WEP Open Key Vs WEP Shared Key

OPEN SYSTEM AUTHENTICATION
Open System Authentication is the default authentication protocol for the 802.11 standard. It consists of a simple authentication request containing the station ID and an authentication response containing success or failure data. Upon successful authentication, both stations are considered mutually authenticated. It can be used with WEP (Wired Equivalent Privacy) protocol to provide better communication security, however it is important to note that the authentication management frames are still sent in clear text during authentication process. WEP is used only for encrypting data once the client is authenticated and associated. Any client can send its station ID in an attempt to associate with the AP. In effect, no authentication is actually done.

SHARED KEY AUTHENTICATION

Shared Key Authentication is a standard challenge and response mechanism that makes use of WEP and a shared secret key to provide authentication. Upon encrypting the challenge text with WEP using the shared secret key, the authenticating client will return the encrypted challenge text to the access point for verification. Authentication succeeds if the access point decrypts the same challenge text.

   In the 802.11 standard, a device first Authenticates to the AP, and then Associates. The original designers intended that there would be a number of different Authentication methods to control who could use an AP.

In the 1999 version of the standard, 2 Authentication methods are defined: Open and Shared. In Open, any device can Authenticate to the AP. In Shared, only devices with the WEP key can successfully Authenticate. Sounds good so far.....

The problem with Authenticate, is that were it is in the process of establishing connectivity, none of the higher-level protocols, like 802.1X can be run inside of the Authenticate 802.11 frames. So 802.11i does not use it, just uses Open Authenticate.

Shared Authenticate has a serious flaw, in that it is a simple challenge/response protocol. This design is very open to offline dictionary attacks. A WEP key would easily be exposed. Additionally, even in Open Authentication, a device that did not have the WEP key would not be able to communicate via the AP, as the AP would discard all data packets from the device.

Bottom line: Shared Authentication does not add any security, and may weaken your security. Don't bother with it.