bugtraq - Re: /dev/random is probably not

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Message-ID: <Pine.NEB.4.62.0507061124220.4246@ukato.freeshell.org>
Date: Wed, 6 Jul 2005 11:37:00 +0000 (UTC)
From: Alexey Toptygin <alexeyt@...eshell.org>
To: Jack Lloyd <lloyd@...dombit.net>
Cc: bugtraq@...urityfocus.com
Subject: Re: /dev/random is probably not

On Tue, 5 Jul 2005, Jack Lloyd wrote:

> Assuming the PRNG is any good, it shouldn't matter if an attacker can 
> manipulate such timings, because (by definition) a good PRNG will still 
> behave correctly even if an attacker does feed it lots of deliberately 
> bad data (as long as the PRNG also has been fed with a sufficient amount 
> of unguessable 'good' input as well, of course).

In the case of Linux, this still causes the estimate of how much 'good' 
entropy is in the pool to be inflated. Some applications may rely on the 
fact that /dev/random is backed by 'real' entropy, whereas /dev/urandom 
can be pure PRNG output.

IMO, all this discussion is well and good, but it would be much more 
productive for someone to settle the question empirically.

 			Alexey