extractSeedAndZero method
Extracts seed and immediately zeros old copy if provided.
Returns the 32-byte seed for key recovery.
Implementation
Future<Uint8List> extractSeedAndZero() async {
final privateKeyBytes = await extractPrivateKeyBytes();
final seed = Uint8List.fromList(privateKeyBytes.sublist(0, 32));
// Zero the full private key bytes
CryptoUtils.zeroMemory(Uint8List.fromList(privateKeyBytes));
return seed;
}