DES加密程序代码(带有比较详细的讲解)

此代码分块复制出来后可以直接运行，并且带有部分文件操作，如果嫌麻烦的话，在我的空间代码库里有整理好的代码，可以参考下，上图也不是特别相信，希望大家有选择的看。

一、准备
首先，头文件与宏定义。
C代码

#include "stdio.h"
#include "memory.h"
#include "time.h"
#include "stdlib.h"

#define PLAIN_FILE_OPEN_ERROR -1
#define KEY_FILE_OPEN_ERROR -2
#define CIPHER_FILE_OPEN_ERROR -3
#define OK 1

#include "stdio.h"
#include "memory.h"
#include "time.h"
#include "stdlib.h"

#define PLAIN_FILE_OPEN_ERROR-1
#define KEY_FILE_OPEN_ERROR -2
#define CIPHER_FILE_OPEN_ERROR-3
#define OK 1
其次，对基本数据类型进行typedef。
这句是不可以少的，请养成良好习惯，不然以后如果你要修改基本数据类型，累死你。
C代码

typedef char ElemType;

typedef char ElemType;

而后，是初始置换表，逆初始置换表，S-Box等已知数据。
C代码

//初始置换表IP 明文置换
int IP_Table[64] = { 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,
56,48,40,32,24,16,8,0,
58,50,42,34,26,18,10,2,
60,52,44,36,28,20,12,4,
62,54,46,38,30,22,14,6};
//逆初始置换表IP^-1
int IP_1_Table[64] = {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,
32,0,40,8,48,16,56,24};

//扩充置换表E
int E_Table[48] = {31, 0, 1, 2, 3, 4,
3, 4, 5, 6, 7, 8,
7, 8,9,10,11,12,
11,12,13,14,15,16,
15,16,17,18,19,20,
19,20,21,22,23,24,
23,24,25,26,27,28,
27,28,29,30,31, 0};

//置换函数P S盒出来的32位进行移位
int P_Table[32] = {15,6,19,20,28,11,27,16,
0,14,22,25,4,17,30,9,
1,7,23,13,31,26,2,8,
18,12,29,5,21,10,3,24};

//S盒
int S[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}}};
//置换选择1
int PC_1[56] = {56,48,40,32,24,16,8,
0,57,49,41,33,25,17,
9,1,58,50,42,34,26,
18,10,2,59,51,43,35,
62,54,46,38,30,22,14,
6,61,53,45,37,29,21,
13,5,60,52,44,36,28,
20,12,4,27,19,11,3};

//置换选择2
int PC_2[48] = {13,16,10,23,0,4,2,27,
14,5,20,9,22,18,11,3,
25,7,15,6,26,19,12,1,
40,51,30,36,46,54,29,39,
50,44,32,46,43,48,38,55,
33,52,45,41,49,35,28,31};

//对左移次数的规定
int MOVE_TIMES[16] = {1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1};

//初始置换表IP
int IP_Table[64] = { 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,
56,48,40,32,24,16,8,0,
58,50,42,34,26,18,10,2,
60,52,44,36,28,20,12,4,
62,54,46,38,30,22,14,6};
//逆初始置换表IP^-1
int IP_1_Table[64] ={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,
32,0,40,8,48,16,56,24};

//扩充置换表E
int E_Table[48] = {31, 0, 1, 2,3, 4,
3, 4, 5, 6, 7, 8,
7, 8,9,10,11,12,
11,12,13,14,15,16,
15,16,17,18,19,20,
19,20,21,22,23,24,
23,24,25,26,27,28,
27,28,29,30,31,0};

//置换函数P
int P_Table[32] ={15,6,19,20,28,11,27,16,
0,14,22,25,4,17,30,9,
1,7,23,13,31,26,2,8,
18,12,29,5,21,10,3,24};

