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Re: /dev/random is probably not
From: "Michael Gnau" <MGnau () ctr pcusa org>
Date: Wed, 06 Jul 2005 15:30:23 -0400

Alexey Toptygin <alexeyt () freeshell org> 7/6/2005 7:37:00 AM >>>
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.


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