V in Signed Message Hash not being calculated properly

[DomAmato]

I have a python application that we were using to work with ethereum and now we are trying to do something similar on osx/ios. I wanted to test signing a string similar to how we were doing it but kept running into an issue where the last 2 characters of the signed message were different.

Here is the swift code:

let message = Web3.Utils.sha3("HelloABC123".data(using: .utf8)!)
let (compressedSignature, _) = SECP256K1.signForRecovery(hash: message!, privateKey: Data(hex: privateKey), useExtraEntropy: false)

Here is the python code:

msg_hash = ethereum.utils.sha3("HelloABC123")
sig_object = w3.eth.account.signHash(msg_hash, private_key=key)

I confirmed the sha3 hash is the same between them
58b105f41aa555ea93c3f91eeebac19de54cd71e528b3317e6c0bbd49aa8f5b1

But the signature comes back and is just ever so slightly different
Swift
5c2b257aaa8810ae7648c15d4361e4c3f080922b98cccfa7304db470ca7fddd16fd1b1d2a42ba4d65787bc3c1971ec728c34bd5baf88a226db17550c54d591b101
Python
5c2b257aaa8810ae7648c15d4361e4c3f080922b98cccfa7304db470ca7fddd16fd1b1d2a42ba4d65787bc3c1971ec728c34bd5baf88a226db17550c54d591b11c

Basically this library always ends the signature with 01 or 00 and the python library ends it in 1c or 1b

According to this discussion about how v is calculated it seems this library is not properly handling it in this instance.

[ashishonmobile]

let web3 = Web3.InfuraRinkebyWeb3()
let message = "HelloABC123"
let signature = try web3.personal.signPersonalMessage(message: message.data(using: .utf8)!, from: , password: )

try this

[DomAmato]

Actually this seems like a bug in the library. It appears that it is not properly handling v in that signature. Instead of doing 27 + (r%2) it might be just applying the modulo. See the discussion here about how v is calculated.
https://bitcoin.stackexchange.com/questions/38351/ecdsa-v-r-s-what-is-v

This would make sense why the signature is always 00 or 01 instead of 1b or 1c

[TonioMacaronio]

Hi, @DomAmato, @ashishonmobile . Thank you for this question, I'll fix it

[TonioMacaronio]

Hi! Sorry for waiting so long, was on my vacation. Made a fix that just a kludge for now.
This whole problem with v arose because of the binding to secp256k1.