Faraday bags a con?

[Jim the Geordie]

Am I missing something here?
I have a car with keyless entry and understand that toerags can snatch
my signal when I open or close using the fob.
OR I can open/close the car with a button on the car door if I am close
enough to it.
That suggests that the fob is constantly sending out a signal, but
clearly not the same signal as when I push the fob button (or perhaps
the car is sending a signal to the fob?)

I see on Amazon and elsewhere that I can buy Faraday Bag to put my key
fob in.
If you don't know: a Faraday bag/box/cage is a metal container that does
not let a signal in or out.

The question is, what use can they be?
If I want to open the car with the fob then it would have to be taken
out of the bag anyway; similarly if using the door button.

[Theo]

Post by Jim the Geordie
Am I missing something here?
I have a car with keyless entry and understand that toerags can snatch
my signal when I open or close using the fob.
OR I can open/close the car with a button on the car door if I am close
enough to it.
That suggests that the fob is constantly sending out a signal, but
clearly not the same signal as when I push the fob button (or perhaps
the car is sending a signal to the fob?)

Many fobs have several keys in them:

1. an active one, where you press the button to eg unlock the doors or open
the boot
2. a passive one, which the car can query to see if it's in range. If so
it'll unlock the doors / start the engine. Could be powered inductively
or battery powered in the fob
3. a mechanical one, for getting into the car if the battery is flat

'Keyless entry' can be some variety of no.2. The button is no.1. The
difference is that in no.1 the fob sends out a signal when activated, while
in no.2 the car is sending out requests all the time and listening for the
fob to answer.

Post by Jim the Geordie
I see on Amazon and elsewhere that I can buy Faraday Bag to put my key
fob in.
If you don't know: a Faraday bag/box/cage is a metal container that does
not let a signal in or out.
The question is, what use can they be?
If I want to open the car with the fob then it would have to be taken
out of the bag anyway; similarly if using the door button.

The usual problem is that your key is sitting on the hall table, but the
miscreant can record the car's challenge standing next to it, walk up to your
front door and replay the challenge. The fob answers and the miscreant
records the response. Then they replay the response next to the car and the
doors open.

If you put the fob in the shielded bag then (in theory) the fob doesn't hear
the challenge and so never replies. That means they can't nick the car
while you are asleep.

When you take the fob out of the bag you're likely standing near to the car
and it doesn't matter if the miscreant unlocks the car because you were
unlocking it anyway. If they're going to steal the car at that point
they'll need to physically overpower you, which they could have done without
any key fob spoofing. But that's a whole different crime from sneaking away
with the car at 3am.

Theo

[Jim the Geordie]

Post by Theo

Post by Jim the Geordie
Am I missing something here?
I have a car with keyless entry and understand that toerags can snatch
my signal when I open or close using the fob.
OR I can open/close the car with a button on the car door if I am close
enough to it.
That suggests that the fob is constantly sending out a signal, but
clearly not the same signal as when I push the fob button (or perhaps
the car is sending a signal to the fob?)

1. an active one, where you press the button to eg unlock the doors or open
the boot
2. a passive one, which the car can query to see if it's in range. If so
it'll unlock the doors / start the engine. Could be powered inductively
or battery powered in the fob
3. a mechanical one, for getting into the car if the battery is flat
'Keyless entry' can be some variety of no.2. The button is no.1. The
difference is that in no.1 the fob sends out a signal when activated, while
in no.2 the car is sending out requests all the time and listening for the
fob to answer.

Post by Jim the Geordie
I see on Amazon and elsewhere that I can buy Faraday Bag to put my key
fob in.
If you don't know: a Faraday bag/box/cage is a metal container that does
not let a signal in or out.
The question is, what use can they be?
If I want to open the car with the fob then it would have to be taken
out of the bag anyway; similarly if using the door button.

The usual problem is that your key is sitting on the hall table, but the
miscreant can record the car's challenge standing next to it, walk up to your
front door and replay the challenge. The fob answers and the miscreant
records the response. Then they replay the response next to the car and the
doors open.
If you put the fob in the shielded bag then (in theory) the fob doesn't hear
the challenge and so never replies. That means they can't nick the car
while you are asleep.
When you take the fob out of the bag you're likely standing near to the car
and it doesn't matter if the miscreant unlocks the car because you were
unlocking it anyway. If they're going to steal the car at that point
they'll need to physically overpower you, which they could have done without
any key fob spoofing. But that's a whole different crime from sneaking away
with the car at 3am.
Theo

Thanks, Theo.

It would help if I kept my keys in a biscuit tin when at home?

[Theo]

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job. Most of the fobs use 433 or 868MHz (315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).

Theo

[Tim Streater]

Post by Theo

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job. Most of the fobs use 433 or 868MHz (315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).

I bought some metalised plastic pouches, two of which I have in my wallet,
with the chip-n-pin cards between them. Couple of quid off Amazon.

[Harry Bloomfield Esq]

Post by Tim Streater
I bought some metalised plastic pouches, two of which I have in my wallet,
with the chip-n-pin cards between them. Couple of quid off Amazon.

Some metallized plastic food packaging, works just as well. The thing
is, to test it - put the key, in a package, and try it near the car.

[Tim Streater]

Post by Harry Bloomfield Esq

Post by Tim Streater
I bought some metalised plastic pouches, two of which I have in my wallet,
with the chip-n-pin cards between them. Couple of quid off Amazon.

Some metallized plastic food packaging, works just as well. The thing
is, to test it - put the key, in a package, and try it near the car.

This was for my credit cards, not a key fob.

[Harry Bloomfield Esq]

Post by Tim Streater
This was for my credit cards, not a key fob.

Same principle, try to pay for an item, contactless, with the card covered..

[nib]

Post by Harry Bloomfield Esq

This was for my credit cards, not  a key fob.

Same principle, try to pay for an item, contactless, with the card covered..

Though that has the same issue as I had with the car. If the screening
is marginal, it might block one reader but not another slightly
higher-powered one!

nib

[David Wade]

Post by nib

Post by Harry Bloomfield Esq

This was for my credit cards, not  a key fob.

