WiFi authentication

The 802.11 standard supports two means of client authentication between the wireless NIC and the AP: open system and shared key.

With shared key, the AP sends the client device a challenge text packet that the client must then encrypt with the correct WEP key and return to the AP. If the client has the wrong key or no key, authentication will fail and the client will not be allowed to associate with the AP. Shared key authentication is not considered secure, because a hacker who detects both the clear-text challenge and the same challenge encrypted with a WEP key can decipher the WEP key.

With open system, authentication involves supplying the correct SSID. Even if a client can complete authentication and associate with an AP, the use of WEP prevents the client from sending data to and receiving data from the AP, unless the client has the correct WEP key.