比特币白皮书（英文版）

比特币白皮书

Bitcoin:APeer-to-PeerElectronicCashSystem

SatoshiNakamoto

satoshin@gmx.com

www.bitcoin.org

Abstract

Bitcoin:APeer-to-PeerElectronicCashSystem

SatoshiNakamoto

satoshin@gmx.com

www.bitcoin.org

1.Introduction

CommerceontheInternethascometorelyalmostexclusivelyonfinancialinstitutionsservingastrustedthirdpartiestoprocesselectronicpayments.Whilethesystemworkswellenoughformosttransactions,itstillsuffersfromtheinherentweaknessesofthetrustbasedmodel.Completelynon-reversibletransactionsarenotreallypossible,sincefinancialinstitutionscannotavoidmediatingdisputes.Thecostofmediationincreasestransactioncosts,limitingtheminimumpracticaltransactionsizeandcuttingoffthepossibilityforsmallcasualtransactions,andthereisabroadercostinthelossofabilitytomakenon-reversiblepaymentsfornonreversibleservices.Withthepossibilityofreversal,theneedfortrustspreads.Merchantsmustbewaryoftheircustomers,hasslingthemformoreinformationthantheywouldotherwiseneed.Acertainpercentageoffraudisacceptedasunavoidable.Thesecostsandpaymentuncertaintiescanbeavoidedinpersonbyusingphysicalcurrency,butnomechanismexiststomakepaymentsoveracommunicationschannelwithoutatrustedparty.

Whatisneededisanelectronicpaymentsystembasedoncryptographicproofinsteadoftrust,allowinganytwowillingpartiestotransactdirectlywitheachotherwithouttheneedforatrustedthirdparty.Transactionsthatarecomputationallyimpracticaltoreversewouldprotectsellersfromfraud,androutineescrowmechanismscouldeasilybeimplementedtoprotectbuyers.Inthispaper,weproposeasolutiontothedouble-spendingproblemusingapeer-to-peerdistributedtimestampservertogeneratecomputationalproofofthechronologicalorderoftransactions.ThesystemissecureaslongashonestnodescollectivelycontrolmoreCPUpowerthananycooperatinggroupofattackernodes.

2.Transactions

Wedefineanelectroniccoinasachainofdigitalsignatures.Eachownertransfersthecointothenextbydigitallysigningahashoftheprevioustransactionandthepublickeyofthenextownerandaddingthesetotheendofthecoin.Apayeecanverifythesignaturestoverifythechainofownership.

昨日比特币区块体积平均数达2.52 MB，再创新高:金色财经报道，BTC.com数据显示，2月12日比特币区块体积平均数达2.52 MB，再创历史新高。

据此前报道，2月7日，比特币矿企Riot Platforms研究副总裁Pierre Rochard发推称，比特币网络NFT协议Ordinal的Inscriptions（铭文）正在消耗50%的比特币区块空间，区块空间利用率为100%，费率中位数下降。[2023/2/13 12:03:15]

Theproblemofcourseisthepayeecan'tverifythatoneoftheownersdidnotdouble-spendthecoin.Acommonsolutionistointroduceatrustedcentralauthority,ormint,thatcheckseverytransactionfordoublespending.Aftereachtransaction,thecoinmustbereturnedtotheminttoissueanewcoin,andonlycoinsissueddirectlyfromthemintaretrustednottobedouble-spent.Theproblemwiththissolutionisthatthefateoftheentiremoneysystemdependsonthecompanyrunningthemint,witheverytransactionhavingtogothroughthem,justlikeabank.

Weneedawayforthepayeetoknowthatthepreviousownersdidnotsignanyearliertransactions.Forourpurposes,theearliesttransactionistheonethatcounts,sowedon'tcareaboutlaterattemptstodouble-spend.Theonlywaytoconfirmtheabsenceofatransactionistobeawareofalltransactions.Inthemintbasedmodel,themintwasawareofalltransactionsanddecidedwhicharrivedfirst.Toaccomplishthiswithoutatrustedparty,transactionsmustbepubliclyannounced,andweneedasystemforparticipantstoagreeonasinglehistoryoftheorderinwhichtheywerereceived.Thepayeeneedsproofthatatthetimeofeachtransaction,themajorityofnodesagreeditwasthefirstreceived.

3.TimestampServer

Thesolutionweproposebeginswithatimestampserver.Atimestampserverworksbytakingahashofablockofitemstobetimestampedandwidelypublishingthehash,suchasinanewspaperorUsenetpost.Thetimestampprovesthatthedatamusthaveexistedatthetime,obviously,inordertogetintothehash.Eachtimestampincludestheprevioustimestampinitshash,formingachain,witheachadditionaltimestampreinforcingtheonesbeforeit.

