How Secure Is Your Wireless Network? Safeguarding Your Wi-Fi LAN

Authentication Spoofing

A variation of the packet injection attack is authentication spoofing. In order to understand how this attack works, let's take another look at the shared key authentication process.

• Step 1— The client sends an authentication request to the AP.
• Step 2— The AP sends the client 128 bytes of challenge text.
• Step 3— The client encrypts the challenge text with its WEP key and sends the challenge response back to the AP.
• Step 4— The AP uses its knowledge of the WEP key to validate the challenge response and determine if the client does, in fact, know the shared secret key.
• Step 5— The AP responds to the client with a success or failure message.

The problem here is that if an attacker can observe this negotiation process, she ...