//S盒
int S[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}}};
//置换选择1
int PC_1[56] ={56,48,40,32,24,16,8,
0,57,49,41,33,25,17,
9,1,58,50,42,34,26,
18,10,2,59,51,43,35,
62,54,46,38,30,22,14,
6,61,53,45,37,29,21,
13,5,60,52,44,36,28,
20,12,4,27,19,11,3};

//置换选择2
int PC_2[48] ={13,16,10,23,0,4,2,27,
14,5,20,9,22,18,11,3,
25,7,15,6,26,19,12,1,
40,51,30,36,46,54,29,39,
50,44,32,46,43,48,38,55,
33,52,45,41,49,35,28,31};

//对左移次数的规定
int MOVE_TIMES[16] ={1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1};
二、模块化。
对面向过程的程序，模块化是否清晰是至关重要的。
下面是函数的声明：
C代码

int ByteToBit(ElemType ch,ElemType bit[8]);
int BitToByte(ElemType bit[8],ElemType *ch);
int Char8ToBit64(ElemType ch[8],ElemType bit[64]);
int Bit64ToChar8(ElemType bit[64],ElemType ch[8]);
int DES_MakeSubKeys(ElemType key[64],ElemType subKeys[16][48]);
int DES_PC1_Transform(ElemType key[64], ElemType tempbts[56]);
int DES_PC2_Transform(ElemType key[56], ElemType tempbts[48]);
int DES_ROL(ElemType data[56], int time);
int DES_IP_Transform(ElemType data[64]);
int DES_IP_1_Transform(ElemType data[64]);
int DES_E_Transform(ElemType data[48]);
int DES_P_Transform(ElemType data[32]);
int DES_SBOX(ElemType data[48]);
int DES_XOR(ElemType R[48], ElemType L[48],int count);
int DES_Swap(ElemType left[32],ElemType right[32]);
int DES_EncryptBlock(ElemType plainBlock[8], ElemType subKeys[16][48], ElemType cipherBlock[8]);
int DES_DecryptBlock(ElemType cipherBlock[8], ElemType subKeys[16][48], ElemType plainBlock[8]);
int DES_Encrypt(char *plainFile, char *keyStr,char *cipherFile);

int DES_Decrypt(char *cipherFile, char *keyStr,char *plainFile);

int ByteToBit(ElemTypech,ElemType bit[8]);
int BitToByte(ElemTypebit[8],ElemType *ch);
int Char8ToBit64(ElemTypech[8],ElemType bit[64]);
int Bit64ToChar8(ElemTypebit[64],ElemType ch[8]);
int DES_MakeSubKeys(ElemTypekey[64],ElemType subKeys[16][48]);
int DES_PC1_Transform(ElemTypekey[64], ElemType tempbts[56]);
int DES_PC2_Transform(ElemTypekey[56], ElemType tempbts[48]);
int DES_ROL(ElemType data[56],int time);
int DES_IP_Transform(ElemTypedata[64]);
int DES_IP_1_Transform(ElemTypedata[64]);
int DES_E_Transform(ElemTypedata[48]);
int DES_P_Transform(ElemTypedata[32]);
int DES_SBOX(ElemTypedata[48]);
int DES_XOR(ElemType R[48],ElemType L[48],int count);
int DES_Swap(ElemTypeleft[32],ElemType right[32]);
int DES_EncryptBlock(ElemTypeplainBlock[8], ElemType subKeys[16][48], ElemType cipherBlock[8]);
int DES_DecryptBlock(ElemTypecipherBlock[8], ElemType subKeys[16][48], ElemType plainBlock[8]);
int DES_Encrypt(char *plainFile,char *keyStr,char *cipherFile);
int DES_Decrypt(char*cipherFile, char *keyStr,char *plainFile);
其实，模块化与速度也是一对矛盾，因为了解函数运行机制的人就知道，我们的计算机在运行某个函数时，是要用栈来保存入口状态的，在运行结束后又要恢复现场，这些操作势必会影像系统性能，但我们不能将所有代码写在Main函数里，虽然那样做我们的加密算法效率又会大增，但是那种代码未免太过于丑陋不堪。因此，为了帅，还是牺牲一下性能吧。
三、实现。
代码里能用移位操作都尽量用了移位操作，能用逻辑运算符的都用了逻辑运算符。
详细的行注相信你可以看懂吧。有问题可以M我。
C代码

