算法介绍

DES算法为密码体制中的对称密码体制，又被称为美国数据加密标准，是1972年美国公司研制的对称密码体制加密算法。 明文按64位进行分组，密钥长64位，密钥事实上是56位参与DES运算(第8、16、24、32、40、48、56、64位是校验位， 使得每个密钥都有奇数个1)分组后的明文组和56位的密钥按位替代或交换的方法形成密文组的加密方。

实现代码

DES密码算法用C语言实现如下：

//头文件、宏定义
#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  
    
//使用typedef定义基本数据
typedef char ElemType; 

//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PC-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PC-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};  

//模块化操作：对功能函数进行声明
int ByteToBit(ElemType ch,ElemType bit[8]);                     //字节转换成二进制  
int BitToByte(ElemType bit[8],ElemType *ch);					//二进制转换成字节  
int Char8ToBit64(ElemType ch[8],ElemType bit[64]);			    //将长度为8的字符串转为二进制位串 
int Bit64ToChar8(ElemType bit[64],ElemType ch[8]);				//将二进制位串转为长度为8的字符串 
int DES_MakeSubKeys(ElemType key[64],ElemType subKeys[16][48]); //生成子密钥  
int DES_PC1_Transform(ElemType key[64], ElemType tempbts[56]);  //密钥置换1 
int DES_PC2_Transform(ElemType key[56], ElemType tempbts[48]);  //密钥置换2  
int DES_ROL(ElemType data[56], int time);						//循环左移  
int DES_IP_Transform(ElemType data[64]);						//IP置换  
int DES_IP_1_Transform(ElemType data[64]);						//IP逆置换  
int DES_E_Transform(ElemType data[48]);							//扩展置换  
int DES_P_Transform(ElemType data[32]);							//P置换 
int DES_SBOX(ElemType data[48]);								//异或 
int DES_XOR(ElemType R[48], ElemType L[48],int count);			//S盒置换  
int DES_Swap(ElemType left[32],ElemType right[32]);				//交换 
int DES_EncryptBlock(ElemType plainBlock[8], ElemType subKeys[16][48], ElemType cipherBlock[8]);  //加密单个分组    
int DES_DecryptBlock(ElemType cipherBlock[8], ElemType subKeys[16][48], ElemType plainBlock[8]);  //解密单个分组 
int DES_Encrypt(char *plainFile, char *keyStr,char *cipherFile);  //加密文件 
int DES_Decrypt(char *cipherFile, char *keyStr,char *plainFile);  //解密文件 

//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PC_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PC_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;  
}  

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;  
}   

算法演示

Step 1：文件1.txt中存储明文信息

5469875321456045

Step 2：Key.txt文件中存储秘钥信息

5987423651456987

Step 3：运行程序

Step 4:文件2.txt存储加密后的信息

文件3.txt存储解密后的信息