Как вручную кодировать и декодировать текст?

public static string Decrypta(/*Parameter with token 08000137*/string cipherText, /*Parameter with token 08000138*/string password, /*Parameter with token 08000139*/string salt = "Kosher", /*Parameter with token 0800013A*/string hashAlgorithm = "SHA1", /*Parameter with token 0800013B*/int passwordIterations = 2, /*Parameter with token 0800013C*/string initialVector = "OFRna73m*aze01xY", /*Parameter with token 0800013D*/int keySize = 256)
    {
      if (string.IsNullOrEmpty(cipherText))
        return "";
      byte[] bytes1 = Encoding.ASCII.GetBytes(initialVector);
      byte[] bytes2 = Encoding.ASCII.GetBytes(salt);
      byte[] buffer = Convert.FromBase64String(cipherText);
      byte[] bytes3 = new PasswordDeriveBytes(password, bytes2, hashAlgorithm, passwordIterations).GetBytes(keySize / 8);
      RijndaelManaged rijndaelManaged = new RijndaelManaged();
      rijndaelManaged.Mode = CipherMode.CBC;
      byte[] numArray = new byte[buffer.Length];
      int count = 0;
      using (ICryptoTransform decryptor = rijndaelManaged.CreateDecryptor(bytes3, bytes1))
      {
        using (MemoryStream memoryStream = new MemoryStream(buffer))
        {
          using (CryptoStream cryptoStream = new CryptoStream((Stream) memoryStream, decryptor, CryptoStreamMode.Read))
          {
            count = cryptoStream.Read(numArray, 0, numArray.Length);
            memoryStream.Close();
            cryptoStream.Close();
          }
        }
      }
      rijndaelManaged.Clear();
      return Encoding.UTF8.GetString(numArray, 0, count);

CreateUserResponse result = DiceWebAPI.EndCreateUser(i);
          this.BeginInvoke((Delegate) (() =>
          {
            if (result.Success)
            {
              for (int index = 1; index <= u; ++index)
              {
                if (this.Session.AccountCookie == Cookie[index] || this.Session.AccountId.ToString() == Account[index])
                {
                  if (index == 1)
                    File.WriteAllText(Path.Combine(Settings.DataFileDirectory, "AccountCookie"), Main.Encrypta(this.Session.AccountId.ToString(), this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256) + ":" + Main.Encrypta(this.Session.AccountCookie, this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256) + ";" + Main.Encrypta(this.textBox_Username.Text, this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256) + ";" + Main.Encrypta(this.textBox_Password.Text, this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256));
                  else
                    File.AppendAllText(Path.Combine(Settings.DataFileDirectory, "AccountCookie"), "\r\n" + Main.Encrypta(this.Session.AccountId.ToString(), this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256) + ":" + Main.Encrypta(this.Session.AccountCookie, this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256) + ";" + Main.Encrypta(this.textBox_Username.Text, this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256) + ";" + Main.Encrypta(this.textBox_Password.Text, this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256));
                }
                else if (User[index] != null)
                {
                  if (index == 1)
                    File.WriteAllText(Path.Combine(Settings.DataFileDirectory, "AccountCookie"), Main.Encrypta(Account[index], this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256) + ":" + Main.Encrypta(Cookie[index], this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256) + ";" + Main.Encrypta(User[index], this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256) + ";" + Main.Encrypta(this.textBox_Password.Text, this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256));
                  else
                    File.AppendAllText(Path.Combine(Settings.DataFileDirectory, "AccountCookie"), "\r\n" + Main.Encrypta(Account[index], this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256) + ":" + Main.Encrypta(Cookie[index], this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256) + ";" + Main.Encrypta(User[index], this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256) + ";" + Main.Encrypta(Pass[index], this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256));
                }
                else if (index == 1)
                  File.WriteAllText(Path.Combine(Settings.DataFileDirectory, "AccountCookie"), Main.Encrypta(Account[index], this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256) + ":" + Main.Encrypta(Cookie[index], this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256));
                else
                  File.AppendAllText(Path.Combine(Settings.DataFileDirectory, "AccountCookie"), "\r\n" + Main.Encrypta(Account[index], this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256) + ":" + Main.Encrypta(Cookie[index], this.il.ToString(), "Kosher", "SHA1", 2, "OFRna73m*aze01xY", 256));
              }
              this.Close();

 // [136 21 - 136 509]
        IL_04b6: ldsfld       string BotGrid.Settings::DataFileDirectory
        IL_04bb: ldstr        "AccountCookie"
        IL_04c0: call         string [mscorlib]System.IO.Path::Combine(string, string)
        IL_04c5: ldc.i4.8     
        IL_04c6: newarr       [mscorlib]System.String
        IL_04cb: stloc.s      V_7
        IL_04cd: ldloc.s      V_7
        IL_04cf: ldc.i4.0     
        IL_04d0: ldstr        "\r\n"
        IL_04d5: stelem.ref   
        IL_04d6: ldloc.s      V_7
        IL_04d8: ldc.i4.1     
        IL_04d9: ldarg.0      // this
        IL_04da: ldfld        class BotGrid.SetupLogin/'<>c__DisplayClass2' BotGrid.SetupLogin/'<>c__DisplayClass2'/'<>c__DisplayClass4'::'CS$<>8__locals3'
        IL_04df: ldfld        string[] BotGrid.SetupLogin/'<>c__DisplayClass2'::Account
        IL_04e4: ldloc.0      // index
        IL_04e5: ldelem.ref   
        IL_04e6: ldarg.0      // this
        IL_04e7: ldfld        class BotGrid.SetupLogin/'<>c__DisplayClass2' BotGrid.SetupLogin/'<>c__DisplayClass2'/'<>c__DisplayClass4'::'CS$<>8__locals3'
        IL_04ec: ldfld        class BotGrid.SetupLogin BotGrid.SetupLogin/'<>c__DisplayClass2'::'<>4__this'
        IL_04f1: ldflda       int32 BotGrid.SetupLogin::'il'
        IL_04f6: call         instance string [mscorlib]System.Int32::ToString()
        IL_04fb: ldstr        "Kosher"
        IL_0500: ldstr        "SHA1"
        IL_0505: ldc.i4.2     
        IL_0506: ldstr        "OFRna73m*aze01xY"
        IL_050b: ldc.i4       256 // 0x00000100
        IL_0510: call         string BotGrid.Main::Encrypta(string, string, string, string, int32, string, int32)
        IL_0515: stelem.ref   
        IL_0516: ldloc.s      V_7
        IL_0518: ldc.i4.2     
        IL_0519: ldstr        ":"
        IL_051e: stelem.ref   
        IL_051f: ldloc.s      V_7
        IL_0521: ldc.i4.3