Fast and powerful cryptographic functions for Flutter.
---
[[Changelog]](./CHANGELOG.md) | [[License]](./LICENSE)
---
## About
The goal of this plugin is to provide a fast and powerful cryptographic functions by calling native libraries. On Android, it uses [javax.cypto](https://developer.android.com/reference/javax/crypto/package-summary), and on iOS, it uses [CommonCrypto](https://opensource.apple.com/source/CommonCrypto/) and [CryptoKit](https://developer.apple.com/documentation/cryptokit/)
I started this projet because I wanted to add cryptographic functions on a Flutter app. But I faced a problem with the well-known [Pointy Castle](https://pub.dev/packages/pointycastle) library: the performance was very poor. Here some benchmarks and comparison:
For comparison, on a *iPhone 13*, you can encrypt/decrypt a message of **2MiB** in **~5.6s** with PointyCastle and in **~40ms** with NativeCrypto. And on an *OnePlus 5*, you can encrypt/decrypt a message of **50MiB** in **~6min30** with PointyCastle and in less than **~1s** with NativeCrypto.
In short, NativeCrypto is incomparable with PointyCastle.
## Usage
First, check compatibility with your targets.
| iOS | Android | MacOS | Linux | Windows | Web |
| --- | ------- | ----- | ----- | ------- | --- |
| ✅ | ✅ | ❌ | ❌ | ❌ | ❌ |
#### Hash
To digest a message, you can use the following function:
```dart
Uint8List hash = await HashAlgorithm.sha256.digest(message);
```
Note that you can find a `toBytes()` method in the example app, to convert a `String` to a `Uint8List`.
> In NativeCrypto, you can use the following hash functions: SHA-256, SHA-384, SHA-512
#### Keys
You can build a `SecretKey` from a utf8, base64, base16 (hex) strings or raw bytes. You can also generate a SecretKey from secure random.
```dart
SecretKey secretKey = SecretKey(Uint8List.fromList([0x73, 0x65, 0x63, 0x72, 0x65, 0x74]));
SecretKey secretKey = SecretKey.fromUtf8('secret');
SecretKey secretKey = SecretKey.fromBase64('c2VjcmV0');
SecretKey secretKey = SecretKey.fromBase16('63657274');
SecretKey secretKey = await SecretKey.fromSecureRandom(256);
```
#### Key derivation
You can derive a `SecretKey` using **PBKDF2**.
First, you need to initialize a `Pbkdf2` object.
```dart
Pbkdf2 pbkdf2 = Pbkdf2(32, 1000, algorithm: HashAlgorithm.sha512);
```
Then, you can derive a `SecretKey` from a password and salt.
```dart
SecretKey secretKey = await pbkdf2.derive(password: password, salt: 'salt');
```
> In NativeCrypto, you can use the following key derivation function: PBKDF2
#### Cipher
And now, you can use the `SecretKey` to encrypt/decrypt a message.
First, you need to initialize a `Cipher` object.
```dart
AES cipher = AES(secretKey, AESMode.gcm);
```
Then, you can encrypt/decrypt your message.
```dart
CipherText encrypted = await cipher.encrypt(message);
Uint8List decrypted = await cipher.decrypt(encrypted);
```
After an encryption, you can use the `CipherText` object to access underlying data.
```dart
Uint8List iv = encrypted.iv;
Uint8List data = encrypted.data;
Uint8List tag = encrypted.tag;
```
Note that data and tag are costly to access, so you should only use them if you need to !