des是对称算法，加密的密钥和解码的密钥是相同的，对于des有两种方案，ecb和cbc。值得注意ecb每次只能对一组数据进行加密，即8位的数据进行加密。cbc则对指定的长度的数据进行加密。
本文测算下ecb和cbc的执行时间对比.
cbc：
#include <openssl/des.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/time.h>
long get_mesl() {
struct timeval tv;
gettimeofday(&tv,NULL);
return tv.tv_sec*1000 + tv.tv_usec/1000;
}
long get_trick() {
struct timeval tv;
gettimeofday(&tv,NULL);
return tv.tv_sec*1000000 + tv.tv_usec;
}
void get_key(DES_cblock *key, unsigned char *keystring) {
if (keystring) {
DES_string_to_key(keystring, key);
} else {
DES_random_key(key);
}
}
int main(int argc, char** argv)
{
unsigned char *keystring = "secrct key text word";
DES_cblock key;
DES_key_schedule key_schedule;
get_key(&key, keystring);
if (DES_set_key_checked(&key, &key_schedule) != 0) {
printf("convert to key_schedule failed.\n");
return -1;
}
int klen = strlen(key);
for (int i = 0; i < klen; ++i)
printf("%02X ", key[i]);
printf("\n");
printf("klen:%d\n", klen);
//需要加密的字符串
unsigned char input[] = "this is a text being encrypted by openssl. this is a text being encrypted by openssl. this is a text being encrypted by openssl. this is a text being encrypted by openssl. this is a text being encrypted by openssl.this is a text being encrypted by openssl. this is a text being encrypted by openssl. this is a text being encrypted by openssl. this is a text being encrypted by openssl. this is a text being encrypted by openssl.";
printf("slen:%d\n", strlen(input));
size_t len = (sizeof(input)+7)/8 * 8;
unsigned char *output = malloc(len+1);
//IV
DES_cblock ivec;
//IV设置为0x0000000000000000
memset((char*)&ivec, 0, sizeof(ivec));
//加密
long start = get_trick();
DES_ncbc_encrypt(input, output, sizeof(input), &key_schedule, &ivec, DES_ENCRYPT);
long spend = get_trick() - start;
printf("encrypt spend:%ld\n", spend);
printf("dlen:%d\n", strlen(output));
//输出加密以后的内容
for (int i = 0; i < len; ++i)
printf("%02X", output[i]);
printf("\n");
memset((char*)&ivec, 0, sizeof(ivec));
//解密
start = get_trick();
DES_ncbc_encrypt(output, input, len, &key_schedule, &ivec, 0);
spend = get_trick() - start;
printf("decrypt spend:%ld\n", spend);
printf("%s\n", input);
free(output);
return EXIT_SUCCESS;
}
ecb:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/time.h>
#include <openssl/des.h>
long get_mesl() {
struct timeval tv;
gettimeofday(&tv,NULL);
return tv.tv_sec*1000 + tv.tv_usec/1000;
}
long get_trick() {
struct timeval tv;
gettimeofday(&tv,NULL);
return tv.tv_sec*1000000 + tv.tv_usec;
}
int main(int argc,char **argv)
{
DES_cblock key;
//随机密钥
DES_random_key(&key);
DES_key_schedule schedule;
//转换成schedule
DES_set_key_checked(&key, &schedule);
const_DES_cblock input = "hehehe";
DES_cblock output;
printf("cleartext: %s\n", input);
//加密
long start = get_trick();
DES_ecb_encrypt(&input, &output, &schedule, DES_ENCRYPT);
long spend = get_trick() - start;
printf("encrypt spend:%ld\n", spend);
//printf("Encrypted!\n");
printf("ciphertext: ");
int i;
for (i = 0; i < sizeof(input); i++)
printf("%02x", output[i]);
printf("\n");
//解密
start = get_trick();
DES_ecb_encrypt(&output, &input, &schedule, DES_DECRYPT);
spend = get_trick() - start;
printf("decrypt spend:%ld\n", spend);
printf("cleartext:%s\n", input);
return 0;
}
注意在gcc编译时要加上-lcrypto，引入openssl的动态库。
