CTF中遇到的有趣異或加密

代碼整理為了C語言.
提取了核心的異或代碼.

unsigned char*  encode(const unsigned char* enbuffer, int enbufferlen)
{
    unsigned char* result = (unsigned char*)malloc(enbufferlen * sizeof(char) + 1);
    if (result == nullptr) return nullptr;
    memset(result, 0, enbufferlen + 1);
    for (int i = 0; i < enbufferlen; i += 3)
    {
        result[i] = enbufferlen ^ (enbuffer[i] + 6);
        result[i + 1] = (enbuffer[i + 1] - 6) ^ enbufferlen;
        result[i + 2] = enbuffer[i + 2] ^ 6 ^ enbufferlen;
    }
    return result;                       // //zerobuffer = flag
}
unsigned char* decode(const unsigned char* debuffer, int debufferlen)
{
    unsigned char* result = (unsigned char*)malloc(debufferlen * sizeof(char));
    if (result == nullptr) return nullptr;
    memset(result, 0, debufferlen + 1);
    for (int i = 0; i < debufferlen; i += 3)
    {
        result[i] = (debufferlen ^ debuffer[i]) -6;
        result[i + 1] = (debuffer[i + 1] ^ debufferlen) + 6;
        result[i + 2] = debuffer[i + 2] ^ 6 ^ debufferlen;
    }
    return result;                     
}

int main(int argc,char**argv)
{
    unsigned char buffer[] = "HelloIBinary";
    int size = sizeof(buffer) / sizeof(buffer[0]);
    unsigned char * CipherText = encode(buffer, size);
    unsigned char * PlantText = decode(CipherText, size);
}