Because if you had such a scheme it would no longer be wifi. WPA needs the device to have a key. You cannot replace WPA with your own key derivation scheme to a

Because if you had such a scheme it would no longer be wifi. WPA needs the device to have a key. You cannot replace WPA with your own key derivation scheme to avoid storing keys to keep this ridiculous statement in the blog post happy. Whatever scheme it is, it's probably compromised by rooting the device storing secrets... To make a reference to the quote used by Raymond Chen, the security flaw "rather involved being on the other side of this airtight hatchway".