While key cloning is possible in some instances - it's far less common than relay theft. Both techniques are feasible ways to steal a keyless entry and keyless ignition car, but with relay thefts, thieves use relay devices to amplify the signal from the key fob in your home to a transmitter near your car, which essentially tricks your car into thinking the key is present. This allows them entry into the car, where they can use the start-stop button to start the car without the key.

However, key cloning is far more sophisticated, requiring precision and devices to steal the key fob code as it generates it to unlock the vehicle. Our understanding is that relay theft and signal jamming are far more common methods. Signal jamming being a technique where a device transmitting on the same frequency as key fobs is used to jam the signal that locks the car. When owners walk away from their car and press the lock button on their key fob, the command is prevented from reaching their vehicle and it remains unlocked.

If, say, you were to walk outside to get into your car, the car would send a signal to your key fob as soon as it detects it - which would then send a generated code back to unlock it. This code changes each time the car locks/unlocks so it can't be used again anyway even if someone did go to the trouble of waiting for you to take your key out of the faraday bag to grab the code to then use to steal your car.

Bottom line: while possible, code stealing isn't nearly as simple as relay theft - meaning most thieves won't attempt it unless their very sophisticated and the car is worth a lot. I would continue to use a faraday bag. If you're very concerned, you can look in the car's manual to see if you can actually deactivate keyless ignition - if not, you can ask your local dealer if it's possible to deactivate it.

Aftermarket immobilisers like the Autowatch Ghost might also be worth researching. And, although it might seem silly, old school security - like steering locks and parking posts - are worth a look if you're concerned about theft. CCTV, or a Ring Video Doorbell, is also an option: amzn.to/2XXFp5v