Same principle, try to pay for an item, contactless, with the card covered..

Though that has the same issue as I had with the car. If the screening
is marginal, it might block one reader but not another slightly higher-
powered one!

The card process is more complex. The card is powered by the wireless
signal from the reader, and transmits back to the reader. The transmit
power from the card is fixed, so no matter how "powerfull" the reader
is, you still get the same signal from the card.

Post by nib
nib

Dave

[nib]

Post by David Wade

Post by nib

Post by Harry Bloomfield Esq

This was for my credit cards, not  a key fob.

Same principle, try to pay for an item, contactless, with the card covered..

Though that has the same issue as I had with the car. If the screening
is marginal, it might block one reader but not another slightly
higher- powered one!

The card process is more complex. The card is powered by the wireless
signal from the reader, and transmits back to the reader. The transmit
power from the card is fixed, so no matter how "powerfull" the reader
is, you still get the same signal from the card.

Post by nib
nib

Dave

Is the power the card can emit fixed, independent of how much power it
receives from the terminal?

nib

[David Wade]

Post by nib

Post by David Wade

Post by nib

Post by Harry Bloomfield Esq

This was for my credit cards, not  a key fob.

Same principle, try to pay for an item, contactless, with the card covered..

Though that has the same issue as I had with the car. If the
screening is marginal, it might block one reader but not another
slightly higher- powered one!

The card process is more complex. The card is powered by the wireless
signal from the reader, and transmits back to the reader. The transmit
power from the card is fixed, so no matter how "powerfull" the reader
is, you still get the same signal from the card.

Post by nib
nib

Dave

Is the power the card can emit fixed, independent of how much power it
receives from the terminal?

Provided it gets enough power yes. Getting the things to actually work
as designed is a challenge. Stopping them working is easier...

Dave

Post by nib
nib

[nib]

Post by David Wade

Post by nib

Post by David Wade

Post by nib

Post by Harry Bloomfield Esq

This was for my credit cards, not  a key fob.

Same principle, try to pay for an item, contactless, with the card covered..

Though that has the same issue as I had with the car. If the
screening is marginal, it might block one reader but not another
slightly higher- powered one!

The card process is more complex. The card is powered by the wireless
signal from the reader, and transmits back to the reader. The
transmit power from the card is fixed, so no matter how "powerfull"
the reader is, you still get the same signal from the card.

Post by nib
nib

Dave

Is the power the card can emit fixed, independent of how much power it
receives from the terminal?

Provided it gets enough power yes. Getting the things to actually work
as designed is a challenge. Stopping them working is easier...
Dave

Post by nib
nib

What about some terminals being more sensitive to the signal from the card?

nib

[The Natural Philosopher]

Post by Theo

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job. Most of the fobs use 433 or 868MHz (315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

[GB]

Post by The Natural Philosopher

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job.  Most of the fobs use 433 or 868MHz
(315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

None of those nasty glass windows, I hope? :)

[The Natural Philosopher]

Post by GB

Post by The Natural Philosopher

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job.  Most of the fobs use 433 or 868MHz
(315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed
plasterboard
Probably good enough

None of those nasty glass windows, I hope? :)

No. small leaded lights. NICE windows

[Dan Green]

On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Theo

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job. Most of the fobs use 433 or 868MHz (315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

[Jeff Layman]

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Theo

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job. Most of the fobs use 433 or 868MHz (315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Out of interest, I've often seen people continue mobile phone
conversations in a lift. I've always assumed that lifts are pretty much
metal boxes (which are earthed via the cable supporting them and metal
guides on the sides). Why do they seem to make such poor Faraday cages
where mobile signals are concerned?

[Dan Green]

Post by Jeff Layman

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Theo

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job. Most of the fobs use 433 or 868MHz (315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Out of interest, I've often seen people continue mobile phone
conversations in a lift. I've always assumed that lifts are pretty much
metal boxes (which are earthed via the cable supporting them and metal
guides on the sides). Why do they seem to make such poor Faraday cages
where mobile signals are concerned?

Lifts are not made to be RF-tight. They have gaps, even if you can't
see them. It only takes a slight opening to let RF through. That's why
the old-fashioned biscuit tins (you don't see them so much these days,
if at all) are so effective. They weren't made to be RF-tight, but
they *were* made to be air-tight, and in an all metal enclosure,
that's the effectively the same thing.

[The Natural Philosopher]

Post by Dan Green

Post by Jeff Layman

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Theo

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job. Most of the fobs use 433 or 868MHz (315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Out of interest, I've often seen people continue mobile phone
conversations in a lift. I've always assumed that lifts are pretty much
metal boxes (which are earthed via the cable supporting them and metal
guides on the sides). Why do they seem to make such poor Faraday cages
where mobile signals are concerned?

Lifts are not made to be RF-tight. They have gaps, even if you can't
see them. It only takes a slight opening to let RF through. That's why
the old-fashioned biscuit tins (you don't see them so much these days,
if at all) are so effective. They weren't made to be RF-tight, but
they *were* made to be air-tight, and in an all metal enclosure,
that's the effectively the same thing.

An RF signal in general will not penetrate an aperture much less than
its wavelength unless there is a wire going through it.

Wavelengh at 2.4GHGz is 5" roughly. Probably any gap less than half an
inch makes sod all difference

Which is why light gets through your microwave door, but your hand
doesn't cook when you open it.

The inside of your phone will have perforated wire mesh in it to shield
Not solid metal.

BUT as I have pointed out, signals can travel along the surface of
incoming wires. It is even possible theoretically to have an aerial on
the lift top that couples to an aerial inside the lift cage, connected
by coax.

Like the old car aerials did

I can definitely say for sure that three layers of foil backed
plasterboard even with two doorways punched in them knocks my Wifi
signal back around 40dB.

If I want 4G I have to stand by a window with my phone. The windows have
apertures of around 4x6" in the lead lights.

