Re: Feistel cipher, shorter string and hex to int

From: "Daniel Verite" <daniel(at)manitou-mail(dot)org>
To: "Ivan Sergio Borgonovo" <mail(at)webthatworks(dot)it>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Feistel cipher, shorter string and hex to int
Date: 2009-07-07 10:07:48
Message-ID: 2c80afeb-7251-4b11-936d-a2b02dd61c1b@mm
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Ivan Sergio Borgonovo wrote:

> r2:=l1 # ((((1366.0*r1+150889)%714025)/714025.0)*32767)::int;
> -- but what about this? where does it come from?

This function:
(1366.0*r1+150889)%714025
implements a known method to get random numbers. I think it comes from
"Numerical recipes" by William Press.
Note that the algorithm is not tied to that function, it could be
replaced by something else (especially one that involves a private
key), but it has to be carefully chosen or the end result won't look so
random.

Best regards,
--
Daniel
PostgreSQL-powered mail user agent and storage:
http://www.manitou-mail.org

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