DES c++ 密码学实验-优快云博客

本文链接：https://blog.youkuaiyun.com/AEliauk/article/details/121253684
#include <iostream>
#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
/*---------------- DES的置换表 ------------------*/ 
// 初始置换IP 
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};
 
// 逆初始置换IP_1
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};
			  
// 选择扩展运算E，(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};
 
// 置换运算P
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 };
		   
/*----------------------DES的S盒定义---------------------*/ 
// 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}  
	} 
};

/*------------------DES密钥编排中使用的表-----------------*/
// 置换选择1，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}; 
 
// 置换选择2，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};
 
// 左循环移位位数 
int shiftBits[] = {1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1};

// 加密函数f 
bitset<32> f(bitset<32> R, bitset<48> k)
{
	bitset<48> expandR;  
	// 第一步：扩展/置换(E表)，32 -> 48
	for(int i=0; i<48; ++i) expandR[i] = R[E[i]-1];
	// 第二步：异或
	expandR = expandR ^ k;
	// 第三步：代换/选择(S盒) 48 -> 32 
	bitset<32> output;
	for(int i=0, j=0; i<48; i+=6,j+=6)
	{
		int row = expandR[i]*2 + expandR[i+5]; //
		int col = expandR[i+1]*8 + expandR[i+2]*4 + expandR[i+3]*2 + expandR[i+4];
		int num = S_BOX[i/6][row][col];
		for(int k=j;num;k++,num>>=1) output[k]=num&1 ;
	}
	// 第四步：P-置换，32 -> 32
	bitset<32> tmp = output;
	for(int i=0; i<32; i++) output[i] = tmp[P[i]-1];
	return output;
}
 
// 对56位密钥的前后部分进行左移
bitset<28> leftShift(bitset<28> k, int shift)
{
	return (k<<shift)|(k>>(28-shift));
}

// 生成16个48位的子密钥保存到subkey中 
void generateKeys()
{
	bitset<28> left;
	bitset<28> right;
	// 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] = key[i];
		for(int i=0; i<28; ++i) right[i] = key[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=0; i<28; ++i) key[i+28] = left[i];
		for(int i=0; i<28; ++i) key[i] = right[i];
		for(int i=0; i<48; ++i) subKey[round][47-i] = key[56 - PC_2[i]];
	}
}


// 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;
}
 
 
/************************** 主程序 **********************************/
int main() {
	string s;
	string k = "ncu@2021";
	// 初始化密钥 
	key = charToBitset(k.c_str());
	// 生成16个子密钥
	generateKeys();   
	printf("请输入明文：") ; 
	cin >> s ;
	bitset<64> plain = charToBitset(s.c_str());
 	bitset<64> cipher = encrypt(plain);
 	cout << "明文为：" << plain << endl;
 	cout << "密文为：" << cipher << endl; 
 	bitset<64> temp_plain = decrypt(cipher);
 	cout << "解密为：" << temp_plain << endl;
 	
	return 0;
}