已阅读5页，还剩9页未读， 继续免费阅读
版权说明：本文档由用户提供并上传，收益归属内容提供方，若内容存在侵权，请进行举报或认领
文档简介
INSIGHTRIVIERACADEMICJOURNAL,VOLUME6,NUMBER2,FALL2010COPYRIGHT2010BYDOUGLASSELENTPUBLISHEDBYRIVIERCOLLEGE,WITHPERMISSION1ISSN15599388ONLINEVERSION,ISSN15599396CDROMVERSIONABSTRACTADVANCEDENCRYPTIONSTANDARDAESISTHECURRENTSTANDARDFORSECRETKEYENCRYPTIONAESWASCREATEDBYTWOBELGIANCRYPTOGRAPHERS,VINCENTRIJMENANDJOANDAEMEN,REPLACINGTHEOLDDATAENCRYPTIONSTANDARDDESTHEFEDERALINFORMATIONPROCESSINGSTANDARD197USEDASTANDARDIZEDVERSIONOFTHEALGORITHMCALLEDRIJNDAELFORTHEADVANCEDENCRYPTIONSTANDARDTHEALGORITHMUSESACOMBINATIONOFEXCLUSIVEOROPERATIONSXOR,OCTETSUBSTITUTIONWITHANSBOX,ROWANDCOLUMNROTATIONS,ANDAMIXCOLUMNITWASSUCCESSFULBECAUSEITWASEASYTOIMPLEMENTANDCOULDRUNINAREASONABLEAMOUNTOFTIMEONAREGULARCOMPUTER1INTRODUCTIONONJANUARY2,1997THENATIONALINSTITUTEOFSTANDARDSANDTECHNOLOGYNISTHELDACONTESTFORANEWENCRYPTIONSTANDARDTHEPREVIOUSSTANDARD,DES,WASNOLONGERADEQUATEFORSECURITYITHADBEENTHESTANDARDSINCENOVEMBER23,1976COMPUTINGPOWERHADINCREASEDALOTSINCETHENANDTHEALGORITHMWASNOLONGERCONSIDEREDSAFEIN1998DESWASCRACKEDINLESSTHANTHREEDAYSBYASPECIALLYMADECOMPUTERCALLEDTHEDESCRACKERTHEDESCRACKERWASCREATEDBYTHEELECTRONICFRONTIERFOUNDATIONFORLESSTHAN250,000ANDWONTHERSADESCHALLENGEII21CURRENTALTERNATIVESTOANEWENCRYPTIONSTANDARDWERETRIPLEDES3DESANDINTERNATIONALDATAENCRYPTIONALGORITHMIDEATHEPROBLEMWASIDEAAND3DESWERETOOSLOWANDIDEAWASNOTFREETOIMPLEMENTDUETOPATENTSNISTWANTEDAFREEANDEASYTOIMPLEMENTALGORITHMTHATWOULDPROVIDEGOODSECURITYADDITIONALLYTHEYWANTEDTHEALGORITHMTOBEEFFICIENTANDFLEXIBLE2AFTERHOLDINGTHECONTESTFORTHREEYEARS,NISTCHOSEANALGORITHMCREATEDBYTWOBELGIANCOMPUTERSCIENTISTS,VINCENTRIJMENANDJOANDAEMENTHEYNAMEDTHEIRALGORITHMRIJNDAELAFTERTHEMSELVES2SUPPOSEDLYRIJNDAELCANONLYBEPRONOUNCEDCORRECTLYBYPEOPLEWHOCANSPEAKDUTCHANDTHECLOSESTENGLISHAPPROXIMATIONIS“RHINEDAHL”3ONNOVEMBER26,2001THEFEDERALINFORMATIONPROCESSINGSTANDARDSPUBLICATION197ANNOUNCEDASTANDARDIZEDFORMOFTHERIJNDAELALGORITHMASTHENEWSTANDARDFORENCRYPTIONTHISSTANDARDWASCALLEDADVANCEDENCRYPTIONSTANDARDANDISCURRENTLYSTILLTHESTANDARDFORENCRYPTION42RIJNDAELBLOCKANDKEYBEFOREAPPLYINGTHEALGORITHMTOTHEDATA,THEBLOCKANDKEYSIZESMUSTBEDETERMINEDAESALLOWSFORBLOCKSIZESOF128,168,192,224,AND256BITSAESALLOWSKEYSIZESOF128,192,AND256BITS2THESTANDARDENCRYPTIONUSESAES128WHEREBOTHTHEBLOCKANDKEYSIZEARE128BITSTHEBLOCKSIZEISCOMMONLYDENOTEDASNBANDTHEKEYSIZEISCOMMONLYDENOTEDASNKNBREFERSTOTHENUMBEROFCOLUMNSINTHEBLOCKWHEREEACHROWINTHECOLUMNCONSISTSOFFOURCELLSOF8BYTESEACHFORAES1285THEFOLLOWINGEXAMPLEWILLSHOWHOWDATAISBROKENUPINTOBLOCKSUSINGAES128MEANSTHATEACHBLOCKWILLCONSISTOF128BITSNBCANBECALCULATEDBYDIVIDING128BY32THE32COMESFROMTHEADVANCEDENCRYPTIONSTANDARDDOUGLASSELENTSTUDENT,MSPROGRAMINCOMPUTERSCIENCE,RIVIERCOLLEGEDOUGLASSELENT2NUMBEROFBYTESINEACHCOLUMNINTHISCASE,NBIS4THEORIGINALPLAINTEXTISSTOREDINBYTESINABLOCKFOREXAMPLE,THETEXT“THISISATEST”WILLBESTOREDINABLOCKASSHOWNBELOWINFIGURE1FIGURE1AES128BLOCKEXAMPLEEACHCHARACTERISSTOREDINACELLOFTHEBLOCKTHEBLANKCELLSSHOWNINTHEDIAGRAMARENOTREALLYBLANKASTHEYREPRESENTTHESPACESINTHETEXTDEPENDINGONHOWTHEALGORITHMISIMPLEMENTEDTHECHARACTERSMAYBESTOREDASINTEGERVALUES,HEXADECIMALVALUES,OREVENBINARYSTRINGSALLTHREEWAYSREPRESENTTHESAMEDATAMOSTDIAGRAMSSHOWTHEHEXADECIMALVALUES,HOWEVERINTEGERANDSTRINGMANIPULATIONISMUCHEASIERTODOWHENACTUALLYPROGRAMMINGAESFIGURE1SHOWSTHEVALUESASCHARACTERSFORDEMONSTRATIONPURPOSESTOSHOWHOWTHETEXTISSTOREDINTOTHEBLOCKTHEPLAINTEXTISSTOREDINTOBLOCKSCOLUMNBYCOLUMNANDBLOCKBYBLOCKUNTILALLTHEDATAISSTORED5INTHEEXAMPLEUSEDABOVETHEREWEREEXACTLY16CHARACTERSUSEDFORSIMPLICITYINORDERTOUSETHERIJNDAELALGORITHMTHEDATAMUSTBEAMULTIPLEOFTHEBLOCKSIZE,SINCEALLBLOCKSNEEDTOBECOMPLETEWHENTHEDATAISNOTAMULTIPLEOFTHEBLOCKSIZESOMEFORMOFPADDINGMUSTBEUSEDPADDINGISWHENEXTRABITSAREADDEDTOTHEORIGINALDATAONEFORMSOFPADDINGINCLUDESADDINGTHESAMEBYTESUNTILTHEDESIREDSIZEISREACHEDANOTHEROPTIONISPADDINGWITHALLZEROSANDHAVINGTHELASTBYTEREPRESENTTHENUMBEROFZEROSPADDINGWITHNULLCHARACTERSORRANDOMCHARACTERSAREALSOFORMSOFPADDINGTHATCANBEUSED6ONCEAFORMOFPADDINGISCHOSENTHEDATAISREPRESENTEDASSOMENUMBEROFCOMPLETEBLOCKSTHELASTTHINGNEEDEDBEFOREUSINGTHEALGORITHMISTHEKEYTHEKEYALSOKNOWNASTHECIPHERKEYISALSOTHESAMESIZEASTHEBLOCKINTHISEXAMPLEUNLIKEMOSTDATAANDTRANSFORMATIONSTHECIPHERKEYCANHAVEANYVALUESCHOSENBYTHEDESIGNERWITHNORESTRICTIONSASLONGASTHEKEYISTHECORRECTLENGTHTHEKEYISALSOSTOREDASABLOCKSIMILARTOTHEPLAINTEXT5WHENTHEPLAINTEXTDATAISSTOREDINTOBLOCKSANDTHEKEYISCHOSENTHERIJNDAELENCRYPTIONALGORITHMCANBEAPPLIEDSOMEOFTHEFOLLOWINGSTEPSCOULDBEDONEBEFORETHEENCRYPTIONPROCESSSTARTS,BUTFORSIMPLICITYTHEYWILLBEDISCUSSEDWHENTHEYARENEEDED3ADVANCEDENCRYPTIONSTANDARD3RIJNDAELROUNDSATABASICLEVELTHERIJNDAELALGORITHMUSESANUMBEROFROUNDSTOTRANSFORMTHEDATAFOREACHBLOCKTHENUMBEROFROUNDSUSEDIS6THEMAXIMUMOFNBANDNKFOLLOWINGFROMTHEPREVIOUSEXAMPLEOFAES128,THENUMBEROFROUNDSIS10THISISCALCULATEDFROM6PLUSTHEMAXIMUMOF4,4SINCENBANDNKAREBOTH4,THENUMBEROFROUNDSIS64102THEINITIALBLOCKALSOKNOWNASASTATEISADDEDTOANEXPANDEDKEYDERIVEDFROMTHEINITIALCIPHERKEYTHENTHEROUNDPROCESSINGOCCURSCONSISTINGOFOPERATIONSOFTHESBOX,SHIFTS,ANDAMIXCOLUMNTHERESULTSTATEISTHENADDEDTOTHENEXTEXPANDEDKEYTHISISDONEFORALLTENROUNDS,WITHTHEEXCEPTIONOFTHEMIXCOLUMNOPERATIONOFTHEFINALROUNDTHEFINALRESULTISTHEENCRYPTEDCIPHERBLOCK54RIJNDAELKEYEXPANSIONTHEORIGINALCIPHERKEYNEEDSTOBEEXPANDEDFROM16BYTESTO16R1BYTESINTHEEXAMPLE,THEREARETENROUNDSSOR10AROUNDKEYISNEEDEDAFTEREACHROUNDANDBEFORETHEFIRSTROUNDEACHROUNDKEYNEEDSTOBE16BYTESBECAUSETHEBLOCKSIZEIS16BYTESTHEREFORE,THECIPHERKEYNEEDSTOBEEXPANDEDFROM16BYTESTO16R1BYTESOR176BYTESTHEEXPANDEDKEYISTHENBROKENUPINTOROUNDKEYSROUNDKEYSAREADDEDTOTHECURRENTSTATEAFTEREACHROUNDANDBEFORETHEFIRSTROUNDTHEDETAILSONTHEKEYEXPANSIONALGORITHMARECOMPLEXANDWILLBESKIPPED45RIJNDAELSBOXTHEFIRSTSTEPTOAROUNDISTODOABYTEBYBYTESUBSTITUTIONWITHALOOKUPTABLECALLEDANSBOXANSBOXISAONETOONEMAPPINGFORALLBYTEVALUESFROM0TO255THESBOXISUSEDTOCHANGETHEORIGINALPLAINTEXTINBYTESTOCIPHERTEXTTHESBOXISSHOWNBELOWINFIGURE2ALLVALUESAREREPRESENTEDINHEXADECIMALNOTATIONTHISISHOWTHESBOXISCOMMONLYVIEWED5FIGURE2SBOXFROMHTTP/WWWSAMIAMORG/SBOXHTMLDOUGLASSELENT4FOREXAMPLEIFWEHADTHEPLAINTEXTOFONECHARACTER“D”ITWOULDTRANSLATETOTHEHEXADECIMALVALUEOF44BYUSINGANASCIILOOKUPTABLEWHENUSINGTHESBOXTHEFIRSTDIGITINHEXADECIMALREPRESENTSTHEROWSOFTHETABLEORTHEVALUESONTHELEFTSIDEGOINGDOWNTHESECONDDIGITREPRESENTSTHECOLUMNOFTHESBOX,WHICH,INTHISEXAMPLE,ISALSO4USINGTHESBOXWEFINDROWNUMBER4ANDCOLUMNNUMBER4ANDFINDTHATTHEHEXADECIMALVALUEINTHATCELLIS“1B”THISISHOWTHESBOXWORKSUSINGTHISMETHODWITHALLTHEPLAINTEXTWILLGENERATETHENEWHEXADECIMALVALUESTHATAREUSEDLATERINTHEALGORITHMTHEOBVIOUSQUESTIONISWHEREDIDTHESBOXCOMEFROMTHISGOESINTOMODULARARITHMETICANDAGALOISFIELDAGALOISFIELDISAFIELDWITHAFINITENUMBEROFELEMENTSTHEGALOISFIELDISALWAYSAFIELDTHATISAPOWEROFAPRIMEFOREACHPRIMENUMBERTHEREEXISTSEXACTLYONEGALOISFIELDTHENOTATIONTOREPRESENTAGALOISFIELDISGFP,WHEREPISTHEPRIMENUMBER8FORTHESBOX,THEFIELDGF28WASCHOSENTHEREARESEVERALREASONSTOWHYTHISFIELDWASCHOSENONEOBVIOUSREASONISTHATTHEPOWEROF8WASCHOSENBECAUSETHEREARE8BITSINABYTETHEPRIME2WASCHOSENBECAUSEBINARYISREPRESENTEDASTWOPOSSIBLEDIGITSA1ORA0INADDITIONARITHMETICISSIMPLETODOINTHISFIELDBECAUSEADDITIONANDSUBTRACTIONAREREDEFINEDASTHEEXCLUSIONORXOROPERATIONINVERTABILITYANDRESISTANCETOALGEBRAICATTACKSWEREALSOCONSIDEREDWHENFORMINGTHESBOX5TOACTUALLYGENERATETHESBOXFROMTHECHOSENFIELDREQUIRESMUCHMOREWORKCAREFULTHOUGHTWASPUTINTOTHETRANSFORMATIONFORSECURITYPURPOSESUSINGPLAINTEXTFORTHENEXTSTEPSOFTHEALGORITHMWOULDMAKEITMOREVULNERABLESOABYTESUBSTITUTIONINTHEFORMOFTHESBOXWASUSEDTHEORIGINALBYTESARETRANSFORMEDBYUSINGTHEMULTIPLICATIVEINVERSEANDANAFFINITYMATRIXSHOWNINFIGURE3TOMAKETHECIPHERTEXTRESISTANTTOALGEBRAICATTACKS7FIGURE3AFFINITYMATRIXFROMHTTP/WWWSAMIAMORG/SBOXHTMLFIGURE4MULTIPLICATIVEINVERSETABLEGF28FROMHTTP/WWWSAMIAMORG/GALOISHTMLINVERSE5ADVANCEDENCRYPTIONSTANDARDTOCALCULATETHEMULTIPLICATIVEINVERSEISCOMPLICATEDANDTOOMUCHOFADIGRESSIONTHEREFORE,AGIVENTABLEWILLBEUSEDINSTEADTHEFIELDOFALLTHEMULTIPLICATIVEINVERSESISSHOWNINFIGURE47USINGANEXAMPLEOFTHEHEXADECIMALVALUE“31”FROMTHEMULTIPLICATIVEINVERSETABLEWEGETTHEVALUE“45”FROMTHETABLETHISISTHEVALUEWEWILLUSEOURAFFINITYMATRIXISINBINARYTHEREFORETHENUMBERMUSTBEINBINARYASWELL45HIS01000101INBINARYANEASIERWAYTOVIEWTHEMATRIXMULTIPLICATIONISASPOLYNOMIALMULTIPLICATIONTHEVALUE01000101CANBEREPRESENTEDASTHEPOLYNOMIAL0X71X60X50X40X31X20X11THISCANBEREWRITTENANDSIMPLIFIEDASX6X21TAKINGTHEFIRSTROWOFTHEAFFINITYMATRIXWECANASSIGNEACHBITAVARIABLETHEREFORE,10001111CANBEREPRESENTEDASN0N1N2N3N4N5N6N7THISISGENERALIZEDTOALLTHEROWS,