cheeseandcereal / pc-dart

Pointy Castle - Dart Derived Bouncy Castle APIs

Pointy Castle

A Dart library for encryption and decryption. In this release, most of the classes are ports of Bouncy Castle from Java to Dart. The porting is almost always direct except for some classes that had been added to ease the use of low level data.

To make sure nothing fails, tests and benchmarks for every algorithm are provided. The expected results are taken from the Bouncy Castle Java version and also from standards, and matched against the results got from Pointy Castle.

This library was adopted from the original project at https://github.com/PointyCastle/pointycastle at the request of the authors to help support ongoing development.

Algorithms

In this release, the following algorithms are implemented:

Block ciphers:

• AES

Asymmetric block ciphers:

• RSA

Asymmetric block cipher encodings:

• PKCS1
• OAEP

Stream ciphers:

• Salsa20

Block cipher modes of operation:

• CBC (Cipher Block Chaining mode)
• CFB (Cipher Feedback mode)
• ECB (Electronic Code Book mode)
• GCTR (GOST 28147 OFB counter mode)
• OFB (Output FeedBack mode)
• CTR (Counter mode)
• SIC

Paddings:

• PKCS7
• ISO7816-4

Digests:

• Blake2b
• MD2
• MD4
• MD5
• RIPEMD-128|160|256|320
• SHA-1
• SHA-224|256|384|512
• SHA-512/t (t=8 to 376 and 392 to 504 in multiples of 8)
• Keccak-224|256|384|512*
• Tiger
• Whirlpool

*Keccak is currently implemented as SHA3Digest.

MACs:

• HMAC
• CMAC

Signatures:

• (DET-)ECDSA
• RSA

Password based key derivators:

• PBKDF2
• scrypt

HMAC based key derivators:

• HKDF

Asymmetric key generators:

• ECDSA
• RSA

Secure PRNGs:

• Based on block cipher in CTR mode
• Based on block cipher in CTR mode with auto reseed (for forward security)
• Based on Fortuna algorithm

Instantiating implementation objects

There are two ways to instantiate objects that implement the algorithms:

• using the registry, or
• without the registry.

Using the registry

Using the registry, the algorithm name is provided to high-level class factories.

This is especially convenient when an algorithm involves multiple algorithm implementation classes to implement. All the necessary classes can all be instantiated with a single name (e.g. "HMAC/SHA-256" or "SHA-1/HMAC/PBKDF2"), and they are automatically combined together with the correct values.

For example,

final sha256 = Digest("SHA-256");
final sha1 = Digest("SHA-1");
final md5 = Digest("MD5");

final hmacSha256 = Mac("SHA-256/HMAC");
final hmacSha1 = Mac("SHA-1/HMAC");
final hmacMd5 = Mac("MD5/HMAC");

final derivator = KeyDerivator("SHA-1/HMAC/PBKDF2");

final signer = Signer("SHA-256/RSA");

Without the registry

Without the registry, each implementation class must be instantiated using its constructor.

If an algorithm involves multiple algorithm implementation classes, they each have to be individually instantiated and combined together with the correct values.

For example,

final sha256 = SHA256Digest();
final sha1 = SHA1Digest();
final md5 = MD5Digest();

final hmacSha256 = HMac(SHA256Digest(), 64);
final hmacSha512 = HMac(SHA512Digest(), 128);
final hmacMd5 = HMac(MD5Digest(), 64);

final derivator = PBKDF2KeyDerivator(HMac(SHA256Digest(), 64));

final signer = RSASigner(SHA256Digest(), '0609608648016503040201');

Registry vs without registry

Using the registry means that all algorithms will be imported by default, which can increase the compiled size of your program.

To avoid this, instantiate all classes directly by using the constructors. But which classes can be instantiated with its constructor will depend on which libraries have been imported.

Importing libraries

A program can take one of these three approaches for importing Point Castle libraries:

• only import pointycastle.dart;
• only import exports.dart; or
• import api.dart and individual libraries as needed.

Only import pointycastle.dart

The "pointycastle.dart" file exports:

• the high-level API; and
• implementations of the interfaces.

But it does not export any of the algorithm implementation classes.

import "package:pointycastle/pointycastle.dart";

With this import, none of the implementation classes can be instantiated directly. The program can only use the registry.

For example,

final sha256 = Digest("SHA-256");
// final md5 = MD5Digest(); // not available
final p = Padding("PKCS7");
// final s = FortunaRandom(); // not available

Only import exports.dart

The "export.dart" file exports:

• the high-level API,
• implementations of the interfaces; and
• every algorithm implementation class.

That is, everything!

import "package:pointycastle/export.dart";

With this import, all of the implementation classes can be instantiated directly. The program can also use the registry.

For example, this works without any additional imports:

final sha256 = Digest("SHA-256");
final md5 = MD5Digest();
final p = Padding("PKCS7");
final s = FortunaRandom();

Import api.dart and individual libraries

The "api.dart" exports only:

• the high-level API.

It does not include the implementations of the interfaces, nor any algorithm implementation class.

import "package:pointycastle/api.dart";
// additional imports will be needed

With this import, only some of the implementation classes can be instantiated directly (i.e. those that are also explicitly imported). The program can also use the registry.

For example, the following only works because of the additional imports:

// In addition to "package:pointycastle/api.dart":
import "package:pointycastle/digests/sha256.dart";
import "package:pointycastle/digests/md5.dart"
import 'package:pointycastle/paddings/pkcs7.dart';

final sha256 = Digest("SHA-256");
final md5 = MD5Digest();
final p = Padding("PKCS7");
// final s = FortunaRandom(); // not available without 'package:pointycastle/random/fortuna_random.dart'

Tutorials

Some articles on how to use some of Pointy Castle's features can be found under the tutorials directory in the sources.

• Calculating a digest - calculating a hash or digest (e.g. SHA-256, SHA-1, MD5)
• Calculating a HMAC - calculating a hash-based message authentication code (e.g. HMAC-SHA256, HMAC-SHA1)
• Using AES-CBC - block encryption and decryption with AES-CBC
• Using RSA - key generation, signing/verifying, and encryption/decryption
• Some tips on using Pointy Castle

Note: the above links are to the most recent versions on the master branch on GitHub. They may be different from the version here.