generateNewPrivateKey function
Generates a new private key using the random instance provided. Please make sure you're using a cryptographically secure generator.
Implementation
BigInt generateNewPrivateKey(Random random) {
  final generator = ECKeyGenerator();
  final keyParams = ECKeyGeneratorParameters(params);
  generator.init(ParametersWithRandom(keyParams, RandomBridge(random)));
  final key = generator.generateKeyPair();
  final privateKey = key.privateKey as ECPrivateKey;
  return privateKey.d!;
}