How third parties generate valid pins for locked to the network devices

[m0nix]

I have read a lot of stuff on this obscure topic, and it seems that low end or old devices can get their codes calculated easy, but the brand new ones like in my case a Sony device, were secure. There are methods of patching the firmware to bypass those checks, you don't remove them just go around them. And those things are hardware keys like the DRM of the stock rom, the hash of the pin is there too, that's why when i flashed new firmware the lock was still there, and bootloader unlock was not allowed, to make the work even harder.. So enough with the boring stuff, i ordered unlock code for sony device (now i wait) and i was wondering how they get them, there has to be a way of calculating that out by the imei, there are calculators but for very old phones.