深入浅出密码学习题答案

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1、SolutionstoHomeworkProblems(OddNumberedProblems)UnderstandingCryptographyATextbookforStudentsandPractitionersbyChristofPaarandJanPelzl12SolutionstoHomeworkProblems(OddNumberedProblems)ProblemsofChapter11.11.Letterfrequencyanalysisoftheciphertext:lettercountfreq[%]lettercountfreq[%]A50.77N172.63

2、B6810.53O71.08C50.77P304.64D233.56Q71.08E50.77R8413.00F10.15S172.63G10.15T132.01H233.56U243.72I416.35V223.41J487.43W477.28K497.59X203.10L81.24Y192.94M629.60Z00.002.BecausethepracticeofthebasicmovementsofkataisthefocusandmasteryofselfistheessenceofMatsubayashiRyukaratedo,Ishalltrytoelucidatethem

3、ovementsofthekataaccordingtomyinterpretationbasedonfortyyearsofstudy.Itisnotaneasytasktoexplaineachmovementanditssignificance,andsomemustremainunexplained.Togiveacompleteexplanation,onewouldhavetobequalifiedandinspiredtosuchanextentthathecouldreachthestateofenlightenedmindcapableofrecognizingso

4、undlesssoundandshapelessshape.Idonotdeemmyselfthefinalauthority,butmyexperiencewithkatahasleftnodoubtthatthefollowingistheproperapplicationandinterpretation.IoffermytheoriesinthehopethattheessenceofOkinawankaratewillremainintact.3.ShoshinNagamine,furtherreading:TheEssenceofOkinawanKarate-DobySh

5、oshinNagamine,TuttlePublishing,1998.1.3Onesearchenginecosts$100includingoverhead.Thus,1milliondollarsbuyus10,000engines.1.keytestspersecond:5·108·104=5·1012keys/secOnaverage,wehavetocheck(2127keys:(2127keys)/(5·1012keys/sec)=3.40·1025sec=1.08·1018yearsThatisabout108=100,000,000timeslongerthanth

6、eageoftheuniverse.Goodluck.2.LetibethenumberofMooreiterationsneededtobringthesearchtimedownto24h:1.08·1018years·365/2i=1day2i=1,08·1018·365days/1dayi=68.42Weroundthisnumberupto69assumingthenumberofMooreiterationsisdiscreet.Thus,wehavetowaitfor:1.5·69=103.5yearsNotethatitisextremelyunlikelythatM

7、oore'sLawwillbevalidforsuchatimeperiod!Thus,a128bitkeyseemsimpossibletobrute-force,evenintheforeseeablefuture.1.51.15·29mod13≡2·3mod13≡6mod132.2·29mod13≡2·3mod13≡6mod133.2·3mod13≡2·3mod13≡6mod134.2·3mod13≡2·3mod13≡6mod13Solutionst