[Cryptography] Tempest and limits on receiving

[Allen]

> Have you tried to buy a shortwave radio that covers all of the frequencies
> from, say, 100MHz to 10GHz? There are quite a few receivers that say they do
> that, until you look at the footnote saying that reception of certain
> frequencies is disabled, because the disabled frequencies are used by some
> cell 'phones. I admit I don't know where the law might be, but something is
> certainly causing all those manufacturers to remove that capability from
> their receivers. This applies to units sold in the USA but built elsewhere
> as well as those built here.

That law was adopted in the US for consumer privacy reasons back when
cell service was analog and unencrypted, and cellular conversations
could be listened to with an off-the-shelf scanner.  It is less
relevant today, but still on the books.  And AFAIK, it has nothing to
do with TEMPEST.