using System;

using Microsoft.VisualBasic;

using Microsoft.VisualBasic.CompilerServices;

​

using System.Text;

​

public class Program

{

    public static void Main() {

        string ara = XOR_Decrypt("4B594921444A59413530412431273E435940","siper");

        Console.WriteLine(ara);

        Console.WriteLine(XOR_Encrypt(ara, "siper"));

        Console.WriteLine(XOR_Encrypt(ara,"retour"));

    }

    public static string XOR_Encrypt(string Input, string pass)

    {

      StringBuilder stringBuilder = new StringBuilder();

      int num = checked (Input.Length - 1);

      int index1 = 0;

      int index2 = 0;

      while (index1 <= num)

      {

        string str = Conversion.Hex(Strings.Asc(Input[index1]) ^ Strings.Asc(pass[index2]));

        if (str.Length == 1)

          str = "0" + str;

        stringBuilder.Append(str);

        if (index2 == checked (pass.Length - 1))

          index2 = 0;

        else

          checked { ++index2; }

        checked { ++index1; }

      }

      return stringBuilder.ToString();

    }

    public static string XOR_Decrypt(string Input, string pass)

    {

      StringBuilder stringBuilder = new StringBuilder();

      int num = checked (Input.Length - 1);

      int startIndex = 0;

      int index = 0;

      while (startIndex <= num)

      {

​

        string str = Conversions.ToString(Strings.Chr(checked ((int) (Conversions.ToLong("&H" + Input.Substring(startIndex, 2)) ^ (long) Strings.Asc(pass[index])))));

        stringBuilder.Append(str);

        if (index == checked (pass.Length - 1))

          index = 0;

        else

          checked { ++index; }

        checked { startIndex += 2; }

      }

      return stringBuilder.ToString();

    }

}

​

​