It only works on an indirect way. You have to install 8.1 with generic key first and after that, you can use your genuine 8 key for activation
You can also add a ei.cfg file in the source folder to avoid having to enter the key during installation. Include the following in Notepad and save as ei.cfg. [EditionID] [Channel] Retail [VL] 0
Can I buy a Windows 8 upgrade key and use it in this manner? I installed 8.1 with a default key. I just got a job at an electronic store that sells windows 8 upgrade licenses, so I will be able to get an employee discount on top of that.