encrypt method

@override List<int> encrypt(List<int> nonce, List<int> plaintext, { List<int>? associatedData, List<int>? dst, })

Encrypts data using the Galois/Counter Mode (GCM) with associated data (AEAD). Parameters:

• nonce: The nonce value used for encryption, must have a length equal to the GCM nonce length (12 bytes).
• plaintext: The data to be encrypted.
• associatedData: (Optional) Additional data that is authenticated but not encrypted.
• dst: (Optional) The destination for the encrypted data and authentication tag. If not provided, a new List<int> is created.

Throws:

• CryptoException if the provided nonce has an incorrect length or if the destination size is incorrect.

Implementation

@override
List<int> encrypt(
  List<int> nonce,
  List<int> plaintext, {
  List<int>? associatedData,
  List<int>? dst,
}) {
  if (nonce.length != nonceLength) {
    throw ArgumentException.invalidOperationArguments(
      "encrypt",
      name: "nonce",
      reason: "Incorrect nonce length.",
      expecteLen: nonceLength,
    );
  }

  final blockSize = _cipher.blockSize;

  final resultLength = plaintext.length + tagLength;
  final List<int> result = dst ?? List<int>.filled(resultLength, 0);
  if (result.length != resultLength) {
    throw ArgumentException.invalidOperationArguments(
      "encrypt",
      name: "dst",
      reason: "Incorrect destination length.",
      expecteLen: resultLength,
    );
  }

  final counter = List<int>.filled(blockSize, 0);
  counter.setAll(0, nonce);

  counter[blockSize - 1] = 1;

  final tagMask = List<int>.filled(blockSize, 0);
  _cipher.encryptBlock(counter, tagMask);

  counter[blockSize - 1] = 2;

  final ctr = CTR(_cipher, counter);
  ctr.streamXOR(plaintext, result);
  ctr.clean();
  final calculatedTag = List<int>.filled(tagLength, 0);
  final cipherText = result.sublist(0, result.length - tagLength);

  _authenticate(calculatedTag, tagMask, cipherText, associatedData);
  result.setRange(result.length - tagLength, result.length, calculatedTag);
  BinaryOps.zero(counter);
  BinaryOps.zero(tagMask);
  return result;
}