SSL/TLS passive sniffing

[Victor Duchovni]

On Wed, Dec 22, 2004 at 07:43:13PM +0100, Florian Weimer wrote:

> > Actually reasoning along these lines is why Lutz Jaenicke implemented
> > PRNGD, it is strongly recommended (at least by me) that mail servers
> > use PRNGD or similar.  PRNGD delivers psuedo-random numbers mixing in
> > real entropy periodically.
> >
> > EGD, /dev/random and /dev/urandom don't produce bits fast enough.
> 
> Is this the only criticism of /dev/urandom (on Linux, at least)?  Even
> on ancient hardware (P54C at 200 MHz), I can suck about 150 kbps out
> of /dev/urandom, which is more than enough for our purposes.  (It's
> not a web server, after all.)
> 
> I'm slightly troubled by claims such as this one:
> 
>   <http://lists.debian.org/debian-devel/2004/12/msg01950.html>
> 

I think I made a mistake, my primary email servers don't have /dev/urandom
and the choice between EGD and PRNGD came down clearly on the PRNGD side,
but indeed /dev/urandom should suffice on Linux and other systems. Postfix
takes additional steps to reduce demand for raw entropy (in the tlsmgr
process, ...) but /dev/urandom works fine as an external entropy source.

I have not followed the debian issue, perhaps that really is just an
Exim+TLS design problem... 

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