Tesla Model S Can Be Stolen in Seconds by Cloning Its Key Fob

The key fob and car contain identical pre-shared random data. (could be gigabytes) Each transaction uses 4 tokens, 2 going in each direction, with each token being 128 bits.

Upon a button press, the key fob selects and destroys the next 1-time-use token it contains. It begins to transmit.

First the key fob sends a token. The car must respond with the correct token, which is checked by the key fob. Failure causes radio silence. After a few padding bits to allow for that checking, the car sends another token. The key fob XORs this one with the key fob's second token, which is then transmitted. The car takes note of the latency.

Each 100 ns delay (a single bit at 10 megabit/second) is worth about 30 meters at the speed of light. The car can use this to exclude key fobs that are excessively distant.

Now consider the repeater attack. The key fob is somehow mistakenly activated. The attacker forwards the signal over a microwave relay to the car, and does likewise for the signal going back to the key fob. Responses arrive late, causing rejection.

You don't much need crypto here. It's just XOR with a 1-time pad. Cheaper cars should just to that alone, with 1-way transmission. Expensive cars should do 2-way and measure the timing, but they don't need fancier crypto.

a) Car companies won't want to hand out fobs that have any sort of writable memory, takes battery, and risks write memory wearout. Never seen a fob or smartcard that has memory which is written with every individual transaction. Having the fob do a computation on every transaction means it will need a lot more battery (in Wh per year) compared to a regular remote-unlock key fob for an ordinary passenger car.

b) High precision RF travel/distance timing, onboard computer system in the car capable of reliably determining to within 100ns timing interval, taking into account randomness in the real world environment such as reflections from nearby low-e class windows, metal structures, and such, may not be cheap or easy to implement.

Even in more recent years, most of them seemingly do not implement

(1) Time of flight checks, e.g. that a radio relay isn't being used to get to the keyfob many more meters away in the house using a relay/amplifier. This is a commonly exploited theft method currently. The Apple watch implements this to unlock your MacBook Pro(!) This has also been shown to be a viable attack method on many contactless payment terminals.

(2) Replay protection - another possible common attack is to receive the rolling code from transmitter, jam it so the car can't hear it and wait for the remote to transmit a second one. Then you jam that also, store that code, but then re-transmit the first code and the car unlocks and now you have a second code to use to unlock the car later. It's possible to both receive and jam the code by using a very precise tuned receiver, and jam in the surrounding the frequencies which in most cases the actual receiver (e.g. car) won't have filtered out. This works particularly well on most garage doors.

(3) Let alone having some kind of recoverable/brute forcible ID scheme, which as we can see here, is also true. I'm sure these aren't the only ones.

It's kindof silly really. I'd be curious to know if any manufacturers have been fixing this in the last couple of years.