encryptSync method
Implementation
SecretBox encryptSync(
List<int> clearText, {
required SecretKeyData secretKeyData,
List<int>? nonce,
List<int> aad = const <int>[],
int keyStreamIndex = 0,
}) {
final actualSecretKeyLength = secretKeyData.bytes.length;
final expectedSecretKeyLength = secretKeyLength;
if (actualSecretKeyLength != expectedSecretKeyLength) {
throw ArgumentError.value(
secretKeyData,
'secretKeyData',
'Expected $secretKeyLength bytes, got $actualSecretKeyLength bytes',
);
}
if (keyStreamIndex < 0 || keyStreamIndex >= 0x10000000) {
throw ArgumentError.value(keyStreamIndex, 'keyStreamIndex');
}
nonce ??= newNonce();
final expandedKey = aesExpandKeyForEncrypting(secretKeyData);
// `h` = AES(zero_block, key)
final h = Uint32List(4);
aesEncryptBlock(h, 0, h, 0, expandedKey);
h[0] = _uint32ChangeEndian(h[0]);
h[1] = _uint32ChangeEndian(h[1]);
h[2] = _uint32ChangeEndian(h[2]);
h[3] = _uint32ChangeEndian(h[3]);
// Calculate initial nonce
var stateBytes = _nonceToBlock(h: h, nonce: nonce);
var state = Uint32List.view(stateBytes.buffer);
// Memorize the state of the first block for calculating MAC later.
final stateOfFirstBlock = Uint32List.fromList(state);
// Increment nonce
bytesIncrementBigEndian(stateBytes, 1 + (keyStreamIndex ~/ 16));
// Allocate space for output bytes + 128 bit hash
final blockCount = (keyStreamIndex % 16 + clearText.length + 15) ~/ 16;
final keyStream = Uint32List((blockCount + 1) * 4);
// For each block
for (var i = 0; i < keyStream.length; i += 4) {
// Encrypt state.
aesEncryptBlock(keyStream, i, state, 0, expandedKey);
// Increment state.
bytesIncrementBigEndian(stateBytes, 1);
}
// cipherText = keyStream[start, end] ^ clearText
final cipherText = Uint8List.view(
keyStream.buffer,
keyStream.offsetInBytes + keyStreamIndex % 16,
clearText.length,
);
for (var i = 0; i < clearText.length; i++) {
cipherText[i] ^= clearText[i];
}
// Calculate MAC
final mac = const DartGcm()._calculateMacSync(
cipherText,
aad: aad,
expandedKey: expandedKey,
h: h,
precounterBlock: stateOfFirstBlock,
);
return SecretBox(cipherText, nonce: nonce, mac: mac);
}