Domov technika Encryption Algorithm

Encryption Algorithm



Briefintroduction

Accordingtorecords,theancientGreeksinventedthesubstitutioncodein400BC.In1881,theworld'sfirsttelephonesecuritypatentappeared.DuringtheSecondWorldWar,theGermanmilitaryusedthe"Enigma"cryptographicmachine,andcryptographyplayedaveryimportantroleinthewar.

Withthedevelopmentofinformationtechnologyanddigitalsociety,people’sawarenessoftheimportanceofinformationsecurityandconfidentialitycontinuestoincrease,soin1997,theAmericanNationalBureauofStandardsannouncedtheimplementationofthe"AmericanDataEncryptionStandard(DES)"Thecivilforcesbegantofullyinterveneintheresearchandapplicationofcryptography,usingencryptionalgorithmssuchasDES,RSA,andSHA.Asthedemandforencryptionstrengthcontinuestoincrease,AESandECChaverecentlyappeared.

Usingcryptographycanachievethefollowingpurposes:

Confidentiality:Preventtheuser'sidentificationordatafrombeingread.

Dataintegrity:Preventdatafrombeingchanged.

Identityverification:toensurethatthedataissentfromaspecificparty.

Classification

Encryptiontechnologyisusuallydividedintotwocategories:"symmetric"and"asymmetric".

Symmetricencryptiontechnology

Symmetricencryptionmeansthatencryptionanddecryptionusethesamekey,usuallycalled"SessionKey".Thisencryptiontechnologyiswidelyusedtoday,suchasTheDESencryptionstandardadoptedbytheUSgovernmentisatypical"symmetric"encryptionmethod,anditsSessionKeylengthis56bits.

Asymmetricencryptiontechnology

Asymmetricencryptionmeansthatencryptionanddecryptiondonotusethesamekey.Thereareusuallytwokeyscalled"publickey"and"Privatekey",thetwoofthemmustbeusedinpairs,otherwisetheencryptedfilecannotbeopened.The"publickey"herereferstotheonethatcanbepublishedtotheoutsideworld,whilethe"privatekey"cannot.Itcanonlybeknownbytheholder.Itssuperioritylieshere,becauseifthesymmetricencryptionmethodistotransmitencryptedfilesonthenetwork,itisdifficultnottotelltheotherpartythekey,nomatterwhatmethodisused,itmaybeeavesdropped.Theasymmetricencryptionmethodhastwokeys,andthe"publickey"canbemadepublic,soyouarenotafraidofothersknowing.Therecipientonlyneedstousehisownprivatekeywhendecrypting,whichworkswell.Itavoidsthetransmissionsecurityproblemofthekey.

Algorithm

AnencryptionsystemScanbedescribedbymathematicalnotationasfollows:

S={P,C,K,E,D}

Amongthem

P——plaintextspace,whichmeansthesetofallpossibleplaintexts,

C——theciphertextspace,meansthesetofallpossibleciphertexts,

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K——keyspace,thekeyisavariableparameterintheencryptionalgorithm,

E——encryptionalgorithm,composedofsomeformulas,rulesorprocedures,

D——Decryptionalgorithm,whichistheinverseofE.

WhenthekeykÎKisgiven,therelationshipbetweenthesymbolsisasfollows:

C=Ek(P),theciphertextCisobtainedafterencryptingtheplaintextP

P=Dk(C)=Dk(Ek(P)),theplaintextPisobtainedafterdecryptingtheciphertextC

IfE-1representstheinverseofE,D-1representsDInversely,thereare:

Ek=Dk-1andDk=Ek-1

Therefore,theencryptiondesignmainlydeterminesE,D,K.

RSAisanencryptionalgorithmbasedonnumbertheoryasymmetry(publickey)proposedbyRivest,ShamirandAdleman.ThehardfactorizationofprimefactorsoflargeintegersisthebasisoftheRSAalgorithm.

RSAhasalreadyenteredthepracticalstageabroad,andavarietyofhigh-speedRSAdedicatedchipshavebeendeveloped.AlthoughmanyfeaturesofRSAarenotveryideal,duetotheactualneedsofinformationsecurity,manyimportantinformationsystemsstilluseRSAasabasicencryptionmechanism.SoonafterRSAwasputforward,relevantdepartmentsofourcountryhavebeenstudyingit.Fromanapplicationpointofview,RSAimplementedbysoftwarehasbeguntobeusedforcomputernetworkencryptiontocompletefunctionssuchaskeydistributionanddigitalsignatures.

