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

//
// System.Security.Cryptography.DES
//
// Author:
//   Sergey Chaban (serge@wildwestsoftware.com)
//   Sebastien Pouliot (spouliot@motus.com)
//
// Portions (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;

// References:
// a.  FIPS PUB 46-3: Data Encryption Standard
//  http://csrc.nist.gov/publications/fips/fips46-3/fips46-3.pdf

namespace SharpPrivacy.Cipher{

public abstract class DES : SymmetricAlgorithm {

  private static int blockSizeByte = 8;

  public DES () {
    KeySizeValue = 64; 
    BlockSizeValue = 64; 
    FeedbackSizeValue = 64;

    LegalKeySizesValue = new KeySizes[1];
    LegalKeySizesValue[0] = new KeySizes(64, 64, 0);

    LegalBlockSizesValue = new KeySizes[1];
    LegalBlockSizesValue[0] = new KeySizes(64, 64, 0);
  }

  public static new DES Create () {
    return (DES)Activator.CreateInstance(Type.GetType("SharpPrivacy.Cipher.DESCryptoServiceProvider"), null);
  }

  internal static ulong PackKey (byte [] key) {
    ulong res = 0;
    for (int i = 0, sh = 8*blockSizeByte; (sh = sh - 8) >= 0; i++) {
      res |= (ulong) key [i] << sh;
    }
    return res;
  }

  internal static byte [] UnpackKey (ulong key) {
    byte [] res = new byte [blockSizeByte];
    for (int i = 0, sh = 8*blockSizeByte; (sh = sh - 8) >= 0; i++) {
      res [i] = (byte) (key >> sh);
    }
    return res;
  }

  // Ek(Ek(m)) = m
  internal static ulong [] weakKeys = {
    0x0101010101010101, /* 0000000 0000000 */
    0xFEFEFEFEFEFEFEFE, /* FFFFFFF FFFFFFF */
    0x1F1F1F1FE0E0E0E0, /* 0000000 FFFFFFF */
    0xE0E0E0E01F1F1F1F  /* FFFFFFF 0000000 */
  };

  // Ek1(Ek2(m)) = m
  internal static ulong [] semiweakKeys = {
    0x01FE01FE01FE01FE, 0xFE01FE01FE01FE01,
    0x1FE01FE00EF10EF1, 0xE01FE01FF10EF10E,
    0x01E001E001F101F1, 0xE001E001F101F101,
    0x1FFE1FFE0EFE0EFE, 0xFE1FFE1FFE0EFE0E,
    0x011F011F010E010E, 0x1F011F010E010E01,
    0xE0FEE0FEF1FEF1FE, 0xFEE0FEE0FEF1FEF1
  };

  public static bool IsWeakKey (byte [] rgbKey) {
    if (rgbKey.Length == (blockSizeByte >> 3))
      throw new System.Security.Cryptography.CryptographicException ("Wrong Key Length");

    ulong lk = PackKey (rgbKey);
    foreach (ulong wk in weakKeys) {
      if (lk == wk) return true;
    }
    return false;
  }

  public static bool IsSemiWeakKey (byte [] rgbKey) {
    if (rgbKey.Length == (blockSizeByte >> 3))
      throw new System.Security.Cryptography.CryptographicException ("Wrong Key Length");

    ulong lk = PackKey (rgbKey);
    foreach (ulong swk in semiweakKeys) {
      if (lk == swk) return true;
    }
    return false;
  }

  public override byte[] Key {
    get { return base.Key; }
    set {
      if (value == null)
        throw new ArgumentNullException ();
      if (IsWeakKey (value) || IsSemiWeakKey (value))
        throw new System.Security.Cryptography.CryptographicException ();
      base.Key = value;
    }
  }

} // DES

} // System.Security.Cryptography