RSA公钥加密C++代码

RSA（Rivest-Shamir-Adleman）是一种非对称加密算法，由三名美国密码学家发明。它基于大数分解的难度，其中一个密钥（公钥）用于加密，另一个密钥（私钥）用于解密。以下是C++的一个简单示例，展示了如何生成公钥和私钥，并使用它们进行加密和解密：

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

// RSA key pair generation (1024-bit default)
RSA* generate_rsa_key_pair() {
    RSA* rsa = RSA_new();
    BIGNUM* e = BN_new(), *n = BN_new();

    // Generate public exponent e (usually 65537)
    BN_set_word(e, RSA_F4);

    // Generate a large random prime p
    unsigned int bits = RSA_num_bits(rsa);
    BIGNUM* p = BN_generate_prime_ex(NULL, bits, NULL, BN_MONT_CTX, NULL);
    if (!p) {
        perror("Failed to generate prime p");
        exit(1);
    }

    // Generate another large random prime q and calculate n = p*q
    BIGNUM* q = BN_generate_prime_ex(NULL, bits, NULL, BN_MONT_CTX, NULL);
    if (!q) {
        perror("Failed to generate prime q");
        exit(1);
    }
    BN_mul(n, p, q, NULL); // n = p * q

    // Calculate the modulus (public key)
    RSA_set_n(rsa, n);
    RSA_generate_key_ex(rsa, RSA_F4, e, NULL, NULL); // Generate private key

    BN_free(p);
    BN_free(q);

    return rsa;
}

// Encrypt message using public key
std::string encrypt(const std::string& plaintext, RSA* pubkey) {
    const int msg_len = plaintext.length();
    unsigned char ciphertext[msg_len * 2 + 1]; // Add room for padding
    int len;

    if ((len = RSA_public_encrypt(msg_len, reinterpret_cast<const unsigned char*>(plaintext.c_str()), ciphertext, pubkey, RSA_PKCS1_OAEP_PADDING)) <= 0) {
        perror("Encryption failed");
        return "";
    }

    return std::string(reinterpret_cast<char*>(ciphertext), len);
}

// Decrypt message using private key
std::string decrypt(const std::string& ciphertext, RSA* privkey) {
    const int crypted_len = ciphertext.length();
    unsigned char decrypted_msg[crypted_len];
    int len;

    if ((len = RSA_private_decrypt(crypted_len, reinterpret_cast<const unsigned char*>(ciphertext.c_str()), decrypted_msg, privkey, RSA_PKCS1_OAEP_PADDING)) <= 0) {
        perror("Decryption failed");
        return "";
    }

    return std::string(reinterpret_cast<char*>(decrypted_msg), len);
}

int main() {
    RSA* rsa = generate_rsa_key_pair();
    // Use rsa for encryption and decryption...
    RSA_free(rsa); // Don't forget to free memory when done

    return 0;
}

注意：这个例子仅做教学演示，实际应用中你需要处理PEM文件的序列化和反序列化以及错误处理。