Fuzzy Public Key

This contract authenticates anyone whose public key contains 0xc0ffee! You know, in ECDSA (opens new window), it takes short time to create a new private key (no time) and its public key?

You might want to use this web3.eth.accounts.create() in web3js (opens new window).

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.11;

contract FuzzyPublicKey {
    address public player;
    bool public completed;

    constructor(address _player) {
        player = _player;
        completed = false;
    }

    function authenticateMe() external {
        bytes20 addr = bytes20(msg.sender);
        bytes20 id   = hex"0000000000000000000000000000000000c0ffee";
        bytes20 mask = hex"0000000000000000000000000000000000ffffff";

        for (uint256 i = 0; i < 40-6+1; i++) {
            if (addr & mask == id) {
                completed = true;
                return;
            }
            mask <<= 4;
            id <<= 4;
        }
        completed = false;
    }
}