From owner-freebsd-hackers  Sun Nov 11 12:56:16 2001
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Date: Sun, 11 Nov 2001 14:56:12 -0600 (CST)
From: Mike Silbersack <silby@silby.com>
To: John Kozubik <john@kozubik.com>
Cc: <freebsd-hackers@FreeBSD.ORG>
Subject: Re: CPU Temp and Fan speed as entropy?
In-Reply-To: <Pine.BSF.4.21.0111102126430.68269-100000@www.kozubik.com>
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On Sat, 10 Nov 2001, John Kozubik wrote:

>
> 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

I tried running one of the monitoring programs after I sent that message,
and found what you guessed above; the accuracy is not early good enough
for entropy use.  The granularity seems to be about 4 degrees, and the
temperature seems to just bounce between two values once every few seconds
or so.

Oh well.

Mike "Silby" Silbersack


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