//字节转换成二进制 就是移位，这里是把byte类型转化为bit，其实就是把byte中的每一位分别存放在bit数组中。ch>>cnt，分别向右移动移动0、1、2、、、、7位，然后与1进行&操作，就可以把每位分别取下来
int ByteToBit(ElemType ch, ElemType bit[8]){
int cnt;
for(cnt = 0;cnt < 8; cnt++){
*(bit+cnt) = (ch>>cnt)&1;
}
return 0;
}

//二进制转换成字节
int BitToByte(ElemType bit[8],ElemType *ch){
int cnt;
for(cnt = 0;cnt < 8; cnt++){
*ch |= *(bit + cnt)<<cnt;
}
return 0;
}

//将长度为8的字符串转为二进制位串
int Char8ToBit64(ElemType ch[8],ElemType bit[64]){
int cnt;
for(cnt = 0; cnt < 8; cnt++){
ByteToBit(*(ch+cnt),bit+(cnt<<3));
}
return 0;
}

//将二进制位串转为长度为8的字符串
int Bit64ToChar8(ElemType bit[64],ElemType ch[8]){
int cnt;
memset(ch,0,8);
//原型是extern void *memset(void *buffer, int c, int count)

buffer为指针或是数组,c是赋给buffer的值,count是buffer的长度.

这个函数在socket中多用于清空数组.




for(cnt = 0; cnt < 8; cnt++){
BitToByte(bit+(cnt<<3),ch+cnt);
}
return 0;
}

//生成子密钥
int DES_MakeSubKeys(ElemType key[64],ElemType subKeys[16][48]){ 16行，每行48位
ElemType temp[56];
int cnt;
DES_PC1_Transform(key,temp);//PC1置换,按照PC1表，64位置换成56位
for(cnt = 0; cnt < 16; cnt++){//16轮跌代，产生16个子密钥
DES_ROL(temp,MOVE_TIMES[cnt]);//循环左移
DES_PC2_Transform(temp,subKeys[cnt]);//PC2置换，产生子密钥
}
return 0;
}

//密钥置换1
int DES_PC1_Transform(ElemType key[64], ElemType tempbts[56]){
int cnt;
for(cnt = 0; cnt < 56; cnt++){
tempbts[cnt] = key[PC_1[cnt]];
}
return 0;
}

//密钥置换2
int DES_PC2_Transform(ElemType key[56], ElemType tempbts[48]){
int cnt;
for(cnt = 0; cnt < 48; cnt++){
tempbts[cnt] = key[PC_2[cnt]];
}
return 0;
}

//循环左移
int DES_ROL(ElemType data[56], int time){
ElemType temp[56];

//保存将要循环移动到右边的位 把C0的第一位放temp[0]中
memcpy(temp,data,time);
原型：extern void *memcpy(void *dest, void *src, unsigned int count);

用法：#include <string.h>

功能：由src所指内存区域复制count个字节到dest所指内存区域。

说明：src和dest所指内存区域不能重叠，函数返回指向dest的指针。
memcpy(temp+time,data+28,time); 把D0的第一位放temp[1]中

//前28位移动
memcpy(data,data+time,28-time);
memcpy(data+28-time,temp,time); 把C0的第一位放最右边

//后28位移动
memcpy(data+28,data+28+time,28-time);
memcpy(data+56-time,temp+time,time); 把D0的第一位放最右边

return 0;
}

//IP置换
int DES_IP_Transform(ElemType data[64]){
int cnt;
ElemType temp[64];
for(cnt = 0; cnt < 64; cnt++){
temp[cnt] = data[IP_Table[cnt]];
}
memcpy(data,temp,64);
return 0;
}

