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
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <openssl/pem.h>
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#include <openssl/rsa.h>
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int main()
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{
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// 原始明文
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char plain[256]="测试测试,hello123";
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// 用来存放密文
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char encrypted[1024];
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// 用来存放解密后的明文
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char decrypted[1024];
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// 公钥和私钥文件
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const char* pub_key="public.pem";
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const char* priv_key="private.pem";
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// -------------------------------------------------------
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// 利用公钥加密明文的过程
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// -------------------------------------------------------
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// 打开公钥文件
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FILE* pub_fp=fopen(pub_key,"r");
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if(pub_fp==NULL){
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printf("failed to open pub_key file %s!\n", pub_key);
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return -1;
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}
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// 从文件中读取公钥
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RSA* rsa1=PEM_read_RSA_PUBKEY(pub_fp, NULL, NULL, NULL);
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if(rsa1==NULL){
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printf("unable to read public key!\n");
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return -1;
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}
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if(strlen(plain)>=RSA_size(rsa1)-41){
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printf("failed to encrypt\n");
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return -1;
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}
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fclose(pub_fp);
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// 用公钥加密
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int len=RSA_public_encrypt(strlen(plain), plain, encrypted, rsa1, RSA_PKCS1_PADDING);
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if(len==-1 ){
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printf("failed to encrypt\n");
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return -1;
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}
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// 输出加密后的密文
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FILE* fp=fopen("out.txt","w");
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if(fp){
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fwrite(encrypted,len,1,fp);
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fclose(fp);
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}
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// -------------------------------------------------------
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// 利用私钥解密密文的过程
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// -------------------------------------------------------
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// 打开私钥文件
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FILE* priv_fp=fopen(priv_key,"r");
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if(priv_fp==NULL){
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printf("failed to open priv_key file %s!\n", priv_key);
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return -1;
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}
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// 从文件中读取私钥
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RSA *rsa2 = PEM_read_RSAPrivateKey(priv_fp, NULL, NULL, NULL);
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if(rsa2==NULL){
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printf("unable to read private key!\n");
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return -1;
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}
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// 用私钥解密
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len=RSA_private_decrypt(len, encrypted, decrypted, rsa2, RSA_PKCS1_PADDING);
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if(len==-1){
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printf("failed to decrypt!\n");
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return -1;
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}
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fclose(priv_fp);
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// 输出解密后的明文
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decrypted[len]=0;
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printf("%s\n",decrypted);
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- }
http://blog.chinaunix.net/uid-23686726-id-3413979.html