computeKeys method

Tuple<MoneroPublicKey, MoneroPublicKey> computeKeys(int minorIndex, int majorIndex)

Compute the subaddress keys based on minor and major indexes.

This method calculates Monero subaddress keys using the provided minorIndex and majorIdx. If the indexes are out of valid range, it throws an ArgumentException. It returns a tuple of subaddress public spend key and subaddress public view key.

Implementation

Tuple<MoneroPublicKey, MoneroPublicKey> computeKeys(
    int minorIndex, int majorIndex) {
  if (minorIndex < 0 || minorIndex > MoneroSubaddressConst.subaddrMaxIdx) {
    throw ArgumentException('Invalid minor index ($minorIndex)');
  }
  if (majorIndex < 0 || majorIndex > MoneroSubaddressConst.subaddrMaxIdx) {
    throw ArgumentException('Invalid major index ($majorIndex)');
  }

  if (minorIndex == 0 && majorIndex == 0) {
    return Tuple(pubSKey, pubVKey);
  }

  List<int> majorIdxBytes = IntUtils.toBytes(majorIndex,
      length: MoneroSubaddressConst.subaddrIdxByteLen,
      byteOrder: Endian.little);
  List<int> minorIdxBytes = IntUtils.toBytes(minorIndex,
      length: MoneroSubaddressConst.subaddrIdxByteLen,
      byteOrder: Endian.little);

  List<int> privVKeyBytes = privVKey.raw;

  List<int> mBytes = QuickCrypto.keccack256Hash(List<int>.from([
    ...MoneroSubaddressConst.subaddrPrefix,
    ...privVKeyBytes,
    ...majorIdxBytes,
    ...minorIdxBytes
  ]));
  BigInt mInt = BigintUtils.fromBytes(Ed25519Utils.scalarReduce(mBytes),
      byteOrder: Endian.little);
  final newPoint =
      pubSKey.pubKey.point + (Curves.generatorED25519 * mInt) as EDPoint;

  MoneroPublicKey subaddrPubSKey = MoneroPublicKey.fromPoint(newPoint);
  MoneroPublicKey subaddrPubVKey = MoneroPublicKey.fromPoint(
      (subaddrPubSKey.pubKey.point *
              BigintUtils.fromBytes(privVKey.raw, byteOrder: Endian.little))
          as EDPoint);

  return Tuple(subaddrPubSKey, subaddrPubVKey);
}