openssl关于RSA算法

rsa为非对称算法，加密和解密的密钥是不同的，一个密钥进行加密，另一个密钥进行解密。这个过程是相互的，用私钥加密，公钥解密，被称为签名。用公钥加密，用私钥解密，就是通常说的加密。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>

#include <openssl/rsa.h>
#include <openssl/pem.h>
#include <openssl/err.h>

#define OPENSSLKEY "test.key"
#define PUBLICKEY "test_pub.key"
#define BUFFSIZE 1024

char* STR = "abcdefghigklm";

char* my_encrypt(char *str,char *path_key);//加密
char* my_decrypt(char *str,char *path_key);//解密

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(void){
    char *source = STR; 
    char *ptr_en,*ptr_de;
    printf("source is:%s, len:%d\n",source, strlen(source));

    long start = get_trick();
    ptr_en=my_encrypt(source,PUBLICKEY);
    long spend = get_trick() - start;
    printf("spend:%ld\n", spend);

    printf("after encrypt len:%d\n", strlen(ptr_en));

    start = get_trick();
    ptr_de=my_decrypt(ptr_en,OPENSSLKEY);
    spend = get_trick() - start;
    printf("spend:%ld\n", spend);
    printf("after decrypt:%s, len:%d\n",ptr_de, strlen(ptr_de));
    if(ptr_en!=NULL){
        free(ptr_en);
    }   
    if(ptr_de!=NULL){
        free(ptr_de);
    }   
    return 0;
}

char *my_encrypt(char *str,char *path_key){
    char *p_en;
    RSA *p_rsa;
    FILE *file;
    int flen,rsa_len;
    if((file=fopen(path_key,"r"))==NULL){
        perror("open key file error");
        return NULL;    
    }   
    if((p_rsa=PEM_read_RSA_PUBKEY(file,NULL,NULL,NULL))==NULL){
        ERR_print_errors_fp(stdout);
        return NULL;
    }   
    flen=strlen(str);
    rsa_len=RSA_size(p_rsa);
    p_en=(unsigned char *)malloc(rsa_len+1);
    memset(p_en,0,rsa_len+1);
    if(RSA_public_encrypt(rsa_len,(unsigned char *)str,(unsigned char*)p_en,p_rsa,RSA_NO_PADDING)<0){
        return NULL;
    }
    RSA_free(p_rsa);
    fclose(file);
    return p_en;
}

char *my_decrypt(char *str,char *path_key){
    char *p_de;
    RSA *p_rsa;
    FILE *file;
    int rsa_len;
    if((file=fopen(path_key,"r"))==NULL){
        perror("open key file error");
        return NULL;
    }
    if((p_rsa=PEM_read_RSAPrivateKey(file,NULL,NULL,NULL))==NULL){
        ERR_print_errors_fp(stdout);
        return NULL;
    }
    rsa_len=RSA_size(p_rsa);
    p_de=(unsigned char *)malloc(rsa_len+1);
    memset(p_de,0,rsa_len+1);
    if(RSA_private_decrypt(rsa_len,(unsigned char *)str,(unsigned char*)p_de,p_rsa,RSA_NO_PADDING)<0){
        return NULL;
    }
    RSA_free(p_rsa);
    fclose(file);
    return p_de;
}

测算的数据显示无论加密还是解密都耗时了1000微妙以上，详细数据调用指令也可以，openssl speed rsa ，这指令的输出很直观，不再赘述。