Difference between WPA1-PSK CCMP and WPA2-PSK CCMP

[Nicholas Chan]

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.

Or did i missed out something from the standard?

Cheers
Nicholas

[Bryan Kadzban]

Post by Nicholas Chan
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.

Both WPA1 and WPA2 can use either TKIP or CCMP encryption. (It is true
that some APs and some clients restrict the combinations, but there are
four possible combinations, and AFAIK all of them are Wi-Fi Alliance
standards. WPA1 with CCMP may not be, but I believe it is.)

The difference between WPA1 and WPA2 is in the information elements that
get put into the beacons, association frames, and 4-way handshake
frames. The data in these IEs is basically the same, but the identifier
used is different. WPA1 uses (one of?) Microsoft's OUI(s) along with an
ID byte or two that Microsoft guarantees is unique as its IE identifier,
while WPA2 uses an IE identifier that the IEEE assigned as part of the
802.11i standard.

So there is a difference, and both supplicants and APs have to
understand the WPA2 IE identifier values to be able to work in WPA2
mode. But the actual behaviors (the key exchange, and the encryption
and decryption processes) are the same in both modes.

Post by Nicholas Chan
Or did i missed out something from the standard?

I'm not sure if it's in the standard or not (I'd assume it is somewhere,
but I don't know for sure), but I noticed the difference while doing
some wireless captures of the association process on WPA1 and WPA2
networks. Ethereal (yes, yes, it's now called Wireshark, but it was
Ethereal at the time) was able to decode the various IEs, and I noticed
that the IE identifiers were different depending on the network mode.

Actually, the difference may only show up if you compare the Wi-Fi
Alliance standards for WPA1 and WPA2. IIRC, the IEEE standard doesn't
mention WPA1 at all.

[Paul Lambert]

Post by Bryan Kadzban

Post by Nicholas Chan
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.

Both WPA1 and WPA2 can use either TKIP or CCMP encryption. (It is true
that some APs and some clients restrict the combinations, but there are
four possible combinations, and AFAIK all of them are Wi-Fi Alliance
standards. WPA1 with CCMP may not be, but I believe it is.)
The difference between WPA1 and WPA2 is in the information elements that
get put into the beacons, association frames, and 4-way handshake
frames. The data in these IEs is basically the same, but the
identifier
used is different. WPA1 uses (one of?) Microsoft's OUI(s) along with an
ID byte or two that Microsoft guarantees is unique as its IE
identifier,
while WPA2 uses an IE identifier that the IEEE assigned as part of the
802.11i standard.

The 4-way handshake for WPA2 is also slightly different than WPA in
the way the 3rd and 4th PDUs are encrypted.


Paul

[Jouni Malinen]

Post by Nicholas Chan
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.