deriveReceiveAddress static method

String deriveReceiveAddress({ required SecretKey myKey, required PaymentCode theirPaymentCode, required int index, required Chain chain, bool segwit = false, })

Derive a receive address at index (Bob <- Alice).

myKey is the receiver's private key at index (b_n). The sender's notification pubkey A_0 is derived from theirPaymentCode, then ECDH(b_n, A_0) == ECDH(a_0, B_n).

Implementation

static String deriveReceiveAddress({
  required SecretKey myKey,
  required PaymentCode theirPaymentCode,
  required int index,
  required Chain chain,
  bool segwit = false,
}) {
  final theirNotificationPubKey = theirPaymentCode.derivePublicKey(0);
  final S = SecretPoint(myKey, theirNotificationPubKey);
  final s = sha256(S.ecdhSecret);

  final tweaked = myKey.publicKey.tweak(s);
  if (tweaked == null) {
    throw StateError('Invalid tweaked key at index $index');
  }

  final pkHash = hash160(tweaked.bytes);
  if (segwit) {
    return P2wpkhAddr(pkHash).encode(chain);
  }
  return P2pkhAddr(pkHash).encode(chain);
}