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スマートコントラクトデザイン / Smart Contract Design
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Kenji Saito
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November 01, 2021
Technology
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スマートコントラクトデザイン / Smart Contract Design
2021年11月1日(月)、慶應義塾大学大学院メディアデザイン研究科「サービスデザインプロジェクト B」2021秋 第4回で使用されたスライドです。
Kenji Saito
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November 01, 2021
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Transcript
B 2021 4 ( ) B 2021 — 4 —
2021-11-01 – p.1/51
https://speakerdeck.com/ks91 ( ) Discord Discord ( / / ) Zoom
URL ( ) B 2021 — 4 — 2021-11-01 – p.2/51
( ) 1 10 11 • 2 10 18 •
3 10 25 • 4 11 1 • 5 11 8 1 6 11 15 2 7 11 22 8 11 29 ( ) 4 ( 3 ) ↓ B 2021 — 4 — 2021-11-01 – p.3/51
brownie (1) : ERC20 (2) : (3) : Web 3.0
B 2021 — 4 — 2021-11-01 – p.4/51
brownie ropsten B 2021 — 4 — 2021-11-01 – p.5/51
infura.io Brownie https://infura.io SIGN UP PROJECT ID infura Ethereum API
infura . . . infura.io PROJECT ID WEB3_INFURA_PROJECT_ID PROJECT ID (~/.bash_profile ) $ export WEB3_INFURA_PROJECT_ID= PROJECT ID B 2021 — 4 — 2021-11-01 – p.6/51
ropsten ETH brownie console ropsten >>> network.disconnect() >>> network.connect(’ropsten’) >>>
len(accounts) 0 >>> accounts.add() <LocalAccount object ’ 16 ’> >>> accounts[0].private_key 16 >>> quit() Ropsten Testnet ETH Faucet 5.0ETH https://faucet.dimensions.network/ ( ) https://metamask.io/ B 2021 — 4 — 2021-11-01 – p.7/51
ropsten ETH brownie console ropsten ETH >>> network.disconnect() >>> network.connect(’ropsten’)
>>> len(accounts) 0 >>> accounts.add( 16 ) <LocalAccount object ’ 16 ’> >>> accounts[0].balace() ETH >>> quit() ( ) ETH >>> accounts[0].transfer(accounts[1], "1 ether") B 2021 — 4 — 2021-11-01 – p.8/51
(1) : ERC20 $ brownie bake token B 2021 —
4 — 2021-11-01 – p.9/51
Solidity JavaScript ( , ) (constructor) ( ) ( )
Ether Ethereum B 2021 — 4 — 2021-11-01 – p.10/51
pragma solidity ˆ0.6.0; /* 0.8.x */ contract Token { (
) : (EVM ) : constructor (...) public { /* */ : } function balanceOf(...) { /* ( ) */ : } : } constructor C (/* */ // ) B 2021 — 4 — 2021-11-01 – p.11/51
ERC20 ERC (Ethereum Request for Comment) 20 https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md contract ERC20
{ function totalSupply() constant returns (uint totalSupply); function balanceOf(address _owner) constant returns (uint balance); function transfer(address _to, uint _value) returns (bool success); function transferFrom(address _from, address _to, uint _value) returns (bool success); function approve(address _spender, uint _value) returns (bool success); function allowance(address _owner, address _spender) constant returns (uint remaining); event Transfer(address indexed _from, address indexed _to, uint _value); event Approval(address indexed _owner, address indexed _spender, uint _value); } name/ , symbol/ , decimals/ approve allowance ERC223 ( ), ERC721 (Non-Fungible) B 2021 — 4 — 2021-11-01 – p.12/51
ERC20 ERC20 ( ) ⇒ ERC20 ( ERC20 ) ERC20
⇒ B 2021 — 4 — 2021-11-01 – p.13/51
(fungible) ERC20 → ERC223 (draft) or ERC777 (non-fungible) ERC721 (
) (partially fungible) ERC1410 (draft) (ERC1400 ) B 2021 — 4 — 2021-11-01 – p.14/51
Token ( ) string public symbol; string public name; uint256
public decimals; uint256 public totalSupply; mapping(address => uint256) balances; . . . name, symbol decimals : 2 100 1.00 mapping balances B 2021 — 4 — 2021-11-01 – p.15/51
Token ( ) event Transfer(address from, address to, uint256 value);
Token function emit Transfer() ( ) B 2021 — 4 — 2021-11-01 – p.16/51
Token ( ) constructor( string memory _symbol, string memory _name,
uint256 _decimals, uint256 _totalSupply ) public { symbol = _symbol; name = _name; decimals = _decimals; totalSupply = _totalSupply; balances[msg.sender] = _totalSupply; } msg.sender _totalSupply B 2021 — 4 — 2021-11-01 – p.17/51
Token balanceOf() function balanceOf(address _owner) public view returns (uint256) {
return balances[_owner]; } B 2021 — 4 — 2021-11-01 – p.18/51
Token transfer() function transfer(address _to, uint256 _value) public returns (bool)
{ balances[msg.sender] = balances[msg.sender].sub(_value); balances[_to] = balances[_to].add(_value); emit Transfer(msg.sender, _to, _value); return true; } ( ↑ ) OpenZeppelin https://openzeppelin.org B 2021 — 4 — 2021-11-01 – p.19/51
(2) : B 2021 — 4 — 2021-11-01 – p.20/51
