4 ms·

I wonder how difficult it is to add some clock syncing and time-of-flight measurements to ensure a certain distance. If the speed of light is to fast, maybe us

I wonder how difficult it is to add some clock syncing and time-of-flight measurements to ensure a certain distance. If the speed of light is to fast, maybe using sound could work.

frankus 8y ago
Apple claims that they use time-of-flight for their "Unlock with Apple Watch" feature on macOS, so it seems like something that a car maker/supplier could pull off, especially if they're willing to throw dedicated hardware at the problem. That said, the fob is much more battery-constrained than a watch that you charge on a daily basis.
- comboy 8y ago
  This is such an obvious solution that maybe some patents are the reason it's not implemented by every car manufacturer.
  - williamscales 8y ago
    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 https://patents.google.com/patent/US8930045
    - comboy 8y ago
      Nice find. Looks like Apple cites it in some of its own patents ("Enhanced automotive passive entry" from 2018-08-16) so maybe they already have rights to it and that's why unlock with Apple watch can work correctly.
    - andrewstuart2 8y ago
      `ping`. They were granted a patent for ping. That seems ridiculous.
      - williamscales 8y ago
        It also describes RADAR, or even LIDAR for that matter. It doesn't seem like one should be able to patent something that is merely an application of a well known physical principal. Maybe I misunderstand what "novel" means.
andrewstuart2 8y ago
The speed of light shouldn't be too fast if the fob is just returning a ping. The car can almost certainly wake up the fob, ping it, then compute the distance. Unless my brief calculations [1] are too simplistic, a 2Ghz processor would have a resolution of increments of 15cm. That should be plenty of resolution to decide if the key is in a certain spot. [1] https://www.google.com/search#q=speed+of+light+%2F+2+ghz https://www.google.com/search#q=speed+of+light+%2F+2+ghz

I wonder how difficult it is to add some clock syncing and time-of-flight measurements to ensure a certain distance. If the speed of light is to fast, maybe using sound could work.

frankus 8y ago

Apple claims that they use time-of-flight for their "Unlock with Apple Watch" feature on macOS, so it seems like something that a car maker/supplier could pull off, especially if they're willing to throw dedicated hardware at the problem. That said, the fob is much more battery-constrained than a watch that you charge on a daily basis.

comboy 8y ago
This is such an obvious solution that maybe some patents are the reason it's not implemented by every car manufacturer.
- williamscales 8y ago
  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 https://patents.google.com/patent/US8930045
  - comboy 8y ago
    Nice find. Looks like Apple cites it in some of its own patents ("Enhanced automotive passive entry" from 2018-08-16) so maybe they already have rights to it and that's why unlock with Apple watch can work correctly.
  - andrewstuart2 8y ago
    `ping`. They were granted a patent for ping. That seems ridiculous.
    - williamscales 8y ago
      It also describes RADAR, or even LIDAR for that matter. It doesn't seem like one should be able to patent something that is merely an application of a well known physical principal. Maybe I misunderstand what "novel" means.

andrewstuart2 8y ago

The speed of light shouldn't be too fast if the fob is just returning a ping. The car can almost certainly wake up the fob, ping it, then compute the distance. Unless my brief calculations [1] are too simplistic, a 2Ghz processor would have a resolution of increments of 15cm. That should be plenty of resolution to decide if the key is in a certain spot. [1] https://www.google.com/search#q=speed+of+light+%2F+2+ghz https://www.google.com/search#q=speed+of+light+%2F+2+ghz