Plutus and Extended UTxO

Transcription

1 Plutus and Extended UTxO Manuel M T Chakravarty, Language IOHK

2 What is Plutus? Innovative development and execution platform for distributed contract applications on Cardano.

3 The Three Pillars of Plutus

4 Safety & Security Superior Ledger Full Stack

5 Safety & Security Superior Ledger Full Stack

6 λ τ functional with modern type

7 functional input output pure function side effects modern type systems

8 functional :: :: β input output typed function safe usage modern type systems

9 local reasoning :: :: β type-directed design input output typed function advanced testing safe usage & verification

10 local reasoning type-directed design advanced testing & verification } understand code find exploits

11 not a core typed FP not a classic virtual machine Plutus Core abstract machine interpreter small, powerful & based on peer-reviewed

12 core Plutus Core Where is it used?

13 Safety & Security Superior Ledger Full Stack

14 imperative mutable entangled functional dataflow compositional shared state UTxO-based Ledger Account-based Ledger

15 Bitcoin minimal What about the expressiveness of smart contracts? Ethereum enough rope

16

17 Input Output ρ: Redeemer core ρ: Redeemer core x: Value σ: State x: Value ν: Validator core ν: Validator core δ: Data core ν(ρ) True ν(ρ, δ, σ, x) True

18 Extended UTxO ρ: Redeemer core Preserves the superior structure of UTxO ledgers x: Value ν: Validator core σ: State Greatly increases the δ: Data core expressive power of scripts ν(ρ, δ, σ, x) True

19 Extended UTxO data flows with value Preserves the superior structure of UTxO ledgers scripts have an Greatly increases the expressive power of scripts invariants across transaction chains

20 Safety & Security Superior Ledger Full Stack

21 What does it take to write a smart contract application?

22 1. Payment into campaign until a payment deadline 2. If funding goal reached, campaign owner can collect funds 3. If funding goal not reached, refunds can be obtained by contributors 4. If campaign owner does not collect by Simple crowdfunding collection deadline, contributors can also obtain refunds

23 pragma solidity ^0.4.6; contract WinnerTakesAll { uint minimumentryfee; uint public deadlineprojects; uint public deadlinecampaign; uint public winningfunds; address public winningaddress; struct Project { address addr; string name; string url; uint funds; bool initialized; } Solidity (on-chain) + var Web3 = require('web3'); var web3 = new Web3(); web3.setprovider(new web3.providers.httpprovider( http: 1. Payment into campaign until a payment deadline 2. If funding goal reached, campaign var accounts = web3.eth.accounts; accounts.foreach(function(v) { $( #supportfrom ).append( <opt $( #projectaddr ).append( <opt }); owner can collect funds 3. If funding goal not reached, refunds can be obtained by contributors var compiled = web3.eth.compile.so 4. If campaign owner does not collect by var code = compiled.code; var abi = compiled.info.abidefinit var contract = web3.eth.contract(a collection deadline, contributors can also obtain refunds JavaScript (off-chain)

24 var Web3 = require('web3'); var web3 = new Web3(); web3.setprovider(new web3.providers.httpprovider( http: var accounts = web3.eth.accounts; accounts.foreach(function(v) { $( #supportfrom ).append( <opt $( #projectaddr ).append( <opt }); var compiled = web3.eth.compile.so off-chain (wallet) var code = compiled.code; var abi = compiled.info.abidefinit var contract = web3.eth.contract(a JavaScript two-level (staged) programming model pragma solidity ^0.4.6; contract WinnerTakesAll { uint minimumentryfee; uint public deadlineprojects; uint public deadlinecampaign; uint public winningfunds; address public winningaddress; struct Project { address addr; string name; string url; uint funds; bool initialized; } on-chain (transaction) Solidity

25 JavaScript off-chain inconvenient (wallet) ad hoc two-level (staged) programming model complex on-chain (transaction) Solidity fragile

26 Haskell off-chain integrated (wallet) meta programming two-level (staged) programming model compact on-chain (transaction) robust Haskell (Plutus Tx)

27 contribute :: Campaign -> Value -> MockWallet () contribute campaign value = do Haskell when (value <= 0) $ throwothererror "Must contribute a positive value" ownpk <- ownpubkey tx <- paytoscript (Ledger.scriptAddress (contributionscript campaign)) value DataScript (Ledger.lifted ownpk) register (refundtrigger campaign) (refundhandler (Ledger.hashTx tx) campaign) contributionscript :: Campaign -> ValidatorScript

28 Haskell contributionscript :: Campaign -> ValidatorScript

29 contributionscript :: Campaign -> ValidatorScript Haskell contributionscript campaign = ValidatorScript (validator `apply` campaign) where validator = Ledger.fromCompiledCode $$(PlutusTx.compile [ (\Campaign{..} action contrib tx -> Plutus Tx let PendingTx ps outs (Height h) = tx isvalid = case action of Refund -> h > collectiondeadline && contributoronly outs && $$(txsignedby) tx contrib Collect -> h > deadline && h <= collectiondeadline && totalinputs >= target && $$(txsignedby) p campaignowner in $$(P.errorIfNot) isvalid ])

30 Safety & Security Superior Ledger Full Stack

31 Safety & Security Superior Ledger Full Stack

32 Safety & Security Superior Ledger Full Stack

33 contribute :: Campaign -> Value -> MockWallet () contribute campaign value = do when (value <= 0) $ throwothererror "Must contribute a positive value" ownpk <- ownpubkey tx <- paytoscript (Ledger.scriptAddress (contributionscript campaign)) value DataScript (Ledger.lifted ownpk) register (refundtrigger campaign) (refundhandler (Ledger.hashTx tx) campaign) core off-chain contributionscript :: Campaign -> ValidatorScript contributionscript campaign = ValidatorScript (validator `apply` campaign) where validator = core Ledger.fromCompiledCode $$(PlutusTx.compile [ (\Campaign{..} action contrib tx -> let PendingTx ps outs (Height h) = tx isvalid = case action of Refund -> h > collectiondeadline && contributoronly outs && $$(txsignedby) tx contrib Collect -> h > deadline && h <= collectiondeadline && totalinputs >= target && $$(txsignedby) p campaignowner in $$(P.errorIfNot) isvalid ]) on-chain

34 This is Plutus! Safety & Security Superior Ledger Full Stack