*taken from above link
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.
Canucklehead wrote:
> http://www.dslreports.com/forum/remark,8645211
>
>
> Bin Chen wrote:
> > Hi,
> >
> > In a manual I found there are two authentication methods, named, "Open"
> > and "Shared", are they relating to WEP? What is the difference?
> >
> > Thanks.
> > ABAI 
Difference between WEP type 
Linear Mode
