How does WPA work ?
In the WPA-enabled network, the client (notebook) first associates with the access point. The access point blocks LAN access until the user can be authenticated. If the client proves credentials to the authentication server, the client is allowed to join the LAN. If not, the client stays blocked from joining the LAN. Once the client joins the LAN, the authentication server distributes a TKIP encryption key to both the client and the access point. The client can then begin communicating on the LAN, encrypting data back and forth with the access point.
