class/corlib/System.Security.Cryptography/KeyedHashAlgorithm.cs

   1 //
   2 // KeyedHashAlgorithm.cs: Handles keyed hash and MAC classes.
   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.Globalization;
  31 using System.Runtime.InteropServices;
  32
  33 namespace System.Security.Cryptography {
  34
  35 [ComVisible (true)]
  36 public abstract class KeyedHashAlgorithm : HashAlgorithm {
  37
  38         protected byte[] KeyValue;
  39
  40         protected KeyedHashAlgorithm () : base ()
  41         {
  42                 // create a random 64 bits key
  43         }
  44
  45         ~KeyedHashAlgorithm ()
  46         {
  47                 Dispose (false);
  48         }
  49
  50         public virtual byte[] Key {
  51                 get {
  52                         return (byte[]) KeyValue.Clone ();
  53                 }
  54                 set {
  55                         // can't change the key during a hashing ops
  56                         if (State != 0) {
  57                                 throw new CryptographicException (
  58                                         Locale.GetText ("Key can't be changed at this state."));
  59                         }
  60                         // zeroize current key material for security
  61                         ZeroizeKey ();
  62                         // copy new key
  63                         KeyValue = (byte[]) value.Clone ();
  64                 }
  65         }
  66
  67         protected override void Dispose (bool disposing)
  68         {
  69                 // zeroize key material for security
  70                 ZeroizeKey();
  71                 // dispose managed resources
  72                 // none so far
  73                 // dispose unmanaged resources
  74                 // none so far
  75                 // calling base class HashAlgorithm
  76                 base.Dispose (disposing);
  77         }
  78
  79         private void ZeroizeKey()
  80         {
  81                 if (KeyValue != null)
  82                         Array.Clear (KeyValue, 0, KeyValue.Length);
  83         }
  84
  85         public static new KeyedHashAlgorithm Create ()
  86         {
  87                 return Create ("System.Security.Cryptography.KeyedHashAlgorithm");
  88         }
  89
  90         public static new KeyedHashAlgorithm Create (string algName)
  91         {
  92                 return (KeyedHashAlgorithm) CryptoConfig.CreateFromName (algName);
  93         }
  94 }
  95
  96 }