carlst99.Rc4Sharp 3.0.0

Rc4Sharp

A managed .NET Standard 2.1 implementation of the RC4 stream cipher. Verified against the test vectors on the RC4 Wikipedia page.

Usage

Installation

You can install Rc4Sharp from NuGet.

# .NET CLI
dotnet add package carlst99.Rc4Sharp

# Visual Studio Package Manager
Install-Package carlst99.Rc4Sharp

Transforming Buffers

The Rc4Cipher class can be used to apply the RC4 cipher to byte buffers. It acts as the default implementation of the IRc4Cipher interface.

To use it, you must first initialize it with an array of bytes containing your key data. Note that this key buffer must be at least one byte in length.

using Rc4Sharp;

// Don't actually use this as a key
const string key = "Secret!";
byte[] keyData = Encoding.ASCII.GetBytes(key);

byte[] toEncrypt = Encoding.ASCII.GetBytes("plaintext");
// The output buffer must always be at
// least as long as the input buffer
byte[] encryptedData = new byte[toEncrypt.Length];

using Rc4Cipher encrypter = new(keyData);
encrypter.Transform(toEncrypt, encryptedData);

Transforming Streams

The Rc4Stream can be used to apply the RC4 cipher to a stream of data. It uses the Rc4Cipher class under the hood, although a constructor overload is provided where you can pass in any object that implements the IRc4Cipher interface.

using Rc4Sharp;

Stream dataStream = new MemoryStream();
using Rc4Stream encrypter = new(dataStream, keyData);

// Reads data from the underlying stream and
// applys the cipher to the output buffer
encrypter.Read(...);

// Applys the cipher to a copy of the input buffer
// then writes it to the underlying stream
encrypter.Write(...);

Note that the Rc4Stream will dispose of its underlying stream when Dispose is called. If you'd like to change this, set the disposeUnderlying constructor parameter to false.

using Rc4Stream encrypter = new Rc4Stream(stream, keyData, disposeUnderlying: false);