下面算法中，属于非对称密钥加密算法的是______。 A: DES(Digital Encryption Standard) B: RC2(Rivest Ciphers 2) C: RC5(Rivest Ciphers 5) D: DSA(Digital Signature Algorithm)
下面算法中，属于非对称密钥加密算法的是______。 A: DES(Digital Encryption Standard) B: RC2(Rivest Ciphers 2) C: RC5(Rivest Ciphers 5) D: DSA(Digital Signature Algorithm)
In block ciphers, the original key is expanded so that a different key is used for each round.
In block ciphers, the original key is expanded so that a different key is used for each round.
Which of the following statements are true？ （） A: RC4 is a stream cipher B: Stream ciphers require padding C: AES is a block cipher D: DES and 3DES are stream ciphers E: AES is a stream cipher F: AES， DES， and 3DES can be used as HMAC algorithms
Which of the following statements are true？ （） A: RC4 is a stream cipher B: Stream ciphers require padding C: AES is a block cipher D: DES and 3DES are stream ciphers E: AES is a stream cipher F: AES， DES， and 3DES can be used as HMAC algorithms
江苏省常州市横山桥高级中学10-11学年高二上学期期中考试（英语Ifyouandyourfriendswishtoshareasecretyoucanwriteitincodeandnooneelsewillbeabletoreadit.Codesareonewayofwritinginsecrets.Ciphers(暗码)areanother.Inthecodeeachwordiswrittenasasecretcodeorwordnumber.Inaciphereachletterischanged.Codesandciphershaveplayedanimportantroleinthehistoryoftheworld.JuliusCaesartheRomanrulerwhodefeatedalmostallthecountriesinEuropeabout2000yearsagousedacipherwhenhesentsecretmessagestohistroops.DuringAmericanRevolutionGeorgeWashington’sspiesusedakindofcodetosendhiminformationabouttheenemybeforehismilitary(军事的)action.InWorldWarIItheAmerican“broke”orfiguredoutJapan’smostimportantnavycodesandgotenoughinformationtodestroyapowerfulJapanesefleet(舰队).Storekeepersusedcodestomarktheirgoods.Thecodesshowedhowmuchwaspaidforthegoodsorwhentheywereaddedtothestock.Businessmenusedcodestohideplansfromtheirbusinessenemies.Sometimespersonallettersordiarieswerewrittenincode.Manypeopleenjoyedfiguringoutcodesandcipherssimplyasahobby.Inthe16thcenturycodesandcipherswereverypopularamongscientists.Theywrotemessagestoeachotherincodesothatnooneelsewouldlearntheirsecrets.GeronimoGardanoanItalianastrologer(星相家)mathematiciananddoctorinventedthetrelliscipher.Hetooktwosheetsofpaperandcutexactlythesameholesineachone.Thenhesentonesheetwhichhecalledatrellistoafriendandkepttheotherforhimself.Wheneverhewantedtowriteamessageheputhistrellisovertheothersheetofpaperandwrotethesecretmessagethroughtheholes.Thenheremovedthetrellisandfilledtherestofthepaperwithwordsthatwouldmakesense.WhenhisfriendsreceiveditHeputhistrellisoverthewritingandreadthesecretmessage.Codesand71_______72.________waystosendinformationDifferent73_______lThetrelliscipherwasthe79_____ofGardano.lSomescientistsuseditto80_____secretinformation.◆In74______codeswereusedtoachievebusinesspurposes.◆Manypeopleenjoyedfiguringoutcodesasan75________.◆Inthe76________tomakethemilitaryleaders77______ofthesituationofthewarcodeswerealsousedto78_______thewar.
江苏省常州市横山桥高级中学10-11学年高二上学期期中考试（英语Ifyouandyourfriendswishtoshareasecretyoucanwriteitincodeandnooneelsewillbeabletoreadit.Codesareonewayofwritinginsecrets.Ciphers(暗码)areanother.Inthecodeeachwordiswrittenasasecretcodeorwordnumber.Inaciphereachletterischanged.Codesandciphershaveplayedanimportantroleinthehistoryoftheworld.JuliusCaesartheRomanrulerwhodefeatedalmostallthecountriesinEuropeabout2000yearsagousedacipherwhenhesentsecretmessagestohistroops.DuringAmericanRevolutionGeorgeWashington’sspiesusedakindofcodetosendhiminformationabouttheenemybeforehismilitary(军事的)action.InWorldWarIItheAmerican“broke”orfiguredoutJapan’smostimportantnavycodesandgotenoughinformationtodestroyapowerfulJapanesefleet(舰队).Storekeepersusedcodestomarktheirgoods.Thecodesshowedhowmuchwaspaidforthegoodsorwhentheywereaddedtothestock.Businessmenusedcodestohideplansfromtheirbusinessenemies.Sometimespersonallettersordiarieswerewrittenincode.Manypeopleenjoyedfiguringoutcodesandcipherssimplyasahobby.Inthe16thcenturycodesandcipherswereverypopularamongscientists.Theywrotemessagestoeachotherincodesothatnooneelsewouldlearntheirsecrets.GeronimoGardanoanItalianastrologer(星相家)mathematiciananddoctorinventedthetrelliscipher.Hetooktwosheetsofpaperandcutexactlythesameholesineachone.Thenhesentonesheetwhichhecalledatrellistoafriendandkepttheotherforhimself.Wheneverhewantedtowriteamessageheputhistrellisovertheothersheetofpaperandwrotethesecretmessagethroughtheholes.Thenheremovedthetrellisandfilledtherestofthepaperwithwordsthatwouldmakesense.WhenhisfriendsreceiveditHeputhistrellisoverthewritingandreadthesecretmessage.Codesand71_______72.________waystosendinformationDifferent73_______lThetrelliscipherwasthe79_____ofGardano.lSomescientistsuseditto80_____secretinformation.◆In74______codeswereusedtoachievebusinesspurposes.◆Manypeopleenjoyedfiguringoutcodesasan75________.◆Inthe76________tomakethemilitaryleaders77______ofthesituationofthewarcodeswerealsousedto78_______thewar.
The index of coincidence: A: can tell you the likelihood that a key is the same length as the ciphertext B: can tell you the likelihood that some ciphertext has the same frequency counts as English C: can distinguish between mono and polyalphabetic substitution ciphers D: a and b only.
The index of coincidence: A: can tell you the likelihood that a key is the same length as the ciphertext B: can tell you the likelihood that some ciphertext has the same frequency counts as English C: can distinguish between mono and polyalphabetic substitution ciphers D: a and b only.