生成私钥:
openssl genrsa -out private.key 2048
生成公钥:
openssl rsa -in privkey.pem -pubout > public.pem
C代码如下所示。
在Linux下的编译:gcc test.c -lcrypto -o test
- #include <stdlib.h>
- #include <stdio.h>
- #include <string.h>
- #include <openssl/pem.h>
- #include <openssl/rsa.h>
- int main()
- {
- // 原始明文
- char plain[256]="测试测试,hello123";
- // 用来存放密文
- char encrypted[1024];
- // 用来存放解密后的明文
- char decrypted[1024];
- // 公钥和私钥文件
- const char* pub_key="public.pem";
- const char* priv_key="private.pem";
- // -------------------------------------------------------
- // 利用公钥加密明文的过程
- // -------------------------------------------------------
- // 打开公钥文件
- FILE* pub_fp=fopen(pub_key,"r");
- if(pub_fp==NULL){
- printf("failed to open pub_key file %s!\n", pub_key);
- return -1;
- }
- // 从文件中读取公钥
- RSA* rsa1=PEM_read_RSA_PUBKEY(pub_fp, NULL, NULL, NULL);
- if(rsa1==NULL){
- printf("unable to read public key!\n");
- return -1;
- }
-
- if(strlen(plain)>=RSA_size(rsa1)-41){
- printf("failed to encrypt\n");
- return -1;
- }
- fclose(pub_fp);
- // 用公钥加密
- int len=RSA_public_encrypt(strlen(plain), plain, encrypted, rsa1, RSA_PKCS1_PADDING);
- if(len==-1 ){
- printf("failed to encrypt\n");
- return -1;
- }
-
- // 输出加密后的密文
- FILE* fp=fopen("out.txt","w");
- if(fp){
- fwrite(encrypted,len,1,fp);
- fclose(fp);
- }
- // -------------------------------------------------------
- // 利用私钥解密密文的过程
- // -------------------------------------------------------
- // 打开私钥文件
- FILE* priv_fp=fopen(priv_key,"r");
- if(priv_fp==NULL){
- printf("failed to open priv_key file %s!\n", priv_key);
- return -1;
- }
-
- // 从文件中读取私钥
- RSA *rsa2 = PEM_read_RSAPrivateKey(priv_fp, NULL, NULL, NULL);
- if(rsa2==NULL){
- printf("unable to read private key!\n");
- return -1;
- }
-
- // 用私钥解密
- len=RSA_private_decrypt(len, encrypted, decrypted, rsa2, RSA_PKCS1_PADDING);
- if(len==-1){
- printf("failed to decrypt!\n");
- return -1;
- }
- fclose(priv_fp);
- // 输出解密后的明文
- decrypted[len]=0;
- printf("%s\n",decrypted);
- }
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