Date: Mon, 04 Sep 2000 13:44:28 +0100 From: Adam Laurie <adam@algroup.co.uk> To: Kris Kennaway <kris@FreeBSD.org> 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: <39B3992B.7B823DEE@algroup.co.uk> References: <Pine.BSF.4.21.0008270011040.64244-100000@freefall.freebsd.org>
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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. cheers, Adam -- Adam Laurie Tel: +44 (20) 8742 0755 A.L. Digital Ltd. Fax: +44 (20) 8742 5995 Voysey House http://www.thebunker.net Barley Mow Passage http://www.aldigital.co.uk London W4 4GB mailto:adam@algroup.co.uk UNITED KINGDOM PGP key on keyservers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message
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