C#设计模式系列 3 Strategy 策略模式 之007大破密码危机

   1.理论定义

       策略模式 定义了 多套算法，这些算法在 客户端 可以任意切换。

   2.应用举例

          需求描述：话说007在皇家赌场赌牌，突然接到M夫人的急电，要求立刻去非洲 寻找一个DES对称算法密钥，以破解敌人的军*情*机*密

　        　1、(英*国*军*情*六*局)MI6=Military Intelligence 6  截获了 一个非*洲战*区军*事*机*密文件，采用 MD5，RAS，加密，解密，都无法破解
　　           后来发现，这文件被DES加密， 必须找回对称密钥，才可以破解
　　        2、邦德 火速赶往 非洲，目标只有一个：找到密钥。

   3.具体编码

      1.定义安全 算法接口，里面有加密和解密方法

      

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Com.Design.Gof.Strategy
{
    public interface ISecurity
    {
        /// <summary>
        /// 加密
        /// </summary>
        /// <param name="EncryptString">要加密字符串</param>
        /// <returns></returns>
        string Encrypt(string EncryptString);
        /// <summary>
        /// 解密
        /// </summary>
        /// <param name="EncryptString">要解密字符串</param>
        /// <returns></returns>
        string Decrypt(string EncryptString);
    }
}

2.MD5加密

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Security.Cryptography;
namespace Com.Design.Gof.Strategy
{
    public class MD5 : ISecurity
    {
        /// <summary>
        /// 用MD5加密
        /// </summary>
        /// <param name="s"></param>
        /// <returns></returns>
        public  string Encrypt(string s)
        {
            byte[] b = Encoding.Default.GetBytes(s);
            b = new MD5CryptoServiceProvider().ComputeHash(b);
            string output = "";
            for (int i = 0; i < b.Length; i++)
                output += b[i].ToString("x").PadLeft(2, '0');
            return output;
        }
        /// <summary>
        /// MD5不提供解密
        /// </summary>
        /// <param name="EncryptString"></param>
        /// <returns></returns>
        public virtual string Decrypt(string EncryptString) { return string.Empty; }
    }

}

3.RSA加密

using System;
using System.Text;
using System.IO;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
namespace Com.Design.Gof.Strategy
{
    public class RSA:ISecurity
    {
        private static readonly string key=new RSACryptoServiceProvider().ToXmlString(true);
      
        /// <summary>
        /// RSA加密函数
        /// </summary>
        /// <param name="xmlPublicKey">说明:KEY必须是XML的行式,返回的是字符串</param>
        /// <param name="EncryptString"></param>
        /// <returns></returns>
        public string Encrypt(string s)
        {
            try
            {
                byte[] PlainTextBArray;
                byte[] CypherTextBArray;
                string Result;
                RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
                rsa.FromXmlString(key);
                PlainTextBArray = (new UnicodeEncoding()).GetBytes(s);
                CypherTextBArray = rsa.Encrypt(PlainTextBArray, false);
                Result = Convert.ToBase64String(CypherTextBArray);
                return Result;
            }
            catch { return "敌人密码太难破解，已经超过了RSA算法的承受能力，要采取分段加密"; }
        }
        /// <summary>
        /// RSA解密函数
        /// </summary>
        /// <param name="xmlPrivateKey"></param>
        /// <param name="DecryptString"></param>
        /// <returns></returns>
        public string Decrypt(string s)
        {
             try
            {
            byte[] PlainTextBArray;
            byte[] DypherTextBArray;
            string Result;
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(key);
            PlainTextBArray = Convert.FromBase64String(s);
            DypherTextBArray = rsa.Decrypt(PlainTextBArray, false);
            Result = (new UnicodeEncoding()).GetString(DypherTextBArray);
            return Result;
            }
             catch { return "敌人密码太难破解，已经超过了RSA算法的承受能力，要采取分段解密"; }
        }

    }

}

4.DES加密

using System;
using System.Text;
using System.IO;
using System.Security.Cryptography;
 /// <summary>
///MethodResult 的摘要说明
/// </summary>
namespace Com.Design.Gof.Strategy
{

    public class DES:ISecurity
    {
        private static byte[] IV = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF }; //密钥向量
        //加密解密key
        public string SymmetricKey { get; set; }
        /// <summary>
        /// 加密
        /// </summary>
        /// <param name="EncryptString">待加密的字符串</param>
        /// <param name="EncryptKey">加密密钥</param>
        /// <returns>加密成功返回加密后的字符串,失败返回源串</returns>
        public  string Encrypt(string EncryptString)
        {
            byte[] byKey = null;
            byKey = System.Text.Encoding.UTF8.GetBytes(SymmetricKey.Substring(0, 8));
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            byte[] inputByteArray = System.Text.Encoding.UTF8.GetBytes(EncryptString);
            MemoryStream ms = new MemoryStream();
            CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(byKey, IV), CryptoStreamMode.Write);
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();
            return Convert.ToBase64String(ms.ToArray());
        }

