Solidity 中的单向支付通道

介绍

在某些业务，市场或行业，存在不允许双向发送付款的场景，即只能从账户A向B发送付款，而不能从账户B向A发送付款。这称为单向支付通道。

Solidity 实现

创建合约

在这一步中，我们将创建一个简单的智能合约，添加一些依赖项来安全地签署交易。这是为了防止重放攻击和重入攻击。

这些依赖项来自OpenZeppelin合约，这是一个用于安全智能合约开发的库。

pragma solidity >=0.7.0 <0.9.0;

import “github.com/OpenZeppelin/openzeppelin-contracts/blob/release-v3.3/contracts/cryptography/ECDSA.sol”; import “github.com/OpenZeppelin/openzeppelin-contracts/blob/release-v3.3/contracts/utils/ReentrancyGuard.sol”;

contract UniDirectionalPaymentChannel is ReentrancyGuard { using ECDSA for bytes32;

address payable public sender;address payable public receiver;constructor(address payable _receiver) payable {    require(_receiver != address(0), "receiver = zero address");    sender = msg.sender;    receiver = _receiver;}

}

签署付款

现在，我们将创建一些函数，用于从发送方签署付款。

我们已经创建了4个不同的函数用于哈希并将哈希转换为EthSignedMessageHash。请注意，我们使用私有函数调用是为了重用代码，以这种方式减少gas使用量。

pragma solidity >=0.7.0 <0.9.0;

contract UniDirectionalPaymentChannel is ReentrancyGuard {

// ...function _getHash(uint _amount) private view returns (bytes32) {    return keccak256(abi.encodePacked(address(this), _amount));}function getHash(uint _amount) external view returns (bytes32) {    return _getHash(_amount);}function _getEthSignedHash(uint _amount) private view returns (bytes32) {    return _getHash(_amount).toEthSignedMessageHash();}function getEthSignedHash(uint _amount) external view returns (bytes32) {    return _getEthSignedHash(_amount);}// ...

}

验证哈希

为了从接收方验证哈希，我们需要创建一个逆函数来“取消签名”交易。在这种情况下，当我们恢复签名时，我们应该获得发送方地址作为结果，这样我们就可以验证金额已经从发送方地址发出。

pragma solidity >=0.7.0 <0.9.0;

contract UniDirectionalPaymentChannel is ReentrancyGuard {

// ...function _verify(uint _amount, bytes memory _sig) private view returns (bool) {    return _getEthSignedHash(_amount).recover(_sig) == sender;}function verify(uint _amount, bytes memory _sig) external view returns (bool) {    return _verify(_amount, _sig);}// ...

}

交易

一旦我们声明了这些函数，以便从一边到另一边签署和恢复信息，我们就可以安全地进行交易了。

pragma solidity >=0.7.0 <0.9.0;

contract UniDirectionalPaymentChannel is ReentrancyGuard {

// ...function send(uint _amount, bytes memory _sig) external nonReentrant {    //  verifing signature and sender != receiver    require(msg.sender == receiver, "sender must be different than receiver");    require(_verify(_amount, _sig), "invalid signature");        (bool sent, ) = receiver.call{value: _amount}("");    require(sent, "Failed to send Ether");    selfdestruct(sender);}// ...

}

完整代码

这是完整的合约。

pragma solidity >=0.7.0 <0.9.0;

contract UniDirectionalPaymentChannel is ReentrancyGuard { using ECDSA for bytes32;

address payable public sender;address payable public receiver;constructor(address payable _receiver) payable {    require(_receiver != address(0), "receiver = zero address");    sender = msg.sender;    receiver = _receiver;}function _getHash(uint _amount) private view returns (bytes32) {    return keccak256(abi.encodePacked(address(this), _amount));}function getHash(uint _amount) external view returns (bytes32) {    return _getHash(_amount);}function _getEthSignedHash(uint _amount) private view returns (bytes32) {    return _getHash(_amount).toEthSignedMessageHash();}function getEthSignedHash(uint _amount) external view returns (bytes32) {    return _getEthSignedHash(_amount);}function _verify(uint _amount, bytes memory _sig) private view returns (bool) {    return _getEthSignedHash(_amount).recover(_sig) == sender;}function verify(uint _amount, bytes memory _sig) external view returns (bool) {    return _verify(_amount, _sig);}function send(uint _amount, bytes memory _sig) external nonReentrant {    //  verifing signature and sender != receiver    require(msg.sender == receiver, "sender must be different than receiver");    require(_verify(_amount, _sig), "invalid signature");        (bool sent, ) = receiver.call{value: _amount}("");    require(sent, "Failed to send Ether");    selfdestruct(sender);