再来一个，常用加密字符串的class,转自OSLeague啊，作者：bigeagle

再来一个，常用加密字符串的class,转自OSLeague啊，作者：bigeagle

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--- 再来一个，常用加密字符串的class,转自OSLeague啊，作者：bigeagle (http://www.webasp.net/article/5/4081.htm)

-- 作者：未知
-- 发布日期： 2003-07-12

using System;
using System.Security ;
using System.Security.Cryptography ;
using System.Diagnostics ;
using System.Web ;
using System.Text ;

namespace Bigeagle.Util
{
 /// <summary>
 /// 一个加密类
 /// Author: Bigeagle@163.net
 /// Date: 2001/09/25
 /// History: 2001/10/25 finished
 /// </summary>
 /// <remarks>
 /// 封装常用的加密算法
 /// </remarks>
 public class Cryptography
 {

 /// <summary>
 /// md5加密指定字符串
 /// </summary>
 /// <param name="a_strValue">要加密的字符串</param>
 /// <returns>加密后的字符串</returns>
 public static string EncryptMD5String(string a_strValue)
 {
#if DEBUG
 Debug.Assert(a_strValue.Trim() != "" , "空字符串" , "空字符串不需要加密") ;
#endif//DEBUG

 //转换成bytearray
 Byte[] hba = ((HashAlgorithm) CryptoConfig.CreateFromName("MD5")).
 ComputeHash(StringToByteArray(a_strValue));

 return ByteArrayToString(hba) ;
 }

 /// <summary>
 /// 判断两个加密字符串是否相同
 /// </summary>
 /// <param name="a_str1"></param>
 /// <param name="a_str2"></param>
 /// <returns>如果相同返回真</returns>
 public static bool IsSame(string a_str1 , string a_str2)
 {
 Byte[] b1 = StringToByteArray(a_str1) ;
 Byte[] b2 = StringToByteArray(a_str2) ;
 if(b1.Length != b2.Length)
 {
 return false ;
 }

 for(int i = 0 ; i < b1.Length ; i ++)
 {
 if(b1[i] != b2[i])
 {
 return false ;
 }
 }

 return true ;
 }

 /// <summary>
 /// 转换string到Byte树组
 /// </summary>
 /// <param name="s">要转换的字符串</param>
 /// <returns>转换的Byte数组</returns>
 public static Byte[] StringToByteArray(String s)
 {
 /*
 Char[] ca = s.ToCharArray();
 Byte[] ba = new Byte[ca.Length];
 for(int i=0; i<ba.Length; i++) ba[i] = (Byte)ca[i];
 return ba;*/

 return Encoding.UTF8.GetBytes(s) ;
 }

 /// <summary>
 /// 转换Byte数组到字符串
 /// </summary>
 /// <param name="a_arrByte">Byte数组</param>
 /// <returns>字符串</returns>
 public static string ByteArrayToString(Byte[] a_arrByte)
 {
 /*
 //char[] ca = new char[a_arrByte.Length] ;
 for(int i = 0 ; i < a_arrByte.Length ; i ++)
 {
 result += (char)a_arrByte[i] ;
 }*/

 return Encoding.UTF8.GetString(a_arrByte) ;
 }

 /// <summary>
 /// 3des加密字符串
 /// </summary>
 /// <param name="a_strString">要加密的字符串</param>
 /// <param name="a_strKey">密钥</param>
 /// <returns>加密后并经base64编码的字符串</returns>
 /// <remarks>静态方法，采用默认ascii编码</remarks>
 public static string Encrypt3DES(string a_strString, string a_strKey)
 {
 TripleDESCryptoServiceProvider DES = new
 TripleDESCryptoServiceProvider();
 MD5CryptoServiceProvider hashMD5 = new MD5CryptoServiceProvider();

 DES.Key = hashMD5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(a_strKey));
 DES.Mode = CipherMode.ECB;

