On Thu, Jul 31, 2014 at 08:56:24PM +0100, David C Brown wrote:
> The key to my old VW is 70mm long, 30m wide and 5mm thick.

That's an astonishingly wide key.  ;-)

> I can slip it in my wallet, hide it in the exhaust pipe, wear it
> comfortably on a lanyard round my neck and safely put it in the
> pocket of my shorts when swimming.  A replacement costs less than
> five dollars.  It would be one heck of a salesman who could persuade
> me to replace that key with a $200 device which has none of those
> virtues.

Yes, it is amazing what crap we'll put up with to get other stuff.

I like referring to the key you describe as a "coded metal bar", where
the coding method uses a file or grinder, and the media is resilient
to many forms of physical attack.  The mechanically erasable read only
memory (MEROM?) has excellent endurance specifications.  Downsides are
that a readout is not replay protected, so loaning a key is tantamount
to giving eternal access if it is copied by impression, and the code
is broadcast in several directions by reflection of light, allowing
copying by photography.

On the other hand, the RF systems can require a bit more work to
copy.

--=20
James Cameron
http://quozl.linux.org.au/
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