pragma solidity ^0.8.13;

contract HashChainReceipt {
    mapping(address => bytes32) public receipts;

    function attest(bytes32 dataHash) external returns (bytes32 newHash) {
        newHash = keccak256(abi.encodePacked(receipts[msg.sender], dataHash));
        receipts[msg.sender] = newHash;
    }
}