Symmetric,orprivate-key,encryptionisbasedonasecretkeythatissharedbybothcommuncatingparties.The()partyusesthesecretkeyaspartofthemathematicaloperationtoencrypt(_____)texttociphertext.Thereceivingpartyusesthesamesecretkeytodecrypttheciphertexttoplaintext.Asymmetric,orpublic-key,encryptionusestwodifferentkeysforeachuser:oneisa()keyknownonlytothisoneuser;theotherisacorrespondingpublickey,whichisaccessibletoanyone.Theprivateandpublickeysaremathematicallyrelatedbytheencryptionalgorithm.Onekeyiausedforencyptionandtheotherfordecryption,dependingonthenatureofthecommunicationservicebeingimplemented.Inaddition,publickeyencryptiontechnoligiesallowdigital()tobeplacedonmessages.Adigitalsignatureusesthesender'sprivatekeytoencryptsomeportionofthemessage.Whenthemessageisreceived,thereceiverusesthesender's()keytpdecipherthedigitalsignaturetoverifythesender'sidentity. 横线处应选().
A.plain B.cipher C.public D.private正确答案A
