スマートコントラクトを理解する 〜解説と実演〜 / Understanding Smart Contracts

2017年6月7日(水)、Interop Tokyo 2017 の同名のセッションにて私用したスライドです。

Transcript

1. ∼ ( 2 ) ∼ SFC ks91@sfc.wide.ad.jp — — 2017-06-07 – p.1/70
2. ( ) SFC ( ) CSO (Chief Science Officer) 1993 M.Eng ( ) 2006 ( ) SFC 16 P2P 2011 → ( ) — — 2017-06-07 – p.2/70
3. 1. 2. 3. 4. 5. : 6. — — 2017-06-07 – p.3/70
4. 1. — — 2017-06-07 – p.4/70
5. Vitalik Buterin, “Ethereum White Paper: A NEXT GENERATION SMART CONTRACT & DECENTRALIZED APPLICATION PLATFORM” 15 — — 2017-06-07 – p.5/70
6. — — 2017-06-07 – p.6/70
7. . . . — — 2017-06-07 – p.7/70
8. vs. — — 2017-06-07 – p.8/70
9. = run — — 2017-06-07 – p.9/70
10. Ether Ethereum EOA : Externally-Owned Account Ether EVM EVM — — 2017-06-07 – p.10/70
11. EVM : Ethereum Virtual Machine Gas — — 2017-06-07 – p.11/70
12. EVM : : Solidity — JavaScript LLL — Lisp — — 2017-06-07 – p.12/70
13. Solidity contract metaCoin { mapping (address => uint) balances; function metaCoin() { balances[msg.sender] = 10000; } function sendCoin(address receiver, uint amount) returns(bool sufficient) { if (balances[msg.sender] < amount) return false; balances[msg.sender] -= amount; balances[receiver] += amount; return true; } } by hshimo — — 2017-06-07 – p.13/70
14. — — 2017-06-07 – p.14/70
15. 2. — — 2017-06-07 – p.15/70
16. ADEPT ADEPT : IBM IoT — — 2017-06-07 – p.16/70
17. — — 2017-06-07 – p.17/70
18. ⇒ — — 2017-06-07 – p.18/70
19. The DAO ( ) The DAO Split ( ) 360 ETH (50∼60 ) (2016/6/17) ( ) ( ; ) (2016/7/20 ) — — 2017-06-07 – p.19/70
20. 3. — — 2017-06-07 – p.20/70
21. 3-1. Hyperledger Fabric (IBM) IBM Digital Asset Holdings http://hyperledger-fabric.readthedocs.io/en/latest/ — — 2017-06-07 – p.21/70
22. (Docker) (chaincode) PBFT (Practical BFT) RocksDB CA PKI v1.0 DB CA — — 2017-06-07 – p.22/70
23. 3-2. Hyperledger Iroha ( ) https://github.com/hyperledger/iroha — — 2017-06-07 – p.23/70
24. JVM (chaincode) Sumeragi (BFT) — — 2017-06-07 – p.24/70
25. 3-3. Corda (R3) R3 https://github.com/corda/corda — — 2017-06-07 – p.25/70
26. JVM ( ) (Uniqueness Services) UTXO X.509 PKI ( ) Corda — — 2017-06-07 – p.26/70
27. 4. Mac OS X (Yosemite 10.10.5) + Homebrew Linux (Ubuntu 16.04) Windows 10 + Bash on Ubuntu on Windows geth, solidity populus — — 2017-06-07 – p.27/70
28. geth GO https://github.com/ethereum/go-ethereum/wiki/Building-Ethereum #installation-instructions geth 1.6.1-stable (5/16 ) $ geth -help — — 2017-06-07 – p.28/70
29. Solidity http://solidity.readthedocs.io/en/latest/installing-solidity.html solc 0.4.11 (5/16 ) $ solc --version — — 2017-06-07 – p.29/70
30. Python pip macOS http://qiita.com/oct_itmt/items/2d066801a7464a676994 (pyenv ) Ubuntu 16.04 — — 2017-06-07 – p.30/70
31. Populus Python http://populus.readthedocs.io/en/latest/quickstart.html Open SSL Populus $ pip install populus version 1.6.9 (5/16 ) — — 2017-06-07 – p.31/70
32. $ populus init contracts/Greeter.sol tests/test_greeter.py $ populus compile $ py.test tests/ — — 2017-06-07 – p.32/70
33. 5. ( ) — — 2017-06-07 – p.33/70
34. — — 2017-06-07 – p.34/70
35. ( ) / / — — 2017-06-07 – p.35/70
36. BcH-smart-contract-programming.zip contracts tests — — 2017-06-07 – p.36/70
37. Solidity JavaScript ( , ) (constructor) ( ) ( ) Ether — — 2017-06-07 – p.37/70
