hostapd: Confusion (IOCTL_SET_KEY)

Jouni Malinen j
Sat Mar 24 15:32:34 PDT 2007

On Fri, Mar 23, 2007 at 08:04:46PM +1100, Nazeer Khan wrote:

> I am using hostapd with madwifi. I have a little confusion about how
> hostapd set and get encryption keys.
> Can someone tell what is the basic difference between the following two.
> madwifi_set_key: alg=CCMP addr=00:13:CE:ED:36:9E key_idx=0
> madwifi_set_key: alg=TKIP addr=00:00:00:00:00:00 key_idx=1

The first one is setting a individual key (unicast) for a station while
the second one is setting a group key (broadcast).

> What is confusing me is that what will be the difference if we specify the
> MAC address of the station or if we specify 00:00:00:00:00:00.

The all-zeros address is not really used. This is a broadcast key, so it
applies to all broadcast/multicast packets regardless of destination.

> Secondly, when hostapd is requesting for the key, it is always using
> 00:00:00:00:00:00 as MAC address, why not the MAC address of the station?

hostapd is only requesting the latest packet number for group
(broadcast/multicast) keys, so there is not a case where it would need
to use a MAC address of a station.

Jouni Malinen                                            PGP id EFC895FA

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