Smart contract
Introductiontotheterm
Theterm"Smartcontract"canbetracedbacktoatleast1995andwasproposedbytheprolificcross-fieldlegalscholarNickSzaboof.Hementionedtheconceptofsmartcontractsinseveralarticlespublishedonhiswebsite,whicharedefinedasfollows:
"Asmartcontractisasetofcommitmentsdefinedindigitalform,includingcontractparticipantsThesepromisedagreementscanbeexecutedonit."
Digitalform
Thedigitalformmeansthatthecontracthastobewrittenintocomputer-readablecode.Thisisnecessarybecauseaslongastheparticipantsreachanagreement,therightsandobligationsestablishedbythesmartcontractareexecutedbyacomputerorcomputernetwork.
Furtherexplanation:
(1)Agreement
Whenwilltheparticipantsofthesmartcontractreachanagreement?Theanswerdependsonthespecificsmartcontractimplementation.Generallyspeaking,whenaparticipantcommitstotheexecutionofthecontractbyinstallingthecontractonthecontracthostplatform,thecontractisdiscovered.
(2)Contractexecution
Thetruemeaningof"execution"alsodependsonimplementation.Generallyspeaking,implementationmeansactiveimplementationthroughtechnicalmeans.
(3)Computer-readablecode
Inaddition,thespecific"digitalform"requiredbythecontractisverydependentontheagreementthattheparticipantsagreetouse.
Agreement
Agreementisatechnicalimplementation(technicalimplementation),onthisbasis,contractpromisesarerealized,orcontractpromisesarerecorded.Whichagreementtochoosedependsonmanyfactors,themostimportantfactoristhenatureoftheassetbeingtradedduringtheexecutionofthecontract.
Takethesalescontractasanexampleagain.AssumethattheparticipantsagreetopayforthegoodsinBitcoin.TheprotocolchosenwillobviouslybetheBitcoinprotocol,onwhichsmartcontractsareimplemented.Therefore,the"digitalform"thatthecontractmustuseistheBitcoinscriptinglanguage.Bitcoinscriptinglanguageisanon-Turingcomplete,imperative,stack-basedprogramminglanguage,similartoForth.
Securityissues
Smartcontractsare"computertransactionagreementsthatenforcecontractterms."Allusersontheblockchaincanseesmartcontractsbasedontheblockchain.However,thiswillcauseallvulnerabilities,includingsecurityvulnerabilities,tobevisibleandmaynotbeabletoberepairedquickly.
Suchattacksaredifficulttosolvequickly.Forexample,thevulnerabilityofTheDAOEtherinJune2016causedalossof50millionUSdollars,andthedeveloperstriedtoreachaconsensussolution.TheDAOprogramhasadelaybeforethehackerdeletesthefunds.AhardforkoftheEthereumsoftwarecompletedtheattacker'sfundrecoveryworkbeforethetimelimitexpired.
TheproblemsinEthereumsmartcontractsincludecontractprogrammingSolidity,compilererrors,Ethereumvirtualmachineerrors,attacksontheblockchainnetwork,immutabilityofprogramerrors,andotherundocumentedattacks.
Cases
Casesfordeployingsmartcontractsinclude:
EthereumhasimplementedakindofnearTuringonitsblockchainCompletelanguage,thisisanoutstandingsmartcontractframework.
RootStock(RSK)isasmartcontractplatformconnectedtotheBitcoinblockchainthroughsidechaintechnology.RSKiscompatiblewiththesmartcontractcreatedforEthereum.
Popculture
KarlSchroeder’s2002novel"Permanence"proposesa"righteconomy"inwhichallphysicalobjectshavecontractsNanomarksarerequiredsothatpaymentscanbeimplementedforallusesofproprietaryinformation.Forexample,deep-spacemilitarymissionsmustcontinuouslyprovethebenefitratioofeachshiportheywillstopworking.
See
Blockchain
Bitcoin
Securemulti-partycomputing
Consensusmechanism
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