DESCryptoServiceProviderクラスの暗号化、復号化

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Security.Cryptography;
using System.IO;

namespace EncryptDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            // Create a new DES key.
            DESCryptoServiceProvider key = new DESCryptoServiceProvider();

            //get the input
            string val = null;
            val=Console.ReadLine().ToString();

            // Encrypt a string to a byte array
            byte[] encryptedByte = Encrypt(val, key);

            //write out the encrypt result
            if (encryptedByte != null)
                for (int i = 0; i < encryptedByte.Length; i++)
                {
                    Console.Write(encryptedByte[i]);
                }

            //Decrypt the encrypted byte array
            val = Decrypt(encryptedByte, key);

            Console.Write("
");

            //write out the original data
            Console.Write(val);

            Console.ReadKey();
        }

        /// <summary>
        /// a method to encrypt the string to a byte array
        /// </summary>
        /// <param name="strToEncrypt">the string need to encrypt</param>
        /// <param name="key"> the CSP DES key</param>
        /// <returns>a byte array</returns>
        public static byte[] Encrypt(string strToEncrypt,SymmetricAlgorithm key)
        {
            //if the string is null, then return 
            if (strToEncrypt == null)
                return null;

            //create a memory stream
            MemoryStream ms = new MemoryStream();

            //create a cryptostream using memory stream and the CSP DES key.  
            CryptoStream encStream = new CryptoStream(ms, key.CreateEncryptor(), CryptoStreamMode.Write);

            //Create a StreamWriter to write a string to the stream.
            StreamWriter sw = new StreamWriter(encStream);

            // Write the strToEncrypt to the stream
            sw.Write(strToEncrypt);

            // Close the StreamWriter and CryptoStream.
            sw.Close();
            encStream.Close();

            // Get an array of bytes that represents
            // the memory stream.
            byte[] result = ms.ToArray();

            // Close the memory stream.
            ms.Close();

            // Return the encrypted byte array.
            return result;
        }

        /// <summary>
        /// a method to decrypt a encrypted byte to its original string
        /// </summary>
        /// <param name="byteToDecrypt">encrypted data, it must be a byte array</param>
        /// <param name="key">the CSP DES key</param>
        /// <returns>original string</returns>
        public static string Decrypt(byte[] byteToDecrypt, SymmetricAlgorithm key)
        {
            //create a memory stream, as it will in read mode, so it must be new with the byteToDecrypt
            MemoryStream ms = new MemoryStream(byteToDecrypt);

            //create a cryptostream using memory stream and the CSP DES key.  
            CryptoStream encStream = new CryptoStream(ms, key.CreateDecryptor(), CryptoStreamMode.Read);

            // Create a StreamReader for reading the stream.
            StreamReader sr = new StreamReader(encStream);

            string result = "";

            // Read the stream as a string.
            result = sr.ReadLine();

            // Close the streams.
            sr.Close();

            encStream.Close();

            ms.Close();

            return result;


        }
    }
}