[ ALIGNMENT ]

[sirdeggen]

Summary

BSM implementation makes it awkward to match go-sdk and bsvjs Bsm implementations.

Motivation

It's deprecated so we didn't focus on making it good but now it's raised its head we should implement this under the hood.

Description

BSM.sign() should return the same base64 you'd expect from older libraries. We should be careful not to break ts-paymail in the process.

Additional References

Here's the solution

// bsv
import bsv from 'bsv'
import Message from 'bsv/message'
// @bsv/sdk
import { BSM, PrivateKey, Utils, Hash, BigNumber } from "@bsv/sdk"
const { toArray, Writer } = Utils

// sign with both libraries and compare signatures
const wif = "L211enC224G1kV8pyyq7bjVd9SxZebnRYEzzM3i7ZHCc1c5E7dQu"

const bsvSdkPk = PrivateKey.fromWif(wif)
const bsvPk = bsv.PrivateKey.fromWIF(wif)
const msgStr = "hello world"

const prefix = 'Bitcoin Signed Message:\n'
export const magicHash = (messageBuf: number[]): number[] => {
  const bw = new Writer()
  bw.writeVarIntNum(prefix.length)
  bw.write(toArray(prefix, 'utf8'))
  bw.writeVarIntNum(messageBuf.length)
  bw.write(messageBuf)
  const buf = bw.toArray()
  const hashBuf = Hash.hash256(buf)
  return hashBuf
}

const bsvSdkSig = BSM.sign(toArray(msgStr), bsvSdkPk)
const h = new BigNumber(magicHash(toArray(msgStr, 'utf8')))
const r = bsvSdkSig.CalculateRecoveryFactor(bsvSdkPk.toPublicKey(), h)
const sig = bsvSdkSig.toCompact(r, true, 'base64')
const bsvSig = new Message(msgStr).sign(bsvPk)

console.log("Sigs:", { sig, bsvSig })

// PRINTS
// 'Sigs:' {
//   sig: 'H4T8Asr0WkC6wYfBESR6pCAfECtdsPM4fwiSQ2qndFi8dVtv/mrOFaySx9xQE7j24ugoJ4iGnsRwAC8QwaoHOXk=',
//   bsvSig: 'H4T8Asr0WkC6wYfBESR6pCAfECtdsPM4fwiSQ2qndFi8dVtv/mrOFaySx9xQE7j24ugoJ4iGnsRwAC8QwaoHOXk='
// }

[shruggr]

In order to keep compatibility with all other libraries which have implemented BSM, can verify use an address rather than a pubKey? Here's the function signatures from go:

func SignMessage(privateKey *ec.PrivateKey, message []byte) ([]byte, error)
func VerifyMessage(address string, sig, data []byte) error

[shruggr]

moneybutton/bsv@1.5.6 Message.verify = function (message, address, signature)

@2.x static verify (messageBuf, sigstr, address)