From owner-freebsd-current Wed Jul 19 12:29:56 2000 Delivered-To: freebsd-current@freebsd.org Received: from hda.hda.com (host65.hda.com [63.104.68.65]) by hub.freebsd.org (Postfix) with ESMTP id 19CA237B95D for ; Wed, 19 Jul 2000 12:29:34 -0700 (PDT) (envelope-from dufault@hda.hda.com) Received: (from dufault@localhost) by hda.hda.com (8.9.3/8.9.3) id PAA99620; Wed, 19 Jul 2000 15:30:42 -0400 (EDT) (envelope-from dufault) From: Peter Dufault Message-Id: <200007191930.PAA99620@hda.hda.com> Subject: Re: randomdev entropy gathering is really weak In-Reply-To: <200007191746.LAA82887@harmony.village.org> from Warner Losh at "Jul 19, 2000 11:46:01 am" To: Warner Losh Date: Wed, 19 Jul 2000 15:30:37 -0400 (EDT) Cc: Peter Dufault , current@FreeBSD.ORG X-Mailer: ELM [version 2.4ME+ PL61 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > In message <200007191308.JAA98111@hda.hda.com> Peter Dufault writes: > : > The reason why ntp is interesting is that we compare the received data > : > with our unpredictable local clock. It is the result of this comparison > : > which is good entropy bits. > : > : Is the resolution of thermal sensors on many new motherboards and > : CPU high enough to get thermal randomness? > > Yes. You'll also find that the voltage drifts as well. However, I > doubt you'd be able to get more than 1 bit out of the voltage > readings. The thermal readings, depending on their precision, would > also yield several random bits. But this several may be only 3 or 4. > The temperature varies based on work load and on the climate controls > in place at the site. I actually meant can you get real randomness, measuring the thermal noise in the on-chip temperature diode should be a good source of randomness. Except they are probably "kind" enough to fully filter it out. Peter -- Peter Dufault (dufault@hda.com) Realtime development, Machine control, HD Associates, Inc. Fail-Safe systems, Agency approval To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message