encrypt method

@override Future<SecretBox> encrypt(List<int> clearText, { required SecretKey secretKey, List<int>? nonce, List<int> aad = const <int>[], int keyStreamIndex = 0, })

Encrypts a cleartext.

Parameter keyStreamIndex allows you to choose offset in the keystream.

For other arguments, see Cipher.encrypt.

Implementation

@override
Future<SecretBox> encrypt(
  List<int> clearText, {
  required SecretKey secretKey,
  List<int>? nonce,
  List<int> aad = const <int>[],
  int keyStreamIndex = 0,
}) async {
  if (keyStreamIndex < 0) {
    throw ArgumentError.value(
      keyStreamIndex,
      'keyStreamIndex',
      'Must be non-negative',
    );
  }
  nonce ??= newNonce();
  if (nonce.length != 12) {
    throw ArgumentError.value(
      nonce,
      'nonce',
      'Nonce must have 12 bytes',
    );
  }
  final macAlgorithm = this.macAlgorithm;
  if (macAlgorithm is DartChacha20Poly1305AeadMacAlgorithm) {
    if (keyStreamIndex != 0) {
      throw ArgumentError.value(
        keyStreamIndex,
        'keyStreamIndex',
        'Must be zero',
      );
    }
    keyStreamIndex = 64;
  }

  final secretKeyData = await secretKey.extract();
  if (secretKeyData.bytes.length != 32) {
    throw ArgumentError.value(
      secretKey,
      'secretKey',
      'length must be 32 bytes',
    );
  }
  final cipherText = _xorSync(
    clearText,
    secretKey: secretKeyData,
    nonce: nonce,
    aad: aad,
    keyStreamIndex: keyStreamIndex,
  );
  final mac = await macAlgorithm.calculateMac(
    cipherText,
    secretKey: secretKey,
    nonce: nonce,
    aad: aad,
  );
  return SecretBox(
    cipherText,
    nonce: nonce,
    mac: mac,
  );
}