OpenSSL AES_cfb128_encrypt C++

2022-01-07 00:00:00 encryption openssl aes c++

我试图实现一个非常"简单的加密/解密示例.我需要它用于我想加密一些用户信息的项目.我无法加密整个数据库，只能加密表中的某些字段.

I tried to implement a "very" simple encryption/decryption example. I need it for a project where I would like to encrypt some user information. I can't encrypt the whole database but only some fields in a table.

数据库和项目的其余大部分工作，除了加密:这是它的简化版本:

The database and most of the rest of the project works, except the encryption: Here is a simplified version of it:

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

using namespace std;

int main()
{
    /* ckey and ivec are the two 128-bits keys necessary to
       en- and recrypt your data.  Note that ckey can be
       192 or 256 bits as well
     */

    unsigned char ckey[] =  "helloworldkey";
    unsigned char ivec[] = "goodbyworldkey";

    int bytes_read;
    unsigned char indata[AES_BLOCK_SIZE];
    unsigned char outdata[AES_BLOCK_SIZE];
    unsigned char decryptdata[AES_BLOCK_SIZE];

    /* data structure that contains the key itself */
    AES_KEY keyEn;

    /* set the encryption key */
    AES_set_encrypt_key(ckey, 128, &keyEn);

    /* set where on the 128 bit encrypted block to begin encryption*/
    int num = 0;

    strcpy( (char*)indata , "Hello World" );
    bytes_read = sizeof(indata);

    AES_cfb128_encrypt(indata, outdata, bytes_read, &keyEn, ivec, &num, AES_ENCRYPT);
    cout << "original data:	" << indata << endl;
    cout << "encrypted data:	" << outdata << endl;

    AES_cfb128_encrypt(outdata, decryptdata, bytes_read, &keyEn, ivec, &num, AES_DECRYPT);
    cout << "input data was:	" << decryptdata << endl;
    return 0;
}

但是解密"数据的输出是一些随机字符，但是每次执行代码后都是一样的.outdata 每次执行都会改变...

But the output of "decrypted" data are some random characters, but they are the same after every execution of the code. outdata changes with every execution...

我尝试调试并寻找解决方案，但找不到任何解决方案.
现在我的问题是，这里出了什么问题?还是我完全误解了提供的功能?

I tried to debug and search for a solution, but I couldn't find any solution for my problem.
Now my question, what is going wrong here? Or do I completely misunderstand the provided functions?

推荐答案

问题在于 AES_cfb128_encrypt 修改了 ivec(为了允许链接，必须这样做).您的解决方案是创建 ivec 的副本并在每次调用 AES_cfb128_encrypt 之前对其进行初始化，如下所示:

The problem is that AES_cfb128_encrypt modifies the ivec (it has to in order to allow for chaining). Your solution is to create a copy of the ivec and initialize it before each call to AES_cfb128_encrypt as follows:

const char ivecstr[AES_BLOCK_SIZE] = "goodbyworldkey";
unsigned char ivec[AES_BLOCK_SIZE];
memcpy( ivec , ivecstr, AES_BLOCK_SIZE);

然后在第二次调用 AES_cfb128_encrypt 之前重复 memcpy.

Then repeat the memcpy before your second call to AES_cfb128_encrypt.

注意 1:您的初始向量太短了一个字节，所以我在它的末尾添加了一个明确的附加 .在复制或传递它们时，您应该确保所有字符串的长度都正确.

Note 1: Your initial vector was a byte too short, so I put an explicit additional at the end of it. You should make sure all of your strings are of the correct length when copying or passing them.

注意 2:任何使用加密的代码都应该真正避免使用 strcpy 或任何其他未检查长度的副本.这是一个危险.

Note 2: Any code which uses encryption should REALLY avoid using strcpy or any other copy of unchecked length. It's a hazard.

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