cryptography 1.2.1

Cryptographic algorithms for encryption, digital signatures, key agreement, authentication, and hashing. AES, Chacha20, ED25519, X25519, and more. Web Crypto support.

Overview

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

This package is:

• Safe. Plenty of tests. No license risks. Used in commercial products.
• Fast. For example, SHA-512 in browsers can be 100 times faster than package:crypto.

Any feedback, issue reports, or pull requests are appreciated!

See our Github repository.

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 handshake protocol.
• Add your project here?

Some things to know

• SHA1 and SHA2 implementations use the package crypto, which is maintained by Google and contains only hash functions and HMAC.
• We wrote pure Dart implementations for X25519, ED25519, RSA-PSS, ChaCha20 / XChacha20, AES-CBC, AES-CTR, AES-GCM, HKDF, HMAC, Poly1305, and BLAKE2S.
• We implemented automatic use of Web Cryptography API (crypto.subtle) when you use SHA1, SHA2, AES, ECDH, ECDSA, or RSA in browsers.
• The APIs generally include both asynchronous and synchronous methods. Only the asynchronous methods are able to use Web Crypto APIs. For instance, you can calculate a SHA-512 hash with sha512.hash(bytes) or sha512.hashSync(bytes). In browsers, asynchronous version can be as much as 100 times faster. In other platforms the synchronous version is slightly faster. We recommend that developers use asynchronous methods.
• If Dart SDK decides to expose BoringSSL functions (SDK issue), we will use them as much as possible.

Cryptographic material classes

• SecretKey is used by symmetric cryptography.
• KeyPair (PrivateKey and PublicKey) is used by asymmetric cryptography.
  • Many data formats exist for storing RSA and elliptic curve keys. This package contains JSON Web Key (JWK) implementations JwkPrivateKey and JwkPublicKey.
• Nonce ("initialization vector", "IV", or "salt") is some non-secret, unique value required by many functions.

Available algorithms

Key exchange algorithms

The following KeyExchangeAlgorithm implementations are available:

• Elliptic curves approved by NIST (read about the algorithm)
  • ecdhP256 (ECDH P256 / secp256r1 / prime256v1)
  • ecdhP384 (ECDH P384 / secp384r1 / prime384v1)
  • ecdhP521 (ECDH P521 / secp521r1 / prime521v1)
  • Currently works only in browsers (Web Cryptography API)
• x25519 (curve25519 Diffie-Hellman)
  • In our benchmarks, the performance is around 1k operations per second in VM.

For more more documentation, see KeyExchangeAlgorithm.

Digital signature algorithms

The following SignatureAlgorithm implementations are available:

• ed25519 (curve25519 EdDSA)
  • In our benchmarks, the performance is around 200 signatures or verifications per second in VM (about 50 in browsers).
• Elliptic curves approved by NIST (read about the algorithm)
  • ecdsaP256Sha256 (ECDSA P256 / secp256r1 / prime256v1 + SHA256)
  • ecdsaP384Sha256 (ECDSA P384 / secp384r1 / prime384v1 + SHA256)
  • ecdsaP384Sha384 (ECDSA P384 / secp384r1 / prime384v1 + SHA384)
  • ecdsaP521Sha256 (ECDSA P521 / secp521r1 / prime521v1 + SHA256)
  • ecdsaP521Sha512 (ECDSA P521 / secp521r1 / prime521v1 + SHA512)
  • Currently works only in browsers (Web Cryptography API)
• RSA
  • RsaPss (RSA-PSS)
  • RsaSsaPkcs1v15 (RSASSA-PKCS1v15)
  • Currently works only in browsers (Web Cryptography API)

Symmetric encryption

The following Cipher implementations are available:

• CipherWithAppendedMac adds authentication (such as HMAC-SHA256) to ciphers without built-in authentication.
• AES (read about the algorithm)
  • aesCbc (AES-CBC)
  • aesCtr (AES-CTR)
  • aesGcm (AES-GCM)
  • In our benchmarks, the performance is around 10-70 MB/s in VM (about 400MB - 700MB/s in browsers).
• Chacha20 family (read about the algorithm)
  • chacha20
  • chacha20Poly1305Aead (AEAD_CHACHA20_POLY1305)
  • xchacha20
  • xchacha20Poly1305Aead (AEAD_XCHACHA20_POLY1305)
  • In our benchmarks, the performance is around 40-140MB/s in VM.

Key derivation algorithms

• HChacha20
• Hkdf

Message authentication codes

The following MacAlgorithm implementations are available:

• Hmac
• poly1305

Cryptographic hash functions

The following HashAlgorithm implementations are available:

• blake2s (BLAKE2S)
• sha1 (SHA1)
• sha224 (SHA2-224)
• sha256 (SHA2-256)
• sha384 (SHA2-384)
• sha512 (SHA2-512)

Adding dependency

In pubspec.yaml:

dependencies:
  cryptography: ^1.1.1

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');
}