SOALLROWSCANBEREPRESENTEDWITHTHESAMEVARIABLESINTHESAMEORDERTODOTHEMULTIPLICATIONSTARTWITHTHEFIRSTROWANDSEEWHICHVARIABLESAREA1INTHEAFFINITYMATRIXSINCETHEFIRSTROWIS10001111,WEONLYHAVETOWORRYABOUTTHEVALUESN0N4N5N6N7NEXT,WELOOKATTHEPOLYNOMIALX6X21THEPOWERSOFTHISPOLYNOMIALAREWHATCORRESPONDTOTHESUBSCRIPTSOFNWHEREVERTHEPOWERINTHEPOLYNOMIALISALSOINTHESUBSCRIPTOFNWECANASSIGNAVALUEOF1OTHERWISEWEASSIGNTHEVALUEOF0THISMAKESN0N4N5N6N7CHANGETO10010AFURTHERSHORTCUTCANBETAKENTOIGNOREALL0SCOMPLETELYTHISCANBEDONEBECAUSEADDITIONINTHEFIELDGF28ISJUSTTHEXOROPERATIONTHEREFORE,ADDINGANEVENNUMBEROF1SWILLRESULTINAVALUEOF0ANDADDINGANODDNUMBEROF1SWILLRESULTINAVALUEOF1SHOWNBELOWINFIGURE5ISTHESIMPLIFIEDMATHEMATICSFORTHEENTIREAFFINETRANSFORMATION7ROW110001111N0N4N5N6N7100100ROW211000111N0N1N5N6N7100100ROW311100011N0N1N2N6N7101101ROW411110001N0N1N2N3N7101000ROW511111000N0N1N2N3N4101000ROW601111100N1N2N3N4N5010001ROW700111110N2N3N4N5N6100010ROW800011111N3N4N5N6N7000101FIGURE5SIMPLIFIEDMULTIPLICATIONEXAMPLEROWSAREMULTIPLIEDBYTHEPOLYNOMIALX6X21THERESULTOFTHEMULTIPLICATIONISTHEVECTOR00100101THEFINALSTEPTOTHETRANSFORMATIONISTOADDTHEVECTOR11000110TOOURVECTORTHISGIVESUSTHEFINALBINARYSTRINGOF11100011SINCEWEWANTTHELASTROWREPRESENTEDASTHEFIRSTBITWENEEDTOREVERSETHISSTRINGGIVINGUSTHENEWBINARYSTRINGOF11000111INHEXADECIMALTHISVALUEISC77WEARENOWFINISHEDTOKNOWTHATWEDIDEVERYTHINGRIGHTWELOOKBACKTOWHEREWESTARTEDWESTARTEDWITHTHEHEXADECIMALVALUEOF31FROMTHEORIGINALTABLEANDAFTERALLTHEWORKOBTAINEDTHEVALUEC7THEREFORE,IFWELOOKATTHESBOXVALUEFOR31,WESHOULDSEEC7ALLTHEVALUESINTHESBOXARECALCULATEDTHESAMEWAYWEDIDFOROUREXAMPLEUSINGTHEPREVIOUSEXAMPLE“THISISATEST”,THEFOLLOWINGBLOCKISARESULTOFTHESBOXSUBSTITUTIONANASCIILOOKUPTABLEWASALSOUSEDTOCONVERTTHECHARACTERVALUESINTOHEXADECIMALVALUESTHERESULTINGBLOCK/STATEHASALLVALUESSHOWNINHEXADECIMALNOTATIONNOTETHATKEYADDITIONWASNOTAPPLIEDIFTHISWEREAREALIMPLEMENTATIONTHEKEYADDITIONWOULDBEAPPLIEDTOTHESTATEBEFOREDOUGLASSELENT6THEFIRSTROUNDTHEREFORE,THESBOXSUBSTITUTIONWOULDBEDONEWITHTHESTATEAFTERTHEKEYADDITIONTHEBLOCKISSHOWNINFIGURE6FIGURE6BLOCK/STATEAFTERSBOXSUBSTITUTION6RIJNDAELSHIFTSTHENEXTSTEPINTHEROUNDISTOSHIFTTHEROWSOFTHESTATETHEROWSARESHIFTEDXNUMBEROFBYTESTOTHELEFTWHEREXISTHEROWNUMBERTHISMEANSROW0WILLNOTBESHIFTED,ROW1WILLBESHIFTED1BYTETOTHELEFT,ROW2WILLBESHIFTED2BYTESTOTHELEFT,ANDROW3WILLBESHIFTED3BYTESTOTHELEFTTHERESULTINGSTATEISSHOWNINFIGURE7BYAPPLYINGTHESHIFTSTOTHEPREVIOUSSTATENOTETHATTHESHIFTSDONOTAFFECTTHEBYTESUBSTITUTIONSOTHESHIFTINGANDSBOXOPERATIONSCOULDBEDONEINADIFFERENTORDER9FIGURE7BLOCK/STATEAFTERSHIFTING7ADVANCEDENCRYPTIONSTANDARD7RIJNDAELMIXCOLUMNAFTERAPPLYINGTHESBOXANDSHIFTSTOTHESTATETHEOPERATIONOFAMIXCOLUMNISUSEDTHEMIXCOLUMNLOOKUPTABLETAKESABYTEANDTRANSFORMSITINTOFOURBYTESTHEMIXCOLUMNTABLEISGENERATEDBYTHEFOLLOWINGALGORITHMEACHELEMENTINTHETABLECONSISTSOFFOURBYTESUSUALLYREPRESENTEDASHEXADECIMALVALUESTHESECONDANDTHIRDBYTESAREALWAYSSAMEASTHEINPUTBYTESOFORTHEVALUEOF54WOULDRESULTINASECONDANDTHIRDVALUEOF54ASWELLTHEFIRSTBYTEISTHEINPUTBYTEMULTIPLIEDBY2IFTHERESULTISGREATERTHAN0XFF,THERESULTISXOREDWITHTHEVALUE0X1BANDMOD100THEREFOREOURTHEBYTE0X54IS54XOR1BMOD100A8THELASTBYTEISTHEINPUTBYTEADDEDTOTHEFIRSTBYTE9SO,THELASTBYTEISA8XOR54FCTHISISASIMPLEWAYTOGENERATETHEMIXCOLUMNTABLESHOWNINFIGURE8FIGURE8MIXCOLUMNTABLEIMAGEFROMNETWORKSECURITYPRIVATECOMMUNICATIONINAPUBLICWORLD,PAGE86DOUGLASSELENT8WHATISREALLYHAPPENINGISAMATRIXMULTIPLICATIONOFTHEINPUTWITHTHEMATRIXINFIGURE9FOROURPURPOSESTHESHORTCUTISMOREPRACTICALATGENERATINGTHETABLEITALSOAVOIDSTHEMULTIPLICATIONOPERATIONWHICHISSOMEWHATCOMPLICATEDINTHEFIELDGF282311123111233112FIGURE9MATRIXFORGENERATINGTHEMIXCOLUMNTABLEFROMHTTP/WWWSAMIAMORG/MIXCOLUMNHTMLTHENEXTQUESTIONISHOWTOUSETHEMIXCOLUMNTABLEFOROUREXAMPLEWENEEDTOSPLITUPOUTSTATEINTOCOLUMNSEACHCOLUMNWILLHAVEITSOWNMIXCOLUMNOPERATIONAPPLIEDTOITUSINGTHELOOKUPTABLEFORALLTHEVALUESINTHEFIRSTCOLUMNOFOURSTATEWEGETTHEFOLLOWING0X20402020600XF9E9F9F9100X923F9292AD0X3162313153FIGURE10FIRSTCOLUMNTRANSFORMEDWITHTHEMIXCOLUMNTABLE9ADVANCEDENCRYPTIONSTANDARDTHEMIXCOLUMNSTEPISBESTSHOWNASADIAGRAMTHEDIAGRAMISSHOWNINFIGURE1140B3F3E9209C553FF92053B56292F96069319210B331AD9C53FIGURE11MIXCOLUMNOPERATIONTHERESULTOFUSINGTHEMIXCOLUMNOPERATIONONTHEFIRSTCOLUMNISTHEBYTES0X49,0X34,0XA7,AND0XBDTHEBLUEVALUESINTHEDIAGRAMINDICATETHATRESULTISUSEDINTHEFINALADDITIONSIMILARLYTHEOTHERCOLUMNSINTHESTATEGOTHROUGHTHESAMEPROCESSTHERESULTISASTATEWITHTHENEWVALUESAFTERTHEMIXCOLUMNPROCESS8RIJNDAELDECRYPTIONDECRYPTIONISSIMPLEAFTERUNDERSTANDINGTHEENCRYPTIONPROCESSITISBASICALLYJUSTTHEINVERSETHEALGORITHMWASDESIGNEDFORALLTHESTEPSTOBEINVERTIBLESODECRYPTIONISBASICALLYLIKEDOINGEVERYTHINGBACKWARDSTHEREFORE,FORDECRYPTIONSTARTSATTHELASTROUNDANDTHELASTROUNDKEYWHENPROCESSINGEACHROUNDDOTHEPROCESSBACKWARDSSO,THEROUNDKEYISADDEDFIRSTTOTHELASTROUNDADDITIONISITSOWNINVERSE,WHICHISNICETHENTHEMIXCOLUMNSTEPISAPPLIEDTHEMIXCOLUMNSTEPISAPPLIEDTOALLROUNDSEXCEPTTHELASTONEALSOTHEINVERSEMIXCOLUMNTABLEISUSED5THISTABLEISGENERATEDWITHANOTHERMATRIXSIMILARTOTHEWAYTHEMIXCOLUMNTABLEWASGENERATEDTHEDIFFERENCEISTHATTHEREARENOSHORTCUTSTOGENERATETHETABLETHEREFORE,THEMATRIXMULTIPLICATIONNEEDSTOBEPERFORMEDINTHEFIELDGF28THEMATRIXISSHOWNINFIGURE12ANDTHEINVERSETABLEISSHOWNINFIGURE13101411139914111313914111113914FIGURE12MATRIXFORGENERATINGTHEINVERSEMIXCOLUMNTABLETHISISTHEINTEGERREPRESENTATIONOFTHEHEXADECIMALDATAINTHETABLEFROMHTTP/CSRCNISTGOV/PUBLICATIONS/FIPS/FIPS197/FIPS197PDF,FIGURE510DOUGLASSELENT10FIGURE13INVERSEMIXCOLUMNTABLEFROMNETWORKSECURITYPRIVATECOMMUNICATIONINAPUBLICWORLD,P88ALLTHESHIFTSAREDONEBACKWARDSASWELLSO,INSTEADOFSHIFTINGLEFT,WESHIFTRIGHTLASTLY,THESBOXISAPPLIEDUSINGTHEINVERSESBOXTABLETHEINVERSESBOXTABLECANEASILYBEGENERATEDBYTAKINGTHESBOXVALUEATSOMEROWANDCOLUMNINDEXANDASSIGNINGTHEROWANDCOLUMNTOTHEINVERSESBOXVALUEATTHEINVERSESBOXINDEXDEFINEDBYTHESBOXVALUEFOREXAMPLE,THESBOXHASAVALUEOF0X00ATINDEX5,2THISTRANSLATESTOTHEINVERSESBOXHAVINGTHEVALUE0X52ATINDEX0,0THEINVERSESBOXTABLEISSHOWNINFIGURE142AFTERALLTHEROUNDSHAVEBEENCOMPLETEDINOPPOSITEORDERTHEFINALSTATEWILLCONTAINTHEORIGINALPLAINTEXT11ADVANCEDENCRYPTIONSTANDARDFIGURE14INVERSESBOXFROMHTTP/WWWSAMIAMORG/SBOXHTML9CONCLUSIONTHERIJNDAELALGORITHMWASCHOSENASTHENEWADVANCEDENCRYPTIONSTANDARDAESFORSEVERALREASONSTHEPURPOSEWASTOCREATEANALGORITHMTHATWASRESISTANTAGAINSTKNOWNATTACKS,SIMPLE,ANDQUICKTOCODECHOOSINGTOUSEFIELDGF28WASAVERYGOODDECISIONTHEINVERSEOFTHEADDITIONOPERATIONWASITSELF,MAKINGMUCHOFTHEALGORITHMEASYTODOINFACT,EVERYOPERATIONISINVERTIBLEBYDESIGNINADDITION,THEBLOCKSIZEANDKEYSIZECANVARYMAKINGTHEALGORITHMVERSATILEAESWASORIGINALLYDESIGNEDFORNONCLASSIFIEDUSGOVERNMENTINFORMATION,BUT,DUETOITSSUCCESS,AES256ISUSABLEFORTOPSECRETGOVERNMENTINFORMATION11ASOFJULY2009,NOPRACTICALATTACKSHAVEBEENSUCCESSFULONAES1210CODESAMPLESTHECODESAMPLESBELOWHAVEBEENDEVELOPEDBYTHEAUTHORTHEFOLLOWINGJAVACODEMODULECREATESTHEINVERSESBOXFROMTHEORIGINALSBOXBOTH“BOXES”STORETHEVALUESOFINTEGERSPUBLICVOIDCREATEINVERSESBOXFORINTI0I128MIXCOLUMNIJ0MIXCOLUMNIJ027256MIXCOLUMNIJ1I16JMIXCOLUMNIJ2I16JMIXCOLUMNIJ3MIXCOLUMNIJ0MIXCOLUMNIJ113ADVANCEDENCRYPTIONSTANDARDTHISMODULEPERFORMSTHESBOXSUBSTITUTIONWITHABYTEREPRESENTEDASANINTEGERPUBLICINTSBOXSUBSTITUTIONINTPLAINTEXTINTTABLESPOTIGETIVALUEPLAINTEXTINTTABLESPOTJPLAINTEXT16RETURNSBOXTABLESPOTITABLESPOTJTHISPROGRAMCREATESTHEBLOCKSOUTOFTHEPLAINTEXTREPRESENTEDASACHARACTERARRAYPUBLICINTCREATESTATESCHARTEXTARRAY,INTNUMSTATESINTSTATESNEWINTNUMSTATES44INTZ0/STATE,ROW,COLUMNFORINTI0INUMSTATESIFORINTJ0J4JFORINTK0K4KSTATESIKJINTTEXTARRAYZZRETURNSTATESTHISMODULEPERFORMSARIJNDAELROUND,BUTITISNOTCOMPLETELYFINISHEDYETPUBLICINTROUNDINTSNUM,INTROUNDNUM,INTSTATES,/EXPANDEDKEY/FORINTI0I4IFORINTJ0J4JSTATESSNUMIJSBOXSUBSTITUTIONSTATESSNUMIJFORINTI1I4IFORINTJ0JIJDOUGLASSELENT14INTTEMPSTATESSNUMI0STATESSNUMI0STATESSNUMI1STATESSNUMI1STATESSNUM
温馨提示
- 1. 本站所有资源如无特殊说明，都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等，如果需要附件，请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸，网页内容里面会有图纸预览，若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对用户上传分享的文档内容本身不做任何修改或编辑，并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容，请与我们联系，我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 技术类测评试题及答案
- 技术笔试题目及答案
- 技能提升篇：竞赛部门面试题库岗位胜任力提升计划
- 前沿挑战者前哨站：早期咨询面试题库更新提示
- 大厂人资招聘策略与技巧：面试题库全面解析
- 教育技术专家香港小学面试题目及答案技术操作解析
- 行业前沿面试问题及答案解析：新兴领域就业方向与发展趋势
- 新媒体运营教学教案（25-26）社群运营
- 12345知识库培训课件
- 广西体育招聘面试实战模拟题及答案解析
- 八师兵团职工考试题库及答案
- 2025临时工合同协议书模板
- 2025年学习贯彻全国教育大会精神网络培训考试答案
- 推拿学基础题库及答案
- 水利工程档案验收项目法人自检工作报告
- 工资管理课件
- 电商客服培训 课件
- 2025社区治理一表通应用规范
- 中国古诗词歌曲课件
- GB/T 26148-2025高压水射流清洗作业安全规范
- 企业法检商品管理制度
评论
0/150
提交评论