openssl 各版本下载

https://openssl-library.org/source/old/index.html

#include <stdio.h>
#include <string.h>
#include <openssl/aes.h>
#include <openssl/rand.h>
#include <openssl/evp.h>

#define AES_KEY_BITS 128
#define GCM_IV_SIZE 12
#define GCM_TAG_SIZE 16

int aes_cbc_encrypt(const unsigned char *plaintext,
        int plaintext_len, const unsigned char *aad,
        int aad_len, const unsigned char *key,
        unsigned char *ciphertext, unsigned char *tag)
{
    EVP_CIPHER_CTX *ctx = NULL;
    int len = 0;
    int ciphertext_len = 0;

    // 创建并初始化 EVP_CIPHER_CTX 对象
    ctx = EVP_CIPHER_CTX_new();
    EVP_EncryptInit_ex(ctx, EVP_aes_128_cbc(), NULL, NULL, NULL);

    // 设置加密密钥
    EVP_EncryptInit_ex(ctx, NULL, NULL, key, NULL);

    // 加密明文数据
    if (EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_len) > 0)
    {
        ciphertext_len = len;
    }
    else
    {
        printf("Error! \n");
    }

    // 结束加密过程，并生成认证标签
    EVP_EncryptFinal_ex(ctx, ciphertext + len, &len);
    ciphertext_len += len;
    EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, GCM_TAG_SIZE, tag);

    // 释放EVP_CIPHER_CTX对象
    EVP_CIPHER_CTX_free(ctx);

    return ciphertext_len;
}

int aes_cbc_decrypt(const unsigned char *ciphertext,
        int ciphertext_len, const unsigned char *aad,
        int aad_len, const unsigned char *tag,
        const unsigned char *key, unsigned char *plaintext)
{
    EVP_CIPHER_CTX *ctx;
    int len;
    int plaintext_len;
    int ret;

    // 创建并初始化EVP_CIPHER_CTX对象
    ctx = EVP_CIPHER_CTX_new();
    EVP_DecryptInit_ex(ctx, EVP_aes_128_cbc(), NULL, NULL, NULL);

    // 设置解密密钥
    EVP_DecryptInit_ex(ctx, NULL, NULL, key, NULL);

    // 设置附加的认证数据（可选）
    EVP_DecryptUpdate(ctx, NULL, &len, aad, aad_len);

    // 解密密文数据
    EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len);
    plaintext_len = len;

    // 设置接收到的认证标签
    EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, GCM_TAG_SIZE, (void *)tag);

    // 结束解密过程，如果认证失败则返回错误
    ret = EVP_DecryptFinal_ex(ctx, plaintext + len, &len);
    plaintext_len += len;

    // 释放EVP_CIPHER_CTX对象
    EVP_CIPHER_CTX_free(ctx);

    return ret == 1 ? plaintext_len : -1;
}

int main()
{
    unsigned char key[AES_KEY_BITS / 8];
    unsigned char iv[GCM_IV_SIZE];
    unsigned char plaintext[] = "Hello, AES 128!";
    unsigned char ciphertext[sizeof(plaintext)];
    unsigned char decryptedtext[sizeof(plaintext)];
    unsigned char tag[GCM_TAG_SIZE];

    // 生成密钥
    if (RAND_bytes(key, sizeof(key)) != 1)
    {
        printf("error  generating AES key.\n");
        return 1;
    }

    printf("key: \n");
    for (int i = 0; i < AES_KEY_BITS / 8; i++)
    {
        printf("0x%0x  ", key[i]);
    }
    printf("\n");

    // 生成初始化向量
    if (RAND_bytes(iv, sizeof(iv)) != 1)
    {
        printf("Error generating GCM IV.\n");
        return 1;
    }
    printf("\n");


    // 加密明文数据
    int ciphertext_len = aes_cbc_encrypt(plaintext, sizeof(plaintext) - 1, NULL, 0, key, ciphertext, tag);

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

    printf("line: %d  Tag: ", __LINE__);
    for (int i = 0; i < GCM_TAG_SIZE; i++)
    {
        printf("%02x", tag[i]);
    }
    printf("\n");

    // 解密密文数据
    int decryptedtext_len = aes_cbc_decrypt(ciphertext, ciphertext_len, NULL, 0, tag, key, decryptedtext);

    decryptedtext[decryptedtext_len] = '\0';

    printf("line: %d  Decrypted text: %s\n", __LINE__, decryptedtext);

    return 0;
}

编译：

gcc main.c -o main -lssl -lcrypto

使用：

./main