38. pragma solidity ˆ0.4.8; contract MyToken { ( ) : (EVM ) : function MyToken(...) { /* */ : } : } function C (/* */ // ) — — 2017-06-07 – p.38/70
39. MyToken string public name; string public symbol; uint8 public decimals; mapping (address => uint256) public balanceOf; name, symbol decimals : 2 100 1.00 mapping balanceOf — — 2017-06-07 – p.39/70
40. MyToken event Transfer(address indexed from, address indexed to, uint256 value); indexed (3 ) MyToken function Transfer() Ethereum-Wallet — — 2017-06-07 – p.40/70
41. MyToken function MyToken(uint256 _supply, string _name, string _symbol, uint8 _decimals) { if (_supply == 0) { _supply = 1000000; /* _supply 1,000,000 */ } balanceOf[msg.sender] = _supply; name = _name; symbol = _symbol; decimals = _decimals; } msg.sender _supply C++ _ — — 2017-06-07 – p.41/70
42. MyToken getBalanceOf() function getBalanceOf(address _addr) returns (uint256 balance) { return (balanceOf[_addr]); } — — 2017-06-07 – p.42/70
43. MyToken transfer() function transfer(address _to, uint256 _value) { if (balanceOf[msg.sender] < _value) { /* */ throw; } if (balanceOf[_to] + _value < balanceOf[_to]) { /* */ throw; } balanceOf[msg.sender] -= _value; balanceOf[_to] += _value; Transfer(msg.sender, _to, _value); } throw (function ) catch — — 2017-06-07 – p.43/70
44. (1) import pytest @pytest.fixture() def token_contract(chain): TokenFactory = chain.get_contract_factory(’MyToken’) deploy_txid = TokenFactory.deploy(args=[ 0, "BcH Coin", "BcH", 0, ]) contract_address = chain.wait.for_contract_address(deploy_txid) return TokenFactory(address=contract_address) populus — — 2017-06-07 – p.44/70
45. (2) def test_my_token(token_contract, chain): account0 = chain.web3.eth.accounts[0] account1 = chain.web3.eth.accounts[1] assert token_contract.call().getBalanceOf(account0) == 1000000 assert token_contract.call().getBalanceOf(account1) == 0 txid = token_contract.transact().transfer(account1, 10) chain.wait.for_receipt(txid) assert token_contract.call().getBalanceOf(account0) == 999990 assert token_contract.call().getBalanceOf(account1) == 10 account0 coinbase account1 account0 account1 10BcH — — 2017-06-07 – p.45/70
46. $ py.test tests/test_my_token.py — — 2017-06-07 – p.46/70
47. — — 2017-06-07 – p.47/70
48. (m2 ) 1 1 — — 2017-06-07 – p.48/70
49. IndivisibleAsset string public _name; string public _symbol; uint256 public _quantity; address public _owner; _name ( ) _symbol _quantity (m2 ) _owner _ Solidity . . . — — 2017-06-07 – p.49/70
50. IndivisibleAsset event Transfer(address indexed from, address indexed to); from to — — 2017-06-07 – p.50/70
51. IndivisibleAsset function IndivisibleAsset(string name, string symbol, uint256 quantity) { _name = name; _symbol = symbol; _quantity = quantity; _owner = msg.sender; } — — 2017-06-07 – p.51/70
52. IndivisibleAsset getOwner() function getOwner() returns (address owner) { return (_owner); } — — 2017-06-07 – p.52/70
53. IndivisibleAsset transfer() function transfer(address to) { if (_owner != msg.sender) { throw; } _owner = to; Transfer(msg.sender, to); } — — 2017-06-07 – p.53/70
