des_pro.c

redhat Linux下DES算法加密的一个例子。

#include "des_pro.h"

static int load_key(char *key_file)
{
  FILE *fp;
  int   id,len,ret,key_len;
  char *buf[512];
  struct keys *gen_key;
  fp=fopen(key_file,"rb");
  key_len=fread(buf,1,512,fp);
  fclose(fp);
  gen_key = (struct keys *)buf;
  
  bcopy(gen_key->key, key, EVP_MAX_KEY_LENGTH);
  bcopy(gen_key->iv, iv, EVP_MAX_IV_LENGTH);
}


/**
 * 产生一个KEY和
 * IV
 */
static void generate_pk(char *key_file)
{
	struct keys gen_key;
	FILE *fp;
	int   id,len,ret,key_len;
	RAND_bytes(key, EVP_MAX_KEY_LENGTH);
	RAND_pseudo_bytes(iv, EVP_MAX_IV_LENGTH);
	bcopy(key,gen_key.key, EVP_MAX_KEY_LENGTH);
	bcopy(iv, gen_key.iv, EVP_MAX_IV_LENGTH);
	fp=fopen(key_file,"wb");
	key_len=fwrite((char *)&gen_key,1, sizeof(struct keys),fp);
	fclose(fp);
}
/**
 * 解密函数
 * 
 */
static char *des_decrypt(unsigned char *data,int len, int *out_len)
{
	int tem;
	EVP_DecryptInit(&ctx,EVP_des_cbc(),key,iv);
	
	unsigned char *pt = (unsigned char*)malloc(len+EVP_CIPHER_CTX_block_size(&ctx)+1);   
	EVP_DecryptUpdate(&ctx,pt,&tem,data,len);
	*out_len = tem - pt[tem-1];
	return pt;
}

static char *des_encrypt(unsigned char *data,int len, int *out_len)
{
	int tmp,ol=0;
	EVP_EncryptInit(&ctx, EVP_des_cbc(),key,iv);
	unsigned char *ret = (unsigned char*)malloc(len+EVP_CIPHER_CTX_block_size(&ctx));
	EVP_EncryptUpdate(&ctx,&ret[ol],&tmp,&data[ol],len);
	ol +=tmp;
	EVP_EncryptFinal(&ctx,&ret[ol], out_len);
	*out_len = ol + tmp;
	return ret;
}
/***********例子*************/
int main()
{
	int src_len,en_len=0,de_len=0;
	char *pstr = "http://www.163.com/qq",*rtns;
	
	rtns = (unsigned char*)malloc(1024);
	memset((char *)rtns,'\0',1024);
	
	//generate_pk("/root/des_key.dat");//生成密
	load_key("/root/des_key.dat");//加载密
	src_len = strlen(pstr);	
	char *mm_str = des_encrypt(pstr, src_len, &en_len);
	char *ptr = des_decrypt(mm_str,en_len, &de_len);
	bcopy(ptr, rtns, de_len);
	printf("\n value=%s", rtns);
	return 0;
}