本文实例讲述了c#设计模式之strategy策略模式解决007大破密码危机问题。分享给大家供大家参考，具体如下：
一、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。
二、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。
三、具体编码
1.定义安全 算法接口，里面有加密和解密方法
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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
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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
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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
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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
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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
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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：完整实例代码点击此处本站下载。
希望本文所述对大家c#程序设计有所帮助。
原文链接：http://www.cnblogs.com/HCCZX/archive/2012/08/01/2618078.html
