スマートコントラクト、Ethereumを使ったDAOというのがあります。
ハッキングされたので有名ですが、ハッキングされる直前にセキュリティを上げるための提案をしていて、そこでプログラマーを雇うスマートコントラクト（法関係を実行するプログラム）が書かれていたので画期的・世界初だと思います。
Slock.it Proposal #1 - DAO.Security (redux)
言語はSolidity(JavaScriptライクな言語）で書かれています。
コード全文はこちらの(リポジトリ）
コード中にあるメソッド
sign:クライアントによるサイン。これが実行されると定期の出金可能になる。
function sign() {
if (msg.sender != address(originalClient) // no good samaritans give us ether
|| msg.value != totalCosts // no under/over payment
|| dateOfSignature != 0) // don't sign twice
throw;
if (!contractor.send(oneTimeCosts))
throw;
dateOfSignature = now;
isContractValid = true;
lastPayment = now;
}
getDailyPayment(): 毎日出金できる。
// Withdraw to the Contractor.
//
// Withdraw the amount of ether the Contractor has right to according to
// the current withdraw limit.
// Executing this function before the Offer is signed off by the Client
// makes no sense as this contract has no ether.
function getDailyPayment() noEther {
if (msg.sender != contractor)
throw;
uint timeSinceLastPayment = now - lastPayment;
// Calculate the amount using 1 second precision.
uint amount = (timeSinceLastPayment * dailyWithdrawLimit) / (1 days);
if (amount > this.balance) {
amount = this.balance;
}
if (contractor.send(amount))
lastPayment = now;
}
解雇もできる。
// "fire the contractor"
function returnRemainingEther() onlyClient {
if (originalClient.DAOrewardAccount().call.value(this.balance)())
isContractValid = false;
}
コード全文は以下(リポジトリ）
contract DAOSecurity {
// The total cost of the Offer. Exactly this amount is transfered from the
// Client to the Offer contract when the Offer is signed by the Client.
// Set once by the Offerer.
uint totalCosts;
// Initial withdraw to the Contractor. It is done the moment the Offer is
// signed.
// Set once by the Offerer.
uint oneTimeCosts;
// The minimal daily withdraw limit that the Contractor accepts.
// Set once by the Offerer.
uint128 minDailyWithdrawLimit;
// The amount of wei the Contractor has right to withdraw daily above the
// initial withdraw. The Contractor does not have to do the withdraws every
// day as this amount accumulates.
uint128 dailyWithdrawLimit;
// The address of the Contractor.
address contractor;
// The hash of the Proposal/Offer document.
bytes32 hashOfTheProposalDocument;
// The time of the last withdraw to the Contractor.
uint lastPayment;
uint dateOfSignature;
DAO client; // address of DAO
DAO originalClient; // address of DAO who signed the contract
bool isContractValid;
modifier onlyClient {
if (msg.sender != address(client))
throw;
_
}
// Prevents methods from perfoming any value transfer
modifier noEther() {if (msg.value > 0) throw; _}
function DAOSecurity(
address _contractor,
address _client,
bytes32 _hashOfTheProposalDocument,
uint _totalCosts,
uint _oneTimeCosts,
uint128 _minDailyWithdrawLimit
) {
contractor = _contractor;
originalClient = DAO(_client);
client = DAO(_client);
hashOfTheProposalDocument = _hashOfTheProposalDocument;
totalCosts = _totalCosts;
oneTimeCosts = _oneTimeCosts;
minDailyWithdrawLimit = _minDailyWithdrawLimit;
dailyWithdrawLimit = _minDailyWithdrawLimit;
}
// non-value-transfer getters
function getTotalCosts() noEther constant returns (uint) {
return totalCosts;
}
function getOneTimeCosts() noEther constant returns (uint) {
return oneTimeCosts;
}
function getMinDailyWithdrawLimit() noEther constant returns (uint128) {
return minDailyWithdrawLimit;
}
function getDailyWithdrawLimit() noEther constant returns (uint128) {
return dailyWithdrawLimit;
}
function getContractor() noEther constant returns (address) {
return contractor;
}
function getHashOfTheProposalDocument() noEther constant returns (bytes32) {
return hashOfTheProposalDocument;
}
function getLastPayment() noEther constant returns (uint) {
return lastPayment;
}
function getDateOfSignature() noEther constant returns (uint) {
return dateOfSignature;
}
function getClient() noEther constant returns (DAO) {
return client;
}
function getOriginalClient() noEther constant returns (DAO) {
return originalClient;
}
function getIsContractValid() noEther constant returns (bool) {
return isContractValid;
}
function sign() {
if (msg.sender != address(originalClient) // no good samaritans give us ether
|| msg.value != totalCosts // no under/over payment
|| dateOfSignature != 0) // don't sign twice
throw;
if (!contractor.send(oneTimeCosts))
throw;
dateOfSignature = now;
isContractValid = true;
lastPayment = now;
}
function setDailyWithdrawLimit(uint128 _dailyWithdrawLimit) onlyClient noEther {
if (_dailyWithdrawLimit >= minDailyWithdrawLimit)
dailyWithdrawLimit = _dailyWithdrawLimit;
}
// "fire the contractor"
function returnRemainingEther() onlyClient {
if (originalClient.DAOrewardAccount().call.value(this.balance)())
isContractValid = false;
}
// Withdraw to the Contractor.
//
// Withdraw the amount of ether the Contractor has right to according to
// the current withdraw limit.
// Executing this function before the Offer is signed off by the Client
// makes no sense as this contract has no ether.
function getDailyPayment() noEther {
if (msg.sender != contractor)
throw;
uint timeSinceLastPayment = now - lastPayment;
// Calculate the amount using 1 second precision.
uint amount = (timeSinceLastPayment * dailyWithdrawLimit) / (1 days);
if (amount > this.balance) {
amount = this.balance;
}
if (contractor.send(amount))
lastPayment = now;
}
// Change the client DAO by giving the new DAO's address
// warning: The new DAO must come either from a split of the original
// DAO or an update via `newContract()` so that it can claim rewards
function updateClientAddress(DAO _newClient) onlyClient noEther {
client = _newClient;
}
function () {
throw; // this is a business contract, no donations
}
}
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