Re: Br/Mul/Unicast WEP Key


From: Xam R. Time (xam_at_chalupa.wi2600.org)
Date: 2002-04-13 13:43:22 UTC


To the best of my knowledge, the situation is quite a bit different than the one you're proposing.

In typical static WEP environments only 1 key is only ever in use at a time. That is, of the (maybe 4) WEP keys configured at the AP and the stations, all the nodes are agreeing on which key to use of the several -- this applies for all frames, and no differentiation is made on Mcast, Bcast, or Ucast.

However, in environments such as ones you could have if using Aironet gear (from Cisco), if for example you're using LEAP, each client uses a private WEP key (read: unique) to exchange Unicast frames with the AP. However, only in a case like this is there a common key that ALL stations use for Tx'ing broadcasts.

Obviously, it's counter intuitive for an AP to re-transmit a broadcast to each and every 802.11 node via. their unique key, so the solution happens to be that, at least on Aironet, WEP Key #1 is used for bcasts, and mcasts as well.

This is the only case I know of where more than a single key is active at one moment.

-Tony Kapela

On Sat, 13 Apr 2002, R Selvaraj wrote:

> Hi,
> Could any of u pls tell me how the Broadcast, Multicast and Unicast WEP keys are used.
> My understanding is that if the destination address is Broadcast then that packet is encrypted based on the Broadcst WEP Key. Similarly for the Multiast and Unicast WEP Key,ie based on destinatoin address.
> If it is the case then how the NIC identifies those key among the four WEP Keys ?
>
> Thanks,
> Selva.
>
>
>
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