4.Proof-of-Work

Toimplementadistributedtimestampserveronapeer-to-peerbasis,wewillneedtouseaproofof-worksystemsimilartoAdamBack'sHashcash,ratherthannewspaperorUsenetposts.Theproof-of-workinvolvesscanningforavaluethatwhenhashed,suchaswithSHA-256,thehashbeginswithanumberofzerobits.Theaverageworkrequiredisexponentialinthenumberofzerobitsrequiredandcanbeverifiedbyexecutingasinglehash.

Forourtimestampnetwork,weimplementtheproof-of-workbyincrementinganonceintheblockuntilavalueisfoundthatgivestheblock'shashtherequiredzerobits.OncetheCPUefforthasbeenexpendedtomakeitsatisfytheproof-of-work,theblockcannotbechangedwithoutredoingthework.Aslaterblocksarechainedafterit,theworktochangetheblockwouldincluderedoingalltheblocksafterit.

Bitfinex比特币合约多空比在9月12日创新高:9月15日消息，TradingView数据显示，Bitfinex上的比特币合约多空比在9月12日达到历史新高。

9月12日，BTC/USD多单持仓是空单持仓的86倍，达到104000 BTC。该指标上一次突破75是在2021年11月9日，不过最终对空头有利，因为当时比特币价格在之后的10天暴跌18%。

此次Bitfinex的空头保证金交易者减少头寸，其中一个原因可能是发生清算，这意味着卖方没有足够的保证金，因为比特币价格在9月6日至12日期间上涨19%。其他因素可能会导致多单持仓和空单持仓之间的异常失衡。例如，投资者可能将抵押品从比特币保证金交易转移到以太坊相关交易，在合并临近时寻求获利。最后，由于美国通胀数据的波动性，空头保证金交易者可能决定暂时平仓。（Cointelegraph）[2022/9/15 6:56:37]

Theproof-of-workalsosolvestheproblemofdeterminingrepresentationinmajoritydecisionmaking.Ifthemajoritywerebasedonone-IP-address-one-vote,itcouldbesubvertedbyanyoneabletoallocatemanyIPs.Proof-of-workisessentiallyone-CPU-one-vote.Themajoritydecisionisrepresentedbythelongestchain,whichhasthegreatestproofof-workeffortinvestedinit.IfamajorityofCPUpoweriscontrolledbyhonestnodes,thehonestchainwillgrowthefastestandoutpaceanycompetingchains.Tomodifyapastblock,anattackerwouldhavetoredotheproof-ofworkoftheblockandallblocksafteritandthencatchupwithandsurpasstheworkofthehonestnodes.Wewillshowlaterthattheprobabilityofaslowerattackercatchingupdiminishesexponentiallyassubsequentblocksareadded.

Tocompensateforincreasinghardwarespeedandvaryinginterestinrunningnodesovertime,theproof-of-workdifficultyisdeterminedbyamovingaveragetargetinganaveragenumberofblocksperhour.Ifthey'regeneratedtoofast,thedifficultyincreases.

5.Network

Thestepstorunthenetworkareasfollows:

1)Newtransactionsarebroadcasttoallnodes.

2)Eachnodecollectsnewtransactionsintoablock.

3)Eachnodeworksonfindingadifficultproof-of-workforitsblock.

4)Whenanodefindsaproof-of-work,itbroadcaststheblocktoallnodes.

5)Nodesaccepttheblockonlyifalltransactionsinitarevalidandnotalreadyspent.

6)Nodesexpresstheiracceptanceoftheblockbyworkingoncreatingthenextblockinthechain,usingthehashoftheacceptedblockastheprevioushash.

Nodesalwaysconsiderthelongestchaintobethecorrectoneandwillkeepworkingonextendingit.Iftwonodesbroadcastdifferentversionsofthenextblocksimultaneously,somenodesmayreceiveoneortheotherfirst.Inthatcase,theyworkonthefirstonetheyreceived,butsavetheotherbranchincaseitbecomeslonger.Thetiewillbebrokenwhenthenextproofof-workisfoundandonebranchbecomeslonger;thenodesthatwereworkingontheotherbranchwillthenswitchtothelongerone.

