用C语言写一个AES-CFB加密程序

好的，我可以回答这个问题。以下是一个用C语言编写的AES-CFB加密程序的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/aes.h>

#define AES_BLOCK_SIZE 16

void aes_cfb_encrypt(unsigned char *in, unsigned char *out, size_t length, unsigned char *key, unsigned char *iv)
{
    AES_KEY aes_key;
    AES_set_encrypt_key(key, 128, &aes_key);

    unsigned char eiv[AES_BLOCK_SIZE];
    memcpy(eiv, iv, AES_BLOCK_SIZE);

    int num = ;
    while (num < length) {
        unsigned char block[AES_BLOCK_SIZE];
        AES_encrypt(eiv, block, &aes_key);

        int i;
        for (i = ; i < AES_BLOCK_SIZE && num < length; i++) {
            out[num] = block[i] ^ in[num];
            eiv[i] = out[num];
            num++;
        }
    }
}

int main()
{
    unsigned char key[] = "0123456789abcdef";
    unsigned char iv[] = "fedcba987654321";
    unsigned char plaintext[] = "Hello, world!";
    size_t plaintext_len = strlen((char *)plaintext);

    unsigned char *ciphertext = malloc(plaintext_len);
    aes_cfb_encrypt(plaintext, ciphertext, plaintext_len, key, iv);

    printf("Plaintext: %s\n", plaintext);
    printf("Ciphertext: ");
    int i;
    for (i = ; i < plaintext_len; i++) {
        printf("%02x", ciphertext[i]);
    }
    printf("\n");

    free(ciphertext);
    return ;
}

这个程序使用了OpenSSL库中的AES加密函数，实现了AES-CFB模式的加密。它接受一个输入字符串、一个密钥和一个初始化向量，并输出加密后的结果。注意，这个程序只是一个示例，实际使用中需要根据具体需求进行修改和优化。