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Ciphertext



Introduction

Theciphertextistheencryptedtext,andtheplaintextisthetextbeforeencryption.Thetermencryptionsometimesreferstociphertext,butitisusuallyusedtorefertothemethodofencryption.Theoutputaftersomedisguiseortransformationisappliedtotheplaintext.Itcanalsobeunderstoodasasetofcharactersorbitsthatcannotbedirectlyunderstood.Butthescrambledmessagesthatcanberestoredbyalgorithmsareoppositetoplaintext.

Ciphertextsaremessagesandsignalsgeneratedbyacryptographicsystem.Ifthecodetextischangedwithoutinstructionsfromthecodetextrecipient,thatis,decryption,otherscannotunderstandit.Thepurposeistoensuretheconfidentialityoftheinformationsent.However,withthedevelopmentofscienceandtechnology,whenpeopleanalyzethenumberofencryptionsteps,encryptionoperations,andencryptionprocessandunderstandtheabovethreeaspects,theycanstillconvertciphertextintoplaintextwithoutknowingthekey..

Basicconcepts

Basicconceptsofciphertexttheory.Itisthetransformationofinformationindigitalcommunicationtoensuretheconfidentialityandauthenticityofinformation.Theinformationhereisexpressedasasequenceonasetofq-aryalphabets,theoriginalinformationiscalledplaintext,andthesequenceobtainedafterencryptionandtransformationiscalledciphertext.Iftheciphertextisobtainedbyrearrangingtheorderoftheelementsintheplaintextaccordingtoacertainrule,suchatransformationiscalledashiftcipher.Ifthereisaone-to-onecorrespondencebetweenthealphabetanditself,andeachelementintheplaintextisreplacedwithitscorrespondingelementtoobtaintheciphertext,suchatransformationiscalledasubstitutionpassword.

Forexample,theciphertext"TURELERT"isencryptedbythekeyandbecomes"2021181412050620".Atthistime,"2021181412050620"istheencryptedciphertext.Thekeyis"1~26"correspondingto"A~Z".

Origin

Inordertoensurenetworksecurity,itisnotenoughtoinstallafirewall.Othertechnologies,suchasuserauthentication,intrusiondetection,andpasswordtechnology,arealsorequired.Sotheciphertextisproduced.

Usuallyweencryptplaintextintociphertextwithakeytoprotectourinformation.

Searchstrategy

Directlymanipulateciphertextdata

Thesecrethomomorphismtechnologyofthedatabaseandthesequenceencryptionofthedatabase,etc.;thesecrethomomorphismtechnologyproposestheencryptionalgorithmCertainconstraintsmaketheapplicationofencryptionalgorithmsthatsatisfythehomomorphicciphertextnotuniversal;thesequenceencryptionmethodofthedatabasemainlyadoptsthesequencecipheralgorithm,andthesequencecipheralgorithmadoptstheexclusiveORoperationmethod.Thekeysequencecannotberepeated.Differentrecordsadoptdifferentkeyseeds,andthekeymanagementistoodifficult.Ifthesamekeyseedsareusedfordifferentrecords,therewillbemanyidenticalorsimilarciphertextfieldvalues,whicharevulnerabletostatisticalattacksandknownplaintext.attack.

Step-by-stepquery

Generally,querydecompositionisrequired.First,performrangequeryonciphertextdata,narrowthedecryptionrange,andperformaccuratequeryafterfastdecryption.ThecoredifficultyofquerystrategyliesinItisnecessarytoimprovetheaccuracyofqueryingtheciphertextdatabaseasmuchaspossible,andreducethescopeoftheciphertextdatareturnedtotheclient.

Duringthedatabaseciphertextsearch,thevalueofthekeywordisusedtodeterminewhichpartitionthekeywordbelongsto,andthenaccordingtothevaluerange,itisdeterminedwhichrecordsinthedatabasemaymeetthesearchconditions.

