derive method

Bip32 derive(int index)

Implementation

Bip32 derive(int index) {
  if (index > uint32Max || index < 0) throw ArgumentError('Expected UInt32');
  final isHardened = index >= highestBit;
  Uint8List data = Uint8List(37);
  if (isHardened) {
    if (isNeutered()) {
      throw ArgumentError('Missing private key for hardened child key');
    }
    data[0] = 0x00;
    data.setRange(1, 33, privateKey!);
    data.buffer.asByteData().setUint32(33, index);
  } else {
    data.setRange(0, 33, publicKey);
    data.buffer.asByteData().setUint32(33, index);
  }
  final i = hmacSHA512(chainCode, data);
  final il = i.sublist(0, 32);
  final ir = i.sublist(32);
  if (!ecc.isPrivate(il)) {
    return derive(index + 1);
  }
  Bip32 hd;
  if (!isNeutered()) {
    final ki = ecc.privateAdd(privateKey!, il);
    if (ki == null) return derive(index + 1);
    hd = Bip32.fromPrivateKey(ki, ir, network);
  } else {
    final ki = ecc.pointAddScalar(publicKey, il, true);
    if (ki == null) return derive(index + 1);
    hd = Bip32.fromPublicKey(ki, ir, network);
  }
  hd.depth = depth + 1;
  hd.index = index;
  hd.parentFingerprint = fingerprint.buffer.asByteData().getUint32(0);
  return hd;
}