Date: Mon, 4 Sep 2000 14:36:30 -0700 (PDT) From: Kris Kennaway <kris@FreeBSD.org> To: Adam Laurie <adam@algroup.co.uk> Cc: James Wyatt <jwyatt@rwsystems.net>, Garrett Wollman <wollman@khavrinen.lcs.mit.edu>, Adam Back <adam@cypherspace.org>, security@FreeBSD.org Subject: Re: yarrow & /dev/random Message-ID: <Pine.BSF.4.21.0009041435490.23825-100000@freefall.freebsd.org> In-Reply-To: <39B3992B.7B823DEE@algroup.co.uk>
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On Mon, 4 Sep 2000, Adam Laurie wrote:
> Kris Kennaway wrote:
> >
> > On Sun, 27 Aug 2000, James Wyatt wrote:
> >
> > > On servers with no regular keyboard or mouse use, there is usually enough
> > > entropy in the disk and network IO to serve the purpose. Small servers
> > > with low net and disk entropy often get used as consoles for busier
> > > servers. Your mileage may vary, of course. What other sources of entropy
> > > might one consider? Maybe an AM radio tuned to static hooked into
> > > /dev/audio to get random samples? - Jy@
> >
> > My observations suggest that a sound card tuned to maximum input gain with
> > no microphone input (i.e. sampling noise in the card) is a very good
> > source of randomness, with at least 6 bits of entropy per 16 bit sample
> > for most cards, which can be sampled at 44Khz (i.e. about 32 kilobytes of
> > randomness per second, far in excess of what Yarrow needs).
> >
> > More than enough for even heavy server needs.
>
> This is only safe to do if you can guarantee that your sound card is
> protected from outside influence - e.g. radio transmissions putting
> known noise into your data. TEMPEST shielding would be a good start.
If interference from men in black is part of your threat model ;-)
Kris
--
In God we Trust -- all others must submit an X.509 certificate.
-- Charles Forsythe <forsythe@alum.mit.edu>
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