rsa算法c++语言实现

为了保证数据传输的安全性，RSA算法是一种非常常见的加密算法。在C语言中，可以使用以下代码实现RSA算法：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/rsa.h>
#include <openssl/pem.h>
#include <openssl/err.h>

#define KEY_LENGTH 2048
#define PUB_EXP 3

int main(int argc, char *argv[]) {
    char *pub_key_path = "public.pem";  // 公钥路径
    char *pri_key_path = "private.pem"; // 私钥路径
    char *plain_text = "Hello, RSA!";   // 明文
    char cipher_text[256] = {0};        // 密文
    char decrypt_text[256] = {0};       // 解密后的明文

    // 1. 生成密钥对
    RSA *rsa = RSA_generate_key(KEY_LENGTH, PUB_EXP, NULL, NULL);
    if (rsa == NULL) {
        printf("RSA_generate_key error.\n");
        return -1;
    }

    // 2. 保存公钥和私钥
    FILE *fp = NULL;
    fp = fopen(pub_key_path, "wb+");
    if (fp == NULL) {
        printf("fopen public key error.\n");
        return -1;
    }
    PEM_write_RSAPublicKey(fp, rsa);
    fclose(fp);

    fp = fopen(pri_key_path, "wb+");
    if (fp == NULL) {
        printf("fopen private key error.\n");
        return -1;
    }
    PEM_write_RSAPrivateKey(fp, rsa, NULL, NULL, 0, NULL, NULL);
    fclose(fp);

    // 3. 使用公钥加密
    fp = fopen(pub_key_path, "rb");
    if (fp == NULL) {
        printf("fopen public key error.\n");
        return -1;
    }
    RSA *public_key = RSA_new();
    if (public_key == NULL) {
        printf("RSA_new public_key error.\n");
        return -1;
    }
    public_key = PEM_read_RSAPublicKey(fp, &public_key, NULL, NULL);
    fclose(fp);

    int rsa_len = RSA_public_encrypt(strlen(plain_text), (unsigned char *)plain_text, (unsigned char *)cipher_text, public_key, RSA_PKCS1_PADDING);
    if (rsa_len == -1) {
        printf("RSA_public_encrypt error.\n");
        return -1;
    }

    printf("cipher text: %s\n", cipher_text);

    // 4. 使用私钥解密
    fp = fopen(pri_key_path, "rb");
    if (fp == NULL) {
        printf("fopen private key error.\n");
        return -1;
    }
    RSA *private_key = RSA_new();
    if (private_key == NULL) {
        printf("RSA_new private_key error.\n");
        return -1;
    }
    private_key = PEM_read_RSAPrivateKey(fp, &private_key, NULL, NULL);
    fclose(fp);

    rsa_len = RSA_private_decrypt(rsa_len, (unsigned char *)cipher_text, (unsigned char *)decrypt_text, private_key, RSA_PKCS1_PADDING);
    if (rsa_len == -1) {
        printf("RSA_private_decrypt error.\n");
        return -1;
    }

    printf("decrypt text: %s\n", decrypt_text);

    return 0;
}

注意，在使用该代码时需要安装openssl库。可以使用以下命令在Ubuntu上安装openssl：

sudo apt-get install libssl-dev