编程实现RSA加解密软件C++语言

下面是一个使用C++语言和OpenSSL库实现的RSA加解密软件的代码示例：

#include <iostream>
#include <cstring>
#include <openssl/rsa.h>
#include <openssl/pem.h>

std::string encrypt(const std::string& public_key_file, const std::string& plaintext) {
    // load public key
    FILE* fp = fopen(public_key_file.c_str(), "rb");
    if (fp == nullptr) {
        throw std::runtime_error("Failed to open public key file");
    }
    RSA* rsa = PEM_read_RSA_PUBKEY(fp, nullptr, nullptr, nullptr);
    fclose(fp);
    if (rsa == nullptr) {
        throw std::runtime_error("Failed to load public key");
    }

    // encrypt plaintext
    int rsa_size = RSA_size(rsa);
    std::string ciphertext(rsa_size, '\0');
    int encrypted_size = RSA_public_encrypt(static_cast<int>(plaintext.length()),
                                            reinterpret_cast<const unsigned char*>(plaintext.c_str()),
                                            reinterpret_cast<unsigned char*>(ciphertext.data()),
                                            rsa, RSA_PKCS1_PADDING);
    RSA_free(rsa);
    if (encrypted_size < 0) {
        throw std::runtime_error("Failed to encrypt plaintext");
    }

    ciphertext.resize(encrypted_size);
    return ciphertext;
}

std::string decrypt(const std::string& private_key_file, const std::string& ciphertext) {
    // load private key
    FILE* fp = fopen(private_key_file.c_str(), "rb");
    if (fp == nullptr) {
        throw std::runtime_error("Failed to open private key file");
    }
    RSA* rsa = PEM_read_RSAPrivateKey(fp, nullptr, nullptr, nullptr);
    fclose(fp);
    if (rsa == nullptr) {
        throw std::runtime_error("Failed to load private key");
    }

    // decrypt ciphertext
    int rsa_size = RSA_size(rsa);
    std::string plaintext(rsa_size, '\0');
    int decrypted_size = RSA_private_decrypt(static_cast<int>(ciphertext.length()),
                                             reinterpret_cast<const unsigned char*>(ciphertext.c_str()),
                                             reinterpret_cast<unsigned char*>(plaintext.data()),
                                             rsa, RSA_PKCS1_PADDING);
    RSA_free(rsa);
    if (decrypted_size < 0) {
        throw std::runtime_error("Failed to decrypt ciphertext");
    }

    plaintext.resize(decrypted_size);
    return plaintext;
}

int main() {
    std::string public_key_file = "public.pem";
    std::string private_key_file = "private.pem";
    std::string plaintext = "hello world";
    std::string ciphertext = encrypt(public_key_file, plaintext);
    std::string decrypted_plaintext = decrypt(private_key_file, ciphertext);

    std::cout << "Plaintext: " << plaintext << std::endl;
    std::cout << "Ciphertext: " << ciphertext << std::endl;
    std::cout << "Decrypted plaintext: " << decrypted_plaintext << std::endl;

    return 0;
}

该代码使用了OpenSSL库的`RSA`模块，其中`PEM_read_RSA_PUBKEY`和`PEM_read_RSAPrivateKey`分别为公钥和私钥加载函数。`RSA_public_encrypt`和`RSA_private_decrypt`分别实现了RSA加密和解密。注意，在使用OpenSSL库的函数时需要注意内存管理和错误处理。