asp.net中对字符的加密和解密

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Security.Cryptography;
using System.Text;
using System.IO;
namespace demo
...{
    /**//// <summary>
    /// WebForm5 的摘要说明。
    /// </summary>
    public class WebForm5 : System.Web.UI.Page
    ...{
        protected System.Web.UI.WebControls.TextBox TextBox2;
        protected System.Web.UI.WebControls.Button Button3;
        protected System.Web.UI.WebControls.Button Button4;
        protected System.Web.UI.WebControls.TextBox TextBox1;
        protected System.Web.UI.WebControls.TextBox EncryptStr;
        protected System.Web.UI.WebControls.TextBox str;

        public SymmetricAlgorithm DES_SP;
        
        private void Page_Load(object sender, System.EventArgs e)
        ...{
            //initDes();
        }
         

        private SymmetricAlgorithm InitDes()
        ...{
                return new DESCryptoServiceProvider();//用DES
        }


        string EncryptString(string Value)
        ...{
            ICryptoTransform ct;
            MemoryStream ms;
            CryptoStream cs;
            byte[] byt;
            ct = DES_SP.CreateEncryptor(DES_SP.Key, DES_SP.IV);
            byt = Encoding.UTF8.GetBytes(Value);
            ms = new MemoryStream();
            cs = new CryptoStream(ms, ct, CryptoStreamMode.Write);
            cs.Write(byt, 0, byt.Length);
            cs.FlushFinalBlock();
            cs.Close();
            return Convert.ToBase64String(ms.ToArray());
        }

        private string DecryptString(string Value)
        ...{
            ICryptoTransform ct;
            MemoryStream ms;
            CryptoStream cs;
            byte[] byt;
            ct = DES_SP.CreateDecryptor((byte[])Session["K"], (byte[])Session["S"]);
            byt = Convert.FromBase64String(Value);
            ms = new MemoryStream();
            cs = new CryptoStream(ms, ct, CryptoStreamMode.Write);
            cs.Write(byt, 0, byt.Length);
            cs.FlushFinalBlock();
            cs.Close();

            return Encoding.UTF8.GetString(ms.ToArray());
        }

        Web 窗体设计器生成的代码#region Web 窗体设计器生成的代码
        override protected void OnInit(EventArgs e)
        ...{
            //
            // CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。
            //
            InitializeComponent();
            base.OnInit(e);
        }
        
        /**//// <summary>
        /// 设计器支持所需的方法 - 不要使用代码编辑器修改
        /// 此方法的内容。
        /// </summary>
        private void InitializeComponent()
        ...{    
            this.Button3.Click += new System.EventHandler(this.Button3_Click);
            this.Button4.Click += new System.EventHandler(this.Button4_Click);
            this.Load += new System.EventHandler(this.Page_Load);

        }
        #endregion

    

        private void Button3_Click(object sender, System.EventArgs e)
        ...{
            DES_SP=InitDes();
            DES_SP.GenerateKey();
            Session["K"]=DES_SP.Key;
            TextBox1.Text=Convert.ToBase64String(DES_SP.Key);
            DES_SP.GenerateIV();
            Session["S"]=DES_SP.IV;
            TextBox2.Text=Convert.ToBase64String(DES_SP.IV);
            
            EncryptStr.Text= EncryptString(str.Text);
        }

        private void Button4_Click(object sender, System.EventArgs e)
        ...{
            try
            ...{
                DES_SP=SetEnc();
                EncryptStr.Text=DecryptString(str.Text);
            }
            catch
            ...{
                Page.RegisterClientScriptBlock("","<script>alert('解密失败!')</script>");
            }
        }



    }
}