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Shouldn't relay attacks be preventable by having the car inspect the timing of the response? A signal that needs to be received, reprocessed, transmitted, reprocessed again and then retransmitted should have a noticeable difference in timing, shouldn't it?

Is there any reason a challenge/response protocol with proper timing filtering isn't safe against relay attacks?

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Currently working in the Car industry, previously in the access control industry (and have developed active RFID systems which include timing information to prevent relay attacks)

Yes, you can do this. I have done this (restricted the negotiation to about 12 meters)--you're essentially racing the speed of light, see DE102012104955A1. Most of the reasonable approaches are patented by NXP.

I see, very interesting! I could've figured someone would patent something like this. Thank you for explaining.

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