viem/utils/signature/recoverPublicKey.ts

TypeScript Interface for Ethereum

import type { ErrorType } from '../../errors/utils.js'
import type { ByteArray, Hex, Signature } from '../../types/misc.js'
import { type IsHexErrorType, isHex } from '../data/isHex.js'
import {
  type HexToNumberErrorType,
  hexToBigInt,
  hexToNumber,
} from '../encoding/fromHex.js'
import { toHex } from '../encoding/toHex.js'

export type RecoverPublicKeyParameters = {
  hash: Hex | ByteArray
  signature: Hex | ByteArray | Signature
}

export type RecoverPublicKeyReturnType = Hex

export type RecoverPublicKeyErrorType =
  | HexToNumberErrorType
  | IsHexErrorType
  | ErrorType

export async function recoverPublicKey({
  hash,
  signature,
}: RecoverPublicKeyParameters): Promise<RecoverPublicKeyReturnType> {
  const hashHex = isHex(hash) ? hash : toHex(hash)

  const { secp256k1 } = await import('@noble/curves/secp256k1')
  const signature_ = (() => {
    // typeof signature: `Signature`
    if (typeof signature === 'object' && 'r' in signature && 's' in signature) {
      const { r, s, v, yParity } = signature
      const yParityOrV = Number(yParity ?? v)!
      const recoveryBit = toRecoveryBit(yParityOrV)
      return new secp256k1.Signature(
        hexToBigInt(r),
        hexToBigInt(s),
      ).addRecoveryBit(recoveryBit)
    }

    // typeof signature: `Hex | ByteArray`
    const signatureHex = isHex(signature) ? signature : toHex(signature)
    const yParityOrV = hexToNumber(`0x${signatureHex.slice(130)}`)
    const recoveryBit = toRecoveryBit(yParityOrV)
    return secp256k1.Signature.fromCompact(
      signatureHex.substring(2, 130),
    ).addRecoveryBit(recoveryBit)
  })()

  const publicKey = signature_
    .recoverPublicKey(hashHex.substring(2))
    .toHex(false)
  return `0x${publicKey}`
}

function toRecoveryBit(yParityOrV: number) {
  if (yParityOrV === 0 || yParityOrV === 1) return yParityOrV
  if (yParityOrV === 27) return 0
  if (yParityOrV === 28) return 1
  throw new Error('Invalid yParityOrV value')
}