Other Directory Sites: SeekWonder | Directory Owners Forum
The following archive was created by hippie-mail 7.98617-22 on Fri Aug 21 1998 - 17:20:08 ADT
Ben Laurie (ben@algroup.co.uk)
Tue, 07 Jul 1998 10:06:50 +0100
Perry E. Metzger wrote:
> Ben Laurie writes:
> > Seems to me like he's being very conservative about the entropy of the
> > data source - 1 bit for two (detected) decays. Surely we can get a bit
> > (or two) more out of it than that?
>
> This is cryptography. Those that are conservative live. Those that are
> "risk-oriented" end up as "don't let this happen to you" stories in
> the pages of a future David Kahn's book on the history of
> cryptography.
>
> Personally, I don't know if one bit per two decays is sufficiently
> conservative for my tastes.
>
> People really have to get it through their heads that this is one
> field where, when you don't know an answer, you *have* to behave as
> though the worst is true, not the best.
That is not a helpful argument. I agree you have to assume the worst,
but you are suggesting that no matter what I assume it isn't bad enough
(because, allegedly, "I haven't got it through my head that this is one
field where, when you don't know an answer, you *have* to behave as
though the worst is true"). Just suppose, as a wild fantasy, that I have
got that through my head. Now, what is the "worst" in this case? If that
can't be answered, then the number of bits of entropy I can get per hit
is zero, surely?
BTW, if you want to use more than three hits per bit, then I suggest you
time 2n intervals (using either 2n+1, 2n+2, 3n or 4n hits, your choice,
though theory says 2n+1 is just as good as 4n, and, indeed is what is
used by John Walker with n=1), compare them in pairs, discard if the
number where the first interval is smaller is equal to the number where
the second is smaller, generate 0 if it is less, 1 if greater.
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 - 17:20:08 ADT