亿万富翁Stanley Druckenmiller：不会做多或做空狗狗币，比特币难以被取代:投资者Stanley Druckenmiller近期分享了他对比特币、以太坊和狗狗币的看法。这位亿万富翁投资者表示，狗狗币“就像NFT，是史上最疯狂货币政策的一种表现。”他补充称：“我认为，由于供应没有限制，我目前真的看不到它的效用。这只是‘博傻理论’中的资金浪潮。话虽如此，我还是不会对其做多或是做空，因为我不喜欢用我的脸来扑灭篝火。所以我就假装狗狗币不存在。我几乎不会想到狗狗币，所以当它价格上涨的时候，我并不会介怀。”

此外，在比特币与以太坊之间，Druckenmiller表示：“我认为比特币赢得了价值储存游戏的胜利”，因为它是“一个已经存在了13到14年的品牌，而且它的供应是有限的。”在谈到其他加密货币是否会取代比特币时，他重申，比特币“将非常非常难被取代。”尽管他承认“智能合约和此类东西的领先地位属于以太坊，”但“我有点怀疑它是否能保持它的地位。这让我想起了Facebook出现之前的Myspace。或者一个更好的比喻是谷歌出现之前的雅虎。”（Bitcoin.com）[2021/5/30 22:56:39]

Newtransactionbroadcastsdonotnecessarilyneedtoreachallnodes.Aslongastheyreachmanynodes,theywillgetintoablockbeforelong.Blockbroadcastsarealsotolerantofdroppedmessages.Ifanodedoesnotreceiveablock,itwillrequestitwhenitreceivesthenextblockandrealizesitmissedone.

6.Incentive

Byconvention,thefirsttransactioninablockisaspecialtransactionthatstartsanewcoinownedbythecreatoroftheblock.Thisaddsanincentivefornodestosupportthenetwork,andprovidesawaytoinitiallydistributecoinsintocirculation,sincethereisnocentralauthoritytoissuethem.Thesteadyadditionofaconstantofamountofnewcoinsisanalogoustogoldminersexpendingresourcestoaddgoldtocirculation.Inourcase,itisCPUtimeandelectricitythatisexpended.

Theincentivecanalsobefundedwithtransactionfees.Iftheoutputvalueofatransactionislessthanitsinputvalue,thedifferenceisatransactionfeethatisaddedtotheincentivevalueoftheblockcontainingthetransaction.Onceapredeterminednumberofcoinshaveenteredcirculation,theincentivecantransitionentirelytotransactionfeesandbecompletelyinflationfree.

Theincentivemayhelpencouragenodestostayhonest.IfagreedyattackerisabletoassemblemoreCPUpowerthanallthehonestnodes,hewouldhavetochoosebetweenusingittodefraudpeoplebystealingbackhispayments,orusingittogeneratenewcoins.Heoughttofinditmoreprofitabletoplaybytherules,suchrulesthatfavourhimwithmorenewcoinsthaneveryoneelsecombined,thantounderminethesystemandthevalidityofhisownwealth.

7.ReclaimingDiskSpace

Oncethelatesttransactioninacoinisburiedunderenoughblocks,thespenttransactionsbeforeitcanbediscardedtosavediskspace.Tofacilitatethiswithoutbreakingtheblock'shash,transactionsarehashedinaMerkleTree,withonlytherootincludedintheblock'shash.Oldblockscanthenbecompactedbystubbingoffbranchesofthetree.Theinteriorhashesdonotneedtobestored.

分析 | 比特币命悬一线:AKG-Chcuk认为：价格走势毋庸置疑的弱，已经到了下跌通道支撑位附近，可以说是命悬一线，投资者关注8000正数关口的支撑情况，弱势行情，参与度进一步降低，抄底的时机一般伴随着交易活跃度的同步抬升，本周将成为未来一个月的行情决定时刻。

（价格参考Coinbase）

关键点位提示：

8550/8800构成日内关键压力位

8400-8500构成日内关键支撑位[2019/11/19]

Ablockheaderwithnotransactionswouldbeabout80bytes.Ifwesupposeblocksaregeneratedevery10minutes,80bytes*6*24*365=4.2MBperyear.Withcomputersystemstypicallysellingwith2GBofRAMasof2008,andMoore'sLawpredictingcurrentgrowthof1.2GBperyear,storageshouldnotbeaproblemeveniftheblockheadersmustbekeptinmemory.

