Search for my lost car key

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mgf909
Posts: 3
Joined: Fri Nov 16, 2018 9:38 pm

Search for my lost car key

Post by mgf909 » Fri Nov 16, 2018 9:48 pm

Hi all,

As per the title i want to search my home for a lost Mercedes car key....

Did you know that MB in Australia want to charge $1275 + labour for a new key!!! What a ripoff!

Ive been aware of RTL SDR for a few years, but never really had an application to get into it with..but i have quite an incentive now. My car has keyless entry/ingition so i imagine the keys have some sort of beacon transmission to tell teh car they are close by.

I was hoping i can use a RTL-SDR to sniff for this beacon and thus try to find the missing key in my home...

Is this possible? I really dont want to spend $1200 to replace the key as as soon as i do the missing one will be found!

Cheers,
Greg

mgf909
Posts: 3
Joined: Fri Nov 16, 2018 9:38 pm

Re: Search for my lost car key

Post by mgf909 » Fri Nov 16, 2018 10:18 pm

Doing some further reading on how these keys work....

Apparently they are more like RFID whereas the car is the "beacon" and the key will only transmit when it receives the "beacon".....

So i would need to build the full "relay attack" setup.... Anyone done this?

chris82
Posts: 2
Joined: Sun Jul 08, 2018 4:25 pm

Re: Search for my lost car key

Post by chris82 » Mon Nov 19, 2018 2:30 pm

A real live relay should not be required. It should be sufficient to record an exemplary beacon from your car and replay this.

However, these beacons are typically sent at LF frequencies like 125 kHz which is outside the RTL-SDR range.
And you would need a TX-capable SDR which covers this LF frequency. Even these professional devices do not always support this.

Finally, your car key should then reply using its normal UHF frequency which can easily be seen e.g. in SDR# using an RTL-SDR.

mgf909
Posts: 3
Joined: Fri Nov 16, 2018 9:38 pm

Re: Search for my lost car key

Post by mgf909 » Mon Nov 19, 2018 9:20 pm

Thanks Chris for your reply.

Now to see what i can find in the way of a 125khz transceiver.....

snn47
Posts: 107
Joined: Tue Dec 27, 2016 11:00 pm

Re: Search for my lost car key

Post by snn47 » Sun Dec 02, 2018 7:34 am

There are car keys where you still insert the card key in the lock, which I assume has a RFID chip and
those without lock and the car is unlocked when you stand in front of it, for which I assume that a different ISDN frequency is used.
While I read a few articles on the attack on those cars via a relay link, one close to the driver and its key, the second one at the car unlocking and starting it with thecode from the drivers key transmitted via the link. The frequency they operate on was never mentioned in the articles I read.
Since to my knowledge the RFID generate the power from the RF-field of the interrogator similar to those standing left and right at the door of shops.

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