DES是一个16轮的Feistel型结构密码，它的分组长度为64比特，用一个56比特的密钥来加密一个64比特的明文串，输出一个64比特的密文串。其中，使用密钥为64比特，实用56比特，另8位用作奇偶校验。加密的过程是先对64位明文分组进行初始置换，然后分左、右两部分分别经过16轮迭代，然后再进行循环移位与变换，最后进行逆变换得出密文。加密与解密使用相同的密钥，因而它属于对称密码体制。假设输入的明文数据是64比特。首先经过初始置换IP后把其左半部分32比特记为L0，右半部分32比特记为R0，即成了置换后的输入；然后把R0与密钥产生器产生的子密钥k1进行运算，其结果计为f (R0,k1);再与L0进行摸2加得到L0+f (R0 , k1), 把R0记为L1放在左边，而把L0+f (R0 , k1)记为R1放在右边，从而完成了第一轮迭代运算。在此基础上，重复上述的迭代过程，一直迭代至第16轮。所得的第16轮迭代结果左右不交换，即L15+f (R15 , k16)记为R16,放在左边，而R15记为L16放在右边，成为预输出，最后经过初始置换的逆置换IP-1运算后得到密文。详细的算法解析在网上有很多，笔者在这里就不一一介绍，核心处理在于f函数，编程过程中谨慎一点儿别抄错数字之类的，一般都没问题。解密过程是加密的逆向，只需要在加密过程中把十六轮子秘钥全部记录下来，在解密时反过来使用一轮，其他的处理算法如出一辙，就能正确得出结果。直接在下面贴出代码（代码有局限，只能接受十六位十六进制数作为明文，十六位十六进制数作为初始秘钥，对于中文的加密以及任意长度的字符串的加密，有需要的朋友可以自行修改代码实现）。初始秘钥和明文从文件中读取，会在后面附上截图。
// DES.cpp : 此文件包含 "main" 函数。程序执行将在此处开始并结束。
//
#include "pch.h"
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
//记录所有的子秘钥
int eachKey[16][48];
int boxS[8][4][16] = { //S1
{ {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}
},
//S2
{ {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}
},
//S3
{ {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}
},
//S4
{ {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}
},
//S5
{ {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}
},
//S6
{ {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}
},
//S7
{ {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}
},
//S8
{ {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}
}
};
//记录左移次数
int leftMove[16] = { 1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1 };
int C[28] = { 0 }, D[28] = { 0 };
int L[32] = { 1 }, R[32] = { 1 };
//p置换
int P[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};
//E扩展
int biteChoiceLabel[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};
//秘钥置换
int keySwap[8][6] = { {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} };
//密文初始置换
int IP[8][8] = { {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 }};
//密文逆置换
int IP_1[8][8] = { {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} };
//64->56选择
int PC_1[8][7] = { {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} };
//初始置换IP
void InitIP(int **input) {
int s[64];
int c = 0;
for(int i = 0;i<8;i++)
for (int j = 0; j < 8; j++) {
s[c++] = input[i][j];
}
int **newIP = new int *[8];
for (int i = 0; i < 8; i++)
newIP[i] = new int[8];
for (int i = 0; i < 8; i++) {
for (int j = 0; j < 8; j++) {
int loc = IP[i][j] - 1; //因为从1开始，这里下标减一
newIP[i][j] = s[loc];
}
}
int l = 0, m = 0;
for(int i = 0;i < 8;i++)
for (int j = 0; j < 8; j++) {
if (i * 8 + j < 32)
L[l++] = newIP[i][j];
else
R[m++] = newIP[i][j];
}
}
//逆初始置换
void reverse() {
int temp[64];
int a[64];
for (int i = 0; i < 32; i++) {
temp[i] = L[i];
temp[i + 32] = R[i];
}