8.SimplifiedPaymentVerification

Itispossibletoverifypaymentswithoutrunningafullnetworknode.Auseronlyneedstokeepacopyoftheblockheadersofthelongestproof-of-workchain,whichhecangetbyqueryingnetworknodesuntilhe'sconvincedhehasthelongestchain,andobtaintheMerklebranchlinkingthetransactiontotheblockit'stimestampedin.Hecan'tcheckthetransactionforhimself,butbylinkingittoaplaceinthechain,hecanseethatanetworknodehasacceptedit,andblocksaddedafteritfurtherconfirmthenetworkhasacceptedit.

Assuch,theverificationisreliableaslongashonestnodescontrolthenetwork,butismorevulnerableifthenetworkisoverpoweredbyanattacker.Whilenetworknodescanverifytransactionsforthemselves,thesimplifiedmethodcanbefooledbyanattacker'sfabricatedtransactionsforaslongastheattackercancontinuetooverpowerthenetwork.Onestrategytoprotectagainstthiswouldbetoacceptalertsfromnetworknodeswhentheydetectaninvalidblock,promptingtheuser'ssoftwaretodownloadthefullblockandalertedtransactionstoconfirmtheinconsistency.Businessesthatreceivefrequentpaymentswillprobablystillwanttoruntheirownnodesformoreindependentsecurityandquickerverification.

9.CombiningandSplittingValue

Althoughitwouldbepossibletohandlecoinsindividually,itwouldbeunwieldytomakeaseparatetransactionforeverycentinatransfer.Toallowvaluetobesplitandcombined,transactionscontainmultipleinputsandoutputs.Normallytherewillbeeitherasingleinputfromalargerprevioustransactionormultipleinputscombiningsmalleramounts,andatmosttwooutputs:oneforthepayment,andonereturningthechange,ifany,backtothesender.

Itshouldbenotedthatfan-out,whereatransactiondependsonseveraltransactions,andthosetransactionsdependonmanymore,isnotaproblemhere.Thereisnevertheneedtoextractacompletestandalonecopyofatransaction'shistory.

行情 | 全球加密货币市值为17,397.9亿人民币 比特币占比提升:根据AICoin数据显示，目前全球加密货币市值17,397.9亿人民币，其中排名第一的是比特币，市值达到6,845亿元人民币，占比达到39.34%；排名第二的是以太坊，市值达到2,956亿元人民币，占比达到16.99%；排名第三的是瑞波币，市值为1,224亿元人民币，占比达到7.04%。[2018/6/25]

10.Privacy

Thetraditionalbankingmodelachievesalevelofprivacybylimitingaccesstoinformationtothepartiesinvolvedandthetrustedthirdparty.Thenecessitytoannouncealltransactionspubliclyprecludesthismethod,butprivacycanstillbemaintainedbybreakingtheflowofinformationinanotherplace:bykeepingpublickeysanonymous.Thepubliccanseethatsomeoneissendinganamounttosomeoneelse,butwithoutinformationlinkingthetransactiontoanyone.Thisissimilartothelevelofinformationreleasedbystockexchanges,wherethetimeandsizeofindividualtrades,the"tape",ismadepublic,butwithouttellingwhothepartieswere.

Asanadditionalfirewall,anewkeypairshouldbeusedforeachtransactiontokeepthemfrombeinglinkedtoacommonowner.Somelinkingisstillunavoidablewithmulti-inputtransactions,whichnecessarilyrevealthattheirinputswereownedbythesameowner.Theriskisthatiftheownerofakeyisrevealed,linkingcouldrevealothertransactionsthatbelongedtothesameowner.

11.Calculations

Weconsiderthescenarioofanattackertryingtogenerateanalternatechainfasterthanthehonestchain.Evenifthisisaccomplished,itdoesnotthrowthesystemopentoarbitrarychanges,suchascreatingvalueoutofthinairortakingmoneythatneverbelongedtotheattacker.Nodesarenotgoingtoacceptaninvalidtransactionaspayment,andhonestnodeswillneveracceptablockcontainingthem.Anattackercanonlytrytochangeoneofhisowntransactionstotakebackmoneyherecentlyspent.

TheracebetweenthehonestchainandanattackerchaincanbecharacterizedasaBinomialRandomWalk.Thesuccesseventisthehonestchainbeingextendedbyoneblock,increasingitsleadby+1,andthefailureeventistheattacker'schainbeingextendedbyoneblock,reducingthegapby-1.

TheprobabilityofanattackercatchingupfromagivendeficitisanalogoustoaGambler'sRuinproblem.Supposeagamblerwithunlimitedcreditstartsatadeficitandplayspotentiallyaninfinitenumberoftrialstotrytoreachbreakeven.Wecancalculatetheprobabilityheeverreachesbreakeven,orthatanattackerevercatchesupwiththehonestchain,asfollows:

Givenourassumptionthatp>q,theprobabilitydropsexponentiallyasthenumberofblockstheattackerhastocatchupwithincreases.Withtheoddsagainsthim,ifhedoesn'tmakealuckylungeforwardearlyon,hischancesbecomevanishinglysmallashefallsfurtherbehind.

