[ntp:questions] Re: Fingerprinting hosts by clock skew

Brian Inglis Brian.Inglis at SystematicSW.Invalid
Wed Mar 9 05:51:27 UTC 2005

On Tue, 8 Mar 2005 20:07:02 -0800 in comp.protocols.time.ntp, Michael
Deutschmann <michael at talamasca.ocis.net> wrote:

>On Sat, 5 Mar 2005, David L. Mills wrote:
>> However, the most useful property of the clock frequency is to track
>> systematic changes, which serves as a quite accurate thermometer.
>> [...] we are talking about millidegrees here.
>> [...] I should add to that proposal using NTP frequency to
>> reveal outdoor temperature if the IT staff would put the computer
>> outside the building in a doghouse on the roof.
>Due to the difficulties of calibrating to real world units, I don't think
>this would be practical.  A sensor such as a thermistor can be waterproofed
>and taken through it's range in a water bath.  You can't do that to a
>computer, especially if it's on.
>A better use for the phenomena would be a simple hardware mod to make NTP
>systems more stable.  Find the oscillator can on the motherboard, glue a
>50kOhm-nominal thermistor to it, and then run leads from it out of the case
>and then back to pins 1 & 3 of the joystick port.  Then (the tricky bit...)
>alter ntpd to search for a correlation between the "Joystick 1 X axis"
>reading and the frequency correction, and start actively compensating when/if
>the estimated curve firms up sufficently.

Would be easier to attach the case thermal sensor to the clock
generator, wherever that is nowadays. 

Thanks. Take care, Brian Inglis 	Calgary, Alberta, Canada

Brian.Inglis at CSi.com 	(Brian[dot]Inglis{at}SystematicSW[dot]ab[dot]ca)
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