int l = 0, m = 0;
for (int i = 0; i < 8; i++) {
for (int j = 0; j < 8; j++) {
a[l++] = temp[IP_1[i][j] - 1];
}
}
l = 0;
for (int i = 0; i < 64; i++)
if (i < 32)
L[l++] = a[i];
else
R[m++] = a[i];
}
//操作函数f
int *f(int n, int flag) {
int *result = new int[32];
int a[48];
int temp[56];
int newKey[48];
for (int i = 0; i < 28; i++) {
temp[i] = C[i];
temp[i + 28] = D[i];
}
int l = 0;
if (flag == 0) {
for (int i = 0; i < 8; i++) {
for (int j = 0; j < 6; j++) {
int loc = keySwap[i][j];
newKey[l++] = temp[loc - 1];
eachKey[15-n][l - 1] = newKey[l - 1]; //记录加密时的全部子秘钥
}
}
}
else {
for (int i = 0; i < 48; i++)
newKey[i] = eachKey[n][i];
}
int newR[48];
for (int i = 0; i < 48; i++)
newR[i] = R[biteChoiceLabel[i]-1];
for (int i = 0; i < 48; i++)
a[i] = (newKey[i]+newR[i])%2;
int b[8][6];
int r[8];
l = 0;
int m = 0;
int k = 0;
for (int i = 0; i < 48; i++) {
b[l][m] = a[i];
if ((i + 1) % 6 == 0) {
int first = b[l][0] * 2 + b[l][5];
int second = b[l][1] * 8 + b[l][2] * 4 + b[l][3] * 2 + b[l][4];
r[l] = boxS[l][first][second];
l++;
m = 0;
}
else
m++;
}
int c[8][4];
l = 0;
for (int i = 0; i < 8; i++) {
int ti = 0;
int aa = r[i] / 8;
int bb = (r[i] - aa * 8) / 4;
int cc = (r[i] - aa * 8 - bb * 4) / 2;
int dd = r[i] - aa * 8 - bb * 4 - cc * 2;
c[i][0] = aa;
c[i][1] = bb;
c[i][2] = cc;
c[i][3] = dd;
}
int tempP[32];
for (int i = 0; i < 8; i++)
for (int j = 0; j < 4; j++) {
tempP[l++] = c[i][j];
}
for (int i = 0; i < 32; i++)
result[i] = tempP[P[i] - 1];
return result;
}
//交换处理
void swap(int n, int flag) {
int tempL[32], tempR[32];
int *Result = new int[32];
//数据备份
for (int i = 0; i < 32; i++) {
tempR[i] = R[i];
tempL[i] = L[i];
}
Result = f(n, flag);
//数据更新计
for (int i = 0; i < 32; i++) {
L[i] = tempR[i];
R[i] = (tempL[i] + Result[i]) % 2;
}
if (n == 15) {
for (int i = 0; i < 32; i++) {
int temp = L[i];
L[i] = R[i];
R[i] = temp;
}
}
}
//产生第一轮秘钥（64位->56位)
int **firstKey(int **key) {
int **fk = new int *[8];
for (int i = 0; i < 8; i++)
fk[i] = new int[7];
int nk[64];
int s = 0;
int l = 0, m = 0;
for (int i = 0; i < 8; i++)
for (int j = 0; j < 8; j++)
nk[s++] = key[i][j];
for (int i = 0; i < 8; i++) {
for (int j = 0; j < 7; j++) {
int loc = PC_1[i][j] - 1;
fk[i][j] = nk[loc];
if (l < 28)
C[l++] = nk[loc];
else
D[m++] = nk[loc];
}
}
return fk;
}
//循环产生子秘钥
void nextKeyLeft(int n) {
int times = leftMove[n];
for (int i = 0; i < times; i++) {
int C0 = C[0];
int D0 = D[0];
for (int j = 1; j < 28; j++) {
C[j - 1] = C[j];
D[j - 1] = D[j];
}
C[27] = C0;
D[27] = D0;
}
}
//十六进制输入转二进制
int **hxTobin(string input) {
int a[64];
int x[16];
int **init_letters = new int *[8];
for (int i = 0; i < 8; i++)
init_letters[i] = new int[8];
int j = 0;
for (int i = 0; i < 16; i++) {
