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The following archive was created by hippie-mail 7.98617-22 on Fri Aug 21 1998 - 17:20:24 ADT
Ben Laurie (ben@algroup.co.uk)
Wed, 15 Jul 1998 10:56:39 +0100
Carl Ellison wrote:
>
> -----BEGIN PGP SIGNED MESSAGE-----
>
> At 11:27 PM 7/14/98 +0100, Ben Laurie wrote:
> >My idea was to poll the mouse once every second or so, rather than 20
> >times a second. This would reduce the loss of entropy because of
> >predictable mouse positions without severe overhead. Even better would
> >be to do it during idle processing (if you are in no hurry to get the
> >entropy).
>
> Ben,
>
> the last time I analyzed pointing data, the real entropy source came from
> high frequency components (of the mouse track, sampled frequently). If you
> sample only once a second, you lose those high frequencies.
I think we've suffered a bit of context loss here: my point was that
sampling at regular intervals seemed to me to be better than sampling at
mouse down/up events. The counterpoint was that sampling 20 times/second
kills the machine, so I opined that once per second was still better
than on mouse up/down events.
> BTW, I also found that if you ask the user to do something non-mouse (e.g.,
> sign his name or sign "John Handcock"), then the high frequency noise is
> even greater -- over 1 bit per mouse sample.
I've noticed that some mice will sometimes do a 1-pixel jitter when you
aren't even touching them. Presumably this looks like useful input but
is actually nearly completely entropy-free.
Cheers,
Ben.
-- Ben Laurie |Phone: +44 (181) 735 0686| Apache Group member Freelance Consultant |Fax: +44 (181) 735 0689|http://www.apache.org/ and Technical Director|Email: ben@algroup.co.uk | A.L. Digital Ltd, |Apache-SSL author http://www.apache-ssl.org/ London, England. |"Apache: TDG" http://www.ora.com/catalog/apache/WE'RE RECRUITING! http://www.aldigital.co.uk/recruit/
The following archive was created by hippie-mail 7.98617-22 on Fri Aug 21 1998 - 17:20:24 ADT