Crackme

CTF101. Crack me if you can!

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

contract Crackme {
    bool public solved = false;

    function solve(uint arg1, string memory arg2, uint arg3) external {
        require(arg3 > 0, "positive nums only baby");
        unchecked {
            if ((arg1 ^ 0x70) == 20) {
                if (keccak256(bytes(decrypt(arg2))) == keccak256(bytes("0ff$hIft Ftw"))) {
                    uint256 check3 = arg3 + 1;
                    if (check3 < 1) {
                        solved = true;
                        return;
                    }
                }
            }
        }
    }

    function decrypt(string memory encrypted_text) private pure returns (string memory) {
        uint256 length = bytes(encrypted_text).length;
        for (uint i = 0; i < length; i++) {
            bytes1 char = bytes(encrypted_text)[i];
            assembly {
                char := byte(0,char)
                if and(gt(char,0x60), lt(char,0x6E))
                { char:= add(0x7B, sub(char,0x61)) }
                if iszero(eq(char, 0x20))
                { mstore8(add(add(encrypted_text,0x20), mul(i,1)), sub(char,16)) }
            }
        }
        return encrypted_text;
    }
}