程序加密类SafeUtil

该类使用著名的加密算法DES来实现网站信息的加密与解密程序。DES属于一种私钥加密，也称为对称加密。所谓对称加密，就是使用一个密钥加密，也必须使用该密钥进行解密。

私钥加密算法的速度非常快，它特别适合用于对较大的数据流执行加密。

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

namespace ECExp
{
    public class SafeUtil
    {
        private string iv = "12345678";//种子
        private string key = "12345678";//密钥
        private Encoding encoding = new UnicodeEncoding();
        private DES des = null;

        /// <summary>
        /// 构造函数
        /// </summary>
        public SafeUtil()
        {
            des = new DESCryptoServiceProvider();
        }

        /// <summary>
        /// 设置密钥
        /// </summary>
        public string EncryptKey
        {
            set
            {
                this.key = value;
            }
        }

        /// <summary>
        /// 设置或获取密文编码格式（默认为UTF-8）
        /// </summary>
        public Encoding EncodingMode
        {
            get { return this.encoding; }
            set { this.encoding = value; }
        }

        /// <summary>
        /// 加密字符串并返回加密后的结果
        /// </summary>
        /// <param name="str">要加密的字符串</param>
        /// <returns></returns>
        public string EncryptString(string str)
        {
            byte[] ivb = Encoding.ASCII.GetBytes(this.iv);
            byte[] keyb = Encoding.ASCII.GetBytes(this.key);//得到加密密钥
            byte[] toEncrypt = this.EncodingMode.GetBytes(str);//得到要加密的内容
            byte[] encrypted;

            //DES加密工具类
            ICryptoTransform encryptor = des.CreateEncryptor(keyb, ivb);
            MemoryStream msEncrypt = new MemoryStream();
            CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write);

            csEncrypt.Write(toEncrypt, 0, toEncrypt.Length);
            csEncrypt.FlushFinalBlock();
            encrypted = msEncrypt.ToArray();
            csEncrypt.Close();
            msEncrypt.Close();
            return Convert.ToBase64String(encrypted);
        }

        /// <summary>
        /// 解密给定的字符串
        /// </summary>
        /// <param name="str">要解密的字符，Base64</param>
        /// <returns></returns>
        public string DecryptString(string str)
        {
            byte[] ivb = Encoding.ASCII.GetBytes(this.iv);
            byte[] keyb = Encoding.ASCII.GetBytes(this.key);
            byte[] toDecrypt = Convert.FromBase64String(str);
            byte[] deCrypted = new byte[toDecrypt.Length];

            ICryptoTransform deCryptor = des.CreateDecryptor(keyb, ivb);
            MemoryStream msDecrypt = new MemoryStream(toDecrypt);
            CryptoStream csDecrypt = new CryptoStream(msDecrypt, deCryptor, CryptoStreamMode.Read);

            try
            {
                csDecrypt.Read(deCrypted, 0, deCrypted.Length);
            }
            catch (Exception err)
            {

                throw new ApplicationException(err.Message);
            }
            finally
            {
                try
                {
                    msDecrypt.Close();
                    csDecrypt.Close();
                }
                catch (Exception)
                {
                    
                }
            }
            return this.EncodingMode.GetString(deCrypted);
        }
    }
}

 如何使用：

            SafeUtil safeutil = new SafeUtil();
            string str = safeutil.EncryptString("456123");
            lblText.Text = str;
            string str2 = safeutil.DecryptString(safeutil.EncryptString("456123"));
            Label1.Text = str2;