Random Commit Reveal

RandomCommitReveal.sol

//SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract RandomCommitReveal {

    // global for testing
    uint256 public randomNumber;

    struct Commitment {
        uint256 entropy;
        uint256 blockNumber;
    }

    mapping (address => Commitment) commitments;

    // 1. Commit a number on chain. Use as entropy
    function commit(uint256 _entropy) public {
        commitments[msg.sender].entropy = _entropy;
        commitments[msg.sender].blockNumber = block.number;
    }

    // 2. After a few blocks, reveal random number
    function reveal() public {
        require(commitments[msg.sender].blockNumber != 0, "Must commit");
        require(commitments[msg.sender].blockNumber < block.number, "Reveal too soon");
        uint256 entropy = commitments[msg.sender].entropy;
        // reset commitment
        commitments[msg.sender].blockNumber = 0;
        commitments[msg.sender].entropy = 0;
        // set random number @TODO logic with this random number
        randomNumber = uint256(keccak256(abi.encodePacked(
            block.timestamp,
            entropy
        ))); 
    }

}