如何扭转这种局面？答案

【问题标题】：How to reverse this?如何扭转这种局面？
【发布时间】：2014-10-24 21:50:38
【问题描述】：

我正在尝试使用加密来反转此解密，但真的很难做到..

unsigned int decrypt(unsigned char *encBuffer, unsigned int encBufferLen, unsigned char *decBuffer)
{
unsigned int decBufferLen = 0;

unsigned char table[] = { NULL, ' ', '-', '.', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 0x0D };

unsigned int offset = 0, i = 0;
unsigned char encStrLen = 0, c = 0;

while (offset < encBufferLen)
{
    if (encBuffer[offset] == 0xFFU) // if byte is 0xFF then add 0x0D to new buffer and continue
    {
        *(decBuffer + decBufferLen++) = 0x0D;
        offset++;
        continue;
    }

    encStrLen = encBuffer[offset++]; // get string length

    i = 0;
    if ((encStrLen & 0x80U) == 0) // if result is 0 then decrypt the string by Xor 33
    {
        while ((i++ < encStrLen) && (offset < encBufferLen))
        {
            *(decBuffer + decBufferLen++) = (encBuffer[offset++] ^ 0x33U);
        }
    }
    else // otherwise
    {
        encStrLen &= 0x7FU;
        while ((i < encStrLen) && (offset < encBufferLen))
        {
            c = encBuffer[offset++]; // c = current byte, increment the index
            *(decBuffer + decBufferLen++) = (table[(c & 0xF0U) >> 4]);

            if (table[c & 0x0FU] != NULL)
            {
                *(decBuffer + decBufferLen++) = table[c & 0x0FU];
            }

            i += 2;
        }
    }
}

return decBufferLen;

}

这是我经过一些测试后得到的

std::vector<unsigned char> encrypt(std::vector<unsigned char> decryptedBuf)
{
    std::vector<unsigned char> vector;

    unsigned int offset = 0, decryptedStringLength = 0;

    unsigned char currentByte = 0;

    while (offset < decryptedBuf.size())
    {
        if (decryptedBuf[offset] == 0x0D)
        {
            vector.push_back(0xFF);
            offset++;
            continue;
        }

        decryptedStringLength = decryptedBuf.size() - 1; // <--- to edit if encrypt works

        vector.push_back(decryptedStringLength); // <--- i'm not sure it will be interpreted right

        if (decryptedStringLength < 0x80) // < '128' Xor 33 http://pastebin.com/b18JfBFK
        {
            for (unsigned int i = 0; i < decryptedStringLength; i++)
                vector.push_back(decryptedBuf[offset++] ^ 0x33);
        }
        else // >= '128' Table
        {
            decryptedStringLength -= 0x80; // & 0x7F http://pastebin.com/THZjZJfs

            for (unsigned int i = 0; i < decryptedStringLength; i += 2)
            {
                currentByte = decryptedBuf[offset++];


            }
        }
    }

    return vector;
}

你知道如何扭转它吗？！我正在尝试 2 天，但我没有任何工作..

【问题讨论】：

-1，代码太多。您应该尽可能少地发布代码。
问题是什么？
@ntoskrnl 你知道如何扭转它吗？

标签： c++ encryption cryptography reverse

【解决方案1】：

decrypt 不是一对一的 - 许多不同的密文可以解密为相同的明文。对应“加密”功能的最简单方法是将明文分成不超过 127 个字节的块，输出块长度后跟块 XOR 0x33。这样，您只练习了一小部分decrypt 算法。 Working example

std::vector<unsigned char> encrypt(std::vector<unsigned char> decryptedBuf) {
  vector<unsigned char> result;

  size_t cur_offset = 0;
  while (cur_offset < decryptedBuf.size()) {
    unsigned char chunk_size = static_cast<unsigned char>(
        min(decryptedBuf.size() - cur_offset, size_t(0x7F)));
    result.push_back(chunk_size);
    result.insert(result.end(), decryptedBuf.begin() + cur_offset,
                  decryptedBuf.begin() + cur_offset + chunk_size);

    for (vector<unsigned char>::iterator it = result.end() - chunk_size;
         it != result.end(); ++it) {
      *it ^= 0x33;
    }

    cur_offset += chunk_size;
  }
  return result;
}

【讨论】：