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工厂方法模式

本次实验属于模仿型实验，通过本次实验学生将掌握以下内容：

1、理解工厂方法模式的动机，掌握该模式的结构；

2、能够利用工厂方法模式解决实际问题。

 

[实验任务一]：加密算法

目前常用的加密算法有DES（Data Encryption Standard）和IDEA（International Data Encryption Algorithm）国际数据加密算法等，请用工厂方法实现加密算法系统。

C++版

#include <iostream>
#include <fstream>
#include <bitset>
#include <string>
using namespace std;

bitset<64> key; // 64位密钥
bitset<48> subKey[16]; // 存放16轮子密钥

// 初始置换表
int IP[] = {58, 50, 42, 34, 26, 18, 10, 2,
60, 52, 44, 36, 28, 20, 12, 4,
62, 54, 46, 38, 30, 22, 14, 6,
64, 56, 48, 40, 32, 24, 16, 8,
57, 49, 41, 33, 25, 17, 9, 1,
59, 51, 43, 35, 27, 19, 11, 3,
61, 53, 45, 37, 29, 21, 13, 5,
63, 55, 47, 39, 31, 23, 15, 7};

// 结尾置换表
int IP_1[] = {40, 8, 48, 16, 56, 24, 64, 32,
39, 7, 47, 15, 55, 23, 63, 31,
38, 6, 46, 14, 54, 22, 62, 30,
37, 5, 45, 13, 53, 21, 61, 29,
36, 4, 44, 12, 52, 20, 60, 28,
35, 3, 43, 11, 51, 19, 59, 27,
34, 2, 42, 10, 50, 18, 58, 26,
33, 1, 41, 9, 49, 17, 57, 25};

/*------------------下面是生成密钥所用表-----------------*/

// 密钥置换表，将64位密钥变成56位
int PC_1[] = {57, 49, 41, 33, 25, 17, 9,
1, 58, 50, 42, 34, 26, 18,
10, 2, 59, 51, 43, 35, 27,
19, 11, 3, 60, 52, 44, 36,
63, 55, 47, 39, 31, 23, 15,
7, 62, 54, 46, 38, 30, 22,
14, 6, 61, 53, 45, 37, 29,
21, 13, 5, 28, 20, 12, 4};

// 压缩置换，将56位密钥压缩成48位子密钥
int PC_2[] = {14, 17, 11, 24, 1, 5,
3, 28, 15, 6, 21, 10,
23, 19, 12, 4, 26, 8,
16, 7, 27, 20, 13, 2,
41, 52, 31, 37, 47, 55,
30, 40, 51, 45, 33, 48,
44, 49, 39, 56, 34, 53,
46, 42, 50, 36, 29, 32};

// 每轮左移的位数
int shiftBits[] = {1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1};

/*------------------下面是密码函数 f 所用表-----------------*/

// 扩展置换表，将 32位 扩展至 48位
int E[] = {32, 1, 2, 3, 4, 5,
4, 5, 6, 7, 8, 9,
8, 9, 10, 11, 12, 13,
12, 13, 14, 15, 16, 17,
16, 17, 18, 19, 20, 21,
20, 21, 22, 23, 24, 25,
24, 25, 26, 27, 28, 29,
28, 29, 30, 31, 32, 1};

