[kismac] Re: WPA-TKIP, Kismac, and my network

  • From: "Brian" <whj6z7602@xxxxxxxxxxxxxx>
  • To: kismac@xxxxxxxxxxxxx
  • Date: Sun, 23 Jan 2005 16:56:57 -0500

On Jan 23, 2005, at 11:01 AM, Brad Knowles brad-at-stop.mail-abuse.org |KisMAC list| wrote:

At 9:40 PM +0800 2005-01-23, Robin L Darroch wrote:

Really? That sounds very interesting indeed! Do you have any references
or links about that?

Oh, see also the article at <http://www.nwfusion.com/reviews/2004/1004wirelesswpa.html>.

From that article: "The innate problem is that a passphrase is easy to guess." Actually, a _poor_ passphrase is easy to guess (dictionary attacks, precomputed hashes, etc.). A "strong" passphrase (WPA-PSK allows for up to 63 chars) is not going to be so easy to brute-force.

I still haven't -- yet! <g> -- seen anyone discussing any weaknesses of WPA besides the offline dictionary attack on the passphrase in PSK mode. Has anyone yet uncovered any actual crypto flaws that shorten the attack from just brute-force?

Sure, if you know the passphrase, you can calculate others' PTKs. But if you know the passphrase and you're already on the network, you have other attacks at your disposal as well (attack the switch or other clients with arp poisoning, etc.). With a single PSK per ESS, you need to trust the people you give the PSK to.

So far, it looks like if you pick a reasonably strong passphrase, maybe change it every once in a while, you should be pretty secure unless you're on the NSA's top-10 list or something. ;-) And still use SSH/SSL/TLS (and PGP/GnuPG for your email) over that link for truly sensitive stuff -- after all, once it leaves _your_ network, even an 802.11i RSN isn't going to keep your data safe. But everything I've read says that the strength of WPA-PSK is dependent on the strength of the passphrase; it needn't be weak *if* the network administrator knows what he's doing.

 - Brian

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