Difference between WPA1-PSK CCMP and WPA2-PSK CCMP

[Jouni Malinen]

On Tue, Aug 29, 2006 at 01:13:48AM +1000, Nicholas Chan wrote:

> Hi i noticed in wpa_supplicant, you have a choice between wpa1-psk
> ccmp and wpa2-psk ccmp.
> 
> I was wonder what is the difference between them? From the 802.11i
> standard, it states that wpa1-psk uses TKIP whereas wpa2-psk uses
> CCMP.

No, it doesn't. IEEE Std 802.11i-2004 does not mention WPA in any way;
not WPA or WPA2 for that matter. WPA and WPA2 are the names that Wi-Fi
Alliance uses for the protocol. WPA was based on an early draft of IEEE
802.11i (D3.0) with the IEs and identifiers changes to be vendor
specific and some functionality removed. Apart from different
identifiers, the main difference in key handshake is that WPA2 (i.e.,
IEEE Std 802.11i-2004) includes the initial group key in the 4-way
handshake and the first group key handshake is skipped whereas WPA needs
to do this extra handshake to deliver the initial group keys. Re-keying
of the group key happens in the same way.

As far as CCMP is concerned, it is almost identical between WPA and
WPA2. There is one difference in handling of fragmented frames that
would make these versions incompatible--at least in theory. However,
most vendor are using the newer definition of CCMP header masking rules
for the fragments and it would be somewhat difficult to even find the
old implementation in any use. Wi-Fi Alliance certification for WPA did
not include CCMP, so this part was not verified at the time and I think
that the current specification for WPA has already dropped the
difference in fragmentation format since no one really wanted to keep
that extra complexity around.

As Bryan already mentioned, both TKIP and CCMP can be used regardless of
which version of WPA is used. WPA was not certified with CCMP, but WPA2
certification includes tests for both TKIP (only for backwards
compatibility with WPA) and CCMP.

There are more differences in how EAP authentication can be optimized in
WPA2 (PMKSA caching and RSN pre-authentication), but those are getting
outside the scope of the question abourt differences in
WPA/WPA2-Personal.

-- 
Jouni Malinen                                            PGP id EFC895FA