Therearetwogeneralapproachestoattackinga()encryptionscheme.Thefirstattackisknownascryptanalysis.Cryptanalyticattacksrelyonthenatureofthealgorithmplusperhapssomeknowledgeofthegeneralcharacteristicsofthe(2)orevensomesampleplaintext-ciphertextpairs.Thistypeof()exploitsthecharacteristicsofthealgorithmtoattempttodeduceaspecificplaintextortodeducethekeybeingused.Iftheattacksucceedsindeducingthekey,theeffectiscatastrophic:Allfutureandpastmessagesencryptedwiththatkeyarecompromised.Thesecondmethod,knownasthe()-forceattack,istotryeverypossiblekeyonapieceof()untilanintelligibletranslationintoplaintextisobtained.Onaverage,halfofallpossiblekeysmustbetriedtoachievesuccess. (2)处应选_________.
A.operation B.publication C.plaintext D.ciphertext正确答案B