//IP逆置换
int DES_IP_1_Transform(ElemType data[64]){
int cnt;
ElemType temp[64];
for(cnt = 0; cnt < 64; cnt++){
temp[cnt] = data[IP_1_Table[cnt]];
}
memcpy(data,temp,64);
return 0;
}

//扩展置换 36扩展到48
int DES_E_Transform(ElemType data[48]){
int cnt;
ElemType temp[48];
for(cnt = 0; cnt < 48; cnt++){
temp[cnt] = data[E_Table[cnt]];
}
memcpy(data,temp,48);
return 0;
}

//P置换 把32位换一下位置
int DES_P_Transform(ElemType data[32]){
int cnt;
ElemType temp[32];
for(cnt = 0; cnt < 32; cnt++){
temp[cnt] = data[P_Table[cnt]];
}
memcpy(data,temp,32);
return 0;
}

//异或 右边32位扩展成48位后与48位密钥异或
int DES_XOR(ElemType R[48], ElemType L[48] ,int count){
int cnt;
for(cnt = 0; cnt < count; cnt++){
R[cnt] ^= L[cnt];
}
return 0;
}

//S盒置换
int DES_SBOX(ElemType data[48]){
int cnt;
int line,row,output;
int cur1,cur2;
for(cnt = 0; cnt < 8; cnt++){
cur1 = cnt*6;
cur2 = cnt<<2;

//计算在S盒中的行与列
line = (data[cur1]<<1) + data[cur1+5]; 左移一位等于乘以2，然后加上第六位得到行
row = (data[cur1+1]<<3) + (data[cur1+2]<<2)
+ (data[cur1+3]<<1) + data[cur1+4]; 23+22+21+20
output = S[cnt][line][row]; output得到一个10进制数，下面要把10进制化成2进制

//化为2进制
data[cur2] = (output&0X08)>>3; 假如 output等于10，二进制为1010，分别与8，4，2，1相与
data[cur2+1] = (output&0X04)>>2;
data[cur2+2] = (output&0X02)>>1;
data[cur2+3] = output&0x01;
}
return 0;
}

//交换
int DES_Swap(ElemType left[32], ElemType right[32]){
ElemType temp[32];
memcpy(temp,left,32);
memcpy(left,right,32);
memcpy(right,temp,32);
return 0;
}

//加密单个分组
int DES_EncryptBlock(ElemType plainBlock[8], ElemType subKeys[16][48], ElemType cipherBlock[8]){
ElemType plainBits[64];
ElemType copyRight[48];
int cnt;

Char8ToBit64(plainBlock,plainBits);
//初始置换（IP置换）
DES_IP_Transform(plainBits);

//16轮迭代
for(cnt = 0; cnt < 16; cnt++){
memcpy(copyRight,plainBits+32,32);
//将右半部分进行扩展置换，从32位扩展到48位
DES_E_Transform(copyRight);
//将右半部分与子密钥进行异或操作
DES_XOR(copyRight,subKeys[cnt],48);
//异或结果进入S盒，输出32位结果
DES_SBOX(copyRight);
//P置换
DES_P_Transform(copyRight);
//将明文左半部分与右半部分进行异或
DES_XOR(plainBits,copyRight,32);
if(cnt != 15){
//最终完成左右部的交换
DES_Swap(plainBits,plainBits+32);
}
}
//逆初始置换（IP^1置换）
DES_IP_1_Transform(plainBits);
Bit64ToChar8(plainBits,cipherBlock);
return 0;
}

//解密单个分组
int DES_DecryptBlock(ElemType cipherBlock[8], ElemType subKeys[16][48],ElemType plainBlock[8]){
ElemType cipherBits[64];
ElemType copyRight[48];
int cnt;

Char8ToBit64(cipherBlock,cipherBits);
//初始置换（IP置换）
DES_IP_Transform(cipherBits);

