c++实现DES加密算法

涉及到非常多的数组变换，使用vector数组向量能很好的解决动态数组大小的问题。

#include <iostream>
#include <algorithm>
#include <string>
#include <cmath>
#include <vector>
#include <cstddef>
#include <functional>
#include <numeric>

using namespace std;

vector<int> no_rp;
vector<int> fi_rp;
vector<int> key64;
vector<int> key56;
vector<int> key48;
vector<int> L;
vector<int> R;
vector<int> L1;
vector<int> R1;
vector<int> C;
vector<int> D;
vector<int> aftersbox_P;
vector<int> temp;
vector<int> result;

void get_plaintxt() {
	string input;
	cout << "请输入明文：(1101100101101111110110100101111001011111011010110011101100000110)" << endl;
	cin >> input;
	for (char digit : input) {
		if (isdigit(digit)) {
			no_rp.push_back(digit - '0');
		}
	}
}

void first_exchange() {
	int ip[64] = {
		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 };
	for (int i = 0;i < 64;i++) {
		fi_rp.push_back(no_rp[ip[i] - 1]);
	}
	for (int i = 0;i < 64;i++) {
		if (i < 32) {
			L.push_back(fi_rp[i]);
		}
		else {
			R.push_back(fi_rp[i]);
		}
	}
}

void get_key() {
	string input;
	cout << "请输入密钥：（00010010 00111101 10101011 01110111 10011111 01100101 10000000 01100111）" << endl;
	cin >> input;
	for (char digit : input) {
		if (isdigit(digit)) {
			key64.push_back(digit - '0');
		}
	}
	int PC1[56] = {
		57,49,41,33,25,17,9,1,
		58,50,42,34,26,18,10,2,
		59,51,43,35,27,19,11,3,
		60,52,44,36,28,20,12,4,
		61,53,45,37,29,21,13,5,
		62,54,46,38,30,22,14,6,
		63,55,47,39,31,23,15,7 };
	for (int i = 0;i < 56;i++) {
		key56.push_back(key64[PC1[i] - 1]);
		if (i < 28) {
			C.push_back(key56[i]);
		}
		else {
			D.push_back(key56[i]);
		}
	}
}

void loop(int n) {
	int tempc = C[0];
	int tempd = D[0];
	int ls[16] = {
		1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1
	};
	for (int i = 0;i < C.size() - 1;i++) {
		C[i] = C[i + ls[n]];
	}
	for (int i = 0;i < D.size() - 1;i++) {
		D[i] = D[i + ls[n]];
	}
	C[C.size() - 1] = tempc;
	D[D.size() - 1] = tempd;
}

void PC2() {
	int PC2[48] = {
		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,
	};
	for (int i = 0;i < 48;i++) {
		if (i < 24) {
			key48.push_back(C[PC2[i] - 1]);
		}
		else {
			key48.push_back(D[PC2[i] - 29]);
		}
	}
}

int two_ten(int a) {
	if (a <= 11) {
		int b = a / 10;
		int c = a - b * 10;
		return c + b * 2;
	}
	else {
		int b = a / 1000;
		int c = a / 100 - b * 10;
		int d = a / 10 - b * 100 - c * 10;
		int e = a - b * 1000 - c * 100 - d * 10;
		return e + d * 2 + c * 4 + b * 8;
	}
}

string ten_two(int a) {
	string ret = "";
	while (a != 0) {
		int temp = a % 2;
		ret = to_string(temp) + ret;
		a /= 2;
	}
	while (ret.length() < 4)
		ret = "0" + ret;
	return ret;
}

void S_BOX(int* PC2E, vector<int>& aftersbox) {
	int sbox[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}
	};
	
	for (int i = 1;i <= 8;i++) {
		int tempx = PC2E[i * 6 - 5] * 1000 + PC2E[i * 6 - 4] * 100 + PC2E[i * 6 - 3] * 10 + PC2E[i * 6 - 2];
		int tempy = PC2E[i * 6 - 6] * 10 + PC2E[i * 6 - 1];
		string get_sbox = ten_two(sbox[two_ten(tempy)][two_ten(tempx)]);
		for (char a : get_sbox) {
			if (isdigit(a)) {
				aftersbox.push_back(a - '0');
			}
		}
	}
}

void wheel_func() {
	int E[48] = {
		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,
	};
	int PC2E[48];
	vector<int> aftersbox;
	for (int i = 0;i < 48;i++) {
		R1.push_back(R[E[i] - 1]);
	}
	for (int i = 0;i < 48;i++) {
		PC2E[i] = bit_xor<int>()(R1[i], E[i]);
	}
	S_BOX(PC2E, aftersbox);
	int P_BOX[32] = {
		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
	};
	for (int i = 0;i < 32;i++) {
		aftersbox_P.push_back(aftersbox[P_BOX[i] - 1]);
	}
}

void second_change() {
	int IP_1[64] = {
		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
	};
	for (int i = 0;i < 64;i++) {
		if (i < 32) {
			temp.push_back(L[i]);
		}
		else {
			temp.push_back(R[i - 32]);
		}
	}
	for (int i = 0;i < 64;i++) {
		result.push_back(temp[IP_1[i] - 1]);
	}
}

int main() {
	get_plaintxt();
	first_exchange();
	get_key();
	for (int i = 0;i < 16;i++) {
		loop(i);
		PC2();
		wheel_func();
		int temp = -1;
		for (int j = 0;j < 32;j++) {
			temp = R[j];
			R[j] = bit_xor<int>()(L[j], aftersbox_P[j]);
			L[j] = temp;
		}
	}
	second_change();
	cout << "密文为：" << endl;
	for (int i : result) {
		cout << i;
	}
	return 0;
}