// S盒，每个S盒是4x16的置换表，6位 -> 4位
int S_BOX[8][4][16] = {
{
{14,4,13,1,2,15,11,8,3,10,6,12,5,9,0,7},
{0,15,7,4,14,2,13,1,10,6,12,11,9,5,3,8},
{4,1,14,8,13,6,2,11,15,12,9,7,3,10,5,0},
{15,12,8,2,4,9,1,7,5,11,3,14,10,0,6,13}
},
{
{15,1,8,14,6,11,3,4,9,7,2,13,12,0,5,10},
{3,13,4,7,15,2,8,14,12,0,1,10,6,9,11,5},
{0,14,7,11,10,4,13,1,5,8,12,6,9,3,2,15},
{13,8,10,1,3,15,4,2,11,6,7,12,0,5,14,9}
},
{
{10,0,9,14,6,3,15,5,1,13,12,7,11,4,2,8},
{13,7,0,9,3,4,6,10,2,8,5,14,12,11,15,1},
{13,6,4,9,8,15,3,0,11,1,2,12,5,10,14,7},
{1,10,13,0,6,9,8,7,4,15,14,3,11,5,2,12}
},
{
{7,13,14,3,0,6,9,10,1,2,8,5,11,12,4,15},
{13,8,11,5,6,15,0,3,4,7,2,12,1,10,14,9},
{10,6,9,0,12,11,7,13,15,1,3,14,5,2,8,4},
{3,15,0,6,10,1,13,8,9,4,5,11,12,7,2,14}
},
{
{2,12,4,1,7,10,11,6,8,5,3,15,13,0,14,9},
{14,11,2,12,4,7,13,1,5,0,15,10,3,9,8,6},
{4,2,1,11,10,13,7,8,15,9,12,5,6,3,0,14},
{11,8,12,7,1,14,2,13,6,15,0,9,10,4,5,3}
},
{
{12,1,10,15,9,2,6,8,0,13,3,4,14,7,5,11},
{10,15,4,2,7,12,9,5,6,1,13,14,0,11,3,8},
{9,14,15,5,2,8,12,3,7,0,4,10,1,13,11,6},
{4,3,2,12,9,5,15,10,11,14,1,7,6,0,8,13}
},
{
{4,11,2,14,15,0,8,13,3,12,9,7,5,10,6,1},
{13,0,11,7,4,9,1,10,14,3,5,12,2,15,8,6},
{1,4,11,13,12,3,7,14,10,15,6,8,0,5,9,2},
{6,11,13,8,1,4,10,7,9,5,0,15,14,2,3,12}
},
{
{13,2,8,4,6,15,11,1,10,9,3,14,5,0,12,7},
{1,15,13,8,10,3,7,4,12,5,6,11,0,14,9,2},
{7,11,4,1,9,12,14,2,0,6,10,13,15,3,5,8},
{2,1,14,7,4,10,8,13,15,12,9,0,3,5,6,11}
}
};

// P置换，32位 -> 32位
int P[] = {16, 7, 20, 21,
29, 12, 28, 17,
1, 15, 23, 26,
5, 18, 31, 10,
2, 8, 24, 14,
32, 27, 3, 9,
19, 13, 30, 6,
22, 11, 4, 25 };

/**********************************************************************/
/* */
/* 下面是DES算法实现 */
/* */
/**********************************************************************/

/**
* 密码函数f，接收32位数据和48位子密钥，产生一个32位的输出
*/
bitset<32> f(bitset<32> R, bitset<48> k)
{
bitset<48> expandR;
// 第一步：扩展置换，32 -> 48
for(int i=0; i<48; ++i)
expandR[47-i] = R[32-E[i]];
// 第二步：异或
expandR = expandR ^ k;
// 第三步：查找S_BOX置换表
bitset<32> output;
int x = 0;
for(int i=0; i<48; i=i+6)
{
int row = expandR[47-i]*2 + expandR[47-i-5];
int col = expandR[47-i-1]*8 + expandR[47-i-2]*4 + expandR[47-i-3]*2 + expandR[47-i-4];
int num = S_BOX[i/6][row][col];
bitset<4> binary(num);
output[31-x] = binary[3];
output[31-x-1] = binary[2];
output[31-x-2] = binary[1];
output[31-x-3] = binary[0];
x += 4;
}
// 第四步：P-置换，32 -> 32
bitset<32> tmp = output;
for(int i=0; i<32; ++i)
output[31-i] = tmp[32-P[i]];
return output;
}

/**
* 对56位密钥的前后部分进行左移
*/
bitset<28> leftShift(bitset<28> k, int shift)
{
bitset<28> tmp = k;
for(int i=27; i>=0; --i)
{
if(i-shift<0)
k[i] = tmp[i-shift+28];
else
k[i] = tmp[i-shift];
}
return k;
}

/**
* 生成16个48位的子密钥
*/
void generateKeys()
{
bitset<56> realKey;
bitset<28> left;
bitset<28> right;
bitset<48> compressKey;
// 去掉奇偶标记位，将64位密钥变成56位
for (int i=0; i<56; ++i)
realKey[55-i] = key[64 - PC_1[i]];
// 生成子密钥，保存在 subKeys[16] 中
for(int round=0; round<16; ++round)
{
// 前28位与后28位
for(int i=28; i<56; ++i)
left[i-28] = realKey[i];
for(int i=0; i<28; ++i)
right[i] = realKey[i];
// 左移
left = leftShift(left, shiftBits[round]);
right = leftShift(right, shiftBits[round]);
// 压缩置换，由56位得到48位子密钥
for(int i=28; i<56; ++i)
realKey[i] = left[i-28];
for(int i=0; i<28; ++i)
realKey[i] = right[i];
for(int i=0; i<48; ++i)
compressKey[47-i] = realKey[56 - PC_2[i]];
subKey[round] = compressKey;
}
}

