Given the number of cars on the roads now, what are the chances of my remote key fob unlocking another car (and vice versa)?
Trevor Campbell
Berrima, Australia
Advertisement
None. Modern cars use an encrypted rolling number system. While I don’t know the length of the cryptographic keys actually used, even short keys by today’s standards, say 512 bits, give an astronomically large number of actual key possibilities.
Furthermore, each key press transmits a completely different code – this means that a hacker can’t use a recording device to capture the code when the owner presses the fob and then replay it at a later time to unlock the vehicle.
The systems used today are also tolerant of missing numbers in the sequence, so if the last number used was 843, then the car would expect 844 as the next valid one, but will actually allow 845, 846, and so on, for some reasonably large sequence of numbers, so you don’t have a problem if you press the fob when not in range. Modern cars usually track two individual key fobs separately. All this complexity is why it is so expensive to replace keys when they are lost.
Helen Taylor
Ferryhill, Durham, UK
Back in the day, I had a remote fob that, when I was in a car park and remote-locked my car, would unlock several other cars. I would unlock it again and they would lock.
I would give up and use the key to lock my car because most people had nicer vehicles than my old Nissan coupe.
Peter Cowley
Quarndon, Derbyshire, UK
Over 50 years ago, when I was a research student with an old Mini Cooper, my car key also opened my Roneo Vickers filing cabinet and vice versa. It was convenient, but gave me little confidence in the security of either.
I also unlocked and climbed into the wrong Mini once, only realising my mistake by the unusual tidiness of the interior.
To answer this question – or ask a new one – email lastword@newscientist.com.
Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.
91av retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.