From owner-freebsd-hackers Sat Nov 10 21:45:54 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from www.kozubik.com (www.kozubik.com [216.188.96.212]) by hub.freebsd.org (Postfix) with ESMTP id DE73E37B419 for ; Sat, 10 Nov 2001 21:45:49 -0800 (PST) Received: from localhost (john@localhost) by www.kozubik.com (8.11.0/8.11.0) with ESMTP id fAB5YqO68734; Sat, 10 Nov 2001 21:34:53 -0800 (PST) (envelope-from john@kozubik.com) Date: Sat, 10 Nov 2001 21:34:52 -0800 (PST) From: John Kozubik To: Mike Silbersack Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: CPU Temp and Fan speed as entropy? In-Reply-To: <20011109095347.R46119-100000@achilles.silby.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG CPU temp and fan speed may or may not be truly random - regardless, I would be wary of using them as random seeds. First, I suspect that the range of values is quite small - how much does your temp and fan speed actually fluctuate over time ? Second, I don't have a bios like this in front of me to examine, but I doubt the granularity is greater than one decimal place. Comments ? Due to the small range that these numbers will fall in, I would think the effectiveness of these values as a random seed are directly related to the number of places to the right of the decimal these values are measured in. ----- John Kozubik - john@kozubik.com - http://www.kozubik.com On Fri, 9 Nov 2001, Mike Silbersack wrote: > > Out of curiousity, has anyone looked into using cpu temperature and fan > speed as an entropy source? The thought came to last time I was in bios, > looking at the temperature stats; to my untrained eye, it sure looks like > those numbers bounce around a lot. I think most motherboards are coming > with such sensors onboard these days, and I also believe that we have > userland support for reading the values. > > I think we're doing just fine wrt entropy in -current, but it would still > be rather neat to harvest hardware-derived entropy on a wide variety of > machines. > > Just curious, > > Mike "Silby" Silbersack > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message