密碼編碼學(xué)與網(wǎng)絡(luò)安全第四版第二章答案翻譯

1、第二章2.1什么是對(duì)稱密碼的本質(zhì)成分？Plaintextencryptionalgithmsecretkeyciphertextdecryptionalgithm.明文加密算法密鑰密文解密算法2.2密碼算法中兩個(gè)基本函數(shù)式什么？Permutationsubstitution.代換和置換P202.3用密碼進(jìn)行通信的兩個(gè)人需要多少密鑰？對(duì)稱密碼只需要一把，非對(duì)稱密碼要兩把P202.4分組密碼和流密碼的區(qū)別是什么？Astreamcipheri

2、sonethatencryptsadigitaldatastreamonebitonebyteatatime.Ablockcipherisoneinwhichablockofplaintextistreatedasawholeusedtoproduceaciphertextblockofequallength.分組密碼每次輸入的一組元素，相應(yīng)地輸出一組元素。流密碼則是連續(xù)地處理輸入元素，每次輸出一個(gè)元素。P202.5攻擊密碼的兩種一般方

3、法是什么？Cryptanalysisbrutefce.密碼分析和暴力破解2.6列出并簡要定力基于攻擊者所知道信息的密碼分析攻擊類型。Ciphertextonly.Onepossibleattackunderthesecircumstancesisthebrutefceapproachoftryingallpossiblekeys.Ifthekeyspaceisverylargethisbecomesimpractical.Thusthe

4、opponentmustrelyonananalysisoftheciphertextitselfgenerallyapplyingvariousstatisticalteststoit.Knownplaintext.Theanalystmaybeabletocaptureonemeplaintextmessagesaswellastheirencryptions.Withthisknowledgetheanalystmaybeable

5、todeducethekeyonthebasisofthewayinwhichtheknownplaintextistransfmed.Chosenplaintext.Iftheanalystisabletochoosethemessagestoencrypttheanalystmaydeliberatelypickpatternsthatcanbeexpectedtorevealthestructureofthekey.2.12一次一

6、密的兩個(gè)問題是什么？1.Thereisthepracticalproblemofmakinglargequantitiesofromkeys.Anyheavilyusedsystemmightrequiremillionsofromactersonaregularbasis.Supplyingtrulyromactersinthisvolumeisasignificanttask.2.Evenmedauntingistheproblem

7、ofkeydistributionprotection.Feverymessagetobesentakeyofequallengthisneededbybothsenderreceiver.Thusamammothkeydistributionproblemexists.書本P332.13什么是置換密碼？Atranspositioncipherinvolvesapermutationoftheplaintextletters.書本P33

8、2.14什么是隱寫術(shù)？Steganographyinvolvesconcealingtheexistenceofamessage.書本P362.7.3習(xí)題2.1a.對(duì)b的取值是否有限制？解釋原因。沒有限制，b只會(huì)使得明文加密后的密文字母統(tǒng)一左移或右移，因此如果是單射的，b改變后依然是單射。注：答案解答得很坑爹，答了等于沒答。現(xiàn)解答如下:??????mod260mod26EkpEkqapbaqbapaqbb??????若要，則不成立，則不