linux下使用openssl 加解密

先附上Linux下安装配置openssl的过程

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安装完成后，产生RSA公钥和私钥

输入openssl进入程序

OpenSSL> genrsa -out test.key 1024

产生了1024bit的私钥，然后根据该私钥产生公钥

rsa -in test.key -pubout -out rsatest_pub.key

创建rsatest.c代码如下

vim rsatest.c

#include<stdio.h>
#include<stdlib.h>
#include<string.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* my_encrypt(char *str,char *path_key);//加密
char* my_decrypt(char *str,char *path_key);//解密
int main(void){
char *source="i like dancing !";
char *ptr_en,*ptr_de;
printf("source is    :%s\n",source);
ptr_en=my_encrypt(source,PUBLICKEY);
printf("after encrypt:%s\n",ptr_en);
ptr_de=my_decrypt(ptr_en,OPENSSLKEY);
printf("after decrypt:%s\n",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;
}

检验结果,gcc rsatest.c -o hello -lssl

最后-lssl 是为了引入共享库ssl