输出一个C语言编程的DES算法

DES算法是一种对称加密算法，它使用相同的密钥进行加密和解密。下面是一个C语言编程的DES算法示例：

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

int main(int argc, char *argv[])
{
DES_cblock key;
DES_key_schedule schedule;
char *plaintext = "Hello, world!";
char ciphertext[64];
char decryptedtext[64];

// Set the encryption key
memset(key, , sizeof(key));
DES_set_key_unchecked(&key, &schedule);

// Encrypt the plaintext
DES_ecb_encrypt((const unsigned char *)plaintext, (unsigned char *)ciphertext, &schedule, DES_ENCRYPT);

// Decrypt the ciphertext
DES_ecb_encrypt((const unsigned char *)ciphertext, (unsigned char *)decryptedtext, &schedule, DES_DECRYPT);

// Print the results
printf("Plaintext: %s\n", plaintext);
printf("Ciphertext: %s\n", ciphertext);
printf("Decrypted text: %s\n", decryptedtext);

return ;
}