[Geek Alert…] 

I was scanning my server logs last night and saw someone had hit this post of mine with the Google search string "can’t pull out key mercedes".  I hope their problem was as absent minded as mine was, or more charitably, that I’d forgotten how you park a car with an automatic transmission.  (Hint: you put it in ‘Park’).  But as I was scanning the Google hits on that string (my post was forth in the list), I got to thinking about the anti-theft technology in it the key itself.

I posted this shot of my new car’s key the night I made a deal with Valley Motors to buy it.  I’m wondering how many others reading it had the same first impression I did when I first laid eyes on a Mercedes-Benz key…  That’s a car key???  It’s more of a dongle then an actual key, which makes sense given where automobile anti-theft technology is going.  The Honda had something in its key too, that the on board computer authenticated it with.  But it was also an actual key, in that it had a ridged steel shank like most keys that moved tumblers of some sort in a lock you turned to actually start the car.  Mercedes just took the next logical step and did away with the steel shank and tumbler lock part altogether.

I’ve wanted one of these cars ever since I was a teenager.  But when I actually took mine home, I found myself stressing out every night about it getting stolen while I was asleep.  I’d wake up at random moments and trudge over to a window and verify the car was still there.  A small, but non-trivial reason why I’m not leaving the car at home and walking to work every morning like I normally do, is because I’m still a bit afraid to leave it alone.  The neighborhood I live in has enough retirees in it that there are always a set of eyes somewhere keeping watch over things.  But I still stress about it.  A few months ago a small SUV was stolen from a guy just a few houses down from me.  But he’d left his doors unlocked, and an expensive tool kit set in plain view.  Still…I read about car thefts and attempted car thefts in the local police blotters for my district.  Lately, I’ve actually started mapping them out to see where the car thieves are most active.

Mine isn’t the only expensive car in the neighborhood…there’s others scattered here and there, and if you count some of the the big SUVs and pickup trucks there are actually quite a few vehicles within a few blocks of mine costing at least as much if not more then Traveler did me.  But a Mercedes sticks out.  I didn’t buy it for that…I really wish it didn’t, but last Halloween I had several dads walking their kids around complement me on the car, and ask me if they could check it out inside.  Of course I happily let them…I know the feeling, I had it myself for decades.  I gave them the whole tour of the car.  But afterwards it worried me that the car sticks out like that.  It’s bound to attract the attention of car thieves.

I’ve found that the best cure for the worries is to learn as much as you can about what’s worrying you.  So that Google hit prompted me to do something I’ve been meaning to do, to ease my worries a tad about someone making off with my new car in the middle of the night.  I started looking around for information about the anti-theft technology Mercedes is using now.  In the process, I got a bit of an education about modern automobile smart, or "VATS" keys.

The GM system, for example, uses a set of fifteen different precision resistance chips that can be embedded in a key.  The onboard computer knows which resistive value is supposed to work on its car and if you put a key with the wrong resistance chip in it in the ignition lock, the car cuts off fuel to the engine and starts a four minute clock that prevents the car from starting even if you insert a key with the right chip in it.  Ford on the other hand, uses a small transponder embedded in the key that transmits a code to the on board computer.  Some Japanese automakers use set of passcodes between the key and the car that rotate each time the car is started.

I was gratified to learn that Mercedes-Benz has a key so complicated it requires its own set of instructions.  Sometimes complexity is a good thing.  The moment you insert the key in the ignition a dialogue takes place between it and the on board computer, and the key’s digital passcode is verified and a new randomly generated passcode is assigned to it by the computer. 

At that point, the steering wheel and ignition systems are unlocked and the car is made ready to start when you turn the key.  I can hear the steering wheel being unlocked the moment I insert the key in the switch, as well as other very faint, gentle whirring sounds coming from somewhere inside the dash that I’m assuming have something to do with the climate control system powering up.  So even before I turn the ignition on and proceed to start the car, it already knows that a valid key is in the switch and its unlocking things and starting up other things.  It also grabs hold of the key slightly…not so much that you can’t pull it right back out again, but enough to make that something you have to deliberately do.  And the moment you pull the key back out the steering wheel re-locks and the faint whirring sounds stop. So the car is, in a sense, unlocked and switched on the moment you insert what it determines is a valid key for that car.

My car came with two keys…I’m not sure if there is an upper limit on the number of keys you can assign to an individual car…but the on board computer keeps track of the keys that belong to that car, and which passcodes it has randomly assigned to what keys.  There’s a set of button batteries in each key that are user replaceable.  Not sure what happens to the passcode a key has when its battery dies, but hopefully its kept in some sort of flash memory.

Other luxury car makers such as BMW also use this system, but Mercedes is unique apparently in that it did away with the steel shank portion of the key altogether.  Given the technology being used here, the shank part is now a tad redundant.  You can probably expect to see steel shanked keys slowly disappear from cars altogether as the on board computer takes on more and more responsibility for preventing theft.

Hence, the current popularity of car jacking.  If car thieves have to have the key in order to steal the car, then obviously they’re gonna try and get the key.  Usually that means getting it away from you.  So now I can rest a tad easier about the chances of my car getting stolen when I go to bed at night, or when I’m away from it.  On the other hand, now I have to worry more about dealing with a car thief face to face.  Ah well.  This was why I was bullied so badly in junior high school…so I could grow eyes in the back of my head for thugs…

[Edited a tad…]