//16轮迭代
for(cnt = 15; cnt >= 0; cnt--){
memcpy(copyRight,cipherBits+32,32);
//将右半部分进行扩展置换，从32位扩展到48位
DES_E_Transform(copyRight);
//将右半部分与子密钥进行异或操作
DES_XOR(copyRight,subKeys[cnt],48);
//异或结果进入S盒，输出32位结果
DES_SBOX(copyRight);
//P置换
DES_P_Transform(copyRight);
//将明文左半部分与右半部分进行异或
DES_XOR(cipherBits,copyRight,32);
if(cnt != 0){
//最终完成左右部的交换
DES_Swap(cipherBits,cipherBits+32);
}
}
//逆初始置换（IP^1置换）
DES_IP_1_Transform(cipherBits);
Bit64ToChar8(cipherBits,plainBlock);
return 0;
}

//加密文件
int DES_Encrypt(char *plainFile, char *keyStr,char *cipherFile){

FILE *plain,*cipher;
int count;
ElemType plainBlock[8],cipherBlock[8],keyBlock[8];
ElemType bKey[64];
ElemType subKeys[16][48];
if((plain = fopen(plainFile,"rb")) == NULL){
return PLAIN_FILE_OPEN_ERROR;
}
if((cipher = fopen(cipherFile,"wb")) == NULL){
return CIPHER_FILE_OPEN_ERROR;
}
//设置密钥
memcpy(keyBlock,keyStr,8);
//将密钥转换为二进制流
Char8ToBit64(keyBlock,bKey);
//生成子密钥
DES_MakeSubKeys(bKey,subKeys);

while(!feof(plain)){
//每次读8个字节，并返回成功读取的字节数
if((count = fread(plainBlock,sizeof(char),8,plain)) == 8){
DES_EncryptBlock(plainBlock,subKeys,cipherBlock);
fwrite(cipherBlock,sizeof(char),8,cipher);
}
}
if(count){
//填充
memset(plainBlock + count,'\0',7 - count);
//最后一个字符保存包括最后一个字符在内的所填充的字符数量
plainBlock[7] = 8 - count;
DES_EncryptBlock(plainBlock,subKeys,cipherBlock);
fwrite(cipherBlock,sizeof(char),8,cipher);
}
fclose(plain);
fclose(cipher);
return OK;
}

//解密文件
int DES_Decrypt(char *cipherFile, char *keyStr,char *plainFile){

FILE *plain, *cipher;
int count,times = 0;
long fileLen;
ElemType plainBlock[8],cipherBlock[8],keyBlock[8];
ElemType bKey[64];
ElemType subKeys[16][48];
if((cipher = fopen(cipherFile,"rb")) == NULL){
return CIPHER_FILE_OPEN_ERROR;
}
if((plain = fopen(plainFile,"wb")) == NULL){
return PLAIN_FILE_OPEN_ERROR;
}

//设置密钥
memcpy(keyBlock,keyStr,8);
//将密钥转换为二进制流
Char8ToBit64(keyBlock,bKey);
//生成子密钥
DES_MakeSubKeys(bKey,subKeys);

//取文件长度
fseek(cipher,0,SEEK_END); //将文件指针置尾
fileLen = ftell(cipher); //取文件指针当前位置
rewind(cipher); //将文件指针重指向文件头
while(1){
//密文的字节数一定是8的整数倍
fread(cipherBlock,sizeof(char),8,cipher);
DES_DecryptBlock(cipherBlock,subKeys,plainBlock);
times += 8;
if(times < fileLen){
fwrite(plainBlock,sizeof(char),8,plain);
}
else{
break;
}
}
//判断末尾是否被填充
if(plainBlock[7] < 8){
for(count = 8 - plainBlock[7]; count < 7; count++){
if(plainBlock[count] != '\0'){
break;
}
}
}
if(count == 7){//有填充
fwrite(plainBlock,sizeof(char),8 - plainBlock[7],plain);
}
else{//无填充
fwrite(plainBlock,sizeof(char),8,plain);
}

fclose(plain);
fclose(cipher);
return OK;
}

//字节转换成二进制
int ByteToBit(ElemType ch,ElemType bit[8]){
int cnt;
for(cnt = 0;cnt < 8; cnt++){
*(bit+cnt) = (ch>>cnt)&1;
}
return 0;
}

