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

namespace DESDemo
{
    class Program
    {
        static byte[] bytes = ASCIIEncoding.ASCII.GetBytes("ZeroCool");

        static void Main(string[] args)
        {
            try
            {
                Console.WriteLine("Original String: ");

                string originalString = Console.ReadLine();
                string cryptedString = Encrypt(originalString);

                Console.ForegroundColor = ConsoleColor.Green;
                Console.WriteLine("\nEncrypt Result: {0}", cryptedString);
                Console.WriteLine("Decrypt Result: {0}", Decrypt(cryptedString));
            }
            catch (Exception ex)
            {
                Console.ForegroundColor = ConsoleColor.Red;
                Console.WriteLine("From: {0}.\nDetail: {1}", ex.Source, ex.Message);
            }
            finally
            {
                Console.ReadLine();
            }
        }

        /// <summary>
        /// Encrypt a string.
        /// </summary>
        /// <param name="originalString">The original string.</param>
        /// <returns>The encrypted string.</returns>
        /// <exception cref="ArgumentNullException">This exception will be thrown when the original string is null or empty.</exception>
        public static string Encrypt(string originalString)
        {
            if (String.IsNullOrEmpty(originalString))
            {
                throw new ArgumentNullException("The string which needs to be encrypted can not be null.");
            }

            DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
            MemoryStream memoryStream = new MemoryStream();
            CryptoStream cryptoStream = new CryptoStream(memoryStream, cryptoProvider.CreateEncryptor(bytes, bytes), CryptoStreamMode.Write);

            StreamWriter writer = new StreamWriter(cryptoStream);
            writer.Write(originalString);
            writer.Flush();
            cryptoStream.FlushFinalBlock();
            writer.Flush();

            return Convert.ToBase64String(memoryStream.GetBuffer(), 0, (int)memoryStream.Length);
        }

        /// <summary>
        /// Decrypt a crypted string.
        /// </summary>
        /// <param name="cryptedString">The crypted string.</param>
        /// <returns>The decrypted string.</returns>
        /// <exception cref="ArgumentNullException">This exception will be thrown when the crypted string is null or empty.</exception>
        public static string Decrypt(string cryptedString)
        {
            if (String.IsNullOrEmpty(cryptedString))
            {
                throw new ArgumentNullException("The string which needs to be decrypted can not be null.");
            }

            DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
            MemoryStream memoryStream = new MemoryStream(Convert.FromBase64String(cryptedString));
            CryptoStream cryptoStream = new CryptoStream(memoryStream, cryptoProvider.CreateDecryptor(bytes, bytes), CryptoStreamMode.Read);
            StreamReader reader = new StreamReader(cryptoStream);

            return reader.ReadToEnd();
        }
    }
}