From: rxh6@po.CWRU.Edu (Randall Holt)
Newsgroups: alt.folklore.urban
Subject: Re: Car Crime
Date: 19 Nov 1992 02:38:21 GMT
Organization: Case Western Reserve University, Cleveland, Ohio (USA)
NNTP-Posting-Host: thor.ins.cwru.edu


ccaamrg@ucl.ac.uk (Mike Gahan) wonders;
 
>AFOM has recently been issued with a company car. It is quite fancy, and
>he took some pleasure in demonstrating the remote door locking/unlocking
>feature, by which it is possible to lock the doors from some distance
>away using a remote control instrument.
>
>Swiveling the mighty searchlight of my intellect upon its smooth gimbals,
>and bringing its harsh, actinic blaze to bear on this matter, the following
>occured to me:
>
>I assume that the remote instrument transmits some coded digital signal,
>electromagnetic or ultrasonic, to the vehicle, which, recognising its
>master, obligingly unlocks itself. The signal must be different for each
>vehicle. To steal a car such as this, I though, would be quite easy.
>
>The thief would merely conceal some piece of electronics, attuned to the
>appropriate frequency, somewhere near the car, possibly disguised as an
>itinerant traffic cone. The unsuspecting owner would use his instrument 
>to open the car, whereupon its cry would be recorded by the devilish
>equipment. The thief then comes and collects his machine, which will
>replay the desired signal to order.
>
>
>Imagine my childlike delight when I hear, from a bloke in a pub, that
>such devices are already available in the crime ridden dens of London's
>seedy East End.
>
>Can anyone substansiate this rumour, so that I can gloatingly tell my
>friend 'I told you so' ?
 
I don't know about confirming the existence of the rumor, but I can tell 
you why this unlocking-device is not practical for nefarious purposes. 
I have a similar device which (as the tech specs reveal) is based on a 
specific sequence of 6 1-byte TTL pulses transmitted at some RF frequency 
that is picked up by the reciever in the locking mechanism. That comes to 
256 to the 6th power possible combinations, or more than 2.81e14 combinations. 
 
If you were transmitting in the RF range, at maybe 50 miliion bits per
second, then you could run through maybe 1 million combinations per second,
and the maximum time to check all combinations would be 2e8 seconds or a
little more than 6 1/2 years. And then you still have to get the Club off
the steering wheel, and hot-wire the ignition.
 
Add to this an additional security measure which exists in the unit on my 
car, a 100 ms delay after a _wrong number_ has been transmitted at the 
correct frequency. Now the delay time is up to greater than 90,000 years. 
 
By which time the natural diffusion of glass in the windows would have 
rendered the excercise moot.
 
Of course, you could get lucky and find a car with the combination 0 0 0 0 0 1.
 
 
Randy 'Or you could just pour liquid nitrogen in the lock, 
       buy a lottery ticket, and then wait for lighting to strike ' Holt
 
 
 
ObUL - The way I heard it was that the _disgruntled_ engineer-designer of the
lock put in a back-door on all the devices that he worked on, and sold it
to a London Mob, who then killed him so he couldn't sell it to the competition
 
-- 
Randall W. Holt      rxh6@cwru.po.edu
Newsgroups: alt.folklore.urban