封装---完整 加密解密方法； .net

using System;
using System.Collections.Generic;
using System.Text;
using System.Security.Cryptography;
using System.Text.RegularExpressions;
using System.IO;
using System.Security.Cryptography;
using System.Diagnostics;

namespace DBCOM
{
    public class Security
    {
        public static string Encrypt111(string passwordString)
        {
            byte[] paByte = new UnicodeEncoding().GetBytes(passwordString);
            byte[] hashByte = ((HashAlgorithm)CryptoConfig.CreateFromName("MD5")).ComputeHash(paByte);
            return BitConverter.ToString(hashByte);
        }

        //加密方法 
        public static string Encrypt(string pToEncrypt)
        {
            string sKey = "CDHBTPSP";
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();

            byte[] inputByteArray = Encoding.Default.GetBytes(pToEncrypt);
            des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
            des.IV = ASCIIEncoding.ASCII.GetBytes(sKey);
            MemoryStream ms = new MemoryStream();
            CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write);
            //Write  the  byte  array  into  the  crypto  stream 
            //(It  will  end  up  in  the  memory  stream) 
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();
            //Get  the  data  back  from  the  memory  stream,  and  into  a  string 
            StringBuilder ret = new StringBuilder();
            foreach (byte b in ms.ToArray())
            {
                //Format  as  hex 
                ret.AppendFormat("{0:X2}", b);
            }
            ret.ToString();
            return ret.ToString();
        }

        /// <summary>
        /// 解密字符串
        /// </summary>
        /// <param name="pToDecrypt">需要解密的字符串</param>
        /// <param name="sKey">string sKey = "CDHBTPSP";</param>
        /// <returns>string</returns>
        public static string Decrypt(string pToDecrypt)
        {
            string sKey = "CDHBTPSP";
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();

            //Put  the  input  string  into  the  byte  array 
            byte[] inputByteArray = new byte[pToDecrypt.Length / 2];
            for (int x = 0; x < pToDecrypt.Length / 2; x++)
            {
                int i = (Convert.ToInt32(pToDecrypt.Substring(x * 2, 2), 16));
                inputByteArray[x] = (byte)i;
            }

            //建立加密对象的密钥和偏移量，此值重要，不能修改 
            des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
            des.IV = ASCIIEncoding.ASCII.GetBytes(sKey);
            MemoryStream ms = new MemoryStream();
            CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);
            //Flush  the  data  through  the  crypto  stream  into  the  memory  stream 
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();

            //Get  the  decrypted  data  back  from  the  memory  stream 
            //建立StringBuild对象，CreateDecrypt使用的是流对象，必须把解密后的文本变成流对象 
            StringBuilder ret = new StringBuilder();

            return System.Text.Encoding.Default.GetString(ms.ToArray());
        } 
    }
}