pre-authentication when using wpa2-psk

Jouni Malinen j at w1.fi
Mon Mar 23 06:24:05 EDT 2009


On Mon, Mar 23, 2009 at 10:59:09AM +0800, zh f wrote:

>     I  want to optimize roaming process for marvell wifi card. And it's
> seems that 4-way handshake takes about 30-200 ms  and it is too long for
> voip service. So I want to enable pre-authentication, but it is seems that
> wpa_supplicant can't do this when using WPA2-PSK. is pre-authentication
> only  for ieee802.1x key management?

There is no point in using RSN pre-authentication with
WPA2-Personal/PSK. Pre-authentication is used to skip the EAP
authentication and it is still using 4-way handshake to derive the
actual encryption keys, i.e., it would not change anything for
WPA2-Personal.

As far as 4-way handshake taking 30-200 ms is concerned, that sounds
like a potential issue somewhere or a very low-performance CPU. It
should be possible to complete 4-way handshake in less than 10 ms in
most cases (just couple of milliseconds with reasonably clear channel
and modern CPU). In other words, I would suggest trying to figure out
what is making the 4-way handshake take that long in this particular
case.

-- 
Jouni Malinen                                            PGP id EFC895FA


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