Blockchain: Applicaons, Security Promises and Internals · 2020. 4. 8. · Cyber Security &...

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Blockchain:Applica.ons,SecurityPromisesandInternals

CyberSecurity&Informa3onSystemsInforma3onAnalysisCenter(CSIAC)

Dr.Yuzhe(Richard)TangDepartmentofEECS,SyracuseUniversity

Dec.19,2017

Outline

1.   Introduc+on

2.  Blockchainapplica.onsandinterfaces

3.  Blockchainsecuritypromises

4.  Blockchaininternals(abrief)

12/19/17 YuzheTang,SyracuseUniv. 2

1.Introduc.on•  Cryptocurrency:– “Acryptocurrencyisadigitalassetdesignedtoworkasamediumofexchangethatusescryptographytosecureitstransac.ons,tocontrolthecrea.onofaddi.onalunits,andtoverifythetransferofassets.”(wiki)

– BitCoin,Etheruem,Litcoin,etc.

1.Introduc.on

• HowtocomparetheconceptofBitCoinwithfiatcurrency(e.g.USdollar)?

What’sSimilaraboutBitcointoUSDollar

Reviewofgov-issued(fiat)currency•  Workflow– Moneycreatedbyamint– Moneycirculatedamongownersthru.transac+ons.–  BitCoinsupportsthesameworkflow

Reviewofgov-issued(fiat)currency•  Threat1:Printfakemoney–  Dollarbillsaresecuredbyan.-counterfeit–  US.mintissafeguarded–  Bitcoinhastodefendthisthreat

•  Threat2:Doublespending(digitalcurrency)–  Visa’sledgerdatabasevalidatestransac.ons–  BitCoinhastopreventdouble-spending

Reviewofgov-issued(fiat)currency•  Threat1:Printfakemoney–  Dollarbillsaresecuredbyan.-counterfeit–  US.mintissafeguarded–  Bitcoinhastodefendthisthreat

•  Threat2:Doublespending(digitalcurrency)–  Visa’sledgerdatabasevalidatestransac.ons–  BitCoinhastopreventdouble-spending

IssueswithUSDollar

•  Usingdollarbills,youimplicitlytrust– Government,mint,credit-cardorg.(Visa)– Thesearetrustedcentralauthori+es

•  Aretheytrustworthy?–  Youmaynotwantgov.towithdrawatxacerit’ssedled.–  Youmaynotwantgov.tofreezeyouraccount–  Youmaynotwantgov.toinflatethecurrencyanddepreciateyoursavings:Zimbabwe

12/19/17 8

Mo.va.ngBitCoin(What’suniqueaboutBitCoin)

•  Getridofcentralauthori.esbydecentraliza+on– NoneedtotrustgovernmentandVisa–  Insteadtrusttheen.repopula.onontheplanet

•  Maketransac.onhistorypublic(Transparency)–  Transparencyinvitestrust

•  Automatetheprocesswithincen+ve-compa+bility– Automa.onlowerscost(transac.onfee)

•  BitcointxhistoryisrecordedinBlockchain– BlockchainistheledgerforBitcoin

BitCoinandBlockchain

Outline

1.  Introduc.on

2.   Blockchainapplica+onsandinterfaces

•  GetyourfirstBitCoin– Exchangeservices:Coinbase,Coindesk,etc.

•  UsingBitCointosellandbuystuff(transac.on)•  Orsellit.llthepricegrowshigher

Scenario1:DoingTransac.ons

Scenario2:Mining

•  AnotherwaytogetBitCoin:Mining– Getthemoneyanonymously

•  Youcanpurchasehardwaretodosome(non-sense)computa.ons– Withsomeprobability,yourcomputa.onwillberewardedinBitCoin

– Theprobabilitydependsonhowpowerfulyourhardwareis

Scenario2:Mining

•  Interestedinmining?– Howmuchisyourbudget?

