryptopeopledontalwaysunderstandthereal-worldproblems.Thereareanumberofreasonsforthis,suchasdifferentprofessionalbackgrounds(comp
4、uterscienceversusmathematics)anddiffer-entresearchfunding(governmentshavetriedtopromotecomputersecurityresearchwhilesuppressingcryptography).Itremindsmeofastorytoldbyamedicalfriend.Whileshewasyoung,sheworkedforafewyearsinacountrywhere,foreconomicreasons,theydshortenedtheirmedicaldegreesan
5、dconcentratedonproducingspecialistsasquicklyaspossible.Oneday,129130Chapter5■Cryptographyapatientwhodhadbothkidneysremovedandwasawaitingatransplantneededherdialysisshuntredone.Thesurgeonsentthepatientbackfromthetheateronthegroundsthattherewasnourinalysisonfile.Itjustdidntoccurtohimthatapat
6、ientwithnokidneyscouldntproduceanyurine.Justasadoctorneedstounderstandphysiologyaswellassurgery,soasecurityengineerneedstobefamiliarwithcryptologyaswellascomputersecurity(andmuchelse).Thischapterisaimedatpeoplewithoutanytrainingincryptology;cryptologistswillfindlittleinitthattheydontalread
7、yknow.AsIonlyhaveafewdozenpages,andaproperexpositionofmoderncryp-tographywouldrunintothousands,Iwontgointomuchofthemathematics(therearelotsofbooksthatdothat;seetheendofthechapterforfurtherreading).Illjustexplainthebasicintuitionsandconstructionsthatseemtocausethemos
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