Signing personal messages

[SeqSEE]

Messages should be able to be signed when requested by a site. It should be done in a standardized way that Ethereum does, in that it is prefixed with a know prefix, hashed and then signed by the user. This signed data is also crafted in such a way as to never allow it to be a valid signed transaction.

• It will allow smart contracts to use ecrcover to verify the signature, and to recover the signers address as well.
• It would also allow MetriMask to be used as a method of web authentication.
• Probably useful for all sorts of cross-chain shenanigans.

an example of how a solidity function might look

   function recoverSigner(bytes memory message, bytes memory signature) internal pure returns (address)
       {
       require(signature.length == 65, "VendorRegistry: Action failed, invalid signature.");
       uint8 v;
       bytes32 r;
       bytes32 s;
       assembly
           {
           r := mload(add(signature, 32))
           s := mload(add(signature, 64))
           v := byte(0, mload(add(signature, 96)))
           }
       return ecrecover(keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", keccak256(message))), v, r, s);
       }

[nibbles83]

So I've merged in bitcoin message signing to Metrimask #23

However this doesnt specifically address the functionality you are looking for. However Qtum have implemented QIP-6 (https://blog.qtum.org/qip-6-87e7a9743e14) which allows the use of btc_ecrecover within a pre-compiled contract. I believe this should allow the functionality you are looking for.

qtumproject/qips#7
qtumproject/qtum#664