使用CBC的密文链模式算法的c语言代码

以下是使用CBC模式进行加密和解密的C语言代码示例：

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

#define KEY_SIZE 16
#define IV_SIZE 16

void handleErrors(void);

int encrypt(unsigned char *plaintext, int plaintext_len, unsigned char *key,
            unsigned char *iv, unsigned char *ciphertext);

int decrypt(unsigned char *ciphertext, int ciphertext_len, unsigned char *key,
            unsigned char *iv, unsigned char *plaintext);

int main(void)
{
    /* 初始化OpenSSL库 */
    OpenSSL_add_all_algorithms();
    OPENSSL_config(NULL);

    /* 输入明文和密钥 */
    unsigned char plaintext[] = "Hello, World!";
    unsigned char key[KEY_SIZE];
    unsigned char iv[IV_SIZE];
    printf("Enter the 16-byte key: ");
    scanf("%s", key);
    printf("Enter the 16-byte IV: ");
    scanf("%s", iv);

    /* 加密明文 */
    int len = strlen((char *)plaintext);
    unsigned char ciphertext[len + EVP_MAX_BLOCK_LENGTH];
    int ciphertext_len = encrypt(plaintext, len, key, iv, ciphertext);
    printf("Ciphertext is: ");
    for (int i = 0; i < ciphertext_len; i++) {
        printf("%02x", ciphertext[i]);
    }
    printf("\n");

    /* 解密密文 */
    unsigned char decryptedtext[len];
    int decryptedtext_len = decrypt(ciphertext, ciphertext_len, key, iv, decryptedtext);
    decryptedtext[decryptedtext_len] = '\0';
    printf("Decrypted text is: %s\n", decryptedtext);

    /* 清理OpenSSL库 */
    EVP_cleanup();
    ERR_free_strings();

    return 0;
}

void handleErrors(void)
{
    printf("Encryption/Decryption failed\n");
    exit(1);
}

int encrypt(unsigned char *plaintext, int plaintext_len, unsigned char *key,
            unsigned char *iv, unsigned char *ciphertext)
{
    EVP_CIPHER_CTX *ctx;

    int len;
    int ciphertext_len;

    /* 创建并初始化Cipher上下文 */
    if (!(ctx = EVP_CIPHER_CTX_new())) handleErrors();

    /* 初始化加密操作 */
    if (1 != EVP_EncryptInit_ex(ctx, EVP_aes_128_cbc(), NULL, key, iv))
        handleErrors();

    /* 加密明文 */
    if (1 != EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_len))
        handleErrors();
    ciphertext_len = len;

    /* 完成加密操作 */
    if (1 != EVP_EncryptFinal_ex(ctx, ciphertext + len, &len)) handleErrors();
    ciphertext_len += len;

    /* 清理Cipher上下文 */
    EVP_CIPHER_CTX_free(ctx);

    return ciphertext_len;
}

int decrypt(unsigned char *ciphertext, int ciphertext_len, unsigned char *key,
            unsigned char *iv, unsigned char *plaintext)
{
    EVP_CIPHER_CTX *ctx;

    int len;
    int plaintext_len;

    /* 创建并初始化Cipher上下文 */
    if (!(ctx = EVP_CIPHER_CTX_new())) handleErrors();

    /* 初始化解密操作 */
    if (1 != EVP_DecryptInit_ex(ctx, EVP_aes_128_cbc(), NULL, key, iv))
        handleErrors();

    /* 解密密文 */
    if (1 != EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len))
        handleErrors();
    plaintext_len = len;

    /* 完成解密操作 */
    if (1 != EVP_DecryptFinal_ex(ctx, plaintext + len, &len)) handleErrors();
    plaintext_len += len;

    /* 清理Cipher上下文 */
    EVP_CIPHER_CTX_free(ctx);

    return plaintext_len;
}

注：以上代码使用OpenSSL库进行加密和解密。编译时需要链接OpenSSL库，例如：

gcc -o cbc_encrypt_decrypt cbc_encrypt_decrypt.c -lcrypto