4 ms·

Am I missing something or is the fix a little computer in the fob to cryptographically sign a one-time challenge sent by the car? I mean, RSA isn't that hard, i

Am I missing something or is the fix a little computer in the fob to cryptographically sign a one-time challenge sent by the car? I mean, RSA isn't that hard, is it? Here's how I see it: the car broadcasts a (short duration) challenge message on short range (10 meters, say), the key fob, once in range, signs the challenge message, transmits it, the car checks the signature with the fob's known public key, and Bob's your uncle. If the fob can compute a signature of the challenge in 500ms, the window doesn't need to be much longer. Sure, people will likely be able to pull private keys from the fob with some effort, and duplicate it that way, but that's no worse than today. Reprogramming the car wouldn't significantly harder than it is today either. If we want convenience and security, it seems fine to make the key fob a little more complicated and beefy. I feel like this is by no means a new idea and maybe I'm missing something. edit: I was missing something.

schwap 9y ago
You are misunderstanding how the attack works (probably because the article misuses the word 'spoofing' IMO). The messages between the car and the key fob are the real messages. They are just using a radio to extend the range of the car/fob communication.
- jagger27 9y ago
  Ah, I feel a bit stupid now. Of course.
  - schwap 9y ago
    Like I said, I think the article is a bit confusing by using the term 'spoofing', which to you and me I think implies a 'fake' message.
zkms 9y ago
> Am I missing something or is the fix a little computer in the fob to cryptographically sign a one-time challenge sent by the car? I mean, RSA isn't that hard, is it? The problem has nothing to do with cryptography. Given radio signals can be relayed at will, and there's no way of knowing so (short of a way to measure quite small latencies), there needs to be a proper way to bind the cryptographic exchange to the person pulling the door open. Relay attacks (which do nothing to exploit cryptographic exchanges -- just relay messages fast) exploit that lack of binding.
X-Istence 9y ago
That's basically what it is doing now... except that the message from the car is relayed over another radio to a radio the attacker is carrying near the victim. The victim's key thinks it is near the car, and signs the message which then is sent back over radio to the car. This isn't about better cryptography. This is about how can the car know that the key is in close proximity to it? We can transmit data long distances. Timing is going to be the key, how much time is allowed to be passed between sending a challenge and getting a response? Right now there is a lot of "slop" to allow the owner with the key to be turned away from the vehicle and things to still work, or have it in your left pocket versus your right when seated in the car. My Subaru WRX requires the key to be right next to the middle console, so I can only keep my key in my right pocket. If I have it in my left pocket I can't start my car. I don't know how much "timing" slop there is though. Could someone relay my keys transmission with a short delay?
londons_explore 9y ago
Cars need this: https://en.wikipedia.org/wiki/Distance-bounding_protocol https://en.wikipedia.org/wiki/Distance-bounding_protocol It really is an oversight from the carmaker not to use it in the design of the keyfob. If the security of the whole system depends on distance, the crypto behind it should verify that distance limit. The same goes for NFC, bluetooth pairing, WPS, wireless credit and debit cards, and apple/android pay. They all have 'nearby' somewhere in their security model, and in no case is 'nearby' actually verified cryptographically.

schwap 9y ago

You are misunderstanding how the attack works (probably because the article misuses the word 'spoofing' IMO). The messages between the car and the key fob are the real messages. They are just using a radio to extend the range of the car/fob communication.

jagger27 9y ago
Ah, I feel a bit stupid now. Of course.
- schwap 9y ago
  Like I said, I think the article is a bit confusing by using the term 'spoofing', which to you and me I think implies a 'fake' message.

zkms 9y ago

> Am I missing something or is the fix a little computer in the fob to cryptographically sign a one-time challenge sent by the car? I mean, RSA isn't that hard, is it? The problem has nothing to do with cryptography. Given radio signals can be relayed at will, and there's no way of knowing so (short of a way to measure quite small latencies), there needs to be a proper way to bind the cryptographic exchange to the person pulling the door open. Relay attacks (which do nothing to exploit cryptographic exchanges -- just relay messages fast) exploit that lack of binding.

X-Istence 9y ago

That's basically what it is doing now... except that the message from the car is relayed over another radio to a radio the attacker is carrying near the victim. The victim's key thinks it is near the car, and signs the message which then is sent back over radio to the car. This isn't about better cryptography. This is about how can the car know that the key is in close proximity to it? We can transmit data long distances. Timing is going to be the key, how much time is allowed to be passed between sending a challenge and getting a response? Right now there is a lot of "slop" to allow the owner with the key to be turned away from the vehicle and things to still work, or have it in your left pocket versus your right when seated in the car. My Subaru WRX requires the key to be right next to the middle console, so I can only keep my key in my right pocket. If I have it in my left pocket I can't start my car. I don't know how much "timing" slop there is though. Could someone relay my keys transmission with a short delay?

londons_explore 9y ago

Cars need this: https://en.wikipedia.org/wiki/Distance-bounding_protocol https://en.wikipedia.org/wiki/Distance-bounding_protocol It really is an oversight from the carmaker not to use it in the design of the keyfob. If the security of the whole system depends on distance, the crypto behind it should verify that distance limit. The same goes for NFC, bluetooth pairing, WPS, wireless credit and debit cards, and apple/android pay. They all have 'nearby' somewhere in their security model, and in no case is 'nearby' actually verified cryptographically.