Passive Keyless Entry & the Security/Ease-of-Use Trade-off

During a TV commercial the other evening my wife asked, “How do those push-button car starters work? Can just anyone start your car if the door is open?” That’s a good question and it has a significant cyber security component.

First — to directly answer her question — no, not just anyone can start the car with the button. To start the car one needs to have a fob or small electronic device somewhat near the button, perhaps in one’s pocket or purse. The system is called PKES or Passive Keyless Entry and Start. (The idea is similar to the “electronic” keys auto manufacturers use to help deter pass keys. These systems have a chip attached to the more-traditional key, generally embedded in some plastic. The chip uses a technology called RFID or Radio Frequency ID. When a key is lost or damaged and needs to be replaced, the vehicle needs to be programmed to accept the new key. This is generally not a difficult process.) PKES systems use a challenge-response scheme and require a processor in the fob.

Passive Keyless Entry Hacks

The attack scenario for Passive Keyless Entry and Start systems is described in a paper by researchers on Relay Attacks on Passive Keyless Entry and Start Systems in Modern Cars from the Department of Computer Science at ETH Zurich. The idea is to relay the signals between the car and the distant fob. So a fob sitting inside the house could be used to enter or start a car parked in a driveway. NetworkWorld reported that the relay device/amplifier could be purchased for about $17USD – that puts it in the hands of just about any thief. Their solution seems to be to put the fob into a Faraday Cage

Most car owners I know neither read NetworkWorld, nor do they search for papers from Swiss researchers.

Securing your Access Card

Physical security is a critical part of cyber security as I have noted before. We’ve all watched police and criminals alike pick locks on TV. Few have watched the cloning of a proximity-type (RFID) card key or fob, though. There are DIY tools, as well as commercial services. And bad guys can clone your entry card even if you keep the key in your pocket. Hopefully data centers are secured with more than just a card, but one can use an IR camera or other means to see what keys on a keypad are used.

The point is that there is almost always a trade-off between security and ease-of-use as we note in Learning Tree’s System and Network Security Introduction. A car with PKES is easy to use, but somewhat difficult, it seems, to secure. RFID entry cards by themselves are easy for entering a room or building, but cloneable. Multi-factor authentication aids in securing the latter, but that reduces ease-of-use. What have you found that is both easy and secure (if anything!)? Let us know in the comments below.

To your safe computing,
John McDermott

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