They are all encoded separately to save on memory and to avoid tampering of such key files.
One method is if you have an osu!stable install then you can completely copy that folder put it onto a thumbdrive and then move it to the new computer, install lazer and migrate the contents of osu!stable to osu!lazer.
The other method which i am not entirely sure if it works is put a thumbdrive into the computer, open osu!lazer, go to the settings, search for the button that allows the user to change the lazer directory, choose the new directory (the thumbdrive), allow it to import, then plug the thumbdrive into the new computer, open osu!lazer, choose directory from lazer's settings, then allow it to export into the new computer under a new directory.