Wenowconsiderhowlongtherecipientofanewtransactionneedstowaitbeforebeingsufficientlycertainthesendercan'tchangethetransaction.Weassumethesenderisanattackerwhowantstomaketherecipientbelievehepaidhimforawhile,thenswitchittopaybacktohimselfaftersometimehaspassed.Thereceiverwillbealertedwhenthathappens,butthesenderhopesitwillbetoolate.

Thereceivergeneratesanewkeypairandgivesthepublickeytothesendershortlybeforesigning.Thispreventsthesenderfrompreparingachainofblocksaheadoftimebyworkingonitcontinuouslyuntilheisluckyenoughtogetfarenoughahead,thenexecutingthetransactionatthatmoment.Oncethetransactionissent,thedishonestsenderstartsworkinginsecretonaparallelchaincontaininganalternateversionofhistransaction.

Therecipientwaitsuntilthetransactionhasbeenaddedtoablockandzblockshavebeenlinkedafterit.Hedoesn'tknowtheexactamountofprogresstheattackerhasmade,butassumingthehonestblockstooktheaverageexpectedtimeperblock,theattacker'spotentialprogresswillbeaPoissondistributionwithexpectedvalue:

Togettheprobabilitytheattackercouldstillcatchupnow,wemultiplythePoissondensityforeachamountofprogresshecouldhavemadebytheprobabilityhecouldcatchupfromthatpoint:

Rearrangingtoavoidsummingtheinfinitetailofthedistribution...

ConvertingtoCcode...

#includedoubleAttackerSuccessProbability(doubleq,intz)

{

doublep=1.0-q;

doublelambda=z*(q/p);

doublesum=1.0;

inti,k;

for(k=0;k<=z;k++)

{

doublepoisson=exp(-lambda);

for(i=1;i<=k;i++)

poisson*=lambda/i;

sum-=poisson*(1-pow(q/p,z-k));

}

returnsum;

}

Runningsomeresults,wecanseetheprobabilitydropoffexponentiallywithz.

q=0.1

z=0P=1.0000000

z=1P=0.2045873

z=2P=0.0509779

z=3P=0.0131722

z=4P=0.0034552

z=5P=0.0009137

z=6P=0.0002428

z=7P=0.0000647

z=8P=0.0000173

z=9P=0.0000046

z=10P=0.0000012

q=0.3

z=0P=1.0000000

z=5P=0.1773523

z=10P=0.0416605

z=15P=0.0101008

z=20P=0.0024804

z=25P=0.0006132

z=30P=0.0001522

z=35P=0.0000379

z=40P=0.0000095

z=45P=0.0000024

z=50P=0.0000006

SolvingforPlessthan0.1%...

P<0.001

q=0.10z=5

q=0.15z=8

q=0.20z=11

q=0.25z=15

q=0.30z=24

q=0.35z=41

q=0.40z=89

q=0.45z=340

12.Conclusion

Wehaveproposedasystemforelectronictransactionswithoutrelyingontrust.Westartedwiththeusualframeworkofcoinsmadefromdigitalsignatures,whichprovidesstrongcontrolofownership,butisincompletewithoutawaytopreventdouble-spending.Tosolvethis,weproposedapeer-to-peernetworkusingproof-of-worktorecordapublichistoryoftransactionsthatquicklybecomescomputationallyimpracticalforanattackertochangeifhonestnodescontrolamajorityofCPUpower.Thenetworkisrobustinitsunstructuredsimplicity.Nodesworkallatoncewithlittlecoordination.Theydonotneedtobeidentified,sincemessagesarenotroutedtoanyparticularplaceandonlyneedtobedeliveredonabesteffortbasis.Nodescanleaveandrejointhenetworkatwill,acceptingtheproof-ofworkchainasproofofwhathappenedwhiletheyweregone.TheyvotewiththeirCPUpower,expressingtheiracceptanceofvalidblocksbyworkingonextendingthemandrejectinginvalidblocksbyrefusingtoworkonthem.Anyneededrulesandincentivescanbeenforcedwiththisconsensusmechanism.

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沙棘财经是沙棘传媒旗下专注大数据、人工智能、区块链、币圈的深度报道的垂直自媒体。微信公众号：shaji-media

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