InadditiontoRSA,thereisalsoDES(DataEncryptionStandard).AlthoughDESdiscloseditsencryptionalgorithmandwaslistedasa"standard"bytheUnitedStates,itwasquicklyabandoned.Encryptiontechnologyhasreturnedtothetraditionof"algorithmicsecrecy".

Commonencryptionalgorithms

DES(DataEncryptionStandard):Symmetricalalgorithm,dataencryptionstandard,faster,suitableforencryptinglargeamountsofdata;

3DES(TripleDES):ItisasymmetricalgorithmbasedonDES.Itusesthreedifferentkeystoencryptapieceofdatathreetimes,whichhashigherstrength;

RC2andRC4:symmetricalgorithms,usevariable-lengthkeysEncryptlargeamountsofdata,fasterthanDES;

IDEA(InternationalDataEncryptionAlgorithm)internationaldataencryptionalgorithm,usinga128-bitkeytoprovideverystrongsecurity;

RSA:InventedbyRSA,itisapublickeyalgorithmthatsupportsvariable-lengthkeys.Thelengthofthefileblockthatneedstobeencryptedisalsovariable,anasymmetricalgorithm;thealgorithmisasfollows:

First,findthreeNumber,p,q,r,

wherep,qaretwodifferentprimenumbers,andrisanumberthatisprimewith(p-1)(q-1).

Thethreenumbersp,q,rareprivatekeys.

Next,findmsothatrm==1mod(p-1)(q-1).....

Thismmustexist,becauserand(p-1)(q-1)arerelativelyprimeandcanbeobtainedbydividingbytossandturns.

Comeagain,calculaten=pq.......

m,nthesetwonumbersarepublickey

DSA(DigitalSignatureAlgorithm):DigitalsignaturealgorithmisastandardDSS(DigitalSignatureStandard),strictlyspeaking,itisnotanencryptionalgorithm;

AES(AdvancedEncryptionStandard):Advancedencryptionstandard,symmetricalgorithm,isthenextgenerationTheencryptionalgorithmstandardisfast,andthesecuritylevelishigh.AnimplementationoftheAESstandardinthe21stcenturyistheRijndaelalgorithm.

BLOWFISH,itusesavariable-lengthkeywithalengthofupto448bits,andrunsveryfast;

MD5:Strictlyspeaking,itisnotanencryptionalgorithm,itcanonlybesaidtobeadigestAlgorithm;

AbriefdescriptionoftheMD5algorithmcanbe:MD5processestheinputinformationin512-bitgroups,andeachgroupisdividedinto1632-bitsub-groups,afteraseriesofprocessing,Theoutputofthealgorithmiscomposedoffour32-bitpackets,andcascadingthesefour32-bitpacketswillgeneratea128-bithashvalue.

IntheMD5algorithm,theinformationneedstobefilledfirst,sothattheresultoftheremainderofthebytelengthof512isequalto448.Therefore,thebytelengthoftheinformation(BitsLength)willbeextendedtoN*512+448,thatis,N*64+56bytes(Bytes),whereNisapositiveinteger.Thefillingmethodisasfollows.Filla1andcountless0satthebackoftheinformation,andstopfillingtheinformationwith0suntiltheaboveconditionsaremet.Then,a64-bitbinaryrepresentationofthelengthofthepre-paddinginformationisappendedtotheresult.Afterthesetwostepsofprocessing,thelengthoftheinformationbyteisnow=N*512+448+64=(N+1)*512,thatis,thelengthisexactlyanintegermultipleof512.Thereasonforthisistomeettherequirementsforinformationlengthinthesubsequentprocessing.(SeetheMD5algorithmentry)

PKCS:ThePublic-KeyCryptographyStandards(PKCS)isasetofpublickeycryptographystandardsdevelopedbytheRSADataSecurityCorporationanditspartnersintheUnitedStates,includingcertificatesAseriesofrelatedagreementsonapplication,certificaterenewal,certificaterevocationformissuance,extendedcertificatecontent,digitalsignature,digitalenvelopeformat,etc.

SSF33,SSF28,SCB2(SM1):ThehiddenandundisclosedcommercialalgorithmsoftheNationalCryptographyBureau,whichareusedindomesticcivilandcommercialapplications,exceptthesearenotallowedtobeused,otherscanbeused;

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Otheralgorithms

SuchasElGamal,Diffie-Hellman,newellipticcurvealgorithmECC,etc.

Typesofencryptionalgorithms

Intoday'sinformationsecurityfield,therearevariousencryptionalgorithmsthatcondensethewisdomofcomputerscientists.Fromamacropointofview,theseencryptionalgorithmscanbesummarizedintothreecategories:hashingalgorithms,symmetricencryptionalgorithms,asymmetricencryptionalgorithm.

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