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);
}
}
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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; }
}
}
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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"; }
}
}
}
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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 "";
}
}
}
}
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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);
}
}
}
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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();
}
}
}
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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