sign method

@override SSHEcdsaSignature sign(Uint8List data)

Implementation

@override
SSHEcdsaSignature sign(Uint8List data) {
  late Digest hash;
  late ECDomainParameters curve;

  switch (curveId) {
    case 'nistp256':
      hash = SHA256Digest();
      curve = ECCurve_secp256r1();
      break;
    case 'nistp384':
      hash = SHA384Digest();
      curve = ECCurve_secp384r1();
      break;
    case 'nistp521':
      hash = SHA512Digest();
      curve = ECCurve_secp521r1();
      break;
    default:
      throw UnsupportedError('Unsupported curve: $curveId');
  }

  final signer = ECDSASigner(hash);

  signer.init(
    true,
    ParametersWithRandom(
      PrivateKeyParameter(ECPrivateKey(d, curve)),
      FortunaRandom()..seed(KeyParameter(randomBytes(32))),
    ),
  );

  final signature = signer.generateSignature(data) as ECSignature;
  return SSHEcdsaSignature('ecdsa-sha2-$curveId', signature.r, signature.s);
}