イーサリアム実習 I / Ethereum Practice 1

2018年7月18日(水)、ブロックチェーンハブ主催で開催されたブロックチェーンアカデミー「イーサリアム実習 I」(【ハンズオン】スマートコントラクトプログラミング (2)) にて使用したスライドです。

Transcript

1. I
   (2)
   CSO / SFC
   ( https://speakerdeck.com/ks91 )
   ks91@blockchainhub.co.jp
   I — (2) — 2018-07-18 – p.1/38
   

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2. 1.
   2.
   3.
   4.
   5.
   I — (2) — 2018-07-18 – p.2/38
   

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3. 1. : ERC20
   2. ∼ ∼
   I — (2) — 2018-07-18 – p.3/38
   

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4. 1. : ERC20
   ERC20
   I — (2) — 2018-07-18 – p.4/38
   

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5. (2018 7 18 )
   BcH-smart-contract-programming.zip
   Solidity
   py.test solidity 0.4.22 + populus
   ongoing
   solidity 0.4.21
   contracts tests
   I — (2) — 2018-07-18 – p.5/38
   

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6. Solidity
   JavaScript
   ( , )
   (constructor)
   ( )
   ( )
   Ether
   I — (2) — 2018-07-18 – p.6/38
   

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7. pragma solidity ˆ0.4.24;
   contract MyToken {
   ( )
   :
   (EVM )
   :
   constructor (...) public { /* */
   :
   }
   function MyToken(...) { /* ( ) */
   :
   }
   :
   }
   constructor
   C (/* */ // )
   I — (2) — 2018-07-18 – p.7/38
   

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8. 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)
   I — (2) — 2018-07-18 – p.8/38
   

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9. MyToken
   string public _name;
   string public _symbol;
   uint8 public _decimals;
   mapping (address => uint256) public _balanceOf;
   uint256 _totalSupply;
   _name, _symbol
   _decimals
   : 2 100 1.00
   mapping _balanceOf
   I — (2) — 2018-07-18 – p.9/38
   

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10. MyToken
    event Transfer(address indexed from, address indexed to, uint256 value);
    indexed (3 )
    MyToken function Transfer()
    I — (2) — 2018-07-18 – p.10/38
    

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11. MyToken
    constructor (uint256 supply, string name, string symbol, uint8 decimals) public {
    if (supply == 0) {
    supply = 1000000; /* supply 1,000,000 */
    }
    _totalSupply = supply;
    _balanceOf[msg.sender] = supply;
    _name = name;
    _symbol = symbol;
    _decimals = decimals;
    }
    msg.sender
    supply
    I — (2) — 2018-07-18 – p.11/38
    

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12. MyToken balanceOf()
    function balanceOf(address tokenOwner) external view returns (uint256) {
    return _balanceOf[tokenOwner];
    }
    I — (2) — 2018-07-18 – p.12/38
    

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13. MyToken transfer()
    function transfer(address to, uint256 value) external returns (bool) {
    require(value <= _balanceOf[msg.sender]); /* */
    require(_balanceOf[to] + value >= _balanceOf[to]); /* */
    _balanceOf[msg.sender] -= value;
    _balanceOf[to] += value;
    Transfer(msg.sender, to, value);
    return true;
    }
    require (function )
    OpenZeppelin
    https://openzeppelin.org
    I — (2) — 2018-07-18 – p.13/38
    

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14. (1)
    import pytest
    @pytest.fixture()
    def token_contract(chain):
    TokenFactory = chain.provider.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
    I — (2) — 2018-07-18 – p.14/38
    

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15. (2)
    def test_my_token(token_contract, chain):
    account0 = chain.web3.eth.accounts[0]
    account1 = chain.web3.eth.accounts[1]
    assert token_contract.call().balanceOf(account0) == 1000000
    assert token_contract.call().balanceOf(account1) == 0
    txid = token_contract.transact().transfer(account1, 10)
    chain.wait.for_receipt(txid)
    assert token_contract.call().balanceOf(account0) == 999990
    assert token_contract.call().balanceOf(account1) == 10
    account0 coinbase
    account1
    account0 account1 10BcH
    I — (2) — 2018-07-18 – p.15/38
    

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16. $ py.test -k test_my_token.py
    I — (2) — 2018-07-18 – p.16/38
    

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17. 2.
    ∼ ∼
    I — (2) — 2018-07-18 – p.17/38
    

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18. A, B
    A-B m
    A B A
    B A B
    . . .
    I — (2) — 2018-07-18 – p.18/38
    

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19. 1. X
    2. X C
    3. C
    1.
    2.
    3.
    reliable multicast
    I — (2) — 2018-07-18 – p.19/38
    

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20. :
    I — (2) — 2018-07-18 – p.20/38
    

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21. (safety)
    (liveness)
    ( )
    ( = )
    I — (2) — 2018-07-18 – p.21/38
    

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22. → / (benign)
    → (Byzantine)
    (malicious)
    I — (2) — 2018-07-18 – p.22/38
    

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23. FLP
    Fischer, Lynch, Paterson
    I — (2) — 2018-07-18 – p.23/38
    

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24. CAP
    Consistency ( )
    Availability ( )
    Partition tolerance ( )
    ⇒ 3
    C
    Eventual consistency ( )
    . . .
    I — (2) — 2018-07-18 – p.24/38
    

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25. Consistency ( )
    Strong consistency ( )
    (safety)
    Eventual consistency ( )
    (liveness)
    ↑
    Weak consistency ( )
    ↑ ( )
    I — (2) — 2018-07-18 – p.25/38
    

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26. n
    =
    f
    ( )
    ⇒
    I — (2) — 2018-07-18 – p.26/38
    

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27. (1)
    1 1, 2
    n ≤ 3f
    I — (2) — 2018-07-18 – p.27/38
    

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28. (2)
    I — (2) — 2018-07-18 – p.28/38
    

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29. CS1 :
    CS2 :
    CS3 :
    CL1 :
    CL2 :
    :
    :
    (e.g. )
    I — (2) — 2018-07-18 – p.29/38
    

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30. (B)FT-CUP (Consensus with Unknown Participants)
    ( / )
    : FT (Fault-Tolerant)
    : BFT (Byzantine Fault-Tolerant)
    P2P
    n FT/BFT
    I — (2) — 2018-07-18 – p.30/38
    

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31. State Machine Replication ( )
    (by ) (since 1984) ( )
    ( )
    . . .
    ( )
    I — (2) — 2018-07-18 – p.31/38
    

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32. ( )
    ( ) ( ) ( )
    (by )
    ⇒ ( )
    I — (2) — 2018-07-18 – p.32/38
    

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33. P2P
    : P2P
    3
    3
    ( )
    strategyproof
    group strategyproof
    I — (2) — 2018-07-18 – p.33/38
    

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34. (Sybil)
    16
    I — (2) — 2018-07-18 – p.34/38
    

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35. again
    n > 3f
    R F
    R > 2F
    ⇒
    I — (2) — 2018-07-18 – p.35/38
    

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36. ( )
    f = 1 ⇒ R
    I — (2) — 2018-07-18 – p.36/38
    

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37. (centralized) (decentralized) (distributed)
    Paul Baran, “On Distributed Communications Networks”, 1964
    (C) (A)
    I — (2) — 2018-07-18 – p.37/38
    

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38. II
    :
    :
    /
    I — (2) — 2018-07-18 – p.38/38
    

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