使用openssl编写RSA加解密算法

好的，下面是使用 OpenSSL 库编写 RSA 加解密算法的示例代码，你可以根据自己的需求进行修改：

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

int main(int argc, char* argv[]) {
    // 生成 RSA 密钥对
    RSA* rsa = RSA_generate_key(2048, RSA_F4, NULL, NULL);
    if (rsa == NULL) {
        printf("RSA_generate_key failed!\n");
        return -1;
    }

    // 保存公钥和私钥到文件中
    FILE* fp = fopen("public_key.pem", "w");
    if (fp == NULL) {
        printf("Open public_key.pem failed!\n");
        return -1;
    }
    PEM_write_RSAPublicKey(fp, rsa);
    fclose(fp);

    fp = fopen("private_key.pem", "w");
    if (fp == NULL) {
        printf("Open private_key.pem failed!\n");
        return -1;
    }
    PEM_write_RSAPrivateKey(fp, rsa, NULL, NULL, 0, NULL, NULL);
    fclose(fp);

    // 加密字符串
    const char* plain_text = "Hello, RSA!";
    int plain_text_len = strlen(plain_text);
    int max_cipher_len = RSA_size(rsa);
    unsigned char* cipher_text = (unsigned char*)malloc(max_cipher_len);
    int cipher_len = RSA_public_encrypt(plain_text_len, (const unsigned char*)plain_text, cipher_text, rsa, RSA_PKCS1_PADDING);
    if (cipher_len < 0) {
        printf("RSA_public_encrypt failed!\n");
        return -1;
    }

    // 解密字符串
    unsigned char* result = (unsigned char*)malloc(plain_text_len + 1);
    int result_len = RSA_private_decrypt(cipher_len, cipher_text, result, rsa, RSA_PKCS1_PADDING);
    if (result_len < 0) {
        printf("RSA_private_decrypt failed!\n");
        return -1;
    }
    result[result_len] = '\0';

    printf("plain_text: %s\n", plain_text);
    printf("cipher_len: %d\n", cipher_len);
    printf("cipher_text: ");
    for (int i = 0; i < cipher_len; i++) {
        printf("%02X ", cipher_text[i]);
    }
    printf("\n");
    printf("result_len: %d\n", result_len);
    printf("result: %s\n", result);

    RSA_free(rsa);
    free(cipher_text);
    free(result);

    return 0;
}

这个示例代码中，我们使用 OpenSSL 库生成了一个 2048 位的 RSA 密钥对，并将公钥和私钥保存到文件中。然后我们加密了一个字符串 "Hello, RSA!"，并对其进行解密，最后输出了加密前后的字符串和加密后的密文。