//二进制转换成字节
int BitToByte(ElemTypebit[8],ElemType *ch){
int cnt;
for(cnt = 0;cnt < 8; cnt++){
*ch |= *(bit + cnt)<<cnt;
}
return 0;
}

//将长度为8的字符串转为二进制位串
int Char8ToBit64(ElemTypech[8],ElemType bit[64]){
int cnt;
for(cnt = 0; cnt < 8; cnt++){
ByteToBit(*(ch+cnt),bit+(cnt<<3));
}
return 0;
}

//将二进制位串转为长度为8的字符串
int Bit64ToChar8(ElemTypebit[64],ElemType ch[8]){
int cnt;
memset(ch,0,8);
for(cnt = 0; cnt < 8; cnt++){
BitToByte(bit+(cnt<<3),ch+cnt);
}
return 0;
}

//生成子密钥
int DES_MakeSubKeys(ElemTypekey[64],ElemType subKeys[16][48]){
ElemType temp[56];
int cnt;
DES_PC1_Transform(key,temp);//PC1置换
for(cnt = 0; cnt < 16; cnt++){//16轮跌代，产生16个子密钥
DES_ROL(temp,MOVE_TIMES[cnt]);//循环左移
DES_PC2_Transform(temp,subKeys[cnt]);//PC2置换，产生子密钥
}
return 0;
}

//密钥置换1
int DES_PC1_Transform(ElemTypekey[64], ElemType tempbts[56]){
int cnt;
for(cnt = 0; cnt < 56; cnt++){
tempbts[cnt] = key[PC_1[cnt]];
}
return 0;
}

//密钥置换2
int DES_PC2_Transform(ElemTypekey[56], ElemType tempbts[48]){
int cnt;
for(cnt = 0; cnt < 48; cnt++){
tempbts[cnt] = key[PC_2[cnt]];
}
return 0;
}

//循环左移
int DES_ROL(ElemType data[56],int time){
ElemType temp[56];

//保存将要循环移动到右边的位
memcpy(temp,data,time);
memcpy(temp+time,data+28,time);

//前28位移动
memcpy(data,data+time,28-time);
memcpy(data+28-time,temp,time);

//后28位移动
memcpy(data+28,data+28+time,28-time);
memcpy(data+56-time,temp+time,time);

return 0;
}

//IP置换
int DES_IP_Transform(ElemTypedata[64]){
int cnt;
ElemType temp[64];
for(cnt = 0; cnt < 64; cnt++){
temp[cnt] = data[IP_Table[cnt]];
}
memcpy(data,temp,64);
return 0;
}

//IP逆置换
int DES_IP_1_Transform(ElemTypedata[64]){
int cnt;
ElemType temp[64];
for(cnt = 0; cnt < 64; cnt++){
temp[cnt] = data[IP_1_Table[cnt]];
}
memcpy(data,temp,64);
return 0;
}

//扩展置换
int DES_E_Transform(ElemTypedata[48]){
int cnt;
ElemType temp[48];
for(cnt = 0; cnt < 48; cnt++){
temp[cnt] = data[E_Table[cnt]];
}
memcpy(data,temp,48);
return 0;
}

//P置换
int DES_P_Transform(ElemTypedata[32]){
int cnt;
ElemType temp[32];
for(cnt = 0; cnt < 32; cnt++){
temp[cnt] = data[P_Table[cnt]];
}
memcpy(data,temp,32);
return 0;
}

//异或
int DES_XOR(ElemType R[48],ElemType L[48] ,int count){
int cnt;
for(cnt = 0; cnt < count; cnt++){
R[cnt] ^= L[cnt];
}
return 0;
}

//S盒置换
int DES_SBOX(ElemTypedata[48]){
int cnt;
int line,row,output;
int cur1,cur2;
for(cnt = 0; cnt < 8; cnt++){
cur1 = cnt*6;
cur2 = cnt<<2;

