Why Snowden Asked Visitors in Hong Kong to Refrigerate Their Phones
thelede.blogs.nytimes.com
Why Snowden Asked Visitors in Hong Kong to Refrigerate Their Phones
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Re: Why Snowden Asked Visitors in Hong Kong to Refrigerate Their Phones
#2I'm pretty sure they tested this out and modern refrigerators don't act as Faraday cages:
http://mentalfloss.com/article/51597/does-refrigerator-make-...
Older ones might have been lead-lined or otherwise different; you might have better results with a microwave. That said, it's a pretty good guarantee that the phones are not surreptitiously recording a conversation.
Re: Why Snowden Asked Visitors in Hong Kong to Refrigerate Their Phones
#3I think a lot of us already saw the various other sources debunking the fridge-as-faraday-cage theory. That said, low temperatures do increase the internal resistance of batteries. If you put your phone in the freezer for a while (probably not a great idea due to the high ambient moisture) then it will turn off, and not turn back on. A little bit later, it'll probably tell you that it can't turn on because of low battery. But once it's back up to room temperature, it should turn on just fine (again, assuming the moisture in the freezer hasn't screwed it up really badly).
Blocking radio signals is one thing, but using a fridge might have been an effective way to deactivate most off-the-shelf batteries in a non-invasive and impermanent way. Does anyone think this idea has any merit?
Re: Why Snowden Asked Visitors in Hong Kong to Refrigerate Their Phones
#4(Full disclosure: I work at Colorado Sensors)
Intentionally building a Faraday cage is really hard.
The major radiation leaks are caused by non-conducting joints at edges of the enclosure. If there are penetrations (e.g., power lines, signal coax, compressor coils, thermocouple wires) then extraordinary measures must be taken to ensure that electro-magnetic radiation remains inside.
It took me about a year to develop a narrow band Faraday cage that achieved > 120dB of attenuation. The secret sauce was gaskets made of Indium and tuned-stub interferometers on each feedthrough.
A typical refrigerator door has a gasket seal that forms a lovely slot antenna. I have a 0dBm transmitter in my kitchen refrigerator that easily communicates with a symmetric receiver in the basement. The link loss is no more than 30dB. (Online demo at http://www.coloradosensors.com).
TL;DR Refrigerators keep cold air in, but let E&M waves out.