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The following archive was created by hippie-mail 7.98617-22 on Fri Aug 21 1998 - 17:20:09 ADT
William H. Geiger III (whgiii@invweb.net)
Tue, 07 Jul 1998 08:42:27 -0500
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In <00c501bda996$76d808e0$83004bca@em.who.net>, on 07/07/98
at 07:00 PM, "Enzo Michelangeli" <em@who.net> said:
>-----Original Message-----
>From: Ben Laurie <ben@algroup.co.uk>
>To: Antonomasia <ant@notatla.demon.co.uk>
>Cc: CodherPlunks@toad.com <CodherPlunks@toad.com>
>Date: Tuesday, July 07, 1998 6:24 PM
>Subject: Re: Random Data from Geiger Counter
>[...]
>>I was suggesting using the length of the intervals to generate more
>>bits, rather than the count in a specified time.
>In fact, I can see no reason why the number of bits cannot be made as
>large as allowed by the resolution of the time counter: after all, the
>time of decay is not quantized. For example, if your digital counter is
>clocked at 100 MHz and gated by the decay events, about one decay per
>second yields counts about 26 bit long. Discard, say, the most
>significant 10 bits, and you'll get something very close to 16 bits of
>entropy per decay event. The distribution should be extremely close to
>uniform, because in a Poisson statistics the chances of getting periods
>2^10 times smaller than the mean value (which would skew the
>distribution) are negligible. To make it safer, discard them after
>performing a hash.
>My point is that the constraints here seem to be only practical
>(frequencies too high for the time counter to accept, or periods too long
>for a comfortable measurement), not theoretical.
I would have to see the math and some test data before I would feel
comfortable with this. There seems to be a big difference between using
the time between to hit to generate X bits and taking the 2 deltas between
3 hits and then generating one bit of data from that.
- --
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William H. Geiger III http://users.invweb.net/~whgiii
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The following archive was created by hippie-mail 7.98617-22 on Fri Aug 21 1998 - 17:20:09 ADT