DES加密算法—实现(C语言)

DES（Data Encrypt Standard数据库加密标准）是迄今为止使用最广泛的加密体制。

初学信息安全的新生，一般都会被老师要求实现DES算法，如果老师不要求，那么有缘来我这里共同学习的朋友，我建议你用C去实现一下，C语言在信息安全领域很重要，更何况隶属于工科的信息安全，你只懂理论是远远不够的。

想用其他语言实现的朋友，如果你用了汇编，那么请您老人家走开不要来看小弟的笑话。如果你用C++或者JAVA，那么我劝您用C吧，因为2年前本人计算过速度，在我的机器上，同样的代码，用C++新建的工程要比用C新建的工程慢了2倍。至于JAVA，我估计要慢10倍。

废话不多说，DES算法的理论我就不聒噪了，想要了解其实现的人，如果不懂其理论就来看这文章，即便是看懂了也会走火入魔，或者是某位学生心怀不轨。

一个加密算法的实现，最最重要的关键词是—速度。

举个例子来说明，速度对加密算法的重要：假设我们实现了两个加密算法DES1.0和DES2.0，其中DES1.0的速度为900KB/S，DES2.0的速度为1000KB/S。假设一个文件有10G，我需要对其进行加密，那么，用DES1.0所耗费的时间为1111s，DES2.0的速度为1000S。DES2.0比DES1.0快了111秒。现实生活里我们要加密的数据还可能远远不止10G。

不要小看这111S，要知道，让CPU尽可能的为用户服务，是我们每一个程序员的职责，不论你是用C，C++还是JAVA。

因此，为了速度，我们必须舍弃一些东西。

有的同学喜欢用动态数组，因为这也是个好东西，可以节约空间，于是有人认为用了动态数组的程序比不用动态数组的程序要高了好几级。

动态数组貌似高深，但如果你用在加密算法里，我只能说这位同学啊你真是吃力不讨好，在计算机世界里，往往静态的东西就是比动态的东西速度要快。

在此我首先声明，如果你不是在练习结构体和malloc/calloc的使用，那么请你果断舍弃这些在加密算法里华而不实的东西。

好了，说了这么多，各位看官都等急了吧，下面我就结合DES算法原理来分步骤讲解我的代码。

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
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};

 //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(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);

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
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);
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]){
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(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
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(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
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
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
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];
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(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(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);
	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]){
	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(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
	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(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
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
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
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];
		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(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;
}

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。

http://www.iteye.com/topic/478024

posted @ 2012-04-24 17:03 wbzhao 阅读(8761) 评论(0) 编辑收藏举报

刷新页面返回顶部

DES加密算法—实现(C语言)

公告