Should I keep my car keys in a Faraday box? Potentially, yes. The invention of keyless entry means we can unlock our cars upon approach, something particularly helpful when you want to open the boot, but have your hands full of shopping.
But relying on an electromagnetic signal (rather than a good, old-fashioned key) to tell your car when to lock and unlock means that, with the right kind of technology, it’s possible for someone to intercept and exploit that digital communication.
There were nearly 130,000 vehicles stolen in the UK between April 2023 and March 2024 and more than half of household incidents involved the thief manipulating a signal from a car key without ever having to get their hands on it.
This is only a problem for cars that have passive keyless entry: where the key only has to be in range of the car for it to unlock, no button-pressing needed. These entry systems work by sending out a signal that, when nearby, the car can detect.
The exact distance depends on the car manufacturer, but theoretically, when your key is in the house and your car is on the driveway, the two are far enough apart that the signal won’t reach.
Yet thieves can obtain devices that extend the reach of your key’s signal. This is called a relay attack, because typically more than one device is involved.
Thief number one will be positioned outside your house somewhere within range of your key, which is sending out a signal in case it’s near your car.
They’ll use their device to capture the exact data within the signal, which is then relayed to their partner in crime, who is holding a second device next to your car. The car recognises the key’s unique signal and dutifully unlocks.
The best way to avoid this scenario – aside from trading in your car for a low-tech model – is to stop your key from emitting a signal outside of the times when you want to unlock your car.
Some manufacturers have introduced ‘sleeping fobs’ for newer models, which have motion-sensor technology that’ll stop sending signals when the key is likely not needed.
Others have developed keys that use a bandwidth that’s much harder to relay.
It may be that one day, we’ll do away with keys altogether, using biometric technology based on fingerprints or facial recognition to unlock our vehicles.
But, for now, if your car uses keyless entry and can’t be put in sleep mode, you might want to find another way to block the signal.
This is where a Faraday box, or pouch, can help. Lined with a conductive material, these containers prevent signals from coming in or out.
You could also try wrapping your key in tin foil, or putting it in the fridge or in the microwave – keeping the latter turned off, of course!
This article is an answer to the question (asked by Radhika Bhatia, via email) 'Should I keep my car keys in a Faraday box?'
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