BoE-數(shù)字英鎊：技術(shù)篇（下）-86正式版

Thedigitalpound:TechnologyWorkingPaperFebruary2023Thedigitalpound:TechnologyWorkingPaperFebruary2023?BankofEngland2023Page3ExecutivesummaryThispaperaccompaniesthedigitalpoundConsultationPaper(CP),‘Thedigitalpound:anewformofmoneyforhouseholdsandbusinesses?’,andoutlinestheBankofEngland’s(theBank’s)thinkingonthetechnicalrequirementsanddesignconsiderationsforaUKcentralbankdigitalcurrency(CBDC).ThispapersetsouttheBank’semergingthinkingonCBDCtechnologyandseeksfeedbackonthepotentialapproachtoimportanttechnologyconsiderations.ThispaperdoesnotsetoutafinaldesignforCBDC.Rather,itsetsoutonepossibleapproachtoCBDCarchitecture.TheBank’sthinkingonthesematterswillevolveasourworkaccelerates.ThispaperandthedigitalpoundCPareproductsofthe‘researchandexplorationphase’ofCBDCdevelopment,andmarkthestartofthe‘designphase’(Figure2).Inthedesignphase,theBankwillconductexperimentationwhichwillinformanevaluationofthetechnologyfeasibilityofCBDCandhelptodeterminetheoptimaldesignandtechnologyarchitecture.ThispaperbuildsonthefunctionalandeconomicdesignchoicesforCBDC,whichareoutlinedinthedigitalpoundCP.TheBankandHisMajesty’sTreasury(HMTreasury)haveidentifiedtwoprimarymotivationsforaUKCBDC:sustainingaccessto,andpromotingtheusefulnessof,centralbankmoney;andpromotinginnovation,choiceandefficiencyindomesticpayments.ThesemotivationshaveinformedthefunctionalandeconomicdesignchoicesforCBDC,whicharesetoutinthedigitalpoundCP.TheplatformmodeliscurrentlythepreferredmodelforofferingaUKCBDC(Figure4).Inthismodel,theBankhoststhecoreledgerandanapplicationprogramminginterface(API)layer.TheAPIlayerwouldallowprivatesectorfirms,knownasPaymentInterfaceProviders(PIPs)andExternalServiceInterfaceProviders(ESIPs),accesstothecoreledgerfunctionalityinordertoprovideuserservices.AccesstothecoreledgerwouldbesubjecttoapprovalbytheBank,basedonobjectiveandtransparentcriteria,andsubjecttoPIPsandESIPshavingappropriateregulatorystatus.Thispaperexploressixtechnologydesignconsiderations,whichhelptoorganiseandguidetheBank’sworkonCBDCtechnology.Thedesignconsiderationsoutlinedinthispaperareprivacy,security,resilience,performance,extensibilityandenergyusage.TheseconsiderationsguidetheBank’scurrentthinkingonthetechnologyrequirementsforaUKCBDCandwilllikelyhavesignificantimpactonthedesignchoicesforCBDC.Page4Privacy:TheprivacydesignconsiderationsareinformedbytheBankandHMTreasury’spublicpolicyobjectivesrelatedtoprivacy.TheCBDCsystemwouldbedesignedtoprotectuserprivacy,whileallowingPIPsandESIPstheminimumnecessaryaccesstotransactiondataneededtoprovideCBDCservicesandtofulfiltheirlegalandregulatoryobligations.TheBankconsidersthatprivacy-enhancingtechnologies(PETs)mightassistinmeetingtheserequirements.However,itisimportanttobemindfulofthecomplexitiesthatPETsmayintroduceandtheimpacttheymighthaveontheothertechnologydesignconsiderations.Security:ItiscriticalthatanyCBDCdesignidentifiesandguardsagainstsecurityrisks.ACBDCmaybeapotentialtargetforcyberthreatsfromarangeofthreatactors.ThesecurityriskscouldincreaseduetoadditionalfunctionalityofaCBDC,aswellasthenumberofecosystemparticipants.Tomanagenewandexistingrisks,theCBDCsystemcouldbedesignedtosupporttherapidadoptionofnewcryptographicalgorithms,usesecureaccessmanagement,andincorporateacomprehensivesecurityassuranceprogramme.TheBankmightalsoemployalayeredsecurityapproach,whichinvolvesmultiplelayersofsecuritycontrols.Resilience:TheCBDCsystemshouldberesilienttodisruption.Disruptionmayhavefar-reachingconsequencesforuserconfidence,dataintegrityandfinancialstability.Resiliencemightbeachievedthroughcontainmentandredundancymechanisms.TheBankhasestablishedpreliminaryresiliencerequirementsforaCBDC,includingoperating24/7.CurrentRTGSandCHAPSserviceshaveatargetuptimeofatleast99.95%,andthatwouldconstituteaminimumexpectationforBank-managedCBDCinfrastructure.However,wewillalsoexplorewhetheranuptimetargetofcloserto100%wouldbeappropriateanddeliverable(inparticular99.999%).Performance:TheCBDCsystemshouldbeabletohandleahighnumberoftransactionsandconfirmandsettlethesetransactionsasquicklyaspossible.TheBankestimatesthatthroughputofapproximately30,000transactionspersecond,andconfirmationandsettlementinunderonesecond,mightbeneeded.Toenablehighperformance,thesystemmightutilisecertaintechniques,includinghorizontalscaling,multi-destinationpaymentsandofflinepayments.Extensibility:Extensibilityreferstotheabilitytoaddnewfunctionalitytoasystem.TheCBDCsystemshouldhaveanextensibledesign,allowingPIPsandESIPstoimplementadditionalfunctionalitywithoutaffectinguserservices.ThereareseveralfactorstoconsiderindesigninganextensibleCBDCsystem,includingusingacomposablearchitecture,whichfocusesondefiningbuildingblocksthatcanbecombinedtoachievetherequiredfunctionalityoftheCBDCsystem.TheBankmightalsoexaminetheimplicationsofusingopen-sourcecomponents,andanyvulnerabilitiesthatmayariseduetothird-partydependencies.Energyusage:TheCBDCsystemshouldbeenergyefficientanddesignedinawaywhichminimisesanyimpactontheenvironment.Therefore,Bank-managedCBDCinfrastructurePage5would,attheveryleast,needtobeasenergyefficientasexistingpaymentinfrastructures.TheBankwillevaluatetheCBDCarchitectureforopportunitiestooptimiseenergyefficiency.Thepapersetsoutanillustrativeconceptualmodel,whichisbasedontheplatformmodelofCBDC.Theconceptualmodelincludesanumberofdifferentcomponents,includingthecoreledger,analytics,aliasserviceandAPIlayer.Thispaperoutlineshowthesecomponentsmightoperateandassessessomeofthewaysthatecosystemparticipants–theBank,PIPs,ESIPs,andusers–wouldinteractwiththesecomponents.ThisincludesthedevicesandpaymentsaCBDCmightneedtoenable,aswellasinteroperability,programmabilityandofflinepayments.Coreledger:ThecoreledgerwouldprovidetheminimumnecessaryfunctionalityforCBDC,andmustmeettheBank’sperformance,resilienceandprivacyrequirements,whilemaintainingconsistencyatalltimes.Distributedledgertechnologiesandblockchain-basedsolutionsmighthaveadvantagesinguaranteeingconsistencyandresilience,buttheyalsopresentprivacy,scalabilityandsecuritychallenges.Centrallygoverned,distributeddatabasetechnologiesmightachievetheledgerrequirementswithoutsuchlimitations.Therefore,thesetechnologiesmightbeappropriateforthecoreledgerdesign.Analytics:TheBankmayneedtocollectoperationalmetadataforanalysisofsystemstatusandperformance.ThiswouldallowtheBanktomaintainthecoreledgerandtheAPIlayer.TheBankcouldalsocollectaggregatedata,subjecttoeffectiveanonymisationandprivacyprotections,inordertoundertakeeconomicandpolicyanalysis.Theseanalyticswouldtakeplaceinadataplatform,awayfromthecoresystems,andwouldnotinvolvethecollectionoranalysisofpersonaldata.Aliasservice:Thealiasservicewouldmanagetherangeofdifferentidentifiersthatmightbeusedtoroutetransactionsbetweenusers.TheCBDCsystemmightalsousealiasestointeroperatewithexistingpaymentinfrastructures.Thiswouldallowuserstochoosebetweenusingwell-knownaliasesanddisposablealiases.Inadditiontoenablinginteroperability,aliaseswouldalsoconcealthecorewalletidentifier.Theinitialaliasdesignmightincludephonenumbers,aprimaryaccountnumber