False negative verifying a message signed with polkadot{.js}

The message is signed client-side with polkadot{.js} using the default cryptography, and the signature is successfully verified with polkadot{.js}. However, when I try to verify the message server-side with py-substrate-interface, verification results with False.

The JS code used client-side to sign and verify the message:

const address = account.address;
const message = 'Of course I own this wallet!';
let signature;
try {
  ({signature} = await signRaw({
    address: address,
    data: util.stringToHex(message),
    type: 'bytes',
  }));
}
catch {
  return;
}
const publicKey = utilCrypto.decodeAddress(account.address);
const hexPublicKey = util.u8aToHex(publicKey);
const isValid = utilCrypto.signatureVerify(
  message,
  signature,
  hexPublicKey,
).isValid;
console.log('Is signature valid?', isValid); // true

Then, address, message and signature are POST-ed over to the server, where this code tries to verify the message:

import substrateinterface as sub

keypair = sub.Keypair(address, ss58_format=42)
print(keypair.verify(message, signature)) # False

[jacogr]

The wrapping the extension applies is exposed here - https://github.com/polkadot-js/common/blob/master/packages/util/src/u8a/wrap.ts#L42

(In the JS libs the verification then first tries the data as-is and then the wrapped version before failing the signature)

TL;DR The extension signs <Bytes>...all data in here...</Bytes> (assuming it (a) is not already wrapped with <Bytes> or (b) it is not an Ethereum-style wrapped message, aka Frontier-like chains)

[metakeller]

Yeah, we also need this update. Would be so thankful to get it!

When do u think you can finish it? 🙏