If you thought your car with its newfangled keyless entry system was as secure as regular car keys, think again.

Researchers at the Swiss Federal Institute of Technology in Zurich found out how to break into a car that uses the radio-frequency technology to open the door and start it. All you need is a piece of cable and an unsuspecting car owner sitting nearby.

By stringing a piece of cable between the car and the fob that is used with it, the team, led by Srdjan Capkun, a professor of computer science, was able to open a car and drive it off. That's because the cable acts as an antenna and retransmits the signal from the key.

They also discovered a more sophisticated method. By setting up a radio receiver near the key, they could pick up the signal the fob sends out. Converting the signal to one of higher frequency to boost its range, they were able to transmit it to another receiver near the car. That receiver retransmits the open command to the car.
The method is simple, as it does not rely on breaking the encryption in the transmission between key and car. All the potential thief has to do is retransmit it.

The problem, Capkun says, is the way that the system is designed. The radio signal the key and the car use is at a frequency of 130 kilohertz (about the middle of the AM radio dial) and is short range, because it is generated by an induction coil rather than a regular radio transmitter. This is done for two reasons: constantly transmitting would drain the car's battery, and the car makers didn't want the range to be too long -- nobody wanted the car doors to open accidentally a half a mile away.

The short range of the signal supposedly offered some security -- in order for the car to open the key has to be able to pick up the signal, and the car has to be able to hear the key's answer. For that to happen they have to be within a few yards of each other or less. The security is compromised because there is no way to turn it off; the key and car are always transmitting to each other.

Capkun and his colleagues wouldn't reveal which car models they tested, but it was a large number Aurélien Francillon, who worked on the project with Capkun, noted that they rented a number of cars to try it out.

Francillon added that the range on the key signal was so large that the team was able to open a car from a key left on a kitchen table inside the house.

Lest one think it would look a bit odd for someone to walk around a parking lot with a cable trailing behind, Capkun notes that in a garage, for example, one could lay a piece of wire down near the parked cars, and put the other end near the payment kiosk. If it were along the wall nobody would notice. The car would be opened and started, ready for a thief to take it away.