By all means use a biscuit tin if you feel paranoid. Just be aware that
you don't need to

A handbag lined with copper mesh will do fine :-)

[The Natural Philosopher]

Post by Jeff Layman

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job.  Most of the fobs use 433 or 868MHz
(315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Out of interest, I've often seen people continue mobile phone
conversations in a lift. I've always assumed that lifts are pretty much
metal boxes (which are earthed via the cable supporting them and metal
guides on the sides). Why do they seem to make such poor Faraday cages
where mobile signals are concerned?

The effect I have just described.

Almost certainly bits of them are *not* metal and they will have a huge
loop of cabling coming into them and that will act as a nice transit
route for centimetric signals.

And these days stuff that people go into is *made* to be (reasonably)
transparent to wifi and mobile phone signals.

Deprive people of their shiny thing and they go very grumpy.

[GB]

Post by The Natural Philosopher

Post by Jeff Layman

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job.  Most of the fobs use 433 or 868MHz
(315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Out of interest, I've often seen people continue mobile phone
conversations in a lift. I've always assumed that lifts are pretty
much metal boxes (which are earthed via the cable supporting them and
metal guides on the sides). Why do they seem to make such poor Faraday
cages where mobile signals are concerned?

The effect I have just described.
Almost certainly bits of them are *not* metal and they will have a huge
loop of cabling coming into them and that will act as a nice transit
route for centimetric signals.

I do wonder what the floors of a lift are made out of, especially those
high speed lifts which add a bit of g force to the weight of the
passengers at the start of the ride. I'm pretty sure that one inch ply
would do nicely. And the lift's ceiling could well be wood.

Post by The Natural Philosopher
And these days stuff that people go into is *made* to be (reasonably)
transparent to wifi and mobile phone signals.
Deprive people of their shiny thing and they go very grumpy.

[nib]

Post by Jeff Layman

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job.  Most of the fobs use 433 or 868MHz
(315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Out of interest, I've often seen people continue mobile phon
conversations in a lift. I've always assumed that lifts are pretty much
metal boxes (which are earthed via the cable supporting them and metal
guides on the sides). Why do they seem to make such poor Faraday cages
where mobile signals are concerned?

I would hope that lifts are designed to let mobile signals in; it would
be very useful for anyone stuck in one to supplement the (presumably)
fixed emergency line to somewhere that you hope is manned?

nib

[Jethro_uk]

Post by nib

Post by Jeff Layman

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job.  Most of the fobs use 433 or 868MHz
(315MHz for some imports) so if you have a good shield against that
signal then it should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed
plasterboard Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Out of interest, I've often seen people continue mobile phon
conversations in a lift. I've always assumed that lifts are pretty much
metal boxes (which are earthed via the cable supporting them and metal
guides on the sides). Why do they seem to make such poor Faraday cages
where mobile signals are concerned?

I would hope that lifts are designed to let mobile signals in; it would
be very useful for anyone stuck in one to supplement the (presumably)
fixed emergency line to somewhere that you hope is manned?

The basic design of a lift predates mobile phones by over a century ...

[nib]

Post by Jethro_uk

Post by nib

Post by Jeff Layman

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job.  Most of the fobs use 433 or 868MHz
(315MHz for some imports) so if you have a good shield against that
signal then it should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed
plasterboard Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Out of interest, I've often seen people continue mobile phon
conversations in a lift. I've always assumed that lifts are pretty much
metal boxes (which are earthed via the cable supporting them and metal
guides on the sides). Why do they seem to make such poor Faraday cages
where mobile signals are concerned?

I would hope that lifts are designed to let mobile signals in; it would
be very useful for anyone stuck in one to supplement the (presumably)
fixed emergency line to somewhere that you hope is manned?

The basic design of a lift predates mobile phones by over a century ...

Well yes, but quite a lot will have been made since about 1990?

nib

[The Natural Philosopher]

Post by nib

Post by Jethro_uk

Post by nib

Post by Jeff Layman

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job.  Most of the fobs use 433 or 868MHz
(315MHz for some imports) so if you have a good shield against that
signal then it should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed
plasterboard Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Out of interest, I've often seen people continue mobile phon
conversations in a lift. I've always assumed that lifts are pretty much
metal boxes (which are earthed via the cable supporting them and metal
guides on the sides). Why do they seem to make such poor Faraday cages
where mobile signals are concerned?

I would hope that lifts are designed to let mobile signals in; it would
be very useful for anyone stuck in one to supplement the (presumably)
fixed emergency line to somewhere that you hope is manned?

The basic design of a lift predates mobile phones by over a century ...

Well yes, but quite a lot will have been made since about 1990?

And it might well be possible to drill a hole for an antenna in the
older ones

If the cables themselves didn't provide a conduit for RF. When you think
about it, the cable loom feeding a lift cage is as long as the whole
shaft. And ends inside the cage at the control panel

Post by nib
nib

[The Natural Philosopher]

Post by Jethro_uk

Post by nib

Post by Jeff Layman

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job.  Most of the fobs use 433 or 868MHz
(315MHz for some imports) so if you have a good shield against that
signal then it should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed
plasterboard Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Out of interest, I've often seen people continue mobile phon
conversations in a lift. I've always assumed that lifts are pretty much
metal boxes (which are earthed via the cable supporting them and metal
guides on the sides). Why do they seem to make such poor Faraday cages
where mobile signals are concerned?

I would hope that lifts are designed to let mobile signals in; it would
be very useful for anyone stuck in one to supplement the (presumably)
fixed emergency line to somewhere that you hope is manned?

The basic design of a lift predates mobile phones by over a century ...

But how many of those are still running?

[Paul]

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job.  Most of the fobs use 433 or 868MHz (315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Out of interest, I've often seen people continue mobile phone conversations in a lift. I've always assumed that lifts are pretty much metal boxes (which are earthed via the cable supporting them and metal guides on the sides). Why do they seem to make such poor Faraday cages where mobile signals are concerned?

There can be a pico-cell or a Wifi, on the ceiling of the elevator.
The car is flooded with signal. In a high crime area, an elevator
might even have surveillance video.

Modern elevators are a lot more sophisticated than the old freight
elevators you traveled in as a young lad at a student job.