Example:FortheretrievalconditionY>450,itcanbedeterminedthatalltherecordsofpartition1andpartition4meettheretrievalconditions,andbydecryptingalltherecordsofpartition5,theremainingdatabasesthatmeettheconditionscanbeaccuratelydeterminedrecord.Establishingadatabasevalueindexonlythroughrangepartitioningislikelytocausedatabaseinformationleakage.Therefore,thedatabasepartitioningmethodusuallyusesHASHtechnology.Afterthevalueishashed,thevalueispartitionedaccordingtotheHASHvaluetoavoidtheproblemofinformationleakage.

Ciphertextdatabaseindexmechanism

1.Directindexofciphertextdata:ThemaindisadvantageofthedirectindexmethodofciphertextdataisthattheaddressdataintheciphertextindextreeisbasedonWhenstoredinplaintext,theattackercansorttheciphertextdataofeachnodeaccordingtoitscorrespondingplaintext,andusethestatisticallawscorrespondingtopartoftheplaintextandciphertexttoobtainkeyinformationthatcanbeusedfordeciphering.

2.Ciphertextindexofaddressencryption:Theciphertextindexmethodofaddressencryptioncansolvetheshortcomingsofdirectciphertextindex,butifanattackercandynamicallytracktheaccessprocessofthedatabaseatthesametime,itispossibletofindoutThecorrespondencebetweentheciphertextandtheciphertextaddresscanbeexploited.

3.Dynamicandsecureciphertextindex:Althoughthedynamicandsecureciphertextindexmethodcaneffectivelycountertheattacker'sdynamictrackingandanalysisofthecorrespondingrelationshipbetweentheciphertextdataandtheindex,itisverycomplicatedtoimplement,Needtousedual-addressindex,aftereachaccesstotheindex,twociphertextdataareaccessed,oneoftheciphertextdataismainlytoproduceaconfusioneffect,theadversarycanfullyknowtheorderoftheciphertextdatathroughdynamicanalysisoftheretrievalprocessandguessingTheprobabilityoftherelationshipisgreatlyreduced,sothatthesecurityoftheciphertextindexisimproved.

Hash-basedciphertextretrievalscheme

1.Hash-basedciphertextretrievalscheme:useHashfunctiontobuildindex,linkarandomnumberbehindtheinformationbeforeencryptiontoensurethesameAftertheplaintextisencrypted,differentciphertextsaregenerated,whichimprovesthesecurity;eachrecordinthedatabasehasmanyfields,selectthefieldssuitableforaccurateretrievalandindexingtoestablishtheindex,andstoretheestablishedindexinthecorrespondingfield;Whensearching,searchinthecorrespondingfieldaccordingtothesearchterm.Ifthematchissuccessful,thecorrespondingentirerecordisretrieved.

2.Hash-basedciphertextfuzzyretrievalscheme:useHashfunctiontoestablishfuzzyretrievalindex,andrealizefuzzyretrievalofciphertextdatathroughfuzzymatching.

Developmentdirectionofciphertextretrieval

Theretrievalofciphertextdatabaseisacomplextask.Efficientandsecureciphertextdatabaseretrievalisahotspotofdatabasesecuritytechnologyresearch;inthefutureInourwork,wewillfurtherstudytheretrievalalgorithmsothatitcanadapttotheciphertextdatabaseretrievalmechanismofvariouscomplexquerymodessuchasfuzzyquery,multi-tablequery,andcompoundconditionquery.

Relatedterms

Ciphertext-onlyattack

Ciphertext-onlyattackisalsoknownas"ciphertextanalysis","ciphertextonlyattack",or"ciphertextonlyattack"Ciphertextdecipheringmethod".Passwordattackwhenonlyciphertextisobtained.

Unknownalgorithmattackmethod

Unknownalgorithmattackmethodisamethodofdecipheringpasswords.Inthismethod,theattackerdoesnotknowtheencryptionanddecryptionalgorithms,andgenerallydoesnotknowthekey.

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