加密|字符串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:  Bigeagle163.net</br>
    ///
Date:    2001/09/25</br>
    ///
History: 2001/10/25 finished</br>
    /// </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


    }
}