cryptography 1.0.2

Cryptographic algorithms for digital signature, key agreement, encryption, message authentication, and hashing. X25519, ED25519, AES, Chacha20, and many more.

Overview

Popular cryptographic algorithms for Dart / Flutter developers. Licensed under the Apache License 2.0.

Any feedback, issue reports, or pull requests are appreciated! See our Github project.

Links

• Github project
• Issue tracker
• Pub package
• API reference

Used by

• kms
  • A Dart package for hardware-based or cloud-based key management solutions.
• kms_flutter
  • Uses native APIs for storing cryptographic keys in Android and iOS.
• noise_protocol
  • An implementation of Noise protocol, which can be used for secure communications.
• Add your project here?

Some things to know

• SHA1 and SHA2 implementations use _package:crypto](https://pub.dev/packages/crypto), which is maintained by Google and limited to hash functions.
• We wrote pure Dart implementations for X25519, ED25519, ChaCha20 family, AES-CBC, AES-CTR, HKDF, HMAC, Poly1305, and BLAKE2S.
• We implemented automatic use of Web Cryptography API (SHA1, SHA2, AES, NIST elliptic curves) in browsers.
• The APIs generally include both asynchronous and synchronous methods. For instance, you can calculate a SHA-256 hash with sha256.hash(bytes) or sha256.hashSync(bytes). We recommend that you use asynchronous methods because they are able to take advantage of asynchronous platform APIs such as Web Cryptography API.

Available algorithms

Key exchange algorithms

• NIST elliptic curves (read about the algorithm)
  • ecdhP256 (ECDH P256 / secp256r1 / prime256v1)
  • ecdhP384 (ECDH P384 / secp384r1 / prime384v1)
  • ecdhP521 (ECDH P521 / secp521r1 / prime521v1)
  • Currently NIST elliptic curves are only supported in browsers (Web Cryptography API).
• x25519 (read about the algorithm)
  • X25519 (curve25519 Diffie-Hellman) is a popular key exchange algorithm and it's our recommendation for new applications. Performance of our Dart implementation is about 1k exchanges per second in VM.

For more more documentation, see KeyExchangeAlgorithm.

Digital signature algorithms

• NIST elliptic curves (read about the algorithm)
  • ecdsaP256Sha256 (ECDSA P256 / secp256r1 / prime256v1)
  • ecdsaP384Sha256 (ECDSA P384 / secp384r1 / prime384v1)
  • ecdsaP521Sha256 (ECDSA P521 / secp521r1 / prime521v1)
  • Currently NIST elliptic curves are only supported in browsers (Web Cryptography API).
• ed25519 (read about the algorithm)
  • ED25519 (curve25519 EdDSA) is a popular signature algorithm and it's our recommendation for new applications. Performance of our Dart implementation is about 200 signatures or verifications per second in VM (about 50 in browsers).

For more more documentation, see SignatureAlgorithm.

Symmetric encryption

• NIST AES (read about the algorithm)
  • aesCbc (AES-CBC)
  • aesCtr (AES-CTR)
  • aesGcm (AES-GCM, browsers-only at the moment)
  • Performance of our Dart implementation is about 10-50 MB/s in VM (about 300MB - 700MB/s in browsers).
• Chacha20 family (read about the algorithm)
  • chacha20
  • chacha20Poly1305Aead (AEAD_CHACHA20_POLY1305)
  • xchacha20
  • xchacha20Poly1305Aead (AEAD_XCHACHA20_POLY1305)
  • Chacha20 (AEAD) is a popular cipher and it's our recommendation for new applications. Performance of our Dart implementation is about 20-100MB/s in VM.

For more more documentation, see Cipher.

Key derivation algorithms

• Hkdf

Message authentication codes

• Hmac
• poly1305

For more more documentation, see MacAlgorithm.

Cryptographic hash functions

• blake2s (BLAKE2S)
• sha1 (SHA1)
• sha224 (SHA2-224)
• sha256 (SHA2-256)
• sha384 (SHA2-384)
• sha512 (SHA2-512)
  • In browsers, performance can be over 100 times faster than package:crypto.

