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I have the following (simplified) contract that uses ECDSA to validate message authenticity:

pragma solidity ^0.8.18;

import "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";

contract ECDSATest {
    address public trustedSigner;

    constructor() {
      trustedSigner = msg.sender;
    }

    function test(bytes calldata signature, string calldata message) public view returns (bool) {
        address signer = ECDSA.recover(keccak256(abi.encodePacked(message)), signature);
        return (signer == trustedSigner);
    }
}

When I create signatures with Python (using Web3.py), valid signatures are recognized as expected. Here is the code on how I create signatures in Python:

message_hash = Web3.solidity_keccak(['string'], ['Hello World'])
signed_message = account.signHash(message_hash)
signature = signed_message.signature

However, I am not able to reproduce the same (valid) signature using ethers.js version 6 via NodeJS. Here I am using the following code to create a signature, but deriving the trustedSigner's address from it fails:

let messageHash = solidityPackedKeccak256(["string"], ["Hello World"]);
let signature = await trustedAccount.signMessage(getBytes(messageHash));

await myContract.connect(user1).test(getBytes(signature), "Hello World");

The account I am using to sign the messages is the same in both version. So I guess there is something wrong with how I create the signature via ethers.js. Any hint on how to do this properly?

1 Answer 1

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For ethers.js version 6, the code will be slightly different:

    let signer = new ethers.SigningKey(privateKey);
    let messageHash = await ethers.solidityPackedKeccak256([ "string", "uint" ], [ message, message.length ] );
    let signature = signer.sign(messageHash);
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  • thanks, this did the trick for me. What should be added is that signature.serialized needs to be passed to the smart contract, which is the concatenation of r, s and v. Dec 7, 2023 at 9:10

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