Similarly, in a mall, there can be RF transceivers on the ceiling
providing services. Broadcast signals from outside the mall, it does
not matter that they can't get into the building, as the building has
"copies" of the function inside the building.

Paul

[The Natural Philosopher]

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Theo

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job. Most of the fobs use 433 or 868MHz (315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

It works well enough to completely bugger Wifi and makes a mess of VHF

Oh and by the way mesh works, or would wouldn't be able to see your food
in the microwave. Its all a matter of wavelength.

I've worked a fair bit with RF back in the day. The game is not as
ArtStudents™ think to 'completely screen' so that nothing, not even air
gets in.

It is to attenuate *enough* . Eg./ In RF design all the wires have to
come out somehow: The key is to stop RF coming along with them , so you
slip ferrite beads on them an s use wall piercing concentric capacitors etc.

Its not perfect, but it is *good enough*.

E.g. If I stand by my window, I can open the car boot,
but once a few feet inside the room, I cant

[The Natural Philosopher]

Post by Dan Green
Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Indeed.   I've been amazed to see people making and receiving mobile
phone calls when in a lift, when it looks like we are inside a metal box
with 6 metal sides joining well at the edges.

so there were no buttons on the lift at all? No controls?

A sheet metail celng with no ventilation holes?

One would think that the

radio signals couldn't get it, but obviously they do.

Plenty of holes even if just to avoid passenger suffocation. Plenty of
wires coming in, and these days probably positive measures to ensure
moibiuole sihgnal penetrate

So one does need

a very careful watch on the size of the gaps to make a Faraday cage out
of a biscuit tin.

Completely false conclusion from a completely false assumption.

Look up RF mesh shielding. It's more holes than metal

[Jethro_uk]

Post by Dan Green
Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio frequency
emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all joins
are overlapped. Unless you're living in some sort of hovel with no
doors or windows - or else they're all shuttered up with grounded metal
- RF will leak in like a sieve.

Indeed. I've been amazed to see people making and receiving mobile
phone calls when in a lift, when it looks like we are inside a metal box
with 6 metal sides joining well at the edges. One would think that the
radio signals couldn't get it, but obviously they do. So one does need
a very careful watch on the size of the gaps to make a Faraday cage out
of a biscuit tin.

And that is before you consider it may have been a design feature.

ISTR that long road tunnels have "leaky feeders" to allow RF (and thus
broadcast radio) to work.

[The Natural Philosopher]

Post by Jethro_uk

Post by Dan Green
Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio frequency
emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all joins
are overlapped. Unless you're living in some sort of hovel with no
doors or windows - or else they're all shuttered up with grounded metal
- RF will leak in like a sieve.

Indeed. I've been amazed to see people making and receiving mobile
phone calls when in a lift, when it looks like we are inside a metal box
with 6 metal sides joining well at the edges. One would think that the
radio signals couldn't get it, but obviously they do. So one does need
a very careful watch on the size of the gaps to make a Faraday cage out
of a biscuit tin.

And that is before you consider it may have been a design feature.
ISTR that long road tunnels have "leaky feeders" to allow RF (and thus
broadcast radio) to work.

They do today.

Older tunnels still make a mess.

[Bob Eager]

Post by Jethro_uk

Post by Dan Green
Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Indeed. I've been amazed to see people making and receiving mobile
phone calls when in a lift, when it looks like we are inside a metal
box with 6 metal sides joining well at the edges. One would think that
the radio signals couldn't get it, but obviously they do. So one does
need a very careful watch on the size of the gaps to make a Faraday
cage out of a biscuit tin.

And that is before you consider it may have been a design feature.
ISTR that long road tunnels have "leaky feeders" to allow RF (and thus
broadcast radio) to work.

Yes, even the Dartford Tunnel has that.

[The Natural Philosopher]

Post by Bob Eager

Post by Jethro_uk

Post by Dan Green
Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Indeed. I've been amazed to see people making and receiving mobile
phone calls when in a lift, when it looks like we are inside a metal
box with 6 metal sides joining well at the edges. One would think that
the radio signals couldn't get it, but obviously they do. So one does
need a very careful watch on the size of the gaps to make a Faraday
cage out of a biscuit tin.

And that is before you consider it may have been a design feature.
ISTR that long road tunnels have "leaky feeders" to allow RF (and thus
broadcast radio) to work.

Yes, even the Dartford Tunnel has that.

It for sure does not.,

I lost VHF radio through it last time I used it

[mm0fmf]

Post by The Natural Philosopher

Post by Bob Eager

Post by Jethro_uk

Post by Dan Green
Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Indeed.   I've been amazed to see people making and receiving mobile
phone calls when in a lift, when it looks like we are inside a metal
box with 6 metal sides joining well at the edges.  One would think that
the radio signals couldn't get it, but obviously they do.  So one does
need a very careful watch on the size of the gaps to make a Faraday
cage out of a biscuit tin.

And that is before you consider it may have been a design feature.
ISTR that long road tunnels have "leaky feeders" to allow RF (and thus
broadcast radio) to work.

Yes, even the Dartford Tunnel has that.

It for sure does not.,
I lost VHF  radio through it last time I used it

Well your radio is fucked or you're using it wrong.


FM
BBC Nationals, BBC Kent and Classic FM are received from Wrotham;
BBC London and Greatest Hits (London) are received from Crystal Palace;
Capital FM, Magic FM and Heart London are received from Croydon;
BBC Essex is received from Benfleet.

MF: Radio 5 and TalkSport are received from Brookmans Park

There's even a sign telling you that information/safety messages are
broadcast on AM/FM at the tunnel entrance. They get inserted over the
stations being rebroadcast on the leaky feeder.

[charles]

Post by Bob Eager

Post by Jethro_uk

Post by Dan Green
Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Indeed. I've been amazed to see people making and receiving mobile
phone calls when in a lift, when it looks like we are inside a metal
box with 6 metal sides joining well at the edges. One would think that
the radio signals couldn't get it, but obviously they do. So one does
need a very careful watch on the size of the gaps to make a Faraday
cage out of a biscuit tin.

And that is before you consider it may have been a design feature.
ISTR that long road tunnels have "leaky feeders" to allow RF (and thus
broadcast radio) to work.

