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posted by martyb on Friday April 17 2015, @07:04PM   Printer-friendly
from the [tin]-foil-your-fob dept.

A NY Times columnist had his car stolen by kids who were possibly using a repeater to rebroadcast his key fob:

Keyless entry systems typically only communicate with their remote fobs over the distance of a few feet, but he thinks that the gadget is capable of extending this range, fooling the car into thinking that the remote is within range even though it was actually in Bilton's House, about 50 feet away. He arrived at this theory after he consulted with Boris Danev, a Swiss-based security expert:

"It's a bit like a loudspeaker, so when you say hello over it, people who are 100 meters away can hear the word, 'hello,'" Mr. Danev said. "You can buy these devices anywhere for under $100." He said some of the lower-range devices cost as little as $17 and can be bought online on sites like eBay, Amazon and Craigslist.

Sounds creative and easy. Maybe those clubs aren't so silly after all.

 
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  • (Score: 3, Informative) by frojack on Friday April 17 2015, @07:40PM

    by frojack (1554) on Friday April 17 2015, @07:40PM (#172167) Journal

    TFA says:

    the perps used an electronic device to simply unlock his Toyota Prius, rather than doing things the old-fashioned way with a slim jim, coat hanger, or brick.

    The article didn't say anything about starting the car.

    The unlocking need not require a button push on the fob (but there is no reason to believe it wasn't.) The story is pretty unclear about this. (Its written by a journalist after all)

    Some Keyless entry systems do not require pushing a fob button.

    Merely putting your hand on the door handle will cause the car to look for your key fob nearby (usually within 5 feet or so), and unlock the door if it sees it.
    (I know nothing about the Prius system, but that is how my car works).

    Properly designed, the system would send out a coded challenge to the fob, and the fob would answer with a proper code. (seems unlikely these fobs would transmit ALL THE TIME, but that can't be discounted). If the car hears the fob, the door unlocks.

    Regardless whether the fob is using a constant broadcast or a response broadcast, the digital encoded key is unlikely to be globally unique. Probably there is under 500 combinations, just like physical keys usually exist in a small number of actual tooth patterns. That would make it easy for their device to broadcast them all in rapid succession.

    Or, they could have just stood near enough to record them, then come back later and burglarize your car.

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  • (Score: 2) by captain normal on Friday April 17 2015, @08:04PM

    by captain normal (2205) on Friday April 17 2015, @08:04PM (#172178)

    Here is how the "Smart Key" works: https://www.youtube.com/watch?v=_5vln1ldUo8 [youtube.com]
    So simple to gain entry by amplifying the fob signal.

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    • (Score: 2, Disagree) by frojack on Friday April 17 2015, @08:24PM

      by frojack (1554) on Friday April 17 2015, @08:24PM (#172183) Journal

      Pretty much the same as my Chrysler. (And not at all clear as to the inner workings).

      But it STILL can't be as simple as amplifying the fob signal, otherwise my fob would open every Chrysler.

      What I suspect:

      1) Fob batteries would not last long enough if they were constantly transmitting. Constant receiving takes very little power.
      2) The car probably sends out a weak "Hello Fob" signal that the fob listens for. This would not need to be unique, but could have an authentication code attached).
      3) Fob sends out a weak transmission of its returning digital key.
      4) Car matches key, and unlocks doors.

      So possible outcomes:
      a) If the returning key can be computed from the Hello Fob call, someone needs to find that engineer and bitch slap him mercilessly. (I don't discount this by the way). And your break in box could simply compute the proper response in real time, and transmit it.

      b) if the fob simply returns a unique key that the the car listens for, you would have to lurk near the car to capture these, and play them back later.

      c) If there are a small set of these semi-unique keys your break-in-box would transmit them all in response to any car's Hello Fob signal.

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      • (Score: 2) by FatPhil on Saturday April 18 2015, @10:58AM

        by FatPhil (863) <{pc-soylent} {at} {asdf.fi}> on Saturday April 18 2015, @10:58AM (#172352) Homepage
        > But it STILL can't be as simple as amplifying the fob signal, otherwise my fob would open every Chrysler.

        You just said the equivalent of: "But it STILL can't be as simple as copying the key, otherwise my key would open every lock."

        How can you not understand the concept of the (electronic) key and the (electronic) lock being paired?
        --
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        • (Score: 2) by FatPhil on Saturday April 18 2015, @11:12AM

          by FatPhil (863) <{pc-soylent} {at} {asdf.fi}> on Saturday April 18 2015, @11:12AM (#172357) Homepage
          After seeing my post, my g/f's just pointed this out to me:

          Why did you say:

          > But it STILL can't be as simple as amplifying the fob signal, otherwise my fob would open every Chrysler.

          rather than:

              But it STILL can't be as simple as amplifying the fob signal, otherwise my fob would open every car.

          ?

          Now think about your answer.

          She never posts, so you'll never get the chance to mod her +1 Insightful. I will happily take them by proxy :-)
          (don't bother, always capped, even after the flamebait storm I got myself in last weekend.)
          --
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          • (Score: 0) by Anonymous Coward on Monday April 20 2015, @11:58PM

            by Anonymous Coward on Monday April 20 2015, @11:58PM (#173330)

            uhh, how many g/f's do you have? You later said she, so I'm guessing just one?

  • (Score: 0) by Anonymous Coward on Friday April 17 2015, @08:49PM

    by Anonymous Coward on Friday April 17 2015, @08:49PM (#172189)

    > The article didn't say anything about starting the car.

    So, you are saying ikanreed picked an appropriate login?

    > Regardless whether the fob is using a constant broadcast or a response broadcast, the digital encoded key is unlikely to be globally unique.
    > Probably there is under 500 combinations, just like physical keys

    That's an awful big assumption. There is no reason it needs to be true. Unlike physical keys the namespace is huge. With just 128 bits there technically could be identical combos but practically there would not.