If the key fob was inside someone's house and a thief used some method
of repeating the signal to start
 the car and drive away, what happens after they get some distance away?
 Does the car shut off? =20
 In other words, doesn't that fob signal have to remain in proximity of
the car to keep it going?
 After all, if you're the rightful owner, and you have the fob in your
pocket and you get into your car=20
 and drive away, no matter where you go, that signal will be in
proximity of the car.  After all, you're
 sitting in the front seat. =20
 But if the signal is being repeated, at some point, that signal will
disappear.  Will the car turn off
 now?  If it does, then the thief would only get a short distance away
before the car stops and he won't
 be able to get it started again unless he copies the signal and
programs a piece of electronic equipment
 to act as the fob from that point.  I guess they could strip it or tow
it after that, but that would seem
 risky to me. =20
=20
 =20

Regards,

Jim

> -------- Original Message --------
> Subject: Re: [EE]:: Wrapping key-FOBs in tinfoil
> From: Denny Esterline <desterline@gmail.com>
> Date: Mon, July 09, 2018 10:25 am
> To: "Microcontroller discussion list - Public." <piclist@mit.edu>
>=20
>=20
> >
> >
> >  It seems to me the only way the key fob is going to be able to be
> > copied is if someone presses one of the
> >  buttons to transmit the signal.  If it is just sitting on a table or
> > hanging on a wall hook, how would
> >  someone outside the home (or bldg.) cause the key fob to transmit?
>=20
>=20
>=20
>=20
> This is a misunderstanding. I cannot claim to know the underlying
> technology, but
> many new car keyfobs today are "proximity devices". Fob in pocket, press
> button
> on dash to start car. Definitely do not have to press any buttons on the
> fob.
>=20
> I've not read Russell's linked article, but I did recently read an articl=
e
> claiming
> thieves were using SDR as a repeater to significantly boost the range of
> what the
> car considers "proximity". The claim was with your keys on a hook by your
> front
> door, they could use a repeater outside and drive the car away.
>=20
> The really fun trick here is they make no effort to capture or crack any
> codes,
> just boost a signal.
>=20
>=20
> -Denny
> --=20
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--=20
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