mcs/class/corlib/System.Security.Cryptography/TripleDESCryptoServiceProvider.cs

   1 //
   2 // TripleDESCryptoServiceProvider.cs: Default TripleDES implementation
   3 //
   4 // Author:
   5 //      Sebastien Pouliot <sebastien@ximian.com>
   6 //
   7 // (C) 2002 Motus Technologies Inc. (http://www.motus.com)
   8 // Copyright (C) 2004-2005 Novell, Inc (http://www.novell.com)
   9 //
  10 // Permission is hereby granted, free of charge, to any person obtaining
  11 // a copy of this software and associated documentation files (the
  12 // "Software"), to deal in the Software without restriction, including
  13 // without limitation the rights to use, copy, modify, merge, publish,
  14 // distribute, sublicense, and/or sell copies of the Software, and to
  15 // permit persons to whom the Software is furnished to do so, subject to
  16 // the following conditions:
  17 //
  18 // The above copyright notice and this permission notice shall be
  19 // included in all copies or substantial portions of the Software.
  20 //
  21 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  22 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  23 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  24 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  25 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  26 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  27 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  28 //
  29
  30 using System.Runtime.InteropServices;
  31 using Mono.Security.Cryptography;
  32
  33 namespace System.Security.Cryptography {
  34
  35         // References:
  36         // a.   FIPS PUB 46-3: TripleDES
  37         //      http://csrc.nist.gov/publications/fips/fips46-3/fips46-3.pdf
  38         // b.   ANSI X9.52
  39         //      not free :-(
  40         //      http://webstore.ansi.org/ansidocstore/product.asp?sku=ANSI+X9%2E52%2D1998
  41
  42         // TripleDES is just DES-EDE
  43         internal class TripleDESTransform : SymmetricTransform {
  44
  45                 // for encryption
  46                 private DESTransform E1;
  47                 private DESTransform D2;
  48                 private DESTransform E3;
  49
  50                 // for decryption
  51                 private DESTransform D1;
  52                 private DESTransform E2;
  53                 private DESTransform D3;
  54
  55                 public TripleDESTransform (TripleDES algo, bool encryption, byte[] key, byte[] iv) : base (algo, encryption, iv)
  56                 {
  57                         if (key == null) {
  58                                 key = GetStrongKey ();
  59                         }
  60                         // note: checking weak keys also checks valid key length
  61                         if (TripleDES.IsWeakKey (key)) {
  62                                 string msg = Locale.GetText ("This is a known weak key.");
  63                                 throw new CryptographicException (msg);
  64                         }
  65
  66                         byte[] key1 = new byte [8];
  67                         byte[] key2 = new byte [8];
  68                         byte[] key3 = new byte [8];
  69                         DES des = DES.Create ();
  70                         Buffer.BlockCopy (key, 0, key1, 0, 8);
  71                         Buffer.BlockCopy (key, 8, key2, 0, 8);
  72                         if (key.Length == 16)
  73                                 Buffer.BlockCopy (key, 0, key3, 0, 8);
  74                         else
  75                                 Buffer.BlockCopy (key, 16, key3, 0, 8);
  76
  77                         // note: some modes (like CFB) requires encryption when decrypting
  78                         if ((encryption) || (algo.Mode == CipherMode.CFB)) {
  79                                 E1 = new DESTransform (des, true, key1, iv);
  80                                 D2 = new DESTransform (des, false, key2, iv);
  81                                 E3 = new DESTransform (des, true, key3, iv);
  82                         }
  83                         else {
  84                                 D1 = new DESTransform (des, false, key3, iv);
  85                                 E2 = new DESTransform (des, true, key2, iv);
  86                                 D3 = new DESTransform (des, false, key1, iv);
  87                         }
  88                 }
  89
  90                 // note: this method is garanteed to be called with a valid blocksize
  91                 // for both input and output
  92                 protected override void ECB (byte[] input, byte[] output)
  93                 {
  94                         DESTransform.Permutation (input, output, DESTransform.ipTab, false);
  95                         if (encrypt) {
  96                                 E1.ProcessBlock (output, output);
  97                                 D2.ProcessBlock (output, output);
  98                                 E3.ProcessBlock (output, output);
  99                         }
 100                         else {
 101                                 D1.ProcessBlock (output, output);
 102                                 E2.ProcessBlock (output, output);
 103                                 D3.ProcessBlock (output, output);
 104                         }
 105                         DESTransform.Permutation (output, output, DESTransform.fpTab, true);
 106                 }
 107
 108                 static internal byte[] GetStrongKey ()
 109                 {
 110                         int size = DESTransform.BLOCK_BYTE_SIZE * 3;
 111                         byte[] key = KeyBuilder.Key (size);
 112                         while (TripleDES.IsWeakKey (key))
 113                                 key = KeyBuilder.Key (size);
 114                         return key;
 115                 }
 116         }
 117 }
 118