ckdPriv function
Implementation
Keys ckdPriv(Keys keys, int index) {
final buffer = Uint8List(4);
ByteData.sublistView(buffer).setUint32(0, index);
final indexBytes = buffer;
final zero = Uint8List.fromList([0]);
final data = <int>[];
data.addAll(zero);
data.addAll(keys.key!);
data.addAll(indexBytes);
final I = hmacSha512(keys.chainCode!, Uint8List.fromList(data));
final IL = I.sublist(0, 32);
final IR = I.sublist(32);
return Keys(key: IL, chainCode: IR);
}