Re:Tesla Plans to Open Car Doors to All Hackers This Summer
by comboy on Tuesday April 28, 2015 @02:11PM
(#9454191)
Couldn't it exchange a few messages with the key and precisely measure the time? I'm not sure if such precise measurement is possible, but given that light travels ~ 1 feet per second with 10Mhz clock you could theoretically test if it was more than 50 feet away (many approximations here, but I guess within an order of magnitude)
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Re:Tesla Plans to Open Car Doors to All Hackers This Summer
by jrockway on Tuesday April 28, 2015 @03:29PM
(#9454581)
HDMI already does this for DRM (it won't cough up device keys if it thinks the TV is too far away), so it's possible to measure with the right precision.
That said, signals in twisted pairs propagate at about .6c whereas signals in air propagate at speeds very close to c, so this use case is a little more challenging.
Re:Tesla Plans to Open Car Doors to All Hackers This Summer
by jffry on Tuesday April 28, 2015 @02:48PM
(#9454391)
You could attempt to time round-trip signal latency directly or via interference patterns, but it's a much shorter timescale. Light travels just shy of 1 billion feet per second, so we're talking differentiating in the 10s of nanoseconds, which requires nontrivial components.
Re:Tesla Plans to Open Car Doors to All Hackers This Summer
by maxerickson on Tuesday April 28, 2015 @02:54PM
(#9454416)
I already posted this link in the epic nope thread that is a sibling to this one, but the paper linked from Wikipedia speaks of an experimental implementation with a return time of 1 ns:
Re:Tesla Plans to Open Car Doors to All Hackers This Summer
by jffry on Wednesday April 29, 2015 @09:28AM
(#9458083)
That's cool. I wonder how difficult it would be to implement in practice.
Re:Tesla Plans to Open Car Doors to All Hackers This Summer
by maxerickson on Wednesday April 29, 2015 @10:32AM
(#9458504)
There are papers going back to at least 2005 (this one, a top search result, is cited 390 times: http://www.cl.cam.ac.uk/~mgk25/sc2005-distance.pdf ), so it would not be all that surprising if there are some existing commercial implementations. The current rash of thefts seem to come down to the systems being completely naive to amplification attacks though.