From: fbauer@access.digex.com (Fred Bauer)
Subject: Re: Identify this key....
Organization: Express Access Online Communications, Greenbelt, MD USA
Date: Thu, 5 Nov 1992 14:44:00 GMT

In article <lairdb.720900457@crash.cts.com> lairdb@crash.cts.com (Laird P. Broadfield) writes:
>The "key" itself is a black plastic doodad, roughly 5/8 inch wide by
>.075 thick, by about 2 1/4 long (not counting the head.)  The head
>is hexagonal, roughly like a Kwikset head, but the only hole is the
>keyring hole.
>
>   /---\_____________________
>  |.  %                      |
>  |   %                      |
>   \___/---------------------
>
.....
>
>The key is a semi-flexible black plastic, slightly rough finish, with
>several mold marks, and appears to have been "built up" from two layers,
>as though there's something embedded between.  
>
>The key is operated by sliding it into a reader, and withdrawing it.  The
>read seems to take place on withdrawal, and the head seems to be in the
>top portion, since pulling slightly up helps get a good read.  The reader
>front is mounted in a standard wallplate, is about 1.75 inches square, and
>has a single light (faceted LED?) just below the slot where the key is
>inserted.  On casual examination they did not have any identifying
>marks.
>
>I suppose the questions, in order, would be:
>  What is it? / Who makes it?

What you have is a Weignad (I think that's the spelling) based key.  I believe
there is only one manufacturer, but I can't recall the name.  (It is a patented
system, I don't know if it has been liscensed to other companies)

>  How does it work?

The "Key" has a set of special wires embedded in it, perpendicular to the
length of the key.  The reader consists of a magnet, and a pick-up coil.
When the key is removed from the reader, the wires pass under the magnet and
become momentairaly magnetized.  As they move away from the magnet, their 
magnetic field collapses, generating a pulse in the read head.  I believe that
there are 24 positions that the wires can be in, (or not be in) giving a
very large number of possible keys.  Note that this is dependent on the key
being moved
at a relatively constant rate of speed, although the speed can usually vary
from fairly slow to fairly fast.

>  Could the key be fabricated (e.g. by placing a stripe onto an appropriate
>   piece of plastic?)

Probably not.  The problem would be in obtaining the special wires used in
the key.

>  Could the key be read by a non-mfr. reader?

I imagine that you could build a reader, but I don't have details concerning
the strength or polarity of the magnetic field.

>  Does it actually check the key against a central database?

Probably.  Depending on the installation, and who is providing the security
system.  Some systems may allow for an "off-line" state, where a certain
group of keys may be allowed if they can't be verified against the
central system.  Others will only allow you in if the key is verified,
and if the central system is off-line, tough.

>  Is the data in the key generable from the number stamped on the head?

The number in the head uniquely defines the key, I don't know if there
is a simple correlation between the number and the binary code imbedded
in the key.  It probably doesn't matter, because if you have the technology
to duplicate the key, you can probably read it anyway. :-).

(zbang or doug.. please correct/add anything I have missed)

--
Fred Bauer
fbauer@access.digex.com