//计算在S盒中的行与列
line = (data[cur1]<<1) + data[cur1+5];
row = (data[cur1+1]<<3) + (data[cur1+2]<<2)
+ (data[cur1+3]<<1) + data[cur1+4];
output = S[cnt][line][row];

//化为2进制
data[cur2] = (output&0X08)>>3;
data[cur2+1] = (output&0X04)>>2;
data[cur2+2] = (output&0X02)>>1;
data[cur2+3] = output&0x01;
}
return 0;
}

//交换
int DES_Swap(ElemType left[32],ElemType right[32]){
ElemType temp[32];
memcpy(temp,left,32);
memcpy(left,right,32);
memcpy(right,temp,32);
return 0;
}

//加密单个分组
int DES_EncryptBlock(ElemTypeplainBlock[8], ElemType subKeys[16][48], ElemType cipherBlock[8]){
ElemType plainBits[64];
ElemType copyRight[48];
int cnt;

Char8ToBit64(plainBlock,plainBits);
//初始置换（IP置换）
DES_IP_Transform(plainBits);

//16轮迭代
for(cnt = 0; cnt < 16; cnt++){
memcpy(copyRight,plainBits+32,32);
//将右半部分进行扩展置换，从32位扩展到48位
DES_E_Transform(copyRight);
//将右半部分与子密钥进行异或操作
DES_XOR(copyRight,subKeys[cnt],48);
//异或结果进入S盒，输出32位结果
DES_SBOX(copyRight);
//P置换
DES_P_Transform(copyRight);
//将明文左半部分与右半部分进行异或
DES_XOR(plainBits,copyRight,32);
if(cnt != 15){
//最终完成左右部的交换
DES_Swap(plainBits,plainBits+32);
}
}
//逆初始置换（IP^1置换）
DES_IP_1_Transform(plainBits);
Bit64ToChar8(plainBits,cipherBlock);
return 0;
}

//解密单个分组
int DES_DecryptBlock(ElemTypecipherBlock[8], ElemType subKeys[16][48],ElemType plainBlock[8]){
ElemType cipherBits[64];
ElemType copyRight[48];
int cnt;

Char8ToBit64(cipherBlock,cipherBits);
//初始置换（IP置换）
DES_IP_Transform(cipherBits);

//16轮迭代
for(cnt = 15; cnt >= 0; cnt--){
memcpy(copyRight,cipherBits+32,32);
//将右半部分进行扩展置换，从32位扩展到48位
DES_E_Transform(copyRight);
//将右半部分与子密钥进行异或操作
DES_XOR(copyRight,subKeys[cnt],48);
//异或结果进入S盒，输出32位结果
DES_SBOX(copyRight);
//P置换
DES_P_Transform(copyRight);
//将明文左半部分与右半部分进行异或
DES_XOR(cipherBits,copyRight,32);
if(cnt != 0){
//最终完成左右部的交换
DES_Swap(cipherBits,cipherBits+32);
}
}
//逆初始置换（IP^1置换）
DES_IP_1_Transform(cipherBits);
Bit64ToChar8(cipherBits,plainBlock);
return 0;
}

//加密文件
int DES_Encrypt(char*plainFile, char *keyStr,char *cipherFile){
FILE *plain,*cipher;
int count;
ElemType plainBlock[8],cipherBlock[8],keyBlock[8];
ElemType bKey[64];
ElemType subKeys[16][48];
if((plain = fopen(plainFile,"rb")) == NULL){
return PLAIN_FILE_OPEN_ERROR;
}
if((cipher = fopen(cipherFile,"wb")) == NULL){
return CIPHER_FILE_OPEN_ERROR;
}
//设置密钥
memcpy(keyBlock,keyStr,8);
//将密钥转换为二进制流
Char8ToBit64(keyBlock,bKey);
//生成子密钥
DES_MakeSubKeys(bKey,subKeys);

