Different signed message hash in Python and Solidity

Question

Context

I am trying to verify a message with Solidity and Python but for some reason the ecrecover is returning an arbitrary address. I have narrowed the problem down to this part here:

messageHashLocal = w3.solidityKeccak(['uint256', 'string', 'uint256'], [amount, message, nonce])
encoded_message = encode_defunct(primitive=messageHashLocal)
signed_messageLocal = w3.eth.account.sign_message(encoded_message, private_key=PRIVATE_KEY)

This is how I get the message hash, encode and sign it.

function getMessageHash(
    uint256 _amount,
    string memory _message,
    uint256 _nonce
) public pure returns (bytes32) {
    return keccak256(abi.encodePacked(_amount, _message, _nonce));
}

function getEthSignedMessageHash(bytes32 _messageHash)
    public
    pure
    returns (bytes32)
{
    return
        keccak256(abi.encodePacked("\x19Ethereum Signed Message: \n32", _messageHash));
}

This is how I am generating the message hash and prefixing the "\x19Ethereuem...." string.

Issue: Signed message hash I get back from getEthSignedMessageHash (in Solidity) and the one inside signed_messageLocal (in python) are different and ecrecover is also returning an arbitrary address.

Any ideas what's wrong here? Thanks!

Answer 1

I recommend passing your string value to "keccak256" by changing it to "bytes", for example, you can pass " _message" like this : keccak256(bytes( _message))

It will work but if it does not work, try to pass values one by one to find a problem. (it needs to change your smart contract and pythons code)