321–330 of 449 posts
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The third party doesn’t need to predict it, just repeat it. The relay doesn’t need to understand or modify the message, just pass it along.
If the message is encrypted with some time component and a pre-shared secret then it is protected from a replay attack no?
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A simple on/off button on the fob would work, and probably extend the battery life by a few years.
An timeout that goes into idle mode until it detects some movement, would be less hassle. It still leaves a small window of opportunity for abuse, but seems like a decent middle ground.
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Since most car manufacturers seem to be vulnerable (to my knowledge), I assume all or most buy the same COTS keyfob + electronic lock product. Much like Takata airbags or Bosch ECUs. Being a step away from the problem probably helps keep that OEM manufacturer from strapping in and solving it. They don't feel any pain from it.
The vulnerability is pretty much inherent to the idea. No amount of encryption can protect you from a relay attack. The only foolproof mitigation is to enforce a short round trip time to ensure the fob is actually close to the car, but with the short distances involved that means the fob has to generate and transmit a response within a few nanoseconds.
And the challenge-response pair must be different for every transaction, otherwise the thief can easily grab a SDR with tx capabilities, get to the car and ask for a transmission, record the spectrum, then go near the car owner door, transmit the car challenge and record the key fob response, go back to the car, wait for another challenge transmission and time the response accordingly. Not even need for a second thief.
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This is such an obvious solution that maybe some patents are the reason it's not implemented by every car manufacturer.
Indeed, the last time this attack vector came up on HN, it was pointed out that one company has patented using time of flight to validate keyless entry. Here's the patent: https://patents.google.com/patent/US8930045
Nothing new, has been going on for a while now. Market is already providing your own "cage of Faraday[0]" for your fob. [0] https://www.amazon.com/faraday-cage-key-fob/s?page=1&rh=i%3A...
I use these Faraday cage pouches for my new car keys (I got the two-pack listed "Amazon choice" in the above link) and they are excellent. As far as I can tell anyhow - my car hasn't been stolen (yet!) and if I keep the key in it's pouch I can neither open the doors or start the engine even if I'm right next to the vehicle. An added bonus, it also makes the keys much more comfortable to have in a pocket, holds them i…
The smallest ones I could find would actually hold two fobs, but when filled were large and uncomfortable enough in my pocket that I preferred to just keep the fobs naked.
I still haven't found a good solution that actually works for keeping passive fobs secure while they are actually in my pocket.
Car makers should use frequency/channel hopping rather than time of flight until doing time of flight gets cheaper. The car and fob would also broadcast on frequencies/channels that are not in the preshared set to detect someone trying to amplify. The hopping pattern should be derived from a good cryptographic protocol that also contains mutual attestation.
How would that affect battery life? To you and me, changing the batteries in a key fob isn't a big deal. But more than once I've seen people walk into the auto dealer's repair center because their fob stopped working, and all the tech did to repair it is replace the battery. (If you think that sounds stupid, I work in healthcare, and we have employees who spend a surprising amount of time teaching people how to put A…
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But then my mom would have to dump out her purse every time she wanted to unlock her car.
How does she unlock her front door?
For many people, there's no need to unlock the front door because it's never locked. Having to lock your door just means you're living in a terrible neighborhood.
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So you have to pull your keys out of your pocket and stick them in your microwave every time you enter your house just to have the convenience of not needing to take them out of your pocket when you approach the car.
I know it's not a practical workaround. I'm just pointing out that most people do technically have a Faraday cage in their homes.
I imagine improvements to the key fob could be made that would require a mechanical coupling with the car in order to start it. That would circumvent this attack.
They are laying on a desk or in a drawer and are not being touched/moved for extended periods.
Maybe a simple mems step counter could help activate them for a short period of n seconds/minutes.
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I'm not sure if this is a joke about old keys being better, but I'd argue you could have the benefits of new keys and old keys combined if you just made it so that new keys have to be inserted into some compartment inside of cars, where they are authenticated by those cars. You can imagine a fob with a USB that has a different authentication code than the wireless one it sends out, and unless the USB is plugged into…
I'm not sure why we can't have some sort of challenge response protocol to prevent MITM...
Maybe it has something to do with the additional battery consumption that doing this incurs, probably something like double/triple consumption, with the hashing.