Yes, even the Dartford Tunnel has that.

That was, I think, where the first leaky feeder trials took place.

[tony sayer]

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Theo

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job. Most of the fobs use 433 or 868MHz (315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Try keeping it in the microwave oven;?...

[Tricky Dicky]

Post by tony sayer
Try keeping it in the microwave oven;?...

Heat on full power for three minutes, stir and allow to stand for 5mins
before use. That should do it!

[The Natural Philosopher]

Post by tony sayer

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Theo

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job. Most of the fobs use 433 or 868MHz (315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Try keeping it in the microwave oven;?...

Exactly. And remember to turn it on before removing it, and its RF
signal will be completely undetectable after that.

[John R Walliker]

Post by The Natural Philosopher

Post by tony sayer

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job.  Most of the fobs use 433 or 868MHz
(315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Try keeping it in the microwave oven;?...

Exactly. And remember to turn it on before removing it, and its RF
signal will be completely undetectable after that.

Microwave ovens are well shielded at around 2.4GHz but not so well
at other frequencies. I just tried putting my DECT phone which
operates at about 1.9GHz in the microwave oven, closing the door and
calling it. It rang.
The door seals rely on using a quarter-wave overlap between the door
and the main body to transform an open circuit into a short circuit,
but only at the intended frequency range.

John

[tony sayer]

Post by John R Walliker

Post by The Natural Philosopher

Post by tony sayer

Post by Dan Green
On Tue, 1 Oct 2024 16:19:14 +0100, The Natural Philosopher

Post by The Natural Philosopher

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job.  Most of the fobs use 433 or 868MHz
(315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

Won't work, Turnip. Nowhere near RF-tight.
An old fashioned biscuit tin is pretty good for keeping radio
frequency emissions out. If anyone's inspected an RF-tight container,
they will be aware that there are *no* gaps in the casing and all
joins are overlapped. Unless you're living in some sort of hovel with
no doors or windows - or else they're all shuttered up with grounded
metal - RF will leak in like a sieve.

Try keeping it in the microwave oven;?...

Exactly. And remember to turn it on before removing it, and its RF
signal will be completely undetectable after that.

Microwave ovens are well shielded at around 2.4GHz but not so well
at other frequencies. I just tried putting my DECT phone which
operates at about 1.9GHz in the microwave oven, closing the door and
calling it. It rang.
The door seals rely on using a quarter-wave overlap between the door
and the main body to transform an open circuit into a short circuit,
but only at the intended frequency range.
John

Indeed my phone rings when called if its in there, local GSM site
operates at 860 odd MHz...

[Ian Jackson]

Post by The Natural Philosopher

Post by Theo

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job. Most of the fobs use 433 or 868MHz (315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
Theo

I've got wire mesh in my walls and on my roof and foil backed plasterboard
Probably good enough

I wouldn't count on it. At those frequencies RF signals can squeeze
through the tiniest of cracks and gaps.

[The Natural Philosopher]

Post by Ian Jackson

Post by The Natural Philosopher

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

 That would probably do the job.  Most of the fobs use 433 or 868MHz
(315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).
 Theo

I've got wire mesh in my walls and on my roof and foil backed
plasterboard
Probably good enough

I wouldn't count on it. At those frequencies RF signals can squeeze
through the tiniest of cracks and gaps.

No, they cant

[RJH]

Post by Theo

Post by Jim the Geordie
It would help if I kept my keys in a biscuit tin when at home?

That would probably do the job. Most of the fobs use 433 or 868MHz (315MHz
for some imports) so if you have a good shield against that signal then it
should work (obviously the lid needs to be on!).

Apparently the microwave is a good place to keep certain types of key . . .
remember to take them out when cooking :-)

[Jethro_uk]

Post by Jim the Geordie

Post by Theo

Post by Jim the Geordie
Am I missing something here?
I have a car with keyless entry and understand that toerags can snatch
my signal when I open or close using the fob.
OR I can open/close the car with a button on the car door if I am
close enough to it.
That suggests that the fob is constantly sending out a signal, but
clearly not the same signal as when I push the fob button (or perhaps
the car is sending a signal to the fob?)

1. an active one, where you press the button to eg unlock the doors or
open the boot 2. a passive one, which the car can query to see if it's
in range. If so it'll unlock the doors / start the engine. Could be
powered inductively or battery powered in the fob 3. a mechanical one,
for getting into the car if the battery is flat
'Keyless entry' can be some variety of no.2. The button is no.1. The
difference is that in no.1 the fob sends out a signal when activated,
while in no.2 the car is sending out requests all the time and
listening for the fob to answer.

Post by Jim the Geordie
I see on Amazon and elsewhere that I can buy Faraday Bag to put my key
fob in.
If you don't know: a Faraday bag/box/cage is a metal container that
does not let a signal in or out.
The question is, what use can they be?
If I want to open the car with the fob then it would have to be taken
out of the bag anyway; similarly if using the door button.

The usual problem is that your key is sitting on the hall table, but
the miscreant can record the car's challenge standing next to it, walk
up to your front door and replay the challenge. The fob answers and
the miscreant records the response. Then they replay the response next
to the car and the doors open.
If you put the fob in the shielded bag then (in theory) the fob doesn't
hear the challenge and so never replies. That means they can't nick
the car while you are asleep.
When you take the fob out of the bag you're likely standing near to the
car and it doesn't matter if the miscreant unlocks the car because you
were unlocking it anyway. If they're going to steal the car at that
point they'll need to physically overpower you, which they could have
done without any key fob spoofing. But that's a whole different crime
from sneaking away with the car at 3am.
Theo

Thanks, Theo.
It would help if I kept my keys in a biscuit tin when at home?

We have a metal bread bin I've started using (see post about
scrotemobiles).

At the end of the day you can only do so much. If these people want your
car, they are getting it. And if that means dragging you (or a loved one)
out of bed with a knife to your throat then that is what they will do.

