TripleDESCryptoServiceProvider.cs :  » Network-Clients » SharpPrivacyLibrary » SharpPrivacy » Cipher » C# / CSharp Open Source

//
// TripleDESCryptoServiceProvider.cs: Default TripleDES implementation
//
// Author:
//  Sebastien Pouliot (spouliot@motus.com)
//
// (C) 2002 Motus Technologies Inc. (http://www.motus.com)
//
// Modified by Daniel Fabian to fit SharpPrivacy's needs.
// This file is part of the SharpPrivacy source code contribution.
// Get get the original SymmetricAlgorithm class, please visit the
// mono project at http://www.go-mono.com.
//

using System;

namespace SharpPrivacy.Cipher{

  // References:
  // a.  FIPS PUB 46-3: TripleDES
  //  http://csrc.nist.gov/publications/fips/fips46-3/fips46-3.pdf
  // b.  ANSI X9.52
  //  not free :-(
  //  http://webstore.ansi.org/ansidocstore/product.asp?sku=ANSI+X9%2E52%2D1998
  
  public sealed class TripleDESCryptoServiceProvider : TripleDES {
  
    public TripleDESCryptoServiceProvider () {}
  
    public override void GenerateIV () 
    {
      IVValue = KeyBuilder.IV (BlockSizeValue >> 3);
    }
    
    public override void GenerateKey () 
    {
      KeyValue = KeyBuilder.Key (KeySizeValue >> 3);
    }
    
    public override ICryptoTransform CreateDecryptor (byte[] rgbKey, byte[] rgbIV) 
    {
      Key = rgbKey;
      IV = rgbIV;
      return new TripleDESTransform (this, false, rgbKey, rgbIV);
    }
    
    public override ICryptoTransform CreateEncryptor (byte[] rgbKey, byte[] rgbIV) 
    {
      Key = rgbKey;
      IV = rgbIV;
      return new TripleDESTransform (this, true, rgbKey, rgbIV);
    }
  }
  
  // TripleDES is just DES-EDE
  internal class TripleDESTransform : SymmetricTransform {
  
    // for encryption
    private DESTransform E1;
    private DESTransform D2;
    private DESTransform E3;
  
    // for decryption
    private DESTransform D1;
    private DESTransform E2;
    private DESTransform D3;
    
    public TripleDESTransform (TripleDES algo, bool encryption, byte[] key, byte[] iv) : base (algo, encryption, iv) 
    {
      byte[] key1 = new byte [8];
      byte[] key2 = new byte [8];
      byte[] key3 = new byte [8];
      DES des = DES.Create ();
      Array.Copy (key, 0, key1, 0, 8);
      Array.Copy (key, 8, key2, 0, 8);
      if (key.Length == 16)
        Array.Copy (key, 0, key3, 0, 8);
      else
        Array.Copy (key, 16, key3, 0, 8);
  
      // note: some modes (like CFB) requires encryption when decrypting
      if ((encryption) || (algo.Mode == CipherMode.CFB)) {
        E1 = new DESTransform (des, true, key1, iv);
        D2 = new DESTransform (des, false, key2, iv);
        E3 = new DESTransform (des, true, key3, iv);
      }
      else {
        D1 = new DESTransform (des, false, key3, iv);
        E2 = new DESTransform (des, true, key2, iv);
        D3 = new DESTransform (des, false, key1, iv);
      }
    }
  
    // note: this method is garanteed to be called with a valid blocksize
    // for both input and output
    protected override void ECB (byte[] input, byte[] output) 
    {
      byte[] temp = new byte [input.Length];
      if (encrypt) {
        E1.ProcessBlock (input, output);
        D2.ProcessBlock (output, temp);
        E3.ProcessBlock (temp, output);
      }
      else {
        D1.ProcessBlock (input, output);
        E2.ProcessBlock (output, temp);
        D3.ProcessBlock (temp, output);
      }
    }
  }
}