aes加密算法c语言实现

以下是使用 OpenSSL 库进行 AES 加密和解密的示例 C 代码：

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

void encrypt(unsigned char *plaintext, int plaintext_len, unsigned char *key,
  unsigned char *iv, unsigned char *ciphertext) {
    AES_KEY aes_key;
    AES_set_encrypt_key(key, 128, &aes_key);
    AES_cbc_encrypt(plaintext, ciphertext, plaintext_len, &aes_key, iv, AES_ENCRYPT);
}

void decrypt(unsigned char *ciphertext, int ciphertext_len, unsigned char *key,
  unsigned char *iv, unsigned char *plaintext) {
    AES_KEY aes_key;
    AES_set_decrypt_key(key, 128, &aes_key);
    AES_cbc_encrypt(ciphertext, plaintext, ciphertext_len, &aes_key, iv, AES_DECRYPT);
}

int main() {
    unsigned char *key = (unsigned char *)"0123456789abcdef"; // 128-bit key
    unsigned char *iv = (unsigned char *)"abcdef0123456789"; // 128-bit IV
    unsigned char plaintext[] = "Hello, world!";
    int plaintext_len = strlen((char *)plaintext);

    // Determine the required size of the ciphertext buffer
    int ciphertext_len = ((plaintext_len - 1) / AES_BLOCK_SIZE + 1) * AES_BLOCK_SIZE;

    // Allocate memory for the ciphertext buffer
    unsigned char *ciphertext = malloc(ciphertext_len);

    // Encrypt the plaintext
    encrypt(plaintext, plaintext_len, key, iv, ciphertext);

    // Print the ciphertext
    printf("Ciphertext: ");
    for (int i = 0; i < ciphertext_len; i++) {
        printf("%02x", ciphertext[i]);
    }
    printf("\n");

    // Allocate memory for the decrypted plaintext buffer
    unsigned char *decrypted_plaintext = malloc(ciphertext_len);

    // Decrypt the ciphertext
    decrypt(ciphertext, ciphertext_len, key, iv, decrypted_plaintext);

    // Print the decrypted plaintext
    printf("Decrypted plaintext: %s\n", decrypted_plaintext);

    // Free memory
    free(ciphertext);
    free(decrypted_plaintext);

    return 0;
}

在上述代码中，我们使用了 OpenSSL 库的 AES 函数来实现加密和解密功能。其中，`AES_set_encrypt_key` 和 `AES_set_decrypt_key` 函数用于设置加密和解密所需的密钥，`AES_cbc_encrypt` 函数用于实现 CBC 模式的加密和解密。在主函数中，我们首先定义了一个 128 位的密钥和 IV，然后分别对明文进行加密和解密，并输出加密后的密文和解密后的明文。需要注意的是，为了方便输出，我们在代码中使用了 `printf` 函数，如果在实际应用中需要保证加密后的密文不被修改，应该使用更安全的输出方式，如将密文写入文件或发送到网络中。