스마트 컨트랙트에 관한 개요와 이더리움의 스마트 컨트랙트 코드를 작성할 수 있는 Solidity에 대해 코드를 통해 알아보는 슬라이드입니다.

1. Smart Contract & Solidity
Solidity
winterj.me@gmail.com
JungWinter

2. Smart Contract

3. Smart Contract
•
• 1994 Nick Szabo
•
•
Transaction

4. Smart Contract

5. •
•
•

6. •
• Contacting external services, Enforcing on-chain
payments
• (= )

7. Ethereum Contract

8. Bitcoin Contract
• Script
• OPCODE
• Output Input Public Key HASH
CHECKSIG Private Key TRUE

9. Ethereum Contract
•
Turing Complete
• APPLY(S)=S’
(APPLY: , S: , S’: )
• Smart Contract
• Loop , Contract Account, Block Transaction
, Gas

10. Loop Gas
• Operation Gas Cost
• Transaction fee = Gas_used * Gas_price[Gwei]
1 Gwei = 0.000000001 ETH
• Gas
= Gas

11. Smart Contract Code
• Smart Contract
Smart Contract Code
• EVM(Ethereum Virtual Machine)
EVM
•
• Mutan: C Deprecated
• LLL: Low level OPCODE
• Serpent: Python
• Solidity: Javascript

12. Smart Contract
(https://maniara.github.io/sc_lecture.pdf)

13. Solidity

14. Solidity Hello World
pragma solidity ^0.4.0;
contract SimpleStorage {
uint storedData;
function set(uint x) {
storedData = x;
}
function get() constant returns (uint retVal) {
return storedData;
}
}
pragma
constant
returns
uint
http://solidity.readthedocs.io/en/develop/introduction-to-smart-contracts.html

15. Solidity Hello World
pragma solidity ^0.4.0;
contract SimpleStorage {
uint storedData;
function set(uint x) {
storedData = x;
}
function get() constant returns (uint retVal) {
return storedData;
}
}
pragma
constant
returns
uint
^0.4.0 Solidity 0.5.0
npm
^1.2.3 → >=1.2.3 <2.0.0
^0.2.3 → >=0.2.3 <0.3.0
^0.0.3 → >=0.0.3 <0.0.4

16. Solidity Hello World
pragma solidity ^0.4.0;
contract SimpleStorage {
uint storedData;
function set(uint x) {
storedData = x;
}
function get() constant returns (uint retVal) {
return storedData;
}
}
pragma
constant
returns
uint
constant
State
constant Gas
Modifier
. 0.4.16 constant view pure constant view alias
pure pure

17. Solidity Hello World
pragma solidity ^0.4.0;
contract SimpleStorage {
uint storedData;
function set(uint x) {
storedData = x;
}
function get() constant returns (uint retVal) {
return storedData;
}
}
pragma
constant
returns
uint
return
1

18. Solidity Hello World
pragma solidity ^0.4.0;
contract SimpleStorage {
uint storedData;
function set(uint x) {
storedData = x;
}
function get() constant returns (uint retVal) {
return storedData;
}
}
pragma
constant
returns
uint
uint unsigned int uint8 uint256
uint uint256

19. Solidity Code → Byte Code
SMART CONTRACT (http://goodjoon.tistory.com/261)

20. SMART CONTRACT (http://goodjoon.tistory.com/261)
dApp
Contract Meta data

21. pragma solidity ^0.4.0;
contract Coin{
address public minter;
mapping (address => uint ) public balances;
event Sent (address from, address to, uint amount);
function Coin() {
minter = msg.sender;
}
function mint(address receiver, uint amount) {
if (msg.sender != minter) return;
balances[receiver] += amount;
}
function send(address receiver, uint amount) {
if (balances[msg.sender] < amount) return;
balances[msg.sender] -= amount;
balances[receiver] += amount;
Sent(msg.sender, receiver, amount);
}
}
http://solidity.readthedocs.io/en/develop/introduction-to-smart-contracts.html
address
public
mapping
event
msg

22. address
public
mapping
event
msg
http://solidity.readthedocs.io/en/develop/introduction-to-smart-contracts.html
20byte( ) balance( ), transfer( )
Python dict . mapping(address => uint) address key uint
value dict
public
address public minter; function minter() returns (address) { return
minter; }
), msg.sender , msg.value
Wei(Ether)
.data, .gas, .sig
. listener

23. (3)—
(https://medium.com/@soonhyungjung/ - - -3- - - -44a9d58d687a)

24. pragma solidity^0.4.0;
contract Bank {
uint totalDeposit;
mapping(address=> uint) balanceOf;
function deposit() payable {
balanceOf[msg.sender] += msg.value;
totalDeposit += msg.value;
}
function withdraw(uint _amount) payable {
balanceOf[msg.sender] -= _amount;
totalDeposit -= _amount;
msg.sender.call.value(_amount)();
// msg.sender.transfer(_amount);
}
function getTotalBalance()
constant returns(uint) {
return totalDeposit;
}
function getBalance(address _account)
constant returns(uint) {
return balanceOf[_account];
}
}
payable

25. payable & modifier
pragma solidity ^0.4.11;
contract Purchase {
address public seller;
modifier onlySeller() { // Modifier
require(msg.sender == seller);
_;
}
function abort() onlySeller { // Modifier usage
// ...
}
}
Solidity modifier payable
(https://medium.com/@ggogun/solidity -modifier- -payable-d892a833920c)
Python Decorator, Ruby on Rails before_filter
_; modifier .

26. TODO
• Solidity Voting
• Campaign & Crowdfunding
• Custom Token

27. • Why Many Smart Contract Use Cases Are Simply Impossible (https://
www.coindesk.com/three-smart-contract-misconceptions/)
• Calculating Costs in Ethereum Contracts (https://hackernoon.com/ether-purchase-
power-df40a38c5a2f)
• Gas Cost from Yellow Paper (http://bit.ly/2xfBHWN)
• SMART CONTRACT - (http://goodjoon.tistory.com/253)
• SMART CONTRACT (http://goodjoon.tistory.com/261)
• dApp (http://www.chaintalk.io/archive/lecture/86)
• Solidity (https://www.gitbook.com/book/ggs134/solidityguide)
• Solidity (https://solidity.readthedocs.io/en/develop/)