[Cryptography] Help investigate cell phone snooping by police nationwide

[Bill Stewart]

My knowledge of TEMPEST hasn't really been updated since the 1980s,
when I managed an RF-shielded lab with a Vax and some Sun equipment.
We did our testing at 450 MHz, which was a blazingly high frequency back then,
with a room that provided about 120dB of shielding when everything was tight.
It didn't take much of a loose joint to let a lot of signal leak out,
so we checked it periodically, and would need to tighten screws or
replace the steel-wool packing or put copper tape over things to fix it.

The cable ports for our fiber communications had
eighth-inch holes a couple inches deep,
and pushing a paperclip partway through
was also enough to trigger leakage.
It's a waveguide effect, so shorter wavelengths penetrate more easily
(though cellphones do put out a lot less power at 700-2100 MHz than 
the Vax did at 10 MHz.)

Basically, a refrigerator is unlikely to be tight enough to help;
it's designed to be airtight, not RF-tight.