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Is Your Vehicle Still Outside?
Zoomup
3516 Posts

Z.

9 Replies
M. Joshi
20 Posts

Apparently the screened (Faraday cage) key pouches prevent this.

keylevel
44 Posts

I've not found one yet that stops my car from being opened when I'm standing next to it, but it may be that they are good enough to stop a relay attack where the distances are greater (so the signal is weaker). I just make sure the key is not kept somewhere where someone would expect it to be.

ebee
1261 Posts

A few years back (early days of PAYG mobile phone ) I was on holiday and had the habit of reading txt messages in the morning then put my mobile in the room safe and go out for the day. On return to the room I opened the safe and messages had come in whilst I was away. Does Faraday effect block the signal or does it pull in with an aerial effect ? Similarly, sometimes, in a bad signal area I get into car and signal bars increase.

Some of our radio boffins might know some answers 

Simon Barker
950 Posts

ebee: 
 

A few years back (early days of PAYG mobile phone ) I was on holiday and had the habit of reading txt messages in the morning then put my mobile in the room safe and go out for the day. On return to the room I opened the safe and messages had come in whilst I was away. Does Faraday effect block the signal or does it pull in with an aerial effect ? Similarly, sometimes, in a bad signal area I get into car and signal bars increase.

Some of our radio boffins might know some answers 

At the high frequencies and short wavelengths used by mobile phones, the signal can sneak though the smallest of gaps.  A loose-fitting safe door won't completely block the signal.

It's worth being a bit wary of hotel safes.  When you get to the room, you will find instructions with the safe to tell you how to set the combination you want to use.  I bought one of those safes a few years ago, to use in my house.  When I got it home and opened it, I found the instructions to set both of the combinations.

Alan Capon
461 Posts

GSM phones also have an adaptive transmit power. They measure the error rate to the base station, then set the transmit power accordingly. This is why your battery doesn’t last as long in the countryside, compared to a city. In a metal box (or even a car boot) you will find the battery capacity drops as the transmit power increases. 
 

Regards,

Alan. 

dcbwhaley
82 Posts

Don't know if it is just a local thing or a coincidence but I seem to be seeing  a lot of those steering locks:  the ones that effectively clamp a long pole across the steering pole so it can't be turned.  

I am told that they don't use electronics but that seems unlikely :-)

mapj1
3923 Posts

At the high frequencies and short wavelengths used by mobile phones, the signal can sneak though the smallest of gaps.  A loose-fitting safe door won't completely block the signal.

seconded.

The typical UK mobile phone uses either 900MHz (wavelength ~ 30cm) or 1800MHz (wavelength 15cm) for the main link to the base staion and higher freqs (shorter wavelengths) for bluetooth, WiFi, 4g/LTE fill in ). 

To make a shielded room of any useful attenuation, all apertures, even hairline ones, need to be very short (less than perhaps 10% of a wavelength) in the longest dimension. I uggest a maximum gap length of 1cm or less to stop a 'phone working.

There is a reason that EMC test facilities are so expensive, and have wire stocking materials in the fixed joints and double rows of offset finger stock contacts on the doors to break any gap into sections millimetres or less between adjacent bridging contacts.

Even so, it is hard to do, and to get really good shielded facility  requires a lot of crawling about with the instruments, looking for the weak spots.

Mike

Chris Pearson
2874 Posts

On the advice of my insurer, I keep the key to my modern car in an old tobacco tin.

Simon Barker
950 Posts

I don't suppose any car manufacturer will ever take responsibility for putting this new technology into production before asking security researchers if it's actually secure.

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