mcs/class/referencesource/mscorlib/system/security/cryptography/pkcs1maskgenerationmethod.cs

   1 // ==++==
   2 //
   3 //   Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 // ==--==
   6 // <OWNER>Microsoft</OWNER>
   7 //
   8
   9 namespace System.Security.Cryptography {
  10 [System.Runtime.InteropServices.ComVisible(true)]
  11     public class PKCS1MaskGenerationMethod : MaskGenerationMethod
  12     {
  13         private String HashNameValue;
  14
  15         //
  16         // public constructors
  17         //
  18
  19         public PKCS1MaskGenerationMethod() {
  20             HashNameValue = "SHA1";
  21         }
  22
  23         //
  24         // public properties
  25         //
  26
  27         public String HashName {
  28             get { return HashNameValue; }
  29             set {
  30                 HashNameValue = value;
  31                 if (HashNameValue == null) {
  32                     HashNameValue = "SHA1";
  33                 }
  34             }
  35         }
  36
  37         //
  38         // public methods
  39         //
  40
  41         public override byte[] GenerateMask(byte[] rgbSeed, int cbReturn)
  42         {
  43 #if MONO
  44             HashAlgorithm hash = HashAlgorithm.Create (HashNameValue);
  45             return Mono.Security.Cryptography.PKCS1.MGF1 (hash, rgbSeed, cbReturn);
  46 #else
  47             HashAlgorithm hash = (HashAlgorithm) CryptoConfig.CreateFromName(HashNameValue);
  48             byte[] rgbCounter = new byte[4];
  49             byte[] rgbT = new byte[cbReturn];
  50
  51             uint counter = 0;
  52             for (int ib=0; ib<rgbT.Length; ) {
  53                 //  Increment counter -- up to 2^32 * sizeof(Hash)
  54                 Utils.ConvertIntToByteArray(counter++, ref rgbCounter);
  55                 hash.TransformBlock(rgbSeed, 0, rgbSeed.Length, rgbSeed, 0);
  56                 hash.TransformFinalBlock(rgbCounter, 0, 4);
  57                 byte[] _hash = hash.Hash;
  58                 hash.Initialize();
  59                 if (rgbT.Length - ib > _hash.Length) {
  60                     Buffer.BlockCopy(_hash, 0, rgbT, ib, _hash.Length);
  61                 } else {
  62                     Buffer.BlockCopy(_hash, 0, rgbT, ib, rgbT.Length - ib);
  63                 }
  64                 ib += hash.Hash.Length;
  65             }
  66             return rgbT;
  67 #endif
  68         }
  69     }
  70 }