if (input[i] >= '0' && input[i] <= '9')
x[i] = input[i] - 48;
else if (input[i] >= 'A' && input[i] <= 'Z')
x[i] = input[i] - 55;
else
x[i] = input[i] - 87;
}
for (int i = 0; i < 16; i++) {
int aa = x[i] / 8;
int bb = (x[i] - aa * 8) / 4;
int cc = (x[i] - aa * 8 - bb * 4) / 2;
int dd = x[i] - aa * 8 - bb * 4 - cc * 2;
a[j] = aa;
a[j + 1] = bb;
a[j + 2] = cc;
a[j + 3] = dd;
j = j + 4;
}
int l = 0;
for (int i = 0; i < 8; i++) {
for (j = 0; j < 8; j++) {
init_letters[i][j] = a[l++];
}
}
return init_letters;
}
//二进制密文转十六进制密文
string binTohx(int a[]) {
string res;
res.resize(16);
int j = 0;
for (int i = 0; i < 64; i+=4) {
int b = a[i] * 8 + a[i + 1] * 4 + a[i + 2] * 2 + a[i + 3];
if (b < 10)
res[j] = b+'0';
else{
switch (b) {
case 10:
res[j] = 'a';
break;
case 11:
res[j] = 'b';
break;
case 12:
res[j] = 'c';
break;
case 13:
res[j] = 'd';
break;
case 14:
res[j] = 'e';
break;
case 15:
res[j] = 'f';
break;
}
}
j++;
}
return res;
}
//解密过程
void decode(string res) {
int **re = new int *[8];
for (int i = 0; i < 8; i++)
re[i] = new int[8];
re = hxTobin(res);
InitIP(re);
for (int i = 0; i < 16; i++) {
swap(i, 1);
}
reverse();
int a[64];
for (int i = 0; i < 32; i++) {
a[i] = L[i];
a[i + 32] = R[i];
}
string input;
input = binTohx(a);
std::cout << input << endl << endl;;
}
int main()
{
string letters;
string keys;
string words;
char flag='n';
int miwen[64];
ifstream file;
file.open("test.txt");
int **fir = new int *[8];
for (int i = 0; i < 8; i++)
fir[i] = new int[8];
cout << "--------- Begin(y/n)? ----------" << endl;
cin >> flag;
while (flag == 'y' &&!file.eof()) {
std::cout << "---------- 读入密文: ----------" << endl;
if (!file) {
std::cout << "---------- 读取失败 ----------" << endl;
exit(0);
}
getline(file, letters);
std::cout << "明文: " << letters << endl << endl;
std::cout << "---------- 读入秘钥: ----------" << endl;
getline(file, keys);
std::cout << "秘钥: " << keys << endl << endl;
fir = hxTobin(keys);
int **getLetters = new int *[8];
for (int i = 0; i < 8; i++)
getLetters[i] = new int[8];
getLetters = hxTobin(letters);
InitIP(getLetters);
int **fk = new int *[8];
for (int i = 0; i < 8; i++)
fk[i] = new int[7];
for (int i = 0; i <= 16; i++) {
if (i == 0) {
fk = firstKey(fir);
}
else {
nextKeyLeft(i - 1);
swap(i - 1, 0);
}
}
reverse();
int k = 0;
for (int i = 0; i < 32; i++) {
miwen[k++] = L[i];
}
for (int i = 0; i < 32; i++) {
miwen[k++] = R[i];
}
words = binTohx(miwen);
std::cout << "密文: " << words << endl;
std::cout << "---------- 解密中 ----------" << endl;
decode(words);
std::cout << "----------- 继续(y/n) ---------" << endl;
std::cin >> flag;
}
std::cout << "---------- End! ----------" << endl;
return 0;
}
测试数据如下图：奇数行是明文，偶数行是对应的测试秘钥
运行截图：
尊重原作，转载请注明，转载自：https://blog.csdn.net/kr2563