keyfile_loop_1.cpp

u_char middle_[17]{};
u_char org_middle_[17]{};

// Generate randomly 
for (size_t i = 0; i < 17; i++)
{
  middle_[i] = 0x20 + rand() % (0x7F - 0x20);
}
std::copy(std::begin(middle_), std::end(middle_), org_middle_);

u_char last_[17]{};

// loop_1
__asm {
  lea esi, middle_;
  mov ecx, 13;
loop_1:
  lodsd;
  xor eax, 0x1BADC0DE;
  bswap eax;
  not al;
  rol eax, cl;
  inc ecx;
  bswap eax;
  ror eax, cl;
  dec ecx;
  not eax;
  xor eax, 0x98765432;
  xchg al, ah;
  mov [esi - 4], eax;
  sub esi, 3;
  loop loop_1;
}

// loop_2
for (size_t i = 0; i < 16; i++)
{
  middle_[i] ^= key[2];
}