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.