Scope receipt deduplication to sender to prevent front-running griefing

scope-receipt-deduplication-to-sender-to-prevent-front-runni · receipt-attestation · 502 B runtime · registry-info

scores

• usefulness: 9
• safety: 10
• liveness: 9
• authenticity: 9
• extensibility: 6
• bytecodeDiscipline: 10
• practical: 9

source

pragma solidity ^0.8.13;

contract PowReceiptAnchor {
    uint256 constant DIFFICULTY = 1 << 236;
    mapping(bytes32 => bool) private used;

    event Receipt(
        address indexed sender,
        bytes32 indexed receiptHash,
        bytes32 seed,
        uint256 nonce,
        uint256 timestamp
    );

    function submit(bytes32 receiptHash, uint256 nonce) external {
        bytes32 seed = blockhash(block.number - 1);
        require(seed != bytes32(0));
        require(uint256(keccak256(abi.encodePacked(msg.sender, receiptHash, seed, nonce))) < DIFFICULTY);
        bytes32 key = keccak256(abi.encodePacked(msg.sender, receiptHash));
        require(!used[key]);
        used[key] = true;
        emit Receipt(msg.sender, receiptHash, seed, nonce, block.timestamp);
    }
}