bugtraq - Re: Algorimic Complexity Attacks

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Message-ID: <20030608102235.B12903@ring.CS.Berkeley.EDU>
Date: Sun, 8 Jun 2003 10:22:35 -0700
From: Nicholas Weaver <nweaver@...berkeley.edu>
To: Pavel Kankovsky <peak@...o.troja.mff.cuni.cz>
Subject: Re: Algorimic Complexity Attacks


On Sun, Jun 08, 2003 at 06:17:38PM +0200, Pavel Kankovsky composed:
> 
> We need a function having a (relatively) small set of results in order to
> build a hash table. We can also assume the information about collisions
> leaks out via a timing channel. Ergo, a persistent attacker can find
> enough collisions by trial and error.

IF the hash is good, FINDING collisions doesn't necessarily help the
attacker, as the attacker really needs to generate lots of collisions
to make the searches O(n) instead of O(1), since that is teh key
behind this attack.

-- 
Nicholas C. Weaver                                 nweaver@...berkeley.edu