Hashchain Receipt Seal

hashchain-receipt-seal · receipt-attestation · 435 B runtime · registry-info

scores

• usefulness: 10
• safety: 10
• liveness: 10
• authenticity: 9
• extensibility: 8
• bytecodeDiscipline: 10
• practical: 10

source

pragma solidity ^0.8.13;

contract HashchainReceiptSeal {
    mapping(address => bytes32) public tip;

    event Attested(
        address indexed agent,
        bytes32 indexed payloadHash,
        bytes32 indexed newTip,
        uint256 blockNumber
    );

    function attest(bytes32 payloadHash) external returns (bytes32 newTip) {
        require(payloadHash != bytes32(0));
        bytes32 currentTip = tip[msg.sender];
        newTip = keccak256(abi.encodePacked(currentTip, payloadHash, msg.sender, block.timestamp));
        tip[msg.sender] = newTip;
        emit Attested(msg.sender, payloadHash, newTip, block.number);
    }
}