decryptBlock method

@override List<int> decryptBlock(List<int> input, [ List<int>? dst ])

Decrypt exactly 1 block (16 bytes)

Implementation

@override
List<int> decryptBlock(List<int> input, [List<int>? dst]) {
  final out = dst ?? List<int>.filled(blockSize, 0);

  if (input.length != blockSize) {
    throw ArgumentException.invalidOperationArguments(
      "decryptBlock",
      name: "input",
      reason: "Invalid input bytes length.",
    );
  }

  // Always copy input first because decryptBlock may mutate the buffer
  final saved = input.clone();

  // Decrypt into tmpBlock (never into input!)
  _cipher.decryptBlock(saved, _tmpBlock);
  // XOR with previous block
  for (int i = 0; i < blockSize; i++) {
    out[i] = (_tmpBlock[i] ^ _prevBlock[i]).toU8;
  }

  // Update chaining value
  _prevBlock.setAll(0, saved);

  return out;
}