实现AES-256-CBC的C语言代码

下面是一个使用C语言实现AES-256-CBC加密和解密的例子：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/aes.h>

void encryptAES_CBC(const unsigned char *plaintext, const unsigned char *key, const unsigned char *iv, unsigned char *ciphertext, size_t length) {
AES_KEY aesKey;
AES_set_encrypt_key(key, 256, &amp;aesKey);
AES_cbc_encrypt(plaintext, ciphertext, length, &amp;aesKey, iv, AES_ENCRYPT);
}

void decryptAES_CBC(const unsigned char *ciphertext, const unsigned char *key, const unsigned char *iv, unsigned char *plaintext, size_t length) {
AES_KEY aesKey;
AES_set_decrypt_key(key, 256, &amp;aesKey);
AES_cbc_encrypt(ciphertext, plaintext, length, &amp;aesKey, iv, AES_DECRYPT);
}

int main() {
const unsigned char *plaintext = (unsigned char *)"Hello World!";
const unsigned char *key = (unsigned char *)"0123456789abcdef0123456789abcdef";
const unsigned char *iv = (unsigned char *)"1234567890abcdef";
size_t length = strlen((const char *)plaintext);

unsigned char ciphertext[length];
encryptAES_CBC(plaintext, key, iv, ciphertext, length);
printf("Ciphertext: ");
for (size_t i = 0; i < length; i++) {
printf("%02x", ciphertext[i]);
}
printf("\n");

unsigned char decrypted[length];
decryptAES_CBC(ciphertext, key, iv, decrypted, length);
printf("Decrypted: %s\n", decrypted);

return 0;
}
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请确保您已经安装了OpenSSL库，并使用以下命令编译和运行代码：
gcc -o aes aes.c -lssl -lcrypto
./aes
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这段代码使用了OpenSSL库中的函数来实现AES-256-CBC加密和解密。它首先定义了两个函数encryptAES_CBC和decryptAES_CBC，分别用于加密和解密操作。然后在main函数中，设置了明文、密钥、初始化向量（IV）和明文长度，并调用encryptAES_CBC函数进行加密，并打印出密文。接着，调用decryptAES_CBC函数进行解密，并打印出解密后的明文。
注意：这只是一个简单的示例，实际应用中需要更多的错误处理和安全考虑。