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Re: Flaw in commonly used bash random seed method

From: Dave English (dave.englishthus.net)
Date: Tue Apr 04 2006 - 03:21:40 CDT

In message
<a260a2190604031256g23cf3645s348f829530982b38mail.gmail.com>, Matthijs
<thottergmail.com> writes

>By the way, if the random function can only generate numbers between 0
>and 32767, won't 2 bytes be enough then? The algorithm will perform a
>modulo calculation anyway, so 4 bytes won't really add anything. Of
>course, it is much better then only one byte.

That will depend on whether the state stored between calls to the PRNG
is only 15-bits, or something larger.

If more state is stored than is enumerated in the result, then the
generator should have more points on its sequence than 32768 . In that
case then, seeding with more than 15 bits would be worthwhile.

I have not looked at Bash myself, to see what it actually does
--
Dave English Senior Software & Systems Engineer
                              Internet Platform Development, Thus plc