[SteveW]

Post by Jethro_uk

Post by Jim the Geordie

Post by Theo

Post by Jim the Geordie
Am I missing something here?
I have a car with keyless entry and understand that toerags can snatch
my signal when I open or close using the fob.
OR I can open/close the car with a button on the car door if I am
close enough to it.
That suggests that the fob is constantly sending out a signal, but
clearly not the same signal as when I push the fob button (or perhaps
the car is sending a signal to the fob?)

1. an active one, where you press the button to eg unlock the doors or
open the boot 2. a passive one, which the car can query to see if it's
in range. If so it'll unlock the doors / start the engine. Could be
powered inductively or battery powered in the fob 3. a mechanical one,
for getting into the car if the battery is flat
'Keyless entry' can be some variety of no.2. The button is no.1. The
difference is that in no.1 the fob sends out a signal when activated,
while in no.2 the car is sending out requests all the time and
listening for the fob to answer.

Post by Jim the Geordie
I see on Amazon and elsewhere that I can buy Faraday Bag to put my key
fob in.
If you don't know: a Faraday bag/box/cage is a metal container that
does not let a signal in or out.
The question is, what use can they be?
If I want to open the car with the fob then it would have to be taken
out of the bag anyway; similarly if using the door button.

The usual problem is that your key is sitting on the hall table, but
the miscreant can record the car's challenge standing next to it, walk
up to your front door and replay the challenge. The fob answers and
the miscreant records the response. Then they replay the response next
to the car and the doors open.
If you put the fob in the shielded bag then (in theory) the fob doesn't
hear the challenge and so never replies. That means they can't nick
the car while you are asleep.
When you take the fob out of the bag you're likely standing near to the
car and it doesn't matter if the miscreant unlocks the car because you
were unlocking it anyway. If they're going to steal the car at that
point they'll need to physically overpower you, which they could have
done without any key fob spoofing. But that's a whole different crime
from sneaking away with the car at 3am.
Theo

Thanks, Theo.
It would help if I kept my keys in a biscuit tin when at home?

We have a metal bread bin I've started using (see post about
scrotemobiles).
At the end of the day you can only do so much. If these people want your
car, they are getting it. And if that means dragging you (or a loved one)
out of bed with a knife to your throat then that is what they will do.

Which they may do for a high-end car, but are less likely to do for a
typical family car.

[Jethro_uk]

Post by SteveW

Post by Jethro_uk

Post by Jim the Geordie

Post by Theo

Post by Jim the Geordie
Am I missing something here?
I have a car with keyless entry and understand that toerags can
snatch my signal when I open or close using the fob.
OR I can open/close the car with a button on the car door if I am
close enough to it.
That suggests that the fob is constantly sending out a signal, but
clearly not the same signal as when I push the fob button (or
perhaps the car is sending a signal to the fob?)

1. an active one, where you press the button to eg unlock the doors
or open the boot 2. a passive one, which the car can query to see if
it's in range. If so it'll unlock the doors / start the engine.
Could be powered inductively or battery powered in the fob 3. a
mechanical one, for getting into the car if the battery is flat
'Keyless entry' can be some variety of no.2. The button is no.1.
The difference is that in no.1 the fob sends out a signal when
activated, while in no.2 the car is sending out requests all the time
and listening for the fob to answer.

Post by Jim the Geordie
I see on Amazon and elsewhere that I can buy Faraday Bag to put my
key fob in.
If you don't know: a Faraday bag/box/cage is a metal container that
does not let a signal in or out.
The question is, what use can they be?
If I want to open the car with the fob then it would have to be
taken out of the bag anyway; similarly if using the door button.

The usual problem is that your key is sitting on the hall table, but
the miscreant can record the car's challenge standing next to it,
walk up to your front door and replay the challenge. The fob answers
and the miscreant records the response. Then they replay the
response next to the car and the doors open.
If you put the fob in the shielded bag then (in theory) the fob
doesn't hear the challenge and so never replies. That means they
can't nick the car while you are asleep.
When you take the fob out of the bag you're likely standing near to
the car and it doesn't matter if the miscreant unlocks the car
because you were unlocking it anyway. If they're going to steal the
car at that point they'll need to physically overpower you, which
they could have done without any key fob spoofing. But that's a
whole different crime from sneaking away with the car at 3am.
Theo

Thanks, Theo.
It would help if I kept my keys in a biscuit tin when at home?

We have a metal bread bin I've started using (see post about
scrotemobiles).
At the end of the day you can only do so much. If these people want
your car, they are getting it. And if that means dragging you (or a
loved one)
out of bed with a knife to your throat then that is what they will do.

Which they may do for a high-end car, but are less likely to do for a
typical family car.

Oh yes.

A few years ago a friends boss had some high end Mercedes or BMW. Either
way the last he saw of it was when he was woken by the puff of air brakes
as the grab loader the scrotes had driven to his house lifted it off the
drive and over the rising bollards.

[nib]

Post by Jim the Geordie
Am I missing something here?
I have a car with keyless entry and understand that toerags can snatch
my signal when I open or close using the fob.
OR I can open/close the car with a button on the car door if I am close
enough to it.
That suggests that the fob is constantly sending out a signal, but
clearly not the same signal as when I push the fob button (or perhaps
the car is sending a signal to the fob?)
I see on Amazon and elsewhere that I can buy Faraday Bag to put my key
fob in.
If you don't know: a Faraday bag/box/cage is a metal container that does
not let a signal in or out.
The question is, what use can they be?
If I want to open the car with the fob then it would have to be taken
out of the bag anyway; similarly if using the door button.

I keep my contactless entry fob in a small foil-lined wallet (from the
big river). Partly to prevent man-in-the-middle attacks by thieves but
also to stop the car noisily unlocking and re-locking every time I walk
past it with the key on me when I'm not wanting to use it.

