Algorithm

[cosboys@erols.com]

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From: "Costello" <cosboys@erols.com>
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Subject: Algorithm
Date: Sun, 28 Feb 1999 14:31:37 -0500
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Okay, here's what's going on and I need some help with it:

Where I work we have cash registers with user logins.  Every employee has a
different login ID and PIN.  Regular employees and supervisors have regular,
low-level access and only a few capabilities.  Managers and technicians,
however, have higher level access and are able to do a lot more important
things.  ( I know I'm being vague on the capabilities of users but I'm
trying to hide the identity of  the company for my own sake.)  Once in a
while I'll be able to shoulder surf a PIN form a technician and do some
snooping on the system, but it is limited and here's where my probem comes
in.

When I shoulder surf a technician's PIN, it's only useful for the hour that
it's being used.  After that hour on that date the password becomes
inactive.  Then it changes and creates a new one.  Here are two examples of
PINs alonog with the dates and hours they were used:

PIN:  719
Date: 02/05/1999
Hour:  1600

PIN:  883
Date:  02/25/1999
Hour:  1300

I'm thinking that there is an algorithm based upon this information allowing
the technicians to calculate it in their heads relatively quickly.

Keep in mind that these PINs listed above are also prime numbers, I believe
that that also has something to do with it.