while(!feof(plain)){
//每次读8个字节，并返回成功读取的字节数
if((count = fread(plainBlock,sizeof(char),8,plain)) == 8){
DES_EncryptBlock(plainBlock,subKeys,cipherBlock);
fwrite(cipherBlock,sizeof(char),8,cipher);
}
}
if(count){
//填充
memset(plainBlock + count,'\0',7 - count);
//最后一个字符保存包括最后一个字符在内的所填充的字符数量
plainBlock[7] = 8 - count;
DES_EncryptBlock(plainBlock,subKeys,cipherBlock);
fwrite(cipherBlock,sizeof(char),8,cipher);
}
fclose(plain);
fclose(cipher);
return OK;
}

//解密文件
int DES_Decrypt(char*cipherFile, char *keyStr,char *plainFile){
FILE *plain, *cipher;
int count,times = 0;
long fileLen;
ElemType plainBlock[8],cipherBlock[8],keyBlock[8];
ElemType bKey[64];
ElemType subKeys[16][48];
if((cipher = fopen(cipherFile,"rb")) == NULL){
return CIPHER_FILE_OPEN_ERROR;
}
if((plain = fopen(plainFile,"wb")) == NULL){
return PLAIN_FILE_OPEN_ERROR;
}

//设置密钥
memcpy(keyBlock,keyStr,8);
//将密钥转换为二进制流
Char8ToBit64(keyBlock,bKey);
//生成子密钥
DES_MakeSubKeys(bKey,subKeys);

//取文件长度
fseek(cipher,0,SEEK_END); //将文件指针置尾
fileLen = ftell(cipher); //取文件指针当前位置
rewind(cipher); //将文件指针重指向文件头
while(1){
//密文的字节数一定是8的整数倍
fread(cipherBlock,sizeof(char),8,cipher);
DES_DecryptBlock(cipherBlock,subKeys,plainBlock);
times += 8;
if(times < fileLen){
fwrite(plainBlock,sizeof(char),8,plain);
}
else{
break;
}
}
//判断末尾是否被填充
if(plainBlock[7] < 8){
for(count = 8 - plainBlock[7]; count < 7; count++){
if(plainBlock[count] != '\0'){
break;
}
}
}
if(count == 7){//有填充
fwrite(plainBlock,sizeof(char),8 - plainBlock[7],plain);
}
else{//无填充
fwrite(plainBlock,sizeof(char),8,plain);
}

fclose(plain);
fclose(cipher);
return OK;
}
最后，写一个简单的main函数来检验它：
C代码

int main()
{
clock_t a,b;
a = clock();
DES_Encrypt("1.txt","key.txt","2.txt");
b = clock();
printf("加密消耗%d毫秒\n",b-a);

system("pause");
a = clock();
DES_Decrypt("2.txt","key.txt","3.txt");
b = clock();
printf("解密消耗%d毫秒\n",b-a);
getchar();
return 0;
}

int main()
{
clock_t a,b;
a = clock();
DES_Encrypt("1.txt","key.txt","2.txt");
b = clock();
printf("加密消耗%d毫秒\n",b-a);

system("pause");
a = clock();
DES_Decrypt("2.txt","key.txt","3.txt");
b = clock();
printf("解密消耗%d毫秒\n",b-a);
getchar();
return 0;
}
运行结果就不重要了，自己去弄几个文件放工程目录下检验去吧。
至此，整个实现完成。该算法在1.79GHZ的CPU上测试的速度是850KB/S。不过大家别过分在代码上追求速度，做到我以上提到的（舍弃动态内存分配）就足够了，况且，这样做也是在加密算法的程序并不复杂的情况下，如果是一个复杂的系统，那么另当别论，更不必过分到连模块化都不要，那样的代码只会让人觉得丑陋，没人愿意维护。加密算法与CPU的运转速度是成线性关系的。随着双核以及多核CPU的出现，硬件的改善讲会成倍的加快算法的运行速度。