私鑰加密的部分內容，需要用公鑰解密下面的實例代碼，由於私鑰加密後的字符串有不可打印字符，所以程序裏面進行了base64，要用的時候先解dec base64

再傳遞給函數 進行解密

#include <stdio.h>
#include <stdlib.h>
#ifdef WIN32
#include <windows.h>
#endif
#include "openssl/rsa.h"
#include "openssl/pem.h"
#include "Base64.h"
#ifdef WIN32
#pragma comment(lib,"User32.lib")
#pragma
 
 comment(lib,"Advapi32.lib")
#pragma comment(lib,"Gdi32.lib")
#pragma comment(lib,"libeay32.lib")
#pragma comment(lib,"ssleay32.lib")
#endif
// 公鑰解密    
std::string rsa_pub_decrypt(const std::string &cipherText, const std::string &pubKey)  
{  
    std::string strRet;  
    RSA *rsa = RSA_new();
    BIO 
 
*keybio= BIO_new_mem_buf((unsigned char *)pubKey.c_str(), -1);  
    rsa=PEM_read_bio_RSA_PUBKEY(keybio,&rsa,NULL,NULL);
  
    int len = RSA_size(rsa);  
    char *decryptedText = (char *)malloc(len + 1);  
    memset(decryptedText, 0, len + 1);  
  
    // 解密函數  
    int ret = RSA_public_decrypt(cipherText.length(), (const
 
 unsigned char*)cipherText.c_str(), (unsigned char*)decryptedText, rsa, RSA_PKCS1_PADDING);  
    if (ret >= 0)  
        strRet = std::string(decryptedText, ret);  
  
    // 釋放內存  
    free(decryptedText);  
    BIO_free_all(keybio);  
    RSA_free(rsa);  
  
    return strRet;  
} 
 
int main(int narg,char** args)
{
    string pubKey="\
-----BEGIN PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAptoreKuW1O+Bb1u+O0LQ\nNAiaj5i0gbqi5uHCfcTxPIScoeidR/FaPFWpG3mHUCd7SfPKlSQ4H4FGwqkPrAJ8\ntb6vfNAY7UPlStaWwCASBBBeHRIFySDIFQnIeXTcZqKgvCAkM3kudyKGMGfZyU6v\nSUCMUJbvtIKrSBpPFOaPF1EjfsTpcRjRwNUxjInvxyOmegdLSgg/NNV9AxUSpGX4\nFs5j3W4u4bfgoH6WiI7QLeVWpw+ZcynndtihPa2Y5rKgTDq1IYnniaYy+bTlWMPC\nus9AjL0qaM0oXKzUByIeA8cWQR99ewSLsEaa7mhpUZ1jg+fDQEqYfgvenfcOe5bn\nNQIDAQAB\n-----END PUBLIC KEY-----\n";
    string encStr="TgaNSiG6yPkKql3pIW9310IsRpcppl4SIt12kdP3ZwR0wWj65P3I3YCaSrb7+lmJ9N\
mpTmHHzwgvTQN3zM+IRpjQr1iAJZ0C/+2uM0WkPwbZhvlzcr4iZFOfhe6CbPGibu1+pRYdkkxgvXT3/0D4hrtzOxMXVYzBLjfd7xXRfVTXGI7FlBGfq6/W+bg3DE3BQbdS07eBBRKQ1Jbl/LPIQP40FK5qdvTDeWTG0m/mLRfpavbIw4pMKnc7845xU9ZZVmxcv14O7AJYmJat72mGzDVpafx+65aanLMIydSY+dly62XeSRd5ghd1fSaTHlVN4h59YYqNPXGxFKTrMvPUDg==";
    Base64 base;
    string encStr2=base.Decode(encStr.c_str(),encStr.length());
    string decStr=rsa_pub_decrypt(encStr2,pubKey);
    printf("---%s---\n",decStr.c_str());
    system("pause");
    return 0;
}

下面的私鑰和公鑰 以及加密字符串

秘鑰位數2048 秘鑰格式PKCD#8

-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAptoreKuW1O+Bb1u+O0LQ
NAiaj5i0gbqi5uHCfcTxPIScoeidR/FaPFWpG3mHUCd7SfPKlSQ4H4FGwqkPrAJ8
tb6vfNAY7UPlStaWwCASBBBeHRIFySDIFQnIeXTcZqKgvCAkM3kudyKGMGfZyU6v
SUCMUJbvtIKrSBpPFOaPF1EjfsTpcRjRwNUxjInvxyOmegdLSgg/NNV9AxUSpGX4
Fs5j3W4u4bfgoH6WiI7QLeVWpw+ZcynndtihPa2Y5rKgTDq1IYnniaYy+bTlWMPC
us9AjL0qaM0oXKzUByIeA8cWQR99ewSLsEaa7mhpUZ1jg+fDQEqYfgvenfcOe5bn
NQIDAQAB
-----END PUBLIC KEY-----

-----BEGIN PRIVATE KEY-----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-----END PRIVATE KEY-----

加密前字符串
73a90acaae2b1ccc0e969709665bc62f
加密後字符串
TgaNSiG6yPkKql3pIW9310IsRpcppl4SIt12kdP3ZwR0wWj65P3I3YCaSrb7+lmJ9NmpTmHHzwgvTQN3zM+IRpjQr1iAJZ0C/+2uM0WkPwbZhvlzcr4iZFOfhe6CbPGibu1+pRYdkkxgvXT3/0D4hrtzOxMXVYzBLjfd7xXRfVTXGI7FlBGfq6/W+bg3DE3BQbdS07eBBRKQ1Jbl/LPIQP40FK5qdvTDeWTG0m/mLRfpavbIw4pMKnc7845xU9ZZVmxcv14O7AJYmJat72mGzDVpafx+65aanLMIydSY+dly62XeSRd5ghd1fSaTHlVN4h59YYqNPXGxFKTrMvPUDg==

C++利用openssl進行公鑰解密