Question

如何用C实现3DES算法..

C实现3DES算法..

Answer 1

//功能：实现DES及3DES加解密的算法

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "des.h"

//函数声明
int Do_DES(char* strSrc, char* strKey, char* strDest, char flag);
int Do_3DES(char* strSrc, char* strKey, char* strDest, char flag);

//主函数
int main(int argc, char** argv)
{
char src16[16+1],key16[16+1],key48[48+1],dest16[16+1];

if(argc != 3)
{
fprintf(stderr,"Usage: [%s -e|-d s|3]\n",argv[0]);
exit(1);
}

if(strcmp(argv[2],"-s") == 0)
{
if(strcmp(argv[1],"-e") == 0)
{
fprintf(stderr,"Please input the string that you want to encrypt(16 hex number):\n");
memset(src16,0,sizeof(src16));
scanf("%s",src16);
fprintf(stderr,"Please input the Key string(16 hex number):\n");
memset(key16,0,sizeof(key16));
scanf("%s",key16);
memset(dest16,0,sizeof(dest16));
Do_DES(src16,key16,dest16,'e');
fprintf(stderr,"Result: [%s]\n",dest16);
}
else if(strcmp(argv[1],"-d") == 0)
{
fprintf(stderr,"Please input the string that you want to decrypt(16 hex number):\n");
memset(src16,0,sizeof(src16));
scanf("%s",src16);
fprintf(stderr,"Please input the Key string(16 hex number):\n");
memset(key16,0,sizeof(key16));
scanf("%s",key16);
memset(dest16,0,sizeof(dest16));
Do_DES(src16,key16,dest16,'d');
fprintf(stderr,"Result: [%s]\n",dest16);
}
else
return -1;
}
else if(strcmp(argv[2],"-3") == 0)
{
if(strcmp(argv[1],"-e") == 0)
{
fprintf(stderr,"Please input the string that you want to encrypt(16 hex number):\n");
memset(src16,0,sizeof(src16));
scanf("%s",src16);
fprintf(stderr,"Please input the Key string(16 hex number):\n");
memset(key48,0,sizeof(key48));
scanf("%s",key48);
memset(dest16,0,sizeof(dest16));
Do_3DES(src16,key48,dest16,'e');
fprintf(stderr,"Result: [%s]\n",dest16);
}
else if(strcmp(argv[1],"-d") == 0)
{
fprintf(stderr,"Please input the string that you want to decrypt(16 hex number):\n");
memset(src16,0,sizeof(src16));
scanf("%s",src16);
fprintf(stderr,"Please input the Key string(16 hex number):\n");
memset(key48,0,sizeof(key48));
scanf("%s",key48);
memset(dest16,0,sizeof(dest16));
Do_3DES(src16,key48,dest16,'d');
fprintf(stderr,"Result: [%s]\n",dest16);
}
else
return -1;
}
else
return -1;

return 0;
}

//做DES加密或解密运算
int Do_DES(char* strSrc, char* strKey, char* strDest, char flag)
{
int i,j;
unsigned char subKey[16][48+1],byte8[8+1],bits[64+1],strTmp[64+1];
unsigned char L0[32+1],R0[32+1],Lx[32+1],Rx[32+1];

if(!( flag == 'e' || flag == 'E' || flag == 'd' || flag == 'D'))
return -1;
if(strSrc == NULL || strKey == NULL)
return -2;

if(flag == 'e' || flag == 'E')
{
memset(byte8,0,sizeof(byte8));
BCDToByte(strKey, 16, byte8);
memset(bits,0,sizeof(bits));
ByteToBit(byte8, 8, bits);

Des_GenSubKey(bits,subKey);

BCDToByte(strSrc, 16, byte8);
ByteToBit(byte8, 8, bits);
Des_IP(bits, strTmp);
memcpy(L0,strTmp,32);
memcpy(R0,strTmp+32,32);

for(i=0;i<16;i++)
{
memcpy(Lx,R0,32);
Des_F(R0,subKey[i],Rx);
Do_XOR(L0,32,Rx);
memcpy(L0,Lx,32);
memcpy(R0,Rx,32);
}
memcpy(bits,R0,32);
memcpy(bits+32,L0,32);
Des_IP_1(bits,strTmp);
BitToByte(strTmp,64,byte8);
ByteToBCD(byte8,8,strDest);
}
else
{
memset(byte8,0,sizeof(byte8));
BCDToByte(strKey, 16, byte8);
memset(bits,0,sizeof(bits));
ByteToBit(byte8, 8, bits);

Des_GenSubKey(bits,subKey);

BCDToByte(strSrc, 16, byte8);
ByteToBit(byte8, 8, bits);
Des_IP(bits, strTmp);
memcpy(L0,strTmp,32);
memcpy(R0,strTmp+32,32);

for(i=0;i<16;i++)
{
memcpy(Lx,R0,32);
Des_F(R0,subKey[15-i],Rx);
Do_XOR(L0,32,Rx);
memcpy(L0,Lx,32);
memcpy(R0,Rx,32);
}
memcpy(bits,R0,32);
memcpy(bits+32,L0,32);
Des_IP_1(bits,strTmp);
BitToByte(strTmp,64,byte8);
ByteToBCD(byte8,8,strDest);
}

return 0;
}

//做3DES加密或解密运算
int Do_3DES(char* strSrc, char* strKey, char* strDest, char flag)
{
unsigned char strBCDKey[32+1],strByteKey[16+1];
unsigned char strMidDest1[16+1],strMidDest2[16+1];
unsigned char strLKey[16+1],strMKey[16+1],strRKey[16+1];

if(!( flag == 'e' || flag == 'E' || flag == 'd' || flag == 'D'))
return -1;
if(strSrc == NULL || strKey == NULL)
return -2;

if(strlen(strKey) < 32)
return -3;

if(flag == 'e' || flag == 'E')
{
memset(strBCDKey,0,sizeof(strBCDKey));
memcpy(strBCDKey,strKey,32);

memset(strLKey,0,sizeof(strLKey));
memcpy(strLKey,strBCDKey,16);
memset(strRKey,0,sizeof(strRKey));
memcpy(strRKey,strBCDKey+16,16);

Do_DES(strSrc,strLKey,strMidDest1,'e');
Do_DES(strMidDest1,strRKey,strMidDest2,'d');
Do_DES(strMidDest2,strLKey,strMidDest1,'e');

memcpy(strDest,strMidDest1,16);
}
else
{
memset(strBCDKey,0,sizeof(strBCDKey));
memcpy(strBCDKey,strKey,32);

memset(strLKey,0,sizeof(strLKey));
memcpy(strLKey,strBCDKey,16);
memset(strRKey,0,sizeof(strRKey));
memcpy(strRKey,strBCDKey+16,16);

Do_DES(strSrc,strLKey,strMidDest1,'d');
Do_DES(strMidDest1,strRKey,strMidDest2,'e');
Do_DES(strMidDest2,strLKey,strMidDest1,'d');

memcpy(strDest,strMidDest1,16);
}

return 0;
}

Answer 2

3DES算法C语言实现，有注释! http://tech.cuit.edu.cn/forum/thread-2448-1-1.html