ALERT: WPA isn't necessarily secure

John Navas · 2006-12-05T01:30:52+00:00

SUMMARY: WPA-PSK is vulnerable to offline attack.TO AVOID THE PROBLEM: USE A PASSPHRASE WITH MORE THAN 20 CHARACTERS. Examples: BAD: "vintage wine" GOOD: "floor hiking dirt ocean" (pick your own words, even longer is better) FOR HIGH SECURITY, USE MORE THAN 32 CHARACTERS.BACKGROUND: Weakness in Passphrase Choice in WPA Interface By Glenn Fleishman By Robert Moskowitz Senior Technical Director ICSA Labs, a division of TruSecure Corp ... The offline PSK dictionary attack ... Just about any 8-character string a user may select will be in the dictionary. As the standard states, passphrases longer than 20 characters are needed to start deterring attacks. This is considerably longer than most people will be willing to use. This offline attack should be easier to execute than the WEP attacks. ... Using Random values for the PSK The PSK MAY be a 256-bit (64 hexadecimal) random number. This is a large number for human entry; 20 character passphrases are considered too long for entry. Given the nature of the attack against the 4-Way Handshake, a PSK with only 128 bits of security is really sufficient, and in fact against current brute-strength attacks, 96 bits SHOULD be adequate. This is still larger than a large passphrase ... ... Summary ... Pre-Shared Keying is provided in the standard to simplify deployments in small, low risk, networks. The risk of using PSKs against internal attacks is almost as bad as WEP. The risk of using passphrase based PSKs against external attacks is greater than using WEP. Thus the only value PSK has is if only truly random keys are used, or for deploy testing of basic WPA or 802.11i functions. PSK should ONLY be used if this is fully understood by the deployers.See also: Passphrase Flaw Exposed in WPA Wireless Security Wi-Fi Protected Access. Security in pre-shared key mode Cracking Wi-Fi Protected Access (WPA) WPA Cracker

Dec 05, 2006 28 Replies

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John Navas 19 years ago

On Thu, 07 Dec 2006 11:50:14 -0600, Peabody wrote in :

"And pigs have wings." $5 says you can't find any such service from RSA.

Bad idea, since the CD-R then becomes a security weakness. If you must use a device, go with a USB drive instead, and

*securely* erase it afterward. Or at least a CD-RW, *securely* erased, *not* just quick erased.

Won't help. "Just say no." Use something else that's better.

Bad idea, since that greatly reduces key entropy.

Hard to say if that would actually be good or bad.

What do you have against dice?

Not necessarily. Security is *HARD*, and not at all intuitive, even to many experts.

That's dangerously naive.

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Mark McIntyre 19 years ago

So? Its Marketing Blurb, not a white paper presented to the latest DefCon meeting. Read the salespitch for /any/ security s/w lately? Noticed any wild hyperbole in ISP's salespitch, or operating system makers' latest offerings ? No? Considered getting a brain transplant?

John is a past master at spreading his very own FUD, so this is quite a funny quote.

Its scary how many people believe all the FUD they read on the web, and even more scary how few people bother to carry out any independent assessment.

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Mark McIntyre 19 years ago

Irrelevant and axiomatic. Any password is insecure once its source is compromised. Even John's.

More to the point, I think.

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John Navas 19 years ago

On Thu, 07 Dec 2006 23:18:27 +0000, Mark McIntyre wrote in :

Including you. ;)

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John Navas 19 years ago

On Thu, 07 Dec 2006 23:20:28 +0000, Mark McIntyre wrote in :

Actually quite relevant.

Mine can't be compromised. Feel free to prove me wrong, if you can.

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Doug Jamal 19 years ago

Your reply was well written and your point is well received. Take care.

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John Navas 19 years ago

On Fri, 08 Dec 2006 02:21:12 GMT, "Doug Jamal" wrote in :

I sincerely thank you for your gracious response. To be clear, notwithstanding our different perspectives, I sincerely respect your point of view.

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Doug Jamal 19 years ago

Thank you, Mr. Navas. I appreciate that.

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Dwiz 19 years ago

Is this insecurity within WPA related to algebraic attacks at all? If it is there is a couple good thesis written on similar + prevention methods for A5/1 & 2. H

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