电子现金分类表

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1、ElectronicCashProtocolsCOMP685CLecture18Acknowledgements:SlidesarefromJinYuan1OutlinenIntroductionnBasicModelandanExemplarySchemenBrands’SchemenDivisibleCoinsnAnonymityControlnSummaryElectronicCashSystemsPage:2ClassificationofElectronicPaymentSystemsnToken-basedvs

2、.account-basednAnonymousvs.un-anonymous:nDoesthebankknowwhohasboughtwhat?nOnlinevs.off-linenIsthebankinvolvedattimeoftransaction?nExamples:Account-based,un-anonymousToken-based,anonymousOnlineEPScards———Off-lineCreditcardsTele.cards,physicalcash,E-cashnE-cash:anon

3、ymous,off-line,token-basedpaymentsystems.ElectronicCashSystemsPage:3PossibleE-cashApplicationsnTeleshoppingnPaidaccesstoInternetservicesnnews,papers,music,video…ElectronicCashSystemsPage:4SignatureSchemeNeedednIne-cash,anelectroniccoinortokenisabitstringtypicallys

4、ignedbythebanktoguaranteeitsvalue.nThesignaturecanbeverified.ElectronicCashSystemsPage:5OutlinenIntroductionBasicModelandanExemplarySchemenBrands’SchemenDivisibleCoinsnAnonymityControlnSummaryElectronicCashSystemsPage:6ABasicModelofE-cashTrustee(Optional)Bank2.Wit

5、hdraws4.Deposits1.OpensAccountUserShop3.Pays1.OpenAccount:Thebanktakesdowntheuser’sidentityinformationandopensanaccount.2.Withdraw:Theusergeneratesthecoinandthebanksignsit.Acoinisactuallyacollectionofbitswithsomecryptographicproperties.3.Pay:Theusergivesthecointot

6、heshopandproveshehassomeknowledgeofthecoin.4.Deposit:Theshopgivesthecoinandpaymenttranscripttothebankforredemption.Thebankverifiesthevalidityofboththecoinandthepaymenttranscript.ElectronicCashSystemsPage:7BasicRequirementsofE-cashnLikephysicalcash:nUnforgeability:

7、bybank’sdigitalsignaturesonthecoins.nUntraceability:thebankcannotlinkadepositedcoinwithawithdrawal.ElectronicCashSystemsPage:8DoubleSpendingProblemnUnlikephysicalcash:nItiseasytocopyanelectroniccoinandtrytospenditmorethanonce!Thisiscalledthedoublespendingproblem.n

8、Whocandouble-spend?nOwnerofthecoin?Becausehecreatedthecoin.nAnyoneelse?It’seasytocopybuteventhebankcan’tspentit.nSolution:nPreventionbyhardware:walletsw