web.config连接字符加解密

 在数据层ConnectionString

string _connectionString = ConfigurationManager.AppSettings["ConnectionString"];      
                string ConStringEncrypt = ConfigurationManager.AppSettings["ConStringEncrypt"];
                if (ConStringEncrypt == "true")
                {
                    _connectionString = DESEncrypt.Decrypt(_connectionString);
                }
                return _connectionString;

using System;
using System.Security.Cryptography;  
using System.Text;
namespace Maticsoft.DBUtility
{
    /**//// <summary>
    /// DES加密/解密类。
    /// </summary>
    public class DESEncrypt
    {
        public DESEncrypt()
        {            
        }

        ========加密========#region ========加密======== 

        /**//// <summary>
        /// 加密
        /// </summary>
        /// <param name="Text"></param>
        /// <returns></returns>
        public static string Encrypt(string Text) 
        {
            return Encrypt(Text,"keyword");
        }
        /**//// <summary> 
        /// 加密数据 
        /// </summary> 
        /// <param name="Text"></param> 
        /// <param name="sKey"></param> 
        /// <returns></returns> 
        public static string Encrypt(string Text,string sKey) 
        { 
            DESCryptoServiceProvider des = new DESCryptoServiceProvider(); 
            byte[] inputByteArray; 
            inputByteArray=Encoding.Default.GetBytes(Text); 
            des.Key = ASCIIEncoding.ASCII.GetBytes(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5").Substring(0, 8)); 
            des.IV = ASCIIEncoding.ASCII.GetBytes(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5").Substring(0, 8)); 
            System.IO.MemoryStream ms=new System.IO.MemoryStream(); 
            CryptoStream cs=new CryptoStream(ms,des.CreateEncryptor(),CryptoStreamMode.Write); 
            cs.Write(inputByteArray,0,inputByteArray.Length); 
            cs.FlushFinalBlock(); 
            StringBuilder ret=new StringBuilder(); 
            foreach( byte b in ms.ToArray()) 
            { 
                ret.AppendFormat("{0:X2}",b); 
            } 
            return ret.ToString(); 
        } 

        #endregion
        
        ========解密========#region ========解密======== 
   

        /**//// <summary>
        /// 解密
        /// </summary>
        /// <param name="Text"></param>
        /// <returns></returns>
        public static string Decrypt(string Text) 
        {
            return Decrypt(Text,"keyword");
        }
        /**//// <summary> 
        /// 解密数据 
        /// </summary> 
        /// <param name="Text"></param> 
        /// <param name="sKey"></param> 
        /// <returns></returns> 
        public static string Decrypt(string Text,string sKey) 
        { 
            DESCryptoServiceProvider des = new DESCryptoServiceProvider(); 
            int len; 
            len=Text.Length/2; 
            byte[] inputByteArray = new byte[len]; 
            int x,i; 
            for(x=0;x<len;x++) 
            { 
                i = Convert.ToInt32(Text.Substring(x * 2, 2), 16); 
                inputByteArray[x]=(byte)i; 
            } 
            des.Key = ASCIIEncoding.ASCII.GetBytes(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5").Substring(0, 8)); 
            des.IV = ASCIIEncoding.ASCII.GetBytes(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5").Substring(0, 8)); 
            System.IO.MemoryStream ms=new System.IO.MemoryStream(); 
            CryptoStream cs=new CryptoStream(ms,des.CreateDecryptor(),CryptoStreamMode.Write); 
            cs.Write(inputByteArray,0,inputByteArray.Length); 
            cs.FlushFinalBlock(); 
            return Encoding.Default.GetString(ms.ToArray()); 
        } 

        #endregion 


    }
}