54. (1) import pytest @pytest.fixture() def asset_contract(chain): AssetFactory = chain.get_contract_factory(’IndivisibleAsset’) deploy_txid = AssetFactory.deploy(args=[ "5322 Endo, Fujisawa", "mˆ2", 300, ]) contract_address = chain.wait.for_contract_address(deploy_txid) return AssetFactory(address=contract_address) SFC (300m2 ) — — 2017-06-07 – p.54/70
55. (2) def test_indivisible_assset(asset_contract, chain): account0 = chain.web3.eth.accounts[0] account1 = chain.web3.eth.accounts[1] assert asset_contract.call().getOwner() == account0 txid = asset_contract.transact().transfer(account1) chain.wait.for_receipt(txid) assert asset_contract.call().getOwner() == account1 account0 account1 — — 2017-06-07 – p.55/70
56. $ py.test tests/test_indivisible_asset.py — — 2017-06-07 – p.56/70
57. — — 2017-06-07 – p.57/70
58. transfer settle, retrieve asset, retrieve token 3 — — 2017-06-07 – p.58/70
59. 1. ( ) 2. ( ) 3. ( ) — — 2017-06-07 – p.59/70
60. OneTimeEscrow settle() function settle() { address addr = this; /* this */ if (_token.getBalanceOf(this) < _price || _asset.getOwner() != addr) { throw; } _token.transfer(_seller , _price); _asset.transfer(_buyer); Settled(); /* */ } settle() transfer — — 2017-06-07 – p.60/70
61. (1) import pytest @pytest.fixture() def token_contract(chain): . . . @pytest.fixture() def asset_contract(chain): . . . — — 2017-06-07 – p.61/70
62. (2) def test_one_time_escrow(token_contract, asset_contract, chain): account0 = chain.web3.eth.accounts[0] account1 = chain.web3.eth.accounts[1] txid = chain.web3.eth.sendTransaction({ ’from’: account0, ’to’: account1, ’value’: chain.web3.toWei(1, "ether") }) chain.wait.for_receipt(txid) txid = token_contract.transact().transfer(account1, 300) chain.wait.for_receipt(txid) account0 account1 1Ether 300BcH 300BcH TX — — 2017-06-07 – p.62/70
63. (3) EscrowFactory = chain.get_contract_factory(’OneTimeEscrow’) txid = EscrowFactory.deploy(args=[ token_contract.address, account1, asset_contract.address, account0, 300, ]) contract_address = chain.wait.for_contract_address(txid) EscrowFactory.address = contract_address; account1 account0 300BcH — — 2017-06-07 – p.63/70
64. (4) txid = token_contract.transact({ ’from’: account1 }).transfer(contract_address, 300) chain.wait.for_receipt(txid) txid = asset_contract.transact().transfer(contract_address) chain.wait.for_receipt(txid) assert token_contract.call().getBalanceOf(account0) == 999700 assert token_contract.call().getBalanceOf(account1) == 0 assert token_contract.call().getBalanceOf(contract_address) == 300 assert asset_contract.call().getOwner() == contract_address account1 300BcH account0 — — 2017-06-07 – p.64/70
65. (5) txid = EscrowFactory.transact().settle(); chain.wait.for_receipt(txid) assert token_contract.call().getBalanceOf(account0) == 1000000 assert token_contract.call().getBalanceOf(account1) == 0 assert token_contract.call().getBalanceOf(contract_address) == 0 assert asset_contract.call().getOwner() == account1 settle() — — 2017-06-07 – p.65/70
66. $ py.test tests/test_one_time_escrow.py : settle() — — 2017-06-07 – p.66/70
67. 6. — — 2017-06-07 – p.67/70
68. ( ) (by ) (since 1984) ( ) ( ) . . . ( ) — — 2017-06-07 – p.68/70
69. ( ) ( ) ( ) ( ) (by ) — — 2017-06-07 – p.69/70
70. — — 2017-06-07 – p.70/70