openssl 的RSA 非对称加密算法

原文地址：http://blog.sina.com.cn/s/blog_4f51dac40100u3co.html

程序将加密密钥和解密密钥写入文件 运行！

#include <openssl/rsa.h>

#include <openssl/pem.h>

//#include <unistd.h>

#include <iostream>

#include <io.h>

const char *g_pPubFile = "public.pem";

const char *g_pPriFile = "private.pem";

//maxCodeByte = g_nBits/8-11

const int g_nBits = 1024;

using namespace std;

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)

{

cout << "rsa_generate_key error" << endl;

return -1;

}

BIO *pBio = BIO_new_file(g_pPubFile,"w");

if (pBio == NULL)

{

cout << "BIO_new_file " << g_pPubFile << " error" << endl;

return -2;

}

if(PEM_write_bio_RSAPublicKey(pBio,pRsa) == 0)

{

cout << "write public key error" << endl;

return -3;

}

BIO_free_all(pBio);

pBio = BIO_new_file(g_pPriFile,"w");

if (pBio == NULL)

{

cout << "BIO_new_file " << g_pPriFile << " error" << endl;

return -4;

}

if(PEM_write_bio_RSAPrivateKey(pBio,pRsa,NULL,NULL,0,NULL,NULL) == 0)

{

cout << "write private key error" << endl;

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,

reinterpret_cast<unsigned char*>(in),

reinterpret_cast<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,

reinterpret_cast<unsigned char*>(in),

reinterpret_cast<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);

cout << "decode: " << szDec << endl;

cin.get();

}