        /// <summary>
        /// 解密
        /// </summary>
        /// <param name="EncryptString">待解密的字符串</param>
        /// <returns>解密成功返回解密后的字符串,失败返源串</returns>
        public  string Decrypt(string EncryptString)
        {
            byte[] byKey = null;
            byte[] inputByteArray = new Byte[EncryptString.Length];
            try
            {
                byKey = System.Text.Encoding.UTF8.GetBytes(SymmetricKey.Substring(0, 8));
                DESCryptoServiceProvider des = new DESCryptoServiceProvider();
                inputByteArray = Convert.FromBase64String(EncryptString);
                MemoryStream ms = new MemoryStream();
                CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(byKey, IV), CryptoStreamMode.Write);
                cs.Write(inputByteArray, 0, inputByteArray.Length);
                cs.FlushFinalBlock();
                System.Text.Encoding encoding = new System.Text.UTF8Encoding();
                return encoding.GetString(ms.ToArray());
            }
            catch
            {
                return "";
            }
        }

   
    }

}

5 (英*国*军*情*六*局)MI6=Military Intelligence 6

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Com.Design.Gof.Strategy
{
    /// <summary>
    /// (英*国*军*情*六*局)MI6=Military Intelligence 6
    /// </summary>
    public class MilitaryIntelligence6
    {/// <summary>
        /// 安全策略
        /// </summary>
        private ISecurity Security { get; set; }
        /// <summary>
        /// 被加密的军*情*信*息
        /// </summary>
        public string ClassifiedInfomation { get; set; }
        /// <summary>
        /// 加密
        /// </summary>
        /// <param name="s"></param>
        /// <returns></returns>
        public string Encrypt() {
            return Security.Encrypt(ClassifiedInfomation);
        }
        /// <summary>
        /// 解密
        /// </summary>
        /// <param name="s"></param>
        /// <returns></returns>
        public string Decrypt(string s) {
            return Security.Decrypt(s);
        }
    }
}

6.主函数

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Com.Design.Gof.Strategy;
namespace Com.Design.Gof.Test
{
    class Program
    {
        /// <summary>
        /// 往期 设计模式测试项目是一起的，想测试谁，就调用谁
        /// </summary>
        /// <param name="args"></param>
        static void Main(string[] args)
        {
            MilitaryIntelligence6 MI6= new MilitaryIntelligence6
            {
                //默认密码策略 MD5
                 Security = new MD5(),
                //被加密的  军*情*信*息
                ClassifiedInfomation = @"+30/SxY2HZ0UtqUVNGMsad0zfajsHQmja1NVC+639zC6y0dE/8XDZJefMl0NwBJ+sUA8LC8k/IPEeTtFqW6OWaaZH9A+TNWzrJ6MSV2qiM3px6wFAyDkJsMKex0mJNe5",
            };
            //用 MD5 破解
            string result_md5 = MI6.Encrypt();
            Console.WriteLine("用MD5破解敌*人机密文件：" + result_md5);
            Console.WriteLine("MD5加密后，还是一团乱麻，机密文件无法破解");
            Console.WriteLine();

            //用 RSA  破解
            MI6.Security = new RSA();
            string Result_RSA = MI6.Encrypt();
            Console.WriteLine(Result_RSA);
           
            //用 DES 破解
            string symmetricKey = "AfricaArea";//007完成使命，拿到了密钥

            MI6.Security = new DES { SymmetricKey = symmetricKey };
         
            //解密后的内容应该是：军-情-机-密-信-息:我军将要攻打 非*洲，战区指挥官：隆美尔，坦克：500辆，飞机：2000架
            Console.WriteLine();
            Console.WriteLine("007获取到了DES解密密码，打开了 军-事-机-密文件，内容如下：" + MI6.Decrypt(MI6.ClassifiedInfomation));
            Console.ReadKey();
        }

    }
}

7.运行结果

8.总结

  RSA算法还值得进一步去看下，字符过长时候，如何进行分段加密。

 借鉴了 孤狼晖 的意见，去除了 枚举和 Switch，直接在客户端New 算法。

  附件里面包括了程序源码。

  这里是附件下载(Download)