c++ openssl rsa 字符串公私钥加解密示例代码

在C++中使用OpenSSL库处理RSA加密解密，你需要包含相关的头文件，并利用`BIO`和`RSA`结构来操作公钥和私钥。下面是一个简单的示例，展示了如何生成密钥对、加密字符串、然后用私钥解密：

#include <openssl/bio.h>
#include <openssl/rsa.h>
#include <openssl/pem.h>
#include <string>

// 生成RSA密钥对
std::string generate_key_pair() {
    RSA *rsa = RSA_new();
    BIGNUM *e = BN_new(), *n = BN_new();

    // 生成大素数n和e(通常e=65537)
    BN_rand_range(n, RSA_NBITS);
    BN_set_word(e, RSA_F4);

    // 创建RSA结构并设置参数
    RSA_generate_key_ex(rsa, RSA modulus bits, e, n, NULL, NULL);

    // 将公钥和私钥转换为PEM格式的字符串
    BIO* bio_pub = BIO_new(BIO_s_mem());
    BIO* bio_priv = BIO_new(BIO_s_mem());
    PEM_write_bio_RSA_PUBKEY(bio_pub, rsa);
    PEM_write_bio_RSAPrivateKey(bio_priv, rsa, NULL, NULL);

    std::string pub_str = BIO_get_mem_data(bio_pub), priv_str = BIO_get_mem_data(bio_priv);
    RSA_free(rsa);
    BN_free(e);
    BN_free(n);
    BIO_free_all(bio_pub);
    BIO_free_all(bio_priv);

    return "Public Key:\n" + pub_str + "\nPrivate Key:\n" + priv_str;
}

// 加密函数
std::string encrypt(const std::string& plaintext, const std::string& public_key) {
    RSA *rsaPub = RSA_new();
    rsaPub = PEM_read_RSA_PUBKEY(RSA_new(), (char*)public_key.c_str(), NULL, NULL);
    BIO* bio_in = BIO_new(BIO_f_base64());
    BIO* bio_out = BIO_new(BIO_s_mem());

    BIO_write(bio_in, plaintext.c_str(), plaintext.length());
    BIO_push(bio_out, bio_in);
    RSA_public_encrypt(plaintext.size(), BIO_get_mem_ptr(bio_out), rsaPub, RSA_PKCS1_OAEP_PADDING);

    std::string ciphertext = BIO_get_mem_data(bio_out);
    BIO_free_all(bio_out);
    RSA_free(rsaPub);
    return ciphertext;
}

// 解密函数
std::string decrypt(const std::string& ciphertext, const std::string& private_key) {
    RSA *rsaPri = RSA_new();
    rsaPri = PEM_read_PrivateKey(RSA_new(), (char*)private_key.c_str(), NULL, NULL);
    BIO* bio_in = BIO_new(BIO_f_base64());
    BIO* bio_out = BIO_new(BIO_s_mem());

    BIO_write(bio_in, ciphertext.c_str(), ciphertext.length());
    BIO_push(bio_out, bio_in);
    RSA_private_decrypt(ciphertext.size(), BIO_get_mem_ptr(bio_in), rsaPri, RSA_PKCS1_OAEP_PADDING);

    std::string plaintext = BIO_get_mem_data(bio_out);
    BIO_free_all(bio_out);
    RSA_free(rsaPri);
    return plaintext;
}

int main() {
    auto key_pairs = generate_key_pair();
    std::cout << "Keys generated.\n";
    std::string encrypted_text = encrypt("Hello, World!", key_pairs.substr(key_pairs.find("\n")+1));
    std::cout << "Text encrypted.\n";
    std::string decrypted_text = decrypt(encrypted_text, key_pairs.substr(0, key_pairs.find("\n")));
    std::cout << "Decrypted text: " << decrypted_text << std::endl;

    return 0;
}

注意：这个示例仅供参考，实际应用中你需要处理错误检查和异常处理。此外，为了安全存储和传输私钥，建议将其保存在安全的地方，而不是明文显示。