c++生成公钥和私钥并对字符串加密和解密

最新推荐文章于 2025-05-27 00:37:04 发布

转载最新推荐文章于 2025-05-27 00:37:04 发布 · 7.8k 阅读

本文提供了一个使用RSA算法进行加密和解密的C语言示例程序。该程序包括生成公钥和私钥、加密数据及解密数据等功能，并演示了如何使用OpenSSL库来实现这些操作。

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#include "cryptotest.h"
#include <string.h>
#include <stdio.h>
#include <openssl/evp.h>
#include <openssl/x509.h>
#include <string.h>

const char *g_pPubFile = "public.pem";
const char *g_pPriFile = "private.pem";

//maxCodeByte = g_nBits/8-11
const int g_nBits = 1024;



int MakeKey()
{
	 /*if (access(g_pPubFile,0) != 0 || access(g_pPriFile,0) != 0)
	 {
	  return 0;
	 }*/
	 //生成key,这里设置了1024，意味着最多可以编解码1024/8-11=117个字节，
	 //RSA_F4为公钥指数，一般情况下使用RSA_F4即可，
	 //其它两个参数可以设置为NULL
	 RSA *pRsa = RSA_generate_key(g_nBits,RSA_F4,NULL,NULL);
	 if (pRsa == NULL)
	 {
		  printf("rsa_generate_key error");
		  return -1;
	 }
 	 BIO *pBio = BIO_new_file(g_pPubFile,"wb");

	 if (pBio == NULL)
	 {
		  printf( "BIO_new_file = %s  error",g_pPubFile);
		  return -2;
	 }
	 if(PEM_write_bio_RSAPublicKey(pBio,pRsa) == 0)
	 {
		  printf("write public key error");
		  return -3;
	 }
	 BIO_free_all(pBio);


	 pBio = BIO_new_file(g_pPriFile,"w");
	 if (pBio == NULL)
	 {
        	printf("BIO_new_file %s error ",g_pPriFile);
		return -4;
	 }
	 if(PEM_write_bio_RSAPrivateKey(pBio,pRsa,NULL,NULL,0,NULL,NULL) == 0)
	 {
		  printf("write private key error");
		  return -5;
	 }
	 BIO_free_all(pBio);
	 RSA_free(pRsa);
	 
	 return 0;
}


int Enc(char *in, int inLen, char *out, int * outLen)
{
	 BIO *pBio = BIO_new_file(g_pPubFile,"r");
	 RSA *pRsa = PEM_read_bio_RSAPublicKey(pBio,NULL,NULL,NULL);
	 BIO_free_all(pBio);
	 *outLen = RSA_public_encrypt(
	 		 (RSA_size(pRsa)-11)>inLen?inLen:RSA_size(pRsa)-11,
	        	(unsigned char *)(in),
		       (unsigned char *)(out),
	  		 pRsa,
	  		 RSA_PKCS1_PADDING);
	 //RSA_free(pRsa);
	 if(*outLen >= 0)
	  return 0;
	 return -1;
}


int Dec(char *in, int inLen, char *out, int * outLen)
{
	BIO *pBio = BIO_new_file(g_pPriFile,"r");
	RSA *pRsa = PEM_read_bio_RSAPrivateKey(pBio,NULL,NULL,NULL);
		BIO_free_all(pBio);
		*outLen = RSA_private_decrypt(
		inLen,
		(unsigned char *)(in),
		(unsigned char *)(out),
		pRsa,
		RSA_PKCS1_PADDING);
	//RSA_free(pRsa);
	if(*outLen >= 0)
	return 0;
	return -1;
}

int main()
{
	 MakeKey();
	 char pOld[100]="for test";
	 char szEnc[1024] = {0};
	 int nEncLen = 0;
	 char szDec[1024] = {0};
	 int nDecLen = 0;
	 Enc(pOld,strlen(pOld),szEnc,&nEncLen);
	 Dec(szEnc,nEncLen,szDec,&nDecLen);
	 printf( "szEnc: %s , nEncLen = %d\n", szEnc,nEncLen);
	 printf( "szDec: %s , nDecLen = %d\n", szDec,nDecLen);

	 return 0;
}