#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/evp.h>
#include <openssl/rand.h>
#include <curl/curl.h>

#define AES_256_KEY_SIZE 32
#define AES_256_IV_SIZE 16

void handleErrors(void) {
    ERR_print_errors_fp(stderr);
    abort();
}

void encryptData(const char *plaintext, unsigned char **ciphertext, int *ciphertext_len, unsigned char *key, unsigned char *iv) {
    EVP_CIPHER_CTX *ctx;

    int len;

    *ciphertext = (unsigned char *)malloc(strlen(plaintext) + AES_256_IV_SIZE);

    if (!(ctx = EVP_CIPHER_CTX_new())) handleErrors();

    if (1 != EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key, iv)) handleErrors();

    if (1 != EVP_EncryptUpdate(ctx, *ciphertext, &len, (unsigned char *)plaintext, strlen(plaintext))) handleErrors();
    *ciphertext_len = len;

    if (1 != EVP_EncryptFinal_ex(ctx, *ciphertext + len, &len)) handleErrors();
    *ciphertext_len += len;

    EVP_CIPHER_CTX_free(ctx);
}

void establishSecureConnection() {
    CURL *curl;
    CURLcode res;

    curl_global_init(CURL_GLOBAL_DEFAULT);
    curl = curl_easy_init();
    if (curl) {
        curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 1L);
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 2L);

        res = curl_easy_perform(curl);
        if (res != CURLE_OK) {
            fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
        } else {
            printf("Secure connection established successfully.\n");
        }

        curl_easy_cleanup(curl);
    }
    curl_global_cleanup();
}

int main() {
    const char *plaintext = "Sensitive Data";
    unsigned char *ciphertext;
    int ciphertext_len;
    unsigned char key[AES_256_KEY_SIZE];
    unsigned char iv[AES_256_IV_SIZE];

    if (!RAND_bytes(key, sizeof(key)) || !RAND_bytes(iv, sizeof(iv))) {
        fprintf(stderr, "RAND_bytes failed\n");
        return 1;
    }

    encryptData(plaintext, &ciphertext, &ciphertext_len, key, iv);
    if (ciphertext) {
        printf("Encrypted Data: ");
        for (int i = 0; i < ciphertext_len; i++) {
            printf("%02x", ciphertext[i]);
        }
        printf("\n");
        free(ciphertext);
    }

    establishSecureConnection();

    return 0;
}