(PAN),accountnumberandsortcode,andwalletaliases.APIlayer:TheAPIlayerwouldallowPIPsandESIPstoaccesscoreledgerfunctionalityinordertoofferservicestousers.TheAPIlayerwouldincludeanAPIgateway,whichisanentrypointforAPIcalls,andanAPIservice,whichwouldimplementthecorefunctionality.Thereareseveralmatterstoconsiderindesigningthis,includingusingsecuritycontrolstopreventdenialofserviceattacksandimplementingauthenticationorauthorisationfunctionalityinastandardisedmanner.APIspecificationsmightstandardisedataandinformationexchangebyorchestratingCBDCpaymentflows.Page6Devicesandpayments:CBDCshouldbewidelyavailableandacceptedin-store,onlineandpeer-to-peer.Usersshouldbeabletomakeandreceivepaymentsusingsmartdevices,smartcards,ecommercewebsitesandapplications,andexistingpoint-of-saletechnologies.TheBankwouldneedtoestablishstandardstoensureaconsistentminimumleveloffunctionalityandsecurity.Userbalanceswouldberecordedonthecoreledger,butitmightbenecessarytostoresomebalanceslocallytosupportofflinepayments.PIPsandESIPswouldcarryoutuserauthentication.Interoperability:CBDCwouldbeinteroperable,allowingconversionbetweenCBDCandotherformsofmoney,particularlycashandbankdeposits.Subjecttofurtherevaluationandtakingaccountofwiderdevelopments,thismightbeenabledthroughutilisingexistingpaymentinfrastructure,suchasFasterPaymentsSystem,NewPaymentsArchitectureorLINK.Furtherintegrationsmightbeaddedlatertosupportspecificpaymentorsettlementneeds.Programmability:TheBankwillnotpursuecentralbank-initiatedprogrammablefunctions.ThismeansthattheBankwillnotprogramCBDCtorestrictitsuse.ButPIPscould,withuserconsent,implementprogrammabilityfeatureswhicharedesignedtogiveusersgreaterfunctionalityfromtheirwalletsandCBDCholdings.Thesecouldincludeautomatedpaymentsorprogrammablewallets.TheCBDCsystemmightalsoenableawiderangeofotherprogrammablefeatures,includingpayment-versus-payment,delivery-versus-paymentandsmartcontractfunctionality,byimplementinglockingmechanisms,whichPIPsandESIPscanaccessthroughtheAPIlayer.Offlinepayments:TheCBDCsystemmightenableofflinepayments.Thiscouldbeusefulinincreasingsystemresilienceintheeventofnetworkdisruption.However,offlinepaymentscouldalsoincreasetheriskofdoublespend,andcreatechallengesinverifyingtheauthenticityoffunds.Additionally,offlinepaymentscouldintroducecomplexitiesthataffectsystemsecurityandperformance.Theconsiderationsraisedinthispaperwillbeexaminedfurtherinthedesignphase.Thispaperrepresentsourhigh-levelapproachtosomeofthekeytechnologyconsiderationsandtechnicalrequirementsforaUKCBDC.Theywillbeexaminedfurtherandadjustediterativelyduringthenextphaseofourwork.TheBankisseekingfeedbackonthematterspresentedinthispaper,particularlyonthespecificquestionsoutlinedinSection5.ThiswillfeedintoourworkonCBDCandensurethatfeedbackandchallengefromstakeholdersistakenintoaccountatanearlystageofourtechnologywork.Page7HowtorespondWrittenresponsestoanyofthequestionsoutlinedinSection5,oranyotherrelevantobservations,arerequestedby7June2023.Pleaserespondviathissurvey.Ifyouhaveanycommentsorenquiries,pleaseaddressthemto:CBDCUnitBankofEnglandThreadneedleStreetLondonEC2R8AHCBDC@bankofengland.co.ukPage81:IntroductionThisTechnologyWorkingPaper(TWP)focusesonthetechnicalrequirementsanddesignconsiderationsrelatedtoadigitalpound.Bysettingout,atanearlystage,ahigh-levelapproachtokeytechnologyconsiderations,andbyproposinganillustrativetechnologymodel,theBankaimstogeneratefeedbackandchallengethatcaninformourfuturetechnologywork.ThedigitalpoundConsultationPaper(CP)explainsthatalthoughnofinaldecisioncanbetakenatthisstage,theBankofEngland(theBank)andHisMajesty’sTreasury(HMTreasury)judgethatadigitalpound(hereaftercentralbankdigitalcurrency(CBDC))islikelytobeneededinthefuture,andtheBankandHMTreasuryareproposingtoaccelerateworkonitsarchitecture.ThedigitalpoundCPisconsultingonthepolicyobjectivesandhigh-leveldesignforaUKCBDC.ItsetsoutwhythereisalikelyneedforaCBDC,itsimplicationsfortheBank’sobjectivesofmonetaryandfinancialstability,theproposedpublic-privatepartnershiptoprovideaCBDC,andthemodelofCBDCtheBankintendstoexaminefurtherinthenextstageofourwork.ThispaperconsidersthetechnologyimplicationsoftheBankandHMTreasury’spolicyobjectivesforaUKCBDC,andtheeconomicandfunctionaldesignchoicessetoutinthedigitalpoundCP,usingtheplatformmodelofCBDCoutlinedinthatpaper.Thispaperaccompaniesthedigitalpoundconsultation.Thispaperisnotaconsultativedocumentaswearenotmakingadecisiononaspecificproposition.Instead,itsetsouttheBank’searlystagethinkingonCBDCtechnologyandseeksfeedbackonthepotentialapproachestoimportanttechnologyconsiderations.BysettingoutanillustrativeconceptualmodelforaUKCBDC,whichbuildsontheplatformmodel,thispaperoffersabasisforfurtherdiscussionandexploration.Weinvitestakeholdersandtechnologyexpertstoprovidefeedbackandchallengeonthematterssetoutinthispaper,includingthespecificquestionslistedinSection5.Page9Figure1:OverviewofthedigitalpoundCPandtheTWPTheBank’sthinkingonthetechnologyimplicationsofCBDCwillmatureandevolveasourworkdevelops.ItistooearlytotakeadecisiononwhethertobuildaUKCBDC.Assuch,itisnotyetnecessarytomakefirmdecisionsonanyoptionsforthearchitecturaldesignortechnologysolutionforaUKCBDC.TheBankandHMTreasury’spriorityistoaccelerateCBDCdevelopmentworktobeinapositiontobuildaCBDC,intheeventthatadecisionismadetodoso.Thefunctionalrequirements,technologyconsiderationsandillustrativetechnologymodelinthispaperrepresenttheBank’semergingthinkingonthesematters.Thetechnologyimplicationsdiscussedarenotexhaustiveandwillbetestedanddevelopedfurtherinthenextphaseofwork.Page10TheBank’s

CBDCroadmapAUKCBDCwouldbeamajorproject,involvingdistinctphasesofwork.Figure2:IndicativeCBDCroadmapThedigitalpoundCPandthisTWPbuildontheBank’spreviousworkonCBDC.InMarch2020,theBankpublishedaDiscussionPaperonCBDC.ItoutlinedonepossibleapproachtothedesignofaCBDC,referredtoastheplatformmodel.ItalsosoughtfeedbackfromawiderangeofstakeholdergroupsandinJune2021,theBankpublishedasummaryoftheresponses.InJune2021,theBanksetoutpossibleopportunitiesandrisksinaDiscussionPaperonnewformsofdigitalmoney.InMarch2022,theBankpublishedasummaryoftheresponses.Page11ThedigitalpoundCPandthisTWPrepresenttheconclusionofthe‘researchandexplorationphase’ofourworkonCBDC.Wewillnowmovetothenextstage,the‘designphase’,todevelop,intechnologyandpolicyterms,theCBDCmodelsetoutinthedigitalpoundCP.Thedesignphasewillequipustorespondtodevelopmentsinthepaymentslandscapeandreducetheleadtime,wereadecisiontobetakentobuildaCBDCinthefuture.ThiswillinvolveinvestmentintheBank’stechnologycapabilities,anambitiousapproachtothetechnologyroadmapandextensiveengagementwiththeprivatesector.Bytheendofthedesignphase,theBankintendstohaveevaluatedthetechnologyfeasibilityofCBDC,determinedtheoptimaldesignandtechnologyarchitecture,andsupportedbusinessmodelinnovationthroughknowledgesharingandcollaborationbetweentheprivateandpublicsectors.ConsistentwiththeBankandHMTreasury’sgoalofacceleratingthedevelopmentofaUKCBDCandpositioningtheauthoritiestorespondtodevelopmentsinthepaymentslandscape,ouraimsforthedesignphaseareto:?

