Maybe the car constantly transmits and key constantly listens and responds when they 'hear' the car, either way thieves have worked out ways and means ... hence the recommendations for a biscuit tin in the hallway to put keys into.
And, of course the key itself. So actually three levels.
But your type only transmits when the button is pressed. All that probably does is just unlock the car. The chip in the key disables the immobiliser when the key is put in the ignition switch.
Keyless entry - such an essential thing to have ;-) - transmits all the time. When the transmitter is in range the car opens. I assume these code readers are somewhat more sensitive than the receiver in the car.
Sort of makes sense. But can't be totally dormant if it can receive a signal.
They read it when you use it. They only have to next to you in the queue when you use it at the tills in a shop.
Just put them in a biscuit tin.
The modern world has cars with keyless entry. they transmit when they receive a signal from the car. the thieves use a radio relay to trick the car into thinking the key is there. Then they press the start button and drive off. The car won't turn off when the key is out of range for safety reasons.
Its hardly surprising you are having trouble understanding if you don't read the bit where it says keyless entry.
No it does not continuously transmit.
It only responds when illuminated by a specific RF signal
Dave Plowman (News) brought next idea :
Well, if that makes them feel their car is secure...
dennis@home expressed precisely :
Exactly !
Some people get some rather peculiar ideas..
Within a yard or so, assuming there are no confusing signals. So they don't need that much screening, to prevent them responding in your pocket.
Dave Plowman (News) was thinking very hard :
If you are suggesting that the key transmits all the time, think about it and how much battery that might need. They transmit, or more correctly respond only when intergated by the car.
I hadn't realised the keyless entry unlocks the car automatically as soon as you get within range. I thought you still have to consciously press a button, to give you control over when you unlocked it. There are many times when there are dodgy-looking people around and I wouldn't want to unlock the doors (preferably just the driver's door) for any longer than I had to.
I can understand you wanting the car to start as soon as you press the button on the dashboard, but not that one would want the car to unlock itself as soon as you get within range. Is it something that is user-configurable - whether the doors unlock automatically or whether you still need to press a unlock button as with a normal central-locking key.
My car's central locking has a very useful feature which I've not seen on other makes (though I've not tried many). If you press the lock button as you approach the car, it flashes the car's indicators so you can find it in a car park. It remains locked until you press the unlock button. On other cars it's necessary to do a quick unlock-lock to make it flash the indicators for locating the car, which is a little less secure.
The thing is, there is no non-action proximity device that you could not insert a dumb relay between the key and the car.
Even if you have a normal challenge-response crypto system between Car and Key, if you stick a relay device with two ends: A and B:
CA----------------BK
If A-B faithfully relay a copy of the signals (NFC, radio, it doesn't matter) - there is no way C doesn't know it's not next to K
They could have the most complex chat possible and it would make no difference.
What they need is something like an on-off switch on the key - like you have to open it to activate and when closed (and it beeps once the car is locked until it is closed) it does nothing.
NY submitted this idea :
Every car I have had since remote locking appeared, has flashed its indicators to confirm lock and a different pattern for unlock. Many/most also make a bleep too. Mine doesn't, the idea being such noise can annoy people late at night. Mine bleeps only when there is a mislock, a door, boot or bonnet not properly closed.
That's non-trivial though, hardly instant from what I've seen of using that interface. If it was easy then it would make the immobiliser pointless and I don't beleive that's true.
Neither of our cars make a sound, presumably to avoid annoying anyone, but they flash the indicators rapidly to show a pillock condition such as a door not being closed. Both cars flash the indicators to indicate that the car has been locked, but my Peugeot will do it even when the doors are *already* locked (as a location device) whereas our Honda only flashes when going from unlocked to locked, and not if the car is already locked, so you can't use it as a location device when you return to the car, unless you do locked->unlocked->locked in rapid succession, and hope that this is too quick for a local scrote to seize the opportunity of a brief interval when the car is unlocked.
Seems to be 'easy enough' from CCTV footage on youtube of cars being nicked, I think they use the OBD to disable the alarm, open the central locking and pair their own key to the car
I have seen them do it on a ford focus (well on the cctv recording). About 90 seconds.
One time key solves that.
Essentially there is a shared secret that means the codes are not reusable.
Example. You have 16K of 256 bit identical code pairs in the transmitter and receiver.
Every time a code is transitted, the key responds with the pair. And increments both a master counter and puts its value in a location associated with the code pair. This means the code pair is now marked as having been used.
Next time a new pair is used. The old pair no longer works. After 16k door open/engine starts you reuse the codes.
The key (sic!) to a technique like this is that to fully replicate the secrets you need to listen to all 16K pair exchanges. And the key is that the secret is immensely large and random.
AS long as each fob and reciever are absolutely uniquely programmed as a matched pair, it works.
Its not impossible to crack, but its hugely non-trivial
As I said there are ways around that, so long as the conversation is not reusable.
Or just better coding
Again this is crap design by the manufacturer.
Making conversations safe from 'man in the middle' attacks is standard net security stuff
And the secret is to have a shared secret that is never fully revealed in any given conversation, and the conversations never repeat.
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