private void button1_Click(object sender, RoutedEventArgs e)
         {             
             BinaryReader br=new BinaryReader(new FileStream(@"c:\hf.dat",FileMode.Open,FileAccess.Read));
             byte[] data = new byte[(int)br.BaseStream.Length];
                  
             int cnt = br.Read(data, 0, (int)br.BaseStream.Length);
              
             int n = (int)br.BaseStream.Length - 32;

             byte[] S=new byte [256];
             int i = 0;
             for (i = 0; i < 256; i++) S[i] = Convert.ToByte(i);
             i = 0;
             int j = 0;
             byte  u = 0;
             byte v = 0;
             while (i < 256)
             {

                 j = j + S[i] + data[n + (i & 31)] & 255;
                 u = S[i];
                 S[i] = S[j];
                 S[j] = u;
                 i = (i + 1);
             }
                    
             if (n > 131072)
             {
                 n=131072;
             }
            int _loc_2 = 0;
                 j=0;
                 i = _loc_2;
                 int k=0;
                 while (k < n)
                 {                     
                     i = i + 1 & 255;
                     u = S[i];
                     j = j + u & 255;
                     v = S[j];
                     S[i] = v;
                     S[j] = u;
                      
                     data[k] =Convert.ToByte(data[k] ^ S[u + v & 255]);
                     k = (k + 1);
                 }
             BinaryWriter bw=new BinaryWriter(new FileStream(@"c:\hf2.dat",FileMode.Create,FileAccess.Write));
             bw.Write(data);
             bw.Close();
             br.Close();
// Плюс файл hf2.dat какой-нибудь стороней программой расжать (алгоритм zlib).
         }