![]() There are many more attacks, and these will continue to multiply as cars get more complex, and have more embedded computer systems to go after. This can be defeated by amplifying these small signals. ![]() This is based on a low power signal that can only be received when the key fob is very close. However, there have been several situations where this is very easy.įinally, there are cars that open when the owner gets close to the car. In general this should be extremely hard. With recorded unused codes, you can open the car.Īnother is to reverse engineer the RKS sequence. One is simply recording the key fob output for a couple of button presses when it is away from the car, or the car is being jammed. I have had to do this a couple times, now (for other reasons). Otherwise, you have to have the dealer rekey the car, for many hundreds of dollars. For the Prius you have to do the “Chicken Dance” to get it to work again, provided you have another working key fob. If it gets a previously used code, it stops responding to the key fob. If it detects one of the expected future codes it opens the car. The car keeps track of the last code it received, and knows what the next several hundred codes might be. This produces a new waveform that depends on the ID of the key fob, a random seed, and how many times the key has been pressed. More thorough attacks give you complete control by basically cloning the remote. The simplest just let you open the car up. There are lots of different attacks that can be used against car remotes, depending on how they work, and what sort of access you are looking for. Some use frequency-shift keying (FSK), where each bit is transmitted as a different frequency, and the envelope is constant. This example is OOK, which is the most common for car remotes. The nice thing about Manchester encoding is that every symbol has a transition, and these are easier to find then when the signal has been high or low for several intervals. A good way to recognize split phase encoding is that you can only have one or two low or high segments in a row. That means that a “0” bit is a rising transition, and a “1” bit is a falling transition. Instead of a “1” being high, and a “0” being low, the information is encoding in the transition from high to low or low to high. It is also almost certainly split phase (or Manchester) encoding. This is fortunate, because if the signal was the same every time, you'd have enough information to steal my car now! If we capture the signal the result is shown belowĪlthough the two start the same, they rapidly diverge. That makes the key (and the car) considerably less useful! However, if the key fob gets too far ahead in the sequence (100s of button pushes) the car won't recognize it. Both the key fob and the car keep in sync, so that the car recognizes the next code. Don't get too carried away pushing the button! The RKS system uses a rolling pseudo-randomly generated code. You may need to shift the frequency band up or down by a couple of MHz to find the signal, mine was almost 2.5 MHz low. When you push a button on the fob, you should see a brief jump in the spectrum. You can figure out what frequency your key fob transmits on using your SDR and use GQRX or SDR# to monitor the spectrum. These will appear long before the official announcement. Watching for new entries is one of the ways people can tell when new car models are coming out. My Prius key turned out to be at 312.590 MHz.The keyfobs are all listed in the FCC database. Key fobs use something called a Remote Keyless System (RKS). We'll start by looking at the key fob for my 2006 Prius. ![]() There are lots of different key fob systems. Problems that less scrupulous people may have already been exploiting. And it isn't until people try to hack these systems that the problems come out. ![]() Unfortunately, that trust is not always warranted. You have no real way to tell whether the car company did a reasonable job with their system, so you have to trust them. The implicit assumption you make is that the key fob system is secure, and that some random person with $50 of hardware can't drive off with your car. You can leave the key fob in your pocket, and never again worry about having a physical key. When you buy a car, the convenience is the compelling feature. Almost all cars currently come with a key fob, which allows you to open the doors, and start the car. ![]()
0 Comments
Leave a Reply. |