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Sig.sol
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Sig.sol
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//SPDX-License-Identifier: MIT
pragma solidity ^0.8.3;
/*
0. message to sign
1. hash (message)
2. sign(hash(message), private key) | offchain
3. ecrecover(hash(message), signature) == signer
*/
contract VerifySig {
function verify(address _signer, string memory _message, bytes memory _sig) external pure returns (bool) {
bytes32 messageHash = getMessageHash(_message);
bytes32 ethSignedMessageHash = getEthSignedMessageHash(messageHash);
return recover(ethSignedMessageHash, _sig) == _signer;
}
function getMessageHash(string memory _message) public pure returns (bytes32) {
return keccak256(abi.encodePacked(_message));
}
function getEthSignedMessageHash(bytes32 _messageHash) public pure returns (bytes32) {
return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", _messageHash));
}
function recover(bytes32 _ethSignedMessageHash, bytes memory _sig) public pure returns (address) {
(bytes32 r, bytes32 s, uint8 v) = _split(_sig);
return ecrecover(_ethSignedMessageHash, v, r, s);
}
function _split(bytes memory _sig) internal pure returns (bytes32 r, bytes32 s, uint8 v) {
require (_sig.length == 65, "invalid signature length");
assembly {
r := mload(add(_sig, 32))
s := mload(add(_sig, 64))
v := byte(0, mload(add(_sig, 96)))
}
}
}