// (c) 2006 Richard Grimes
// www.grimes.demon.co.uk

using System;
using System.Security.Cryptography;
using System.Text;
using System.IO;

class App
{
   static void Main()
   {
      Rijndael r = Rijndael.Create();
      string phrase = "daisy, daisy, give me your answer to";
      PasswordDeriveBytes pdb = new PasswordDeriveBytes(phrase, new byte[0]);
      r.Key = pdb.GetBytes(r.KeySize >> 3);
      string data = "The quick brown fox jumps over the lazy dog.";
      ICryptoTransform en = r.CreateEncryptor();
      byte[] input = Encoding.ASCII.GetBytes(data);
      input = CryptoTransform(input, en, true);
      Console.WriteLine(BitConverter.ToString(input));
      ICryptoTransform de = r.CreateDecryptor();
      byte[] output = CryptoTransform(input, de, false);
      Console.WriteLine(Encoding.ASCII.GetString(output));
   }
   static byte[] CryptoTransform(byte[] input, ICryptoTransform en, bool bEncrypt)
   {
      MemoryStream sInput = new MemoryStream(input);
      MemoryStream sOutput = new MemoryStream();
      CryptoStream cs = new CryptoStream(sOutput, en, CryptoStreamMode.Write);
      SHA256 sha256 = SHA256.Create();
      Stream data = null;
      if (bEncrypt)
         data = new CryptoStream(sInput, sha256, CryptoStreamMode.Read);
      else
         data = sInput;

      byte[] buffer = new byte[1024];
      while (true)
      {
         int read = data.Read(buffer, 0, buffer.Length);
         if (read == 0) break;
         cs.Write(buffer, 0, read);
      }
      if (bEncrypt)
         cs.Write(sha256.Hash, 0, sha256.Hash.Length);
      cs.FlushFinalBlock();
      cs.Clear();
      if (!bEncrypt)
      {
         byte[] hash = new byte[sha256.HashSize >> 3];
         sOutput.Position = sOutput.Length - hash.Length;
         sOutput.Read(hash, 0, hash.Length);
         sOutput.Position = 0;
         sOutput.SetLength(sOutput.Length - hash.Length);
         byte[] newHash = sha256.ComputeHash(sOutput);
         for (int x = 0; x < hash.Length; ++x)
         {
            if (hash[x] != newHash[x])
               throw new CryptographicException("Data is corrupt!");
         }
      }
      return sOutput.ToArray();
   }
}