 ICryptoTransform DESEncrypt = DES.CreateEncryptor();

 byte[] Buffer = ASCIIEncoding.ASCII.GetBytes(a_strString);
 return Convert.ToBase64String(DESEncrypt.TransformFinalBlock
 (Buffer, 0, Buffer.Length));
 }//end method

 /// <summary>
 /// 3des加密字符串
 /// </summary>
 /// <param name="a_strString">要加密的字符串</param>
 /// <param name="a_strKey">密钥</param>
 /// <param name="encoding">编码方式</param>
 /// <returns>加密后并经base63编码的字符串</returns>
 /// <remarks>重载，指定编码方式</remarks>
 public static string Encrypt3DES(string a_strString, string a_strKey , Encoding encoding)
 {
 TripleDESCryptoServiceProvider DES = new
 TripleDESCryptoServiceProvider();
 MD5CryptoServiceProvider hashMD5 = new MD5CryptoServiceProvider();

 DES.Key = hashMD5.ComputeHash(encoding.GetBytes(a_strKey));
 DES.Mode = CipherMode.ECB;

 ICryptoTransform DESEncrypt = DES.CreateEncryptor();

 byte[] Buffer = encoding.GetBytes(a_strString);
 return Convert.ToBase64String(DESEncrypt.TransformFinalBlock
 (Buffer, 0, Buffer.Length));
 }

 /// <summary>
 /// 3des解密字符串
 /// </summary>
 /// <param name="a_strString">要解密的字符串</param>
 /// <param name="a_strKey">密钥</param>
 /// <returns>解密后的字符串</returns>
 /// <exception cref="">密钥错误</exception>
 /// <remarks>静态方法，采用默认ascii编码</remarks>
 public static string Decrypt3DES(string a_strString, string a_strKey)
 {
 TripleDESCryptoServiceProvider DES = new
 TripleDESCryptoServiceProvider();
 MD5CryptoServiceProvider hashMD5 = new MD5CryptoServiceProvider();

 DES.Key = hashMD5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(a_strKey));
 DES.Mode = CipherMode.ECB;

 ICryptoTransform DESDecrypt = DES.CreateDecryptor();

 string result = "";
 try
 {
 byte[] Buffer = Convert.FromBase64String(a_strString);
 result = ASCIIEncoding.ASCII.GetString(DESDecrypt.TransformFinalBlock
 (Buffer, 0, Buffer.Length));
 }
 catch(Exception e)
 {
#if DEBUG
 Console.WriteLine("错误：{0}" , e) ;
#endif//DEBUG
 throw(new Exception("Invalid Key or input string is not a valid base64 string" , e)) ;
 }

 return result ;
 }//end method

 /// <summary>
 /// 3des解密字符串
 /// </summary>
 /// <param name="a_strString">要解密的字符串</param>
 /// <param name="a_strKey">密钥</param>
 /// <param name="encoding">编码方式</param>
 /// <returns>解密后的字符串</returns>
 /// <exception cref="">密钥错误</exception>
 /// <remarks>静态方法，指定编码方式</remarks>
 public static string Decrypt3DES(string a_strString, string a_strKey , Encoding encoding)
 {
 TripleDESCryptoServiceProvider DES = new
 TripleDESCryptoServiceProvider();
 MD5CryptoServiceProvider hashMD5 = new MD5CryptoServiceProvider();

 DES.Key = hashMD5.ComputeHash(encoding.GetBytes(a_strKey));
 DES.Mode = CipherMode.ECB;

 ICryptoTransform DESDecrypt = DES.CreateDecryptor();

 string result = "";
 try
 {
 byte[] Buffer = Convert.FromBase64String(a_strString);
 result = encoding.GetString(DESDecrypt.TransformFinalBlock
 (Buffer, 0, Buffer.Length));
 }
 catch(Exception e)
 {
#if DEBUG
 Console.WriteLine("错误：{0}" , e) ;
#endif//DEBUG
 throw(new Exception("Invalid Key or input string is not a valid base64 string" , e)) ;
 }

 return result ;
 }//end method

 }
}

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