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Testing Phone-Sized Faraday Bags

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Re: Testing Phone-Sized Faraday Bags

#171

Post by newaccount74 »

causi wrote: post #26
pdkl95 wrote: post #15

I really like Snowden's recommended Faraday cage for phones or other devices of similar size: two drink-shaker cups[1]. Drink shakers are cheap and widely available. The average hotel room in any medium/large hotel chain probably includes a shaker as a standard item as part of the minibar. The simple two-cup style (as seen in [1]) is preferred over the fancier "strainer top" style because you can press the two cups t…

What's the physics behind being able to make a container light-tight with a couple of right angle corners yet radio waves seem to leak out like water?

There are two important differences between light and radio waves:

Difference 1 is the wavelength. Light has a wavelengths of 400-700nm, whereas radio waves used by phones have wavelengths in the mm and cm range.

If structures are of similar size to the wavelength, then waves can "bend around" obstacles. This effect is called diffraction and can be observed with sound waves, electromagnetic waves, water waves, etc.

Difference 2 is the photon energy / frequency. How well radiation is absorbed depends on the photon energy. There are lots of molecules that absorb visible light very well, so it's easy to make surfaces that absorb light. But there are few things that absorb radio waves as well, so it's hard to make things that neither reflect nor transmit radio waves.

Re: Testing Phone-Sized Faraday Bags

#172

Post by lvs »

wolverine876 wrote: post #156
SamuelAdams wrote: post #57

This is a super cool blog post. However I think it alludes to a much larger problem. For many products today, it’s very difficult or impossible for most people to verify the product works. For a network switch, there are free and open source tools like iPerf to test and verify speeds are as advertised. For a faraday box, you have to go through all these steps (and knowledge learned) just to be able to test these. Wha…

> What about for vitamins, or pet food, or any other “durable” products that are supposed to last for X years? We could, as a society, make rules that prohibit these things and create organizations with the expertise and power to enforce those rules. We are hardly helpless, but the political trend is to forgo and even decry that power, do nothing, and then whine about how helpless we are.

It's called consumer protection, and it's weaker in the US than many other advanced countries.

Re: Testing Phone-Sized Faraday Bags

#173

Post by newaccount74 »

hammock wrote: post #43
causi wrote: post #26

Earlier quoted context omitted.

What's the physics behind being able to make a container light-tight with a couple of right angle corners yet radio waves seem to leak out like water?

A couple of right angles not really make it light tight either. I remember going caving and we would have to go 100m or more through many different turns before we all turned our lamps off and truly experienced perfect dark.

There's an old man made cave near me that consists of two small connected chambers, and once you are in the second chamber it is pitch black.

Re: Testing Phone-Sized Faraday Bags

#174

Post by duskwuff »

BenjiWiebe wrote: post #147
habi wrote: post #145

Earlier quoted context omitted.

This really depends on the X-ray machine, a powerful x-ray source might easily penetrate a small appliance. A faraday cage/bag does not protect x-ray since it ‘only’ blocks electromagnetic fields. So I guess in the case you mention it’s more hiding in the insulation/empty space of an appliance.

X-rays _are_ electromagnetic radiation.

Technically speaking, yes. But they're way off on the other side of the EM spectrum, giving them dramatically different properties. You can shield against radio with a shell of any conductive material -- even a wire mesh for longer wavelengths -- but X-rays are only absorbed by high-atomic-weight atoms, like lead.

Re: Testing Phone-Sized Faraday Bags

#175

Post by _0w8t »

I visited at the end of eighties a research institute in a former USSR. They had a whole room with computers put in a Faraday cage to prevent any data leaks with supposedly secret information. The cage was a mesh made of thin metal sheets with 1mm holes. As I remember the whole thing was done seriously, not a fake to please some inspector. It had double doors, all cables were put into metal tubes, all lights were outside I suppose to minimize the cabling.

Re: Testing Phone-Sized Faraday Bags

#176

Post by alliao »

parkertomatoes wrote: post #72

I was hoping they would test chip bags, because it was a plot device in the most recent Terminator movie. After searching, I found that Kaspersky has a blog post on the topic: https://usa.kaspersky.com/blog/terminator-dark-fate-chips/18... It surprised me that chip bags were more effective in their test than cookie tins, but only when they double-bagged it

truck drivers used them too to avoid tracking from their employer

https://arstechnica.com/information-technology/2017/11/austr...

Re: Testing Phone-Sized Faraday Bags

#177

Post by habi »

BenjiWiebe wrote: post #147
habi wrote: post #145

Earlier quoted context omitted.

This really depends on the X-ray machine, a powerful x-ray source might easily penetrate a small appliance. A faraday cage/bag does not protect x-ray since it ‘only’ blocks electromagnetic fields. So I guess in the case you mention it’s more hiding in the insulation/empty space of an appliance.

X-rays _are_ electromagnetic radiation.

Of course the are, but - if I'm correct - they don't produce an electromagnetic field. And are not shielded by a bit of mesh wire (I work with desktop microCT machines...).

Re: Testing Phone-Sized Faraday Bags

#178

Post by wolverine876 »

jagged-chisel wrote: post #159
wolverine876 wrote: post #157

What is the use case for disabling wireless communication for your phone? How will you use it? How will anyone call you? If you don't want to use wireless functions, buy a tablet that lacks all the radio hardware.

Bad Guys can't follow you using the signal. That's about it. Sure, they can tail you, but that's Work. And they'll know where you are the moment you take it out, but hopefully they're too far away to act on it. All in all, if you NEED something like this, your opec had better include more than this.

> Bad Guys can't follow you using the signal. That's about it. Sure, they can tail you, but that's Work. And they'll know where you are the moment you take it out, but hopefully they're too far away to act on it.

Why have the phone if it's not connected to the network? It's a communication device. Just leave the phone home.

Re: Testing Phone-Sized Faraday Bags

#180

Post by sanirank »

Tronno wrote: post #162

What's the use case for these products? Even if the radio is blocked, how does that stop a device from collecting data anyway, and exfiltrating it the moment it finds a network? Won't it look for a network the moment you take it out of the bag? And don't you have to remove it from the bag to use it practically? Ultimately, if your device is compromised or untrustworthy to the extent that it has to be policed this way…

I still wonder why phone cases with physical blockers for camera and mic aren’t in high demand, and why there aren’t hundreds of pirated copies on the market for the ones that have been developed.
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