•  Constantcapital:buymachines,Variablecapital:electricityconsump.on

– Whoyouareupagainst(inwinningthereward)?•  State-levelminers,bitcoinfarm,datacenters

Scenario3:DevelopApplica.ons

•  DistributedappoverBlockchain(Dapp)– FinTech:Insurance,trade,riskmanagement,accoun.ng,etc.•  Examples:ERP,micro-payments,wallet,currencyexchange,etc.

– Otherdomains:Legal,medical/healthcare,IT,science/research,etc.

•  “Blockchainissettodisruptmanyindustries”

•  Dapparchitecture:On-chain/off-chain– On-chaindata:“Transac.ons”ormeta-data– Off-chaindata:someprivatedata(e.g.keys)

•  Interac.ngBlockchainthru.transac.onAPI:– send_tx(sender,receiver,money#,memo)– Likewri.ngapersonalcheck

•  Designissues– Par..oningapplica.onlogictosuiton-/off-chain– Designingincen.veschemes(whattorewardmining?)

– Dealingwiththelimita.onofBlockchain(e.g.deferredfinality)

•  BuildingaBitCoinwalletDapp– DeveloperworkingforCoinBase

Outline

1.  Introduc.on

3.   Blockchainsecuritypromises

Security:ImmutableStorage

•  Blockchainabstrac.onastxstorage– Readabletothepublic(transparency)– Appendablebyhonestminers– Cannotbemodified(immutability)

•  Buildingatrusted.mestampserviceforlegaldocuments(signingcontract,applyingpatentetc)

Security:NoDoubleSpending

•  Nodouble-spending(An.-counterfeit)

•  Smartproperty– Smart.cket:UseBitCointorepresentbaseball.ckets.

Security:UnstoppableExecu.on•  Programminglang.onBlockchain:Smartcontract– Smart-contractprogramisanobj.runningonBlockchain

– SolidityinEthereum•  Securityproper.es:– Autonomouslyexecuted,unstoppable– Transac.onfairness:•  IfIpaidyou,tobefair,Ineedtoreceiveyourgoods.

Security:UnstoppableExecu.on•  Smart-contractapplica.ons:–  ImplementIFTTTlogicthatdecideshowtosendtx

•  Astock-exchangeapplica.on– Alicewilltrade10sharesfor$10,000whenthestockpriceisbelow$1000.

Acknowledge:Prof.AriJuels12/19/17 YuzheTang,SyracuseUniv. 22

Outline

1.  Introduc.on

4.   Blockchaininternals(abrief)

Blockchaininternals

1.  Blockchain:Immutabletxstorage

2.  Blockchainconsensus:–  Howtoaddtransac.onto

Blockchaininadecentralizedway?

Blockchain:ImmutableTxStorage

•  Createmoney– coinX=mint.CreateCoin()bybkc_as_mint.signmint_skey(“CoinXiscreated”)

•  Circulatemoneybytransac.ons– alice.PayCoin(bob,coinX)bytx=alice.signalice_skey(“CoinXispaidtoBobbob_pkey”)bkc_as_visa.validate(tx)

– Txrepresenta.on•  Howtorepresentcoins,owneriden.ty,ownership(bindingbtwncoinandiden.ty)?

Blockchain:ImmutableTxStorage

•  Hashpointer:Represen.ngcoinsinatx– Bob’scoinspentinatxisthetx’shashpointerpoin.ngtoapriortxwhereBobreceivesthecoin.

•  Hashchainoftransac.ons

•  Blockchainoftransac.ons

Consensus

•  Transac.on-addworkflow– Valida.on,Append

•  Consensusmechanisms– Randomiza.on– PoWmining– Asmint:Incen.ve-compa.bility– Bootstrapthetrust

Contact: Yuzhe (Richard) Tang Assistant Professor Dept. of EECS Syracuse University ytang100@syr.edu ecs.syr.edu/faculty/yuzhe

Thankyou!

Blockchain: Applicaons, Security Promises and Internals · 2020. 4. 8. · Cyber Security &...

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