GitHub git clone $ git clone https://github.com/ks91/sample-smart-contracts.git sample-smart-contracts contracts, scripts
tests token Token Solidity 0.5 0.6/0.7 (Token ) Solidity B 2021 — 4 — 2021-11-01 – p.21/51
(m2 ) 1 1 B 2021 — 4 — 2021-11-01
– p.22/51
IndivisibleAsset string public _name_; string public _symbol_; uint256 public _quantity_;
address public _owner_; _name_ ( ) _symbol_ _quantity_ (m2 ) _owner_ ‘_’ Solidity . . . B 2021 — 4 — 2021-11-01 – p.23/51
IndivisibleAsset event Transfer(address indexed from, address indexed to); from to
indexed B 2021 — 4 — 2021-11-01 – p.24/51
IndivisibleAsset constructor (string name, string symbol, uint256 quantity) public {
_name_ = name; _symbol_ = symbol; _quantity_ = quantity; _owner_ = msg.sender; } B 2021 — 4 — 2021-11-01 – p.25/51
IndivisibleAsset getOwner() function getOwner() public view returns (address) { return
(_owner_); } B 2021 — 4 — 2021-11-01 – p.26/51
IndivisibleAsset transfer() function transfer(address to) public returns (bool) { require(_owner_
== msg.sender); _owner_ = to; emit Transfer(msg.sender, to); return true; } require (function ) ( ) $ brownie compile B 2021 — 4 — 2021-11-01 – p.27/51
scripts/indivisible asset.py from brownie import * def main(): accounts[0].deploy(IndivisibleAsset, "5322
Endo, Fujisawa", "mˆ2", 300) SFC (300m2 ) ( ) B 2021 — 4 — 2021-11-01 – p.28/51
from brownie import * import pytest def test_owner_and_transfer(IndivisibleAsset): asset =
accounts[0].deploy(IndivisibleAsset, "5322 Endo", "mˆ2", 300) assert asset.getOwner() == accounts[0] asset.transfer(accounts[1], {’from’: accounts[0]}) assert asset.getOwner() == accounts[1] try: asset.transfer(accounts[0], {’from’: accounts[0]}) done = 1 except: done = 0 assert done == 0 accounts[0] accounts[1] B 2021 — 4 — 2021-11-01 – p.29/51
$ pytest tests/test_indivisible_asset.py B 2021 — 4 — 2021-11-01 –
p.30/51
(3) : B 2021 — 4 — 2021-11-01 – p.31/51
transfer settle, retrieve asset, retrieve token 3 B 2021 —
4 — 2021-11-01 – p.32/51
1. ( ) 2. ( ) 3. ( ) B
2021 — 4 — 2021-11-01 – p.33/51
OneTimeEscrow settle() function settle() public returns (bool) { require(_token_.balanceOf(address(this)) >=
_price_); /* this */ require(_asset_.getOwner() == address(this)); _token_.transfer(_seller_ , _price_); _asset_.transfer(_buyer_); emit Settled(); /* */ return true; } settle() transfer ( / ) $ brownie compile B 2021 — 4 — 2021-11-01 – p.34/51
(1) from brownie import * import pytest def test_deploy_and_settle(Token, IndivisibleAsset,
OneTimeEscrow): asset = accounts[0].deploy(IndivisibleAsset, "5322 Endo", "mˆ2", 300) token = accounts[0].deploy(Token, "Test Token", "TEST", 18, "1000 ether") brownie console ropsten . . . ← accounts[0] seller, accounts[1] buyer buyer Ether (gas ) B 2021 — 4 — 2021-11-01 – p.35/51
(2) token.transfer(accounts[1], 300, {’from’: accounts[0]}) escrow = accounts[0].deploy(OneTimeEscrow, token, accounts[1],
asset, accounts[0], 300) accounts[0] accounts[1] 300 300 TX accounts[1] accounts[0] 300 bake Token 300 ETH wei B 2021 — 4 — 2021-11-01 – p.36/51
(3) token.transfer(escrow, 300, {’from’: accounts[1]}) asset.transfer(escrow, {’from’: accounts[0]}) assert token.balanceOf(accounts[0])
== 999999999999999999700 assert token.balanceOf(accounts[1]) == 0 assert token.balanceOf(escrow) == 300 assert asset.getOwner() == escrow accounts[1] ( ) 300 accounts[0] ( ) B 2021 — 4 — 2021-11-01 – p.37/51
(4) escrow.settle({’from’: accounts[0]}) assert token.balanceOf(accounts[0]) == 1000000000000000000000 assert token.balanceOf(accounts[1]) ==
0 assert token.balanceOf(escrow) == 0 assert asset.getOwner() == accounts[1] settle() accounts[0] OK B 2021 — 4 — 2021-11-01 – p.38/51
$ pytest tests/test_one_time_escrow.py : settle() ⇒ Discord B 2021 —
4 — 2021-11-01 – p.39/51
B 2021 — 4 — 2021-11-01 – p.40/51
1. (1) (2) Ethereum 1 2 2020 10 30 (
) 23:59 JST B 2021 — 4 — 2021-11-01 – p.41/51
. . . . . . 5 3 ( )
( ) (← ) (← ) ( ) ( ) B 2021 — 4 — 2021-11-01 – p.42/51
O ⇒ B 2021 — 4 — 2021-11-01 – p.43/51
K NFT ⇒ NFT SNS TikTok SNS ⇒ ( )
. . . B 2021 — 4 — 2021-11-01 – p.44/51
C ⇒ ( ) B 2021 — 4 — 2021-11-01
– p.45/51
Web 3.0 Web 3.0 HTTPS B 2021 — 4 —
2021-11-01 – p.46/51
NFT SNS ↑ B 2021 — 4 — 2021-11-01 –
p.47/51
miro ( ) ( ) B 2021 — 4 —
2021-11-01 – p.48/51
B 2021 — 4 — 2021-11-01 – p.49/51
2. API (1) ( ) (2) Web API 2020 11
6 ( ) 23:59 JST B 2021 — 4 — 2021-11-01 – p.50/51
B 2021 — 4 — 2021-11-01 – p.51/51