Byzantine Generals Question

Origins

ByzantiumislocatedinIstanbul,Turkey,thecapitaloftheEasternRomanEmpire.DuetothevastterritoryoftheByzantineRomanEmpireatthattime,inordertoachievethepurposeofdefense,eacharmywasseparatedveryfar,andthegeneralscouldonlyrelyonmessengerstospreadthenews.Duringwar,allgeneralsandadjutantsintheByzantinearmymustreachaconsensusanddecidewhetherthereisachanceofwinningbeforeattackingtheenemy'scamp.However,theremaybetraitorsandenemyspiesinthearmy,whichwillinfluencethedecisionsofthegeneralsanddisrupttheorderoftheoverallarmy.Whenconsensusisreached,theresultsdonotrepresenttheopinionsofthemajority.Atthistime,whenmembersareknowntohaverebelled,howtheremainingloyalgeneralscanreachanagreementwithouttheinfluenceofthetraitors,andtheByzantineproblemhasbeenformed.

Introduction

TheByzantinegeneralsissueisamatterofagreement.ThegeneralsoftheByzantineEmpiremustunanimouslydecidewhethertoattackanenemy.Theproblemisthatthesegeneralsaregeographicallyseparated,andtherearetraitorsamongthegenerals.Traitorscanactarbitrarilytoachievethefollowinggoals:deceivesomegeneralsintotakingoffensiveactions;facilitateadecisionthatnotallgeneralsagreewith,suchasfacilitatingoffensiveactionswhenthegeneralsdonotwanttoattack;orconfusecertaingeneralssothattheycannotmakethem.Decide.Ifthetraitorachievesoneofthesegoals,theresultofanyattackisdoomedtofailure,andonlyafullyagreedeffortcanwin.

Byzantinehypothesisisamodeloftherealworld.Duetohardwareerrors,networkcongestionordisconnection,andmaliciousattacks,computersandnetworksmayexhibitunexpectedbehavior.

Connotation

The"ByzantineGeneralsProblem"extendstoInternetlife,anditsconnotationcanbesummarizedas:inthecontextoftheInternet,whenitisnecessarytoexchangevaluewithanunfamiliarcounterpartyHowcanpeoplepreventthemfrombeingdeceivedandconfusedbymalicioussaboteurstomakewrongdecisions.Furtherextendingthe"ByzantineGeneralsProblem"tothetechnicalfield,itsconnotationcanbesummarizedas:intheabsenceofatrustedcentralnodeandtrustedchannel,howeachnodedistributedinthenetworkshouldreachaconsensus.

Thefundamentalproblem

BeforeSatoshiNakamotoinventedBitcoin,therewasnoperfectwaytosolvethe"ByzantineGeneralsProblem".

Atitsroot,the"ByzantineGeneralsProblem"ultimatelywantstosolvefourproblemsintheprocessofInternettransactionsandcooperation:

(1)Tracingtheidentityoftheinformationsent;

(2)Privacyofinformation;

(3)Signaturethatcannotbeforged;

(4)Rulesforsendinginformation.

The"ByzantineGeneralsProblem"isactuallythemodelingoftheonlineworld.

TakingtheBitcoinworldasanexample,wecanregardeveryBitcointransactionaccountasageneral.Theseaccountsaredistributedallovertheworldandcannotbegatheredtogether.Theremaybemaliciousaccounts.Inter-communicationisalsolikelytobedamagedduetomachinebreakdown,networkdisconnection,hackerattacks,etc.,andthediscussionaboutwhethertheaccountshouldbepaidandhowmuchtopaywillalsowastealotoftime.

Solution

Blockchaineasilysolvesthisproblem.Itaddscosttoinformationtransmission,reducestherateofinformationtransmission,andaddsarandomelementtoOnlyonegeneralcanbroadcastamessageforacertainperiodoftime.Thecostmentionedhereisthe"proofofwork"basedontherandomhashalgorithmintheblockchainsystem.Whatthehashalgorithmdoesistocalculatetheobtainedinputandgetastringof64-bitrandomnumbersandletters.

Theinputdatacalculatedbytheblockchainsystemreferstotheentiregeneralledgersentbythenodeatthecurrenttime.Thecurrentcomputingpowerofthecomputermakesitpossibletocalculateasinglehashvalueinrealtime,buttheblockchainsystemonlyacceptsthehashvalueresultwhosefirst13charactersare0asa"proofofwork".Itisveryrarethatthefirst13charactersofthehashvalueare0.Ittakestheentirenetwork10minutestofindoneamongthehundredsofmillionsofdata.Beforeavalidhashvalueiscalculated,countlessinvalidvalues​​havebeenproducedinthenetwork.Thisisthe"proofofwork"thatreducestheinformationtransferrateandmakestheentiresystemrunsuccessfully.

IntheByzantinegeneralsproblem,thefirstgeneraltobroadcastinformationisthefirstcomputertodiscoveravalidhashvalue,aslongasothergeneralsreceiveandverifythevalidhashvalueandattachtoitTheycanonlyusethenewinformationtoupdatetheircopyoftheledger,andthenrecalculatethehashvalue.Thenextgeneralwhocalculatestheeffectivehashvaluecanattachhisupdatedinformationtotheeffectivehashvalueandbroadcastittoeveryone.Thenthehashcalculationcompetitionrestartsfromanewstartingpoint.Duetothecontinuoussynchronizationofnetworkinformation,allcomputersonthenetworkusethesameversionofthegeneralledger.

ThetimeintervalfortheBitcoinblockchainsystemtofindavalidhashvalueis10minutes,whichissetbythealgorithm.Thealgorithmdifficultyisadjustedeverytwoweekstoensurethis10-minuteinterval,nomoreornoless.Every10minutes,theinformationinthegeneralledgerwillbeupdatedontheblockchainandsynchronizedacrosstheentirenetwork.Therefore,thescatteredtransactionrecordsarereconciledandsynchronizedbetweenallcomputersonthenetwork.

Whenindividualusersinitiateatransactionintheblockchainsystem,theywillusetheprivatekeyandpublickeytosignthetransaction,whilethestandardpublickeyembeddedintheBitcoinsystemisresponsibleforTheroleofencryptiontoolscorrespondstotheByzantineGeneralsproblem.Theencryptiontoolisasealusedtosignandverifymessages.

Therefore,therestrictionofthehashalgorithmontheinformationtransferrateandtheencryptiontoolsmaketheblockchainconstituteatrustlessdatainteractionsystem.Ontheblockchain,participantscanreachconsensusonaseriesoftransactions,timeagreements,domainnamerecords,politicalvotingsystems,oranyotherplacewhereadistributedagreementneedstobeestablished.

Extension

The"ByzantineGeneralsProblem"canbefurtherextendedtovariousfields.WhenpeopleconductdatatransactionsontheInternet,theyalwaysrelyonpowerfulthird-partyplatformsfortrustguarantees.However,thesethirdpartiesthatsolvepeople'strustproblemsaregraduallyfailing,becausetherearealwayshackerswhocanseizetheloopholesinthird-partyplatformstocarryoutfinancialfraud.The"traitor"inthe"ByzantineGeneralsProblem"isthe"liar"inInternetfinancialtransactions.Ifathird-partyplatformhasamajorloopholeorathird-partytrustedinstitutionisremovedinordertoavoidtoomanysteps,the"traitor"willusetheinformation"Cheating"iscarriedoutwithouttheguaranteeofathird-partytrustagency.Withoutspendingalotoftimeandresourcestouncoverthis"traitor",thewaythatbothpartiescantrusteachotherandconductnormaltransactionsisblockchain.