using System;

using System.IO;

using System.Security.Cryptography;

using System.Text;

public class CryptographyHelper

{

    private static string sKey = "";

    private static string sIV = "ABCDEFGH";

    /// <summary>

    /// 进行DES加密。

    /// </summary>

    /// <param name="pToEncrypt">要加密的字符串。</param>

    /// <param name="sKey">密钥，且必须为8位。</param>

    /// <returns>以Base64格式返回的加密字符串。</returns>

    public static string Encrypt(string pToEncrypt)

    {

        if (string.IsNullOrEmpty(pToEncrypt))

            return string.Empty;

        using (DESCryptoServiceProvider des = new DESCryptoServiceProvider())

        {

            byte[] inputByteArray = Encoding.UTF8.GetBytes(pToEncrypt);

            des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);

            des.IV = ASCIIEncoding.ASCII.GetBytes(sIV);

            System.IO.MemoryStream ms = new System.IO.MemoryStream();

            using (CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write))

            {

                cs.Write(inputByteArray, , inputByteArray.Length);

                cs.FlushFinalBlock();

                cs.Close();

            }

            string str = Convert.ToBase64String(ms.ToArray());

            ms.Close();

            return str;

        }

    }

    /// <summary>

    /// 进行DES解密。

    /// </summary>

    /// <param name="pToDecrypt">要解密的以Base64</param>

    /// <param name="sKey">密钥，且必须为8位。</param>

    /// <returns>已解密的字符串。</returns>

    public static string Decrypt(string pToDecrypt)

    {

        if (string.IsNullOrEmpty(pToDecrypt))

            return string.Empty;

        byte[] inputByteArray = Convert.FromBase64String(pToDecrypt.Replace(" ", "+"));

        using (DESCryptoServiceProvider des = new DESCryptoServiceProvider())

        {

            des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);

            des.IV = ASCIIEncoding.ASCII.GetBytes(sIV);

            System.IO.MemoryStream ms = new System.IO.MemoryStream();

            using (CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write))

            {

                cs.Write(inputByteArray, , inputByteArray.Length);

                cs.FlushFinalBlock();

                cs.Close();

            }

            string str = Encoding.UTF8.GetString(ms.ToArray());

            ms.Close();

            return str;

        }

    }

}