The web-interface of OpenWRT's "white russian" 0.9 version allows you to select WPA as encryption, which suggests that it works out of the box.
I've configured the WLAN with WPA/TKIP (WPAv1) and tried to connect with a client:
Did not work.
The reason for that is, that the package "nas", which is needed for handling encryption for WPA is not installed by default, because it's non-free.
[SOLUTION]
Thanks to the old FAQ collection of OpenWRT, I've been pointed at that package.
With "white russian"'s web interface, it's dead easy to install the missing "nas" package:
1) Open the OpenWRT web interface of your router
2) Go to the "System > Installed Software" page
3) On the right side, click on "Update package lists" link.
4) Now, scroll down and select "install" of the package called "nas"
5) Reboot the router.
Now, WPA should work.
[REFERENCES]