Switch.sol

/**
 *Submitted for verification at Etherscan.io on 2022-08-13
 */

// SPDX-License-Identifier: MIT

pragma solidity >=0.8.0;

/**
 * @title Claim ownership of the contract below to complete this level
 * @dev Implement one time hackable smart contract (Switch)
 */
contract Switch {
    address public owner;

    modifier onlyOwner() {
        require(msg.sender == owner, "caller is not the owner");
        _;
    }

    constructor() {
        owner = msg.sender;
    }

    // Changes the ownership of the contract. Can only be called by the owner
    function changeOwnership(address _owner) public onlyOwner {
        owner = _owner;
    }

    // Allows the owner to delegate the change of ownership to a different address by providing the owner's signature
    function changeOwnership(
        uint8 v,
        bytes32 r,
        bytes32 s
    ) public {
        require(
            ecrecover(generateHash(owner), v, r, s) != address(0),
            "signer is not the owner"
        );
        owner = msg.sender;
    }

    // Generates a hash compatible with EIP-191 signatures
    function generateHash(address _addr) private pure returns (bytes32) {
        bytes32 addressHash = keccak256(abi.encodePacked(_addr));
        return
            keccak256(
                abi.encodePacked(
                    "\x19Ethereum Signed Message:\n32",
                    addressHash
                )
            );
    }
}