Can Other People Unlock My Car Door With Their Remote?

By: Patrick E. George  | 

Rolling Codes and Encryption

Modern keyless entry systems broadcast on a frequency between 300 and 400 MHz (megahertz). But if your keyfob sent out just a single signal, then every fob would open every car of that make and model. To ensure that no one can use their fob to open your car door, it's necessary produce a signal that is unique to every car.

This is where rolling codes, also known as hopping codes, come in. Rolling codes change with each use. Whenever you press the button and unlock your car, the exact frequency transmitted by the fob changes. The particular receiver inside your car will recognize the new frequency and only the new frequency. In other words, the code "rolls" or "hops" each time you use it. A controller chip inside the car receives the signal and is responsible for changing the code each time the lock or unlock button is pushed.


Before this rolling code system was developed, thieves were able to use electronic devices called "code grabbers" to lock onto your keyfob's unique signal. With rolling codes, the signal is unique every time, rendering a code grabber device useless.

In addition, the code is stored inside the car, not within the keyfob. A thief would need to break into the car to access the code, which defeats the purpose of getting it in the first place.

The numbers generated when the code hops are random. However, in theory, an astute hacker dead-set on stealing your car could find a way to anticipate the next code in the sequence. For this reason, the codes are encrypted as well, meaning that each electronic keyfob has billions of possible codes.

However, no security system is totally foolproof. In 2007, a group of researchers discovered vulnerability in the algorithm used by nearly every car manufacturer to encrypt their security codes. With this vulnerability, they found they were able to unlock any car made by that automaker with the keyfob from just one of them [source: Zetter]. In the years since, a handful of different vehicle models have proven vulnerable to keyfob hacks.

Do you need to worry about your vehicle being stolen from your parking lot this way? Probably not. After all, the method mentioned above is extremely high-tech and actually very complicated. That puts it out of the scope of most car thieves. It's simply easier and faster for a car thief to just try their luck by smashing a window and attempting to hot-wire the ignition.

In this next section, we'll take a look at more advanced anti-theft systems built into your keys, and analyze whether or not they're worth the cost.

So how about even more advanced anti-theft systems? Are they worth the extra cost? Read the next page to find out.