I'm on my second one because the first one didn't really work, it mostly
stopped the car seeing the key but sometimes it still did see it. So I
deduce that some of them only just reduce the signal enough, and maybe
that may not be enough to stop high-power repeaters from seeing them?

nib

[GB]

Post by nib

Post by Jim the Geordie
Am I missing something here?
I have a car with keyless entry and understand that toerags can snatch
my signal when I open or close using the fob.
OR I can open/close the car with a button on the car door if I am
close enough to it.
That suggests that the fob is constantly sending out a signal, but
clearly not the same signal as when I push the fob button (or perhaps
the car is sending a signal to the fob?)
I see on Amazon and elsewhere that I can buy Faraday Bag to put my key
fob in.
If you don't know: a Faraday bag/box/cage is a metal container that
does not let a signal in or out.
The question is, what use can they be?
If I want to open the car with the fob then it would have to be taken
out of the bag anyway; similarly if using the door button.

I keep my contactless entry fob in a small foil-lined wallet (from the
big river). Partly to prevent man-in-the-middle attacks by thieves but
also to stop the car noisily unlocking and re-locking every time I walk
past it with the key on me when I'm not wanting to use it.
I'm on my second one because the first one didn't really work, it mostly
stopped the car seeing the key but sometimes it still did see it. So I
deduce that some of them only just reduce the signal enough, and maybe
that may not be enough to stop high-power repeaters from seeing them?

It's not the foil. Tiny thicknesses of foil are sufficient. But, the
construction of the bag matters - whether the opening is properly
covered, for example. It probably also helps if there's electrical
continuity between the front and the back.

[jon]

Post by GB

Post by nib

Post by Jim the Geordie
Am I missing something here?
I have a car with keyless entry and understand that toerags can snatch
my signal when I open or close using the fob.
OR I can open/close the car with a button on the car door if I am
close enough to it.
That suggests that the fob is constantly sending out a signal, but
clearly not the same signal as when I push the fob button (or perhaps
the car is sending a signal to the fob?)
I see on Amazon and elsewhere that I can buy Faraday Bag to put my key
fob in.
If you don't know: a Faraday bag/box/cage is a metal container that
does not let a signal in or out.
The question is, what use can they be?
If I want to open the car with the fob then it would have to be taken
out of the bag anyway; similarly if using the door button.

I keep my contactless entry fob in a small foil-lined wallet (from the
big river). Partly to prevent man-in-the-middle attacks by thieves but
also to stop the car noisily unlocking and re-locking every time I walk
past it with the key on me when I'm not wanting to use it.
I'm on my second one because the first one didn't really work, it
mostly stopped the car seeing the key but sometimes it still did see
it. So I deduce that some of them only just reduce the signal enough,
and maybe that may not be enough to stop high-power repeaters from
seeing them?

It's not the foil. Tiny thicknesses of foil are sufficient. But, the
construction of the bag matters - whether the opening is properly
covered, for example. It probably also helps if there's electrical
continuity between the front and the back.

We don't want a resonant cavity either.

[The Natural Philosopher]

Post by jon

Post by GB

Post by nib

Post by Jim the Geordie
Am I missing something here?
I have a car with keyless entry and understand that toerags can snatch
my signal when I open or close using the fob.
OR I can open/close the car with a button on the car door if I am
close enough to it.
That suggests that the fob is constantly sending out a signal, but
clearly not the same signal as when I push the fob button (or perhaps
the car is sending a signal to the fob?)
I see on Amazon and elsewhere that I can buy Faraday Bag to put my key
fob in.
If you don't know: a Faraday bag/box/cage is a metal container that
does not let a signal in or out.
The question is, what use can they be?
If I want to open the car with the fob then it would have to be taken
out of the bag anyway; similarly if using the door button.

I keep my contactless entry fob in a small foil-lined wallet (from the
big river). Partly to prevent man-in-the-middle attacks by thieves but
also to stop the car noisily unlocking and re-locking every time I walk
past it with the key on me when I'm not wanting to use it.
I'm on my second one because the first one didn't really work, it
mostly stopped the car seeing the key but sometimes it still did see
it. So I deduce that some of them only just reduce the signal enough,
and maybe that may not be enough to stop high-power repeaters from
seeing them?

It's not the foil. Tiny thicknesses of foil are sufficient. But, the
construction of the bag matters - whether the opening is properly
covered, for example. It probably also helps if there's electrical
continuity between the front and the back.

We don't want a resonant cavity either.

You have to work bloody hard to get that.

[SteveW]

Post by Jim the Geordie
Am I missing something here?
I have a car with keyless entry and understand that toerags can snatch
my signal when I open or close using the fob.
OR I can open/close the car with a button on the car door if I am close
enough to it.
That suggests that the fob is constantly sending out a signal, but
clearly not the same signal as when I push the fob button (or perhaps
the car is sending a signal to the fob?)
I see on Amazon and elsewhere that I can buy Faraday Bag to put my key
fob in.
If you don't know: a Faraday bag/box/cage is a metal container that does
not let a signal in or out.
The question is, what use can they be?
If I want to open the car with the fob then it would have to be taken
out of the bag anyway; similarly if using the door button.

When you use the buttons on the fob, it locks or unlocks the car as
required and then changes the code, so no-one can copy and re-use it -
called a "rolling code".

When you use the button on the door handle, the car sends a signal to
the fob and the fob replies, opening the car. This is where there is a
vulnerability. If your fob is in the house someone can stand near the
car with a transeiver, while an accomplice stands near the house with
another one. When the first person presses the button on the car, the
car sends a signal, but the fob is too far away. However, the first
transeiver picks up the signal, passes it to the second and that sends
it to the nearby fob. The fob replies, but again is too far from the
car. The second transeiver picks up the signal, passes it to the first
and the first sends it to the car, which unlocks and can be started -
known as a "relay attack".

The Faraday pouch stops the fob from responding to the car's signal,
whether directly or relayed and so prevents a relay attack when your car
is locked up and your keys are in the house.

[mm0fmf]

Post by SteveW

Post by Jim the Geordie
Am I missing something here?
I have a car with keyless entry and understand that toerags can snatch
my signal when I open or close using the fob.
OR I can open/close the car with a button on the car door if I am
close enough to it.
That suggests that the fob is constantly sending out a signal, but
clearly not the same signal as when I push the fob button (or perhaps
the car is sending a signal to the fob?)
I see on Amazon and elsewhere that I can buy Faraday Bag to put my key
fob in.
If you don't know: a Faraday bag/box/cage is a metal container that
does not let a signal in or out.
The question is, what use can they be?
If I want to open the car with the fob then it would have to be taken
out of the bag anyway; similarly if using the door button.

When you use the buttons on the fob, it locks or unlocks the car as
required and then changes the code, so no-one can copy and re-use it -
called a "rolling code".
When you use the button on the door handle, the car sends a signal to
the fob and the fob replies, opening the car. This is where there is a
vulnerability. If your fob is in the house someone can stand near the
car with a transeiver, while an accomplice stands near the house with
another one. When the first person presses the button on the car, the
car sends a signal, but the fob is too far away. However, the first
transeiver picks up the signal, passes it to the second and that sends
it to the nearby fob. The fob replies, but again is too far from the
car. The second transeiver picks up the signal, passes it to the first
and the first sends it to the car, which unlocks and can be started -
known as a "relay attack".
The Faraday pouch stops the fob from responding to the car's signal,
whether directly or relayed and so prevents a relay attack when your car
is locked up and your keys are in the house.

On many BMWs you have to touch the door handle to trigger the unlock.
(Touch handle, car sends signal, fob responds, doors unlock.) You can
disable it by removing the cable from the handles. Then it doesn't
detect the touch and query the fob. You unlock it by pressing the fob
button. By far the most sensible way to unlock a car... unlock when I
physically demand it.

[Jethro_uk]

Post by mm0fmf

Post by SteveW

Post by Jim the Geordie
Am I missing something here?
I have a car with keyless entry and understand that toerags can snatch
my signal when I open or close using the fob.
OR I can open/close the car with a button on the car door if I am
close enough to it.
That suggests that the fob is constantly sending out a signal, but
clearly not the same signal as when I push the fob button (or perhaps
the car is sending a signal to the fob?)
I see on Amazon and elsewhere that I can buy Faraday Bag to put my key
fob in.
If you don't know: a Faraday bag/box/cage is a metal container that
does not let a signal in or out.
The question is, what use can they be?
If I want to open the car with the fob then it would have to be taken
out of the bag anyway; similarly if using the door button.

When you use the buttons on the fob, it locks or unlocks the car as
required and then changes the code, so no-one can copy and re-use it -
called a "rolling code".
When you use the button on the door handle, the car sends a signal to
the fob and the fob replies, opening the car. This is where there is a
vulnerability. If your fob is in the house someone can stand near the
car with a transeiver, while an accomplice stands near the house with
another one. When the first person presses the button on the car, the
car sends a signal, but the fob is too far away. However, the first
transeiver picks up the signal, passes it to the second and that sends
it to the nearby fob. The fob replies, but again is too far from the
car. The second transeiver picks up the signal, passes it to the first
and the first sends it to the car, which unlocks and can be started -
known as a "relay attack".
The Faraday pouch stops the fob from responding to the car's signal,
whether directly or relayed and so prevents a relay attack when your
car is locked up and your keys are in the house.

On many BMWs you have to touch the door handle to trigger the unlock.
(Touch handle, car sends signal, fob responds, doors unlock.) You can
disable it by removing the cable from the handles. Then it doesn't
detect the touch and query the fob. You unlock it by pressing the fob
button. By far the most sensible way to unlock a car... unlock when I
physically demand it.

My SEAT is the same. If the fob is in vicinity *and* you touch the door
handle it unlocks.

[Tim Lamb]

Post by Jethro_uk

Post by mm0fmf

Post by SteveW
The Faraday pouch stops the fob from responding to the car's signal,
whether directly or relayed and so prevents a relay attack when your
car is locked up and your keys are in the house.

On many BMWs you have to touch the door handle to trigger the unlock.
(Touch handle, car sends signal, fob responds, doors unlock.) You can
disable it by removing the cable from the handles. Then it doesn't
detect the touch and query the fob. You unlock it by pressing the fob
button. By far the most sensible way to unlock a car... unlock when I
physically demand it.

My SEAT is the same. If the fob is in vicinity *and* you touch the door
handle it unlocks.

Also my ancient 2012 VW Passat.

[Davey]

On Wed, 2 Oct 2024 11:49:23 +0100

Post by Tim Lamb

Post by Jethro_uk

Post by mm0fmf

Post by SteveW
The Faraday pouch stops the fob from responding to the car's
signal, whether directly or relayed and so prevents a relay
attack when your car is locked up and your keys are in the house.

On many BMWs you have to touch the door handle to trigger the
unlock. (Touch handle, car sends signal, fob responds, doors
unlock.) You can disable it by removing the cable from the
handles. Then it doesn't detect the touch and query the fob. You
unlock it by pressing the fob button. By far the most sensible way
to unlock a car... unlock when I physically demand it.

My SEAT is the same. If the fob is in vicinity *and* you touch the
door handle it unlocks.

Also my ancient 2012 VW Passat.

Thankfully, my BMW does not do that. I'm glad, one less thing to go
wrong!

[Brian]

Post by Jim the Geordie
Am I missing something here?
I have a car with keyless entry and understand that toerags can snatch
my signal when I open or close using the fob.
OR I can open/close the car with a button on the car door if I am close
enough to it.
That suggests that the fob is constantly sending out a signal, but
clearly not the same signal as when I push the fob button (or perhaps
the car is sending a signal to the fob?)
I see on Amazon and elsewhere that I can buy Faraday Bag to put my key
fob in.
If you don't know: a Faraday bag/box/cage is a metal container that does
not let a signal in or out.
The question is, what use can they be?
If I want to open the car with the fob then it would have to be taken
out of the bag anyway; similarly if using the door button.

Some cars, eg Toyotas, have keyless door locks. The fobs emit a broadcast
the car detects.

They detect the fob in your pocket / handbag etc as you near the car and
unlock it when you touch the handle.

By ‘relaying’ the signal from the fob sitting in your house to your drive,
they make the car ‘think’ a fob is near….

I assume a similar process works to start it.

On Toyotas, you can inhibit the ‘broadcast’ very easily. This also saves
fob battery life.