/**
* 工具函数：将char字符数组转为二进制
*/
bitset<64> charToBitset(const char s[8])
{
bitset<64> bits;
for(int i=0; i<8; ++i)
for(int j=0; j<8; ++j)
bits[i*8+j] = ((s[i]>>j) & 1);
return bits;
}

/**
* DES加密
*/
bitset<64> encrypt(bitset<64>& plain)
{
bitset<64> cipher;
bitset<64> currentBits;
bitset<32> left;
bitset<32> right;
bitset<32> newLeft;
// 第一步：初始置换IP
for(int i=0; i<64; ++i)
currentBits[63-i] = plain[64-IP[i]];
// 第二步：获取 Li 和 Ri
for(int i=32; i<64; ++i)
left[i-32] = currentBits[i];
for(int i=0; i<32; ++i)
right[i] = currentBits[i];
// 第三步：共16轮迭代
for(int round=0; round<16; ++round)
{
newLeft = right;
right = left ^ f(right,subKey[round]);
left = newLeft;
}
// 第四步：合并L16和R16，注意合并为 R16L16
for(int i=0; i<32; ++i)
cipher[i] = left[i];
for(int i=32; i<64; ++i)
cipher[i] = right[i-32];
// 第五步：结尾置换IP-1
currentBits = cipher;
for(int i=0; i<64; ++i)
cipher[63-i] = currentBits[64-IP_1[i]];
// 返回密文
return cipher;
}

/**
* DES解密
*/
bitset<64> decrypt(bitset<64>& cipher)
{
bitset<64> plain;
bitset<64> currentBits;
bitset<32> left;
bitset<32> right;
bitset<32> newLeft;
// 第一步：初始置换IP
for(int i=0; i<64; ++i)
currentBits[63-i] = cipher[64-IP[i]];
// 第二步：获取 Li 和 Ri
for(int i=32; i<64; ++i)
left[i-32] = currentBits[i];
for(int i=0; i<32; ++i)
right[i] = currentBits[i];
// 第三步：共16轮迭代（子密钥逆序应用）
for(int round=0; round<16; ++round)
{
newLeft = right;
right = left ^ f(right,subKey[15-round]);
left = newLeft;
}
// 第四步：合并L16和R16，注意合并为 R16L16
for(int i=0; i<32; ++i)
plain[i] = left[i];
for(int i=32; i<64; ++i)
plain[i] = right[i-32];
// 第五步：结尾置换IP-1
currentBits = plain;
for(int i=0; i<64; ++i)
plain[63-i] = currentBits[64-IP_1[i]];
// 返回明文
return plain;
}

/**********************************************************************/
/* 测试： */
/* 1.将一个 64 位的字符串加密， 把密文写入文件 a.txt */
/* 2.读取文件 a.txt 获得 64 位密文，解密之后再写入 b.txt */
/**********************************************************************/

int main() {
string s = "romantic";
string k = "12345678";
bitset<64> plain = charToBitset(s.c_str());
key = charToBitset(k.c_str());
// 生成16个子密钥
generateKeys();
// 密文写入 a.txt
bitset<64> cipher = encrypt(plain);
fstream file1;
file1.open("C:\\Users\\Lenovo\\Desktop\\test\\a.txt", ios::binary | ios::out);
file1.write((char*)&cipher,sizeof(cipher));
file1.close();

// 读文件 a.txt
bitset<64> temp;
file1.open("C:\\Users\\Lenovo\\Desktop\\test\\a.txt", ios::binary | ios::in);
file1.read((char*)&temp, sizeof(temp));
file1.close();

// 解密，并写入文件 b.txt
bitset<64> temp_plain = decrypt(temp);
file1.open("C:\\Users\\Lenovo\\Desktop\\test\\b.txt", ios::binary | ios::out);
file1.write((char*)&temp_plain,sizeof(temp_plain));
file1.close();

return 0;
}