If you're not up on how a wireless key fob works, here's a basic primer: The fob sends out a low-level signal and when it's close enough to the car, it tells the vehicle's receiver to unlock the doors and eventually turn the engine over. The researchers in Switzerland discovered that all they need is a pair of antennas – one within 26 feet of the keyfob and another near the vehicle – to extend the signal to unlock the doors and start the car. And it doesn't matter if the fob is encrypted. Granted, this doesn't affect vehicles with the old-school push-to-unlock/lock system, it's just fobs with the proximity setup. Regardless, we'd understand if you decided to line your pockets with aluminum foil.
[Source: Technology Review via CNet]