Car locks / keys?

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jkp
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Joined: Thu Jan 18, 2018 11:08 am

Car locks / keys?

Post by jkp » Thu Jan 18, 2018 11:08 am

Anyone happen to have investigated receiving car key (remote lock open/close) codes with the duo?

Some time ago, I noticed that my car key happened to output a signal which changed the state of a remote control socket. From googling, frequency seems to be the same.

I'm thinking of something like turning house outdoor lights on/off with the car keys if necessary when leaving / arriving at the house. (As a more specific case, for me particularly, could also be useful for debugging whether my car remote lock issue is with the car or they key).

Sending the codes (if even possible, not sure how the resync works) with a Tellstick might be a bit of a security risk - if one can record codes & replay them (and resync the car & key for a fresh start so the recorded keys will work), it would in principle make it possible for someone else also to record &replay the codes.

Zapper
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Location: Där det är kallt

Re: Car locks / keys?

Post by Zapper » Thu Jan 18, 2018 11:08 am

Car keys usually have coded rotations of the signal to avoid some forms of replay attacks so I think they might be a bit hard to get to work without having to modify the firmware of the tellstick. More modern cars probably have even more measures to prevent such things.

jkp
Posts: 42
Joined: Thu Jan 18, 2018 11:08 am

Re: Car locks / keys?

Post by jkp » Thu Jan 18, 2018 11:08 am

Modifying tellstick (Duo) firmware isn't a problem now that the code is available.

Yes, I'm aware of the rotations, but at least in one protocol description I read, the key was sending also a fixed id string, so it could perhaps be possible to recognize a specific car key even not handling the rotation.

I did some experiments with modified Duo firmware, and did get the Duo to read data sent by the key. Didn't figure out the encoding yet, though that might also be documented elsewhere. At least for my key, it's required that the key is quite close, e.g. a few centimeters from the Duo. I wonder if this is normal or signifies that my key is broken (also with the car, it needs to be close to the car and doesn't always work even then, even with a new battery). I guess it would be possible to use the Duo as an amplifier for the car key signal :-)

Using car key reception might also offer a bit more secure way of controlling home automation than the usual unprotected radio codes. Though of course that'd require the rotation algorithms present also on the receiving end, and doesn't help much if the actual device control is done without protection.

jkp
Posts: 42
Joined: Thu Jan 18, 2018 11:08 am

Re: Car locks / keys?

Post by jkp » Thu Jan 18, 2018 11:08 am

I set up a simple system to graph the 433,92 radio traffic - wire from a thermometer RFDAT contact to computer audio input and then run audacity on the computer. Bit density in the car key signal is higher than with the sensors & controls I have. Looks like visualizing the traffic this way will be helpful in figuring out the encoding and creating a firmware which could do something useful with car key data.

MaggieHarmon
Posts: 1
Joined: Thu Jan 18, 2018 11:08 am

Re: Car locks / keys?

Post by MaggieHarmon » Thu Jan 18, 2018 11:08 am

There are so many types of car locks now that you can install for your vehicle.

Locksmith University Park Texas

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