From: Chael Hall <nowhere@chaos.bsu.edu>
Date: Tue, 26 Jul 94 16:25:00 PDT
To: sidney@taurus.apple.com (Sidney Markowitz)
Subject: Re: CYPHERPUNKS TO THE RESCUE
In-Reply-To: <9407261836.AA07639@federal-excess.apple.com>
Message-ID: <199407262322.SAA04283@chaos.bsu.edu>
MIME-Version: 1.0
Content-Type: text/plain


>I recently used a smart card system for secure remote access to a network.
>It looked like both the card and the remote system had clocks that were in
>synch and both ran the same PRNG to produce a new number every minute. Part
>of the login procedure was to enter the number currently being displayed on
>the card.

     We use this for accessing our Ameritech database.  What I recall 
overhearing when they were training the CENTREX people on the smart cards 
was that it looks at how far off the numbers are over a period of time 
and determines how much faster or slower your card is, then figures that 
into its calculations when you call.  So after, say, twenty sessions over 
a two-week period, it knows not to accept the code from two minutes ago.

Chael

-- 
Chael Hall, nowhere@chaos.bsu.edu