用RSA加密AES的密钥k，后用AES加密数据 用c语言实现

以下是用C语言实现RSA加密AES密钥和AES加密数据的代码，其中使用了OpenSSL库来实现RSA和AES加密算法：

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

#define AES_KEY_SIZE 256
#define AES_BLOCK_SIZE 128
#define RSA_KEY_SIZE 2048

int main() {
    // 生成AES密钥
    unsigned char aes_key[AES_KEY_SIZE/8];
    if (RAND_bytes(aes_key, AES_KEY_SIZE/8) != 1) {
        printf("Error generating AES key\n");
        return 1;
    }

    // AES加密数据
    unsigned char plaintext[] = "Hello, world!";
    int plaintext_len = strlen(plaintext);
    int ciphertext_len;
    unsigned char iv[AES_BLOCK_SIZE/8];
    RAND_bytes(iv, AES_BLOCK_SIZE/8);
    unsigned char ciphertext[plaintext_len + AES_BLOCK_SIZE/8];
    EVP_CIPHER_CTX *ctx;
    if (!(ctx = EVP_CIPHER_CTX_new())) {
        printf("Error creating AES context\n");
        return 1;
    }
    if (EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, aes_key, iv) != 1) {
        printf("Error initializing AES encryption\n");
        return 1;
    }
    if (EVP_EncryptUpdate(ctx, ciphertext, &ciphertext_len, plaintext, plaintext_len) != 1) {
        printf("Error encrypting AES data\n");
        return 1;
    }
    int final_len;
    if (EVP_EncryptFinal_ex(ctx, ciphertext + ciphertext_len, &final_len) != 1) {
        printf("Error finalizing AES encryption\n");
        return 1;
    }
    ciphertext_len += final_len;
    EVP_CIPHER_CTX_free(ctx);

    // RSA加密AES密钥
    RSA *rsa_keypair = RSA_generate_key(RSA_KEY_SIZE, RSA_F4, NULL, NULL);
    int rsa_len = RSA_size(rsa_keypair);
    unsigned char rsa_plaintext[rsa_len];
    memcpy(rsa_plaintext, aes_key, AES_KEY_SIZE/8);
    unsigned char rsa_ciphertext[rsa_len];
    if (RSA_public_encrypt(AES_KEY_SIZE/8, rsa_plaintext, rsa_ciphertext, rsa_keypair, RSA_PKCS1_OAEP_PADDING) == -1) {
        printf("Error encrypting AES key with RSA\n");
        return 1;
    }

    // 输出加密结果
    printf("AES ciphertext: ");
    for (int i = 0; i < ciphertext_len; i++) {
        printf("%02x", ciphertext[i]);
    }
    printf("\nRSA ciphertext: ");
    for (int i = 0; i < rsa_len; i++) {
        printf("%02x", rsa_ciphertext[i]);
    }
    printf("\n");

    RSA_free(rsa_keypair);
    return 0;
}

在实际应用中，需要将RSA加密的AES密钥和AES加密的数据一起传输给接收方，接收方需要先使用RSA解密AES密钥，再使用解密后的AES密钥来解密AES加密的数据。