For more more documentation, see HashAlgorithm.

Adding dependency

In pubspec.yaml:

dependencies:
  cryptography: ^1.0.2

Examples

Key agreement with X25519

In this example, we use x25519.

import 'package:cryptography/cryptography.dart';

Future<void> main() async {
  // Let's generate two X25519 keypairs.
  final localKeyPair = await x25519.newKeyPair();
  final remoteKeyPair = await x25519.newKeyPair();

  // We can now calculate a shared 256-bit secret
  final secretKey = await x25519.sharedSecret(
    localPrivateKey: localKeyPair.privateKey,
    remotePublicKey: remoteKeyPair.publicKey,
  );

  final secretBytes = await secretKey.extract();
  print('Shared secret: $secretBytes');
}

Digital signature with ED25519

In this example, we use ed25519.

import 'package:cryptography/cryptography.dart';

Future<void> main() async {
  // The message that we will sign
  final message = <int>[1,2,3];

  // Generate a random ED25519 keypair
  final keyPair = await ed25519.newKeyPair();

  // Sign
  final signature = await ed25519.sign(
    message,
    keyPair,
  );

  print('Signature: ${signature.bytes}');
  print('Public key: ${signature.publicKey.bytes}');

  // Verify signature
  final isSignatureCorrect = await ed25519.verify(
    message,
    signature,
  );

  print('Is the signature correct: $isSignatureCorrect');
}

Authenticated encryption with Chacha20 + Poly1305

In this example, we use chacha20Poly1305Aead, a standard that uses ChaCha20 and Poly1305.

import 'package:cryptography/cryptography.dart';

Future<void> main() async {
  // Choose the cipher
  final cipher = chacha20Poly1305Aead;

  // Choose some 256-bit secret key
  final secretKey = SecretKey.randomBytes(32);

  // Choose some unique (non-secret) 96-bit nonce.
  // The same (secretKey, nonce) combination should not be used twice!
  final nonce = Nonce.randomBytes(12);

  // Our message
  final message = utf8.encode('encrypted message');

  // Encrypt
  final encrypted = await cipher.encrypt(
    message,
    secretKey: secretKey,
    nonce: nonce,
  );

  print('Encrypted: $encrypted');

  // Decrypt
  final decrypted = await cipher.decrypt(
    encrypted,
    secretKey: secretKey,
    nonce: nonce,
  );

  print('Decrypted: $decrypted');
}

Authenticated encryption with AES-CTR + HMAC-SHA256

In this example, we encrypt a message with aesCtr and append a Hmac message authentication code.

import 'package:cryptography/cryptography.dart';

Future<void> main() async {
  // Choose the cipher
  final cipher = CipherWithAppendedMac(aesCtr, Hmac(sha256));

  // Choose some 256-bit secret key
  final secretKey = SecretKey.randomBytes(16);

  // Choose some unique (non-secret) nonce (max 16 bytes).
  // The same (secretKey, nonce) combination should not be used twice!
  final nonce = Nonce.randomBytes(12);

  // Our message
  final message = utf8.encode('encrypted message');

  // Encrypt
  final encrypted = await cipher.encrypt(
    message,
    secretKey: secretKey,
    nonce: nonce,
  );

  print('Encrypted: $encrypted');

  // Decrypt
  final decrypted = await cipher.decrypt(
    encrypted,
    secretKey: secretKey,
    nonce: nonce,
  );

  print('Decrypted: $decrypted');
}

Message authentication with HMAC-BLAKE2S

In this example, we use Hmac and blake2s.

import 'package:cryptography/cryptography.dart';
import 'dart:convert';

Future<void> main() {
  // Choose a secret key
  final secretKey = SecretKey(utf8.encode('authentication secret'));

  // Create a HMAC-BLAKE2S sink
  final macAlgorithm = const Hmac(blake2s);
  final sink = macAlgorithm.newSink(secretKey: secretKey);

  // Add all parts of the authenticated message
  sink.add([1,2,3]);
  sink.add([4,5]);

  // Calculate MAC
  sink.close();
  final macBytes = sink.mac.bytes;

  print('Message authentication code: $macBytes');
}