cutlead-timesonCBDCdevelopmentandequipourselveswiththeknowledgeandcapabilitiestomoveintoabuildphase,ifrequired;?

determinethetechnologyfeasibilityandinvestmentneededtobuildCBDC;?

articulate,indetail,whatthetechnologyandoperationalarchitectureforaUKCBDCwouldlooklike;?

assessandevaluatethebenefitsandcostsoftheCBDCarchitecture;?

deepentheBank’sknowledgeofCBDCtechnologyandsupportstakeholderunderstandingofourtechnologyapproach;?

supportthedevelopmentofthebroaderUKdigitalcurrencytechnologyindustrythroughcollaboration,knowledge-sharing,experimentationandproofsofconcept;and?

providethebasisforafuturedecisiononwhethertointroduceaCBDCandmovetoabuildphase.Consistentwiththoseaims,thedesignphasehastwofocusareas,bothaimingtoacceleratethedevelopmentofaUKCBDC.Thefirstobjectiveofthedesignphaseistodevelopacomprehensive,conceptualarchitecturewhichcanbeusedastheblueprintforconstructionofaUKCBDC,shouldweproceedtoabuildphase.ThiswillrequireustosetoutindetailthecomprehensiveandpreciserequirementsforCBDCtechnology,thearchitectureandoperatingmodel,andhigh-levelrulesforparticipationinaCBDCecosystem.ThiswillallowstakeholderstounderstandtheBank’sapproachtotechnology,requirementsfortechnologysolutions,andthecommercialandoperationalimplicationsofaCBDC.Page12Thesecondobjectiveisexperimentationandproofsofconcept,incollaborationwithprivatesectorinnovators,aimstoinformthedevelopmentoftheCBDCarchitectureandbuildboththeBank,andtheprivatesector’sdigitalcurrencytechnologyknow-how.TheBankwilloperateanopenandtransparentprocessforparticipationinproofsofconceptandsharethelessonslearnedfromthoseexperiments.ThedesignphasewillpresentopportunitiesforprivatesectorbusinessmodelinnovationandsupporttechnologycapabilityintheUKfintechsector.ThesearebenefitsweexpecttoendureevenifwedonotproceedtobuildaCBDC.ThedesignphasewillpresentbenefitsforthewiderUKfintechcommunity.TechnologiesforaCBDCarealsorelevanttoprivatelyissueddigitalmoney,likestablecoins.Bypartneringonproofsofconceptandexperiments,theBankandHMTreasuryseektocatalyseprivateinnovationindigitalcurrencytechnologies,encourageinnovativedigitalmoneybusinessmodelsandsupportknowledgesharingacrosstheUKfintechsector.ThedesignworkwillalsobenefittheBankassupervisoroffinancialinstitutionsthatmightseektousesuchtechnologiesbyhelpingustobetterassesstheirimplicationsforfinancialstabilityandthesafetyandsoundnessofPRAregulatedfirms.Givenourexpectationthatdigitalcurrencytechnologieswillbeasignificantareashapingthefutureoffinance,thebenefitsofthedesignphaseareexpectedtoendureevenifwedonotbuildaCBDC.Afterthedesignphase,therewillbeadecisiononwhethertobuildaCBDC.Oncompletionofthedesignphase,followingfurtherconsultationandinlightoftheongoingdevelopmentsinthepaymentslandscape,theBankandtheGovernmentwilldecidewhethertobuildaCBDC.Workundertakenduringthedesignphasewillhelptogenerateevidencetosupportathoroughevaluationofbenefitsandcosts.Ifwedecidetomoveintoabuildphaseitwouldinvolvedevelopingprototype(s)ofCBDCtechnologyinasimulatedenvironment,beforemovingtopilottests.ACBDCwouldonlybelaunchedif,amongotherthings,itmetallourexactingstandardsforsecurity,resilience,andperformance.Adecisiononwhethertoproceedtoabuildphasecouldbemadearoundthemiddleofthedecade.ThesecondhalfofthedecadeistheearliestaUKCBDCmightbecomeoperational.ACBDCwouldbeamajorinfrastructureprojectandwouldrequiresignificantinvestment.Anydecisiononwhethertobuildonewouldrequireextensiveevidencegathering,carefulevaluationandcomprehensivestakeholderengagement.ThelegalbasisforaUKCBDCwillbedeterminedalongsideconsiderationofitsdesign.WejudgethatthesecondhalfofthedecadeistheearliestpointatwhichaCBDCmightbelaunched.Itwouldtaketimetobuildinfrastructurethatissecure,resilient,andhighperforming.Experiencefromoverseasdigitalcurrencyprojects,andfromdigitalinnovationPage13moregenerally,indicatesthatbuildinguserfamiliarityandunderstanding,andensuringthatinnovativeandcustomerfriendlyapplicationsemerge,willbecriticaltosuccess.Wewillengagestakeholdersextensivelyandbetransparentaboutourwork.Transparencyaroundourwork,andengagementwithawidegroupofstakeholders,willbemoreimportantthanever.Thiswillbuilduponourapproachtodate,includingourEngagementandTechnologyForums.Wewillalsocontinueengagementwithcivilsociety,academics,technologists,andbusinessesacrosstheUK.Page142:FunctionalrequirementsFigure3:OverviewoftheTWP–functionalrequirementsforaUKCBDCTheBankandHMTreasury’spublicpolicyobjectivesdetermineCBDCfunctionalityandtechnologychoices.ThedesignofaUKCBDCmustdelivertheGovernmentandBank’spolicyobjectives.ThedigitalpoundCPsetsouttwopublicpolicyobjectives:1a)TosustainaccesstoUKcentralbankmoney–ensuringitsroleasananchorforconfidenceandsafetyinourmonetarysystem,andtounderpinmonetaryandfinancialstabilityandsovereignty;andb)Topromoteinnovation,choice,andefficiencyindomesticpaymentsasourlifestylesandeconomybecomemoredigital.TheplatformmodelistheproposedmodelforCBDC.ThedigitalpoundCPproposesthataUKCBDCwouldbebasedontheplatformmodel,asoriginallysetoutintheBank’s2020DiscussionPaper.Intheplatformmodel,theBankwouldbuildafast,secure,andresilientplatform–the‘coreledger’–whichwouldprovidetheminimumnecessaryfunctionalityforaCBDC.Regulatedprivatefirms,PaymentInterfaceProviders(PIPs)andExternalServiceInterfaceProviders(ESIPs),couldthenaccessthecoreinfrastructureviaanapplicationprogramminginterface(API)layer.1SeePartDofthedigitalpoundConsultationPaper.Page15Figure4:TheplatformmodelTheplatformmodelisbasedonapublic-privatepartnership.TheplatformmodelspecifiestherolesandresponsibilitiesofthepublicandprivatesectorintheprovisionofaCBDC.TheBankprovidesthecoreinfrastructureuponwhichtheprivatesectorbuilds,innovatesanddeliversvalue-addservicestohouseholdsandbusinesses.Page16PIPsfunctionasgatewaystotheCBDCecosystem,offeringusersdigital‘pass-through’wallets2tointeractwith,andmanage,theirCBDCholdings.ESIPsmightprovidenon-payment,value-addservices,suchasbusinessanalytics,budgetingtoolsandfraudmonitoring.Weexpectin-store,onlineandpeer-to-peer(P2P)paymentstobetheinitialfocusofaUKCBDC.Overtime,abroaderrangeofpaymentsmaybeenabled.ThedigitalpoundCPproposesthatCBDCwouldbeusedbyhouseholdsandbusinessesfortheireverydaypaymentneeds.Assuch,uponintroduction,theCBDCsystemwouldsupporttwoessentialtypesofpayments,person-to-business(P2B),bothin-storeandonline,andP2P.Overthelongerterm,innovationandevolvinguserneedsmaymeanabroaderrangeofCBDCpaymenttypescouldbeoffered.Forexample,offlineandcross-borderpaymentscouldsupportpublicpolicyobjectives,butmighttaketimetodelivergiventhetechnologicalandoperationalcomplexitiesinvolved.Batch,split,andmicropaymentsareadditionalpaymenttypesthatcouldhelptosupportinnovationandmeetuserneeds.CBDCwouldbeaccessedviasmartdevicesandcards.ThedigitalpoundCPoutlineshowuserswouldinteractwiththeirCBDCholdings.UserscouldaccessCBDCthroughwalletsonsmartdevices.Thismeansthattheywouldbeabletoopenawalletusingthesedevices,whichwouldenablethemtomanagetheirbalanceandmakepayments.Smartdevicesmightincludesmartphones,laptops,InternetofThings(IoT)devicesandwearables.Noteveryonehasasmartdeviceorfindsiteasytouseone,souserscouldalsohavephysicalcardoptionsforCBDCpayments.ItshouldbefastandeasytotransferbetweenCBDCandotherformsofmoney,includingcashandbankdeposits.Householdsandbusinessescurrentlymakepaymentsusingamixofbankdepositsandcash.Itshouldbesimple,fastandconvenienttomovebetweenCBDCandotherformsofmoney,particularlycash3andbankdeposits.AUKCBDCshouldimplementeconomicdesignchoicesassetoutinthedigitalpoundCP.ThedigitalpoundCPsetsouteconomicdesignchoicesforaUKCBDC.Twoofthosechoiceshaveparticularimplicationsfortechnology:2Theyarecalled‘pass-through’walletsastheusers’holdingsarerecordedontheBank’scoreledger,andthewalletsimplypassesinstructionsfromtheusertothecoreledger.3Thephysicalnatureofcashmakesmovingbetweenitandotherformsofmoneymorechallengingthandigitalmoney,butitisimportantthattheaimremainstoachievesimple,fastandconvenientmovement.Thisislikelytorequireworkingwithexistingcashdistributionmarketparticipants.Page17First,aUKCBDCwouldbesubjecttosomelimitsonindividuals’holdings,atleastduringitsintroductoryperiod.Thetechnologydesignshouldsupporttheimplementationoftheselimits,including,ifneeded,theabilitytochangeeitherthedesignorthelevelofanylimit.Second,theremayalsoneedtoberestrictionsoncorporates’holdingsofCBDC.Giventhatcorporatesvarysignificantlyinsize,transactionvolumeandtheactivitytheyundertake,thedesignofcorporatelimitswillbesubjecttofurtherresearch.Technologysolutions,suchasbalancesweeping,mighthaveapplicationswithrespecttolimitsoncorporateholdingsbyallowingcorporatestofreelyreceiveCBDCpayments,butpreventingthemfromstoringvalueinCBDCinawaywhichmightbedetrimentaltofinancialstabilitybydisintermediatingcriticalmoneymarkets.CBDCcouldofferabroadrangeoffunctionalitiesandfeatures.TableAbelowsummarisespotentialfunctionalityandfeaturesofaCBDCdiscussedinthedigitalpoundCP.Ta