Shared Key Authentication
802.11 shared key authentication goes a step further than open system authentication by using the
common WEP key to authenticate radio cards. This is a four-way handshaking process:
1. The radio card sends an authentication request.
2. The access point responds with an authentication frame containing challenge text, which is a
string of unencrypted text.
3. The radio card encrypts the challenge text with the WEP key and sends the result to the access
point.
4. The access point decrypts the challenge text with the common WEP key. If the challenge text
is the same text that the access point initially sent, then the access point assumes that the radio
card has the correct WEP key and that the radio card is a legitimate user.
Unfortunately, shared key authentication is easy to hack. In fact, a hacker can use freely
available tools to readily find the WEP key. As a result, it is strongly advisable to not use shared
key authentication.