beforeData method

@override void beforeData({ required SecretKeyData secretKey, required List<int> nonce, List<int> aad = const [], })

A protected method required by DartChacha20Poly1305AeadMacAlgorithm implementation.

Implementation

@override
void beforeData({
  required SecretKeyData secretKey,
  required List<int> nonce,
  List<int> aad = const [],
}) {
  // Add Additional Authenticated Data (AAD)
  final aadLength = aad.length;
  _aadLength = aadLength;
  if (aadLength != 0) {
    add(aad);

    // Add padding until 16-byte aligned
    final rem = aad.length % 16;
    if (rem != 0) {
      // Fill `tmp` with zeroes
      final tmp = _tmpAsByteData;
      tmp.setUint32(0, 0);
      tmp.setUint32(4, 0);
      tmp.setUint32(8, 0);
      tmp.setUint32(12, 0);
      final paddingLength = 16 - rem;
      addSlice(_tmpAsUint8List, 0, paddingLength, false);
    }
  }

  // Initialize ChaCha20 initial state
  super.beforeData(
    secretKey: secretKey,
    nonce: nonce,
    aad: const [],
  );
}