[Cryptography] shielding
John Denker
jsd at av8n.com
Tue Feb 28 17:04:16 EST 2017
On 02/28/2017 02:28 PM, Tom Mitchell wrote:
> Quantifying the level of shielding deployed or needed is hard.
> It is almost easy to build a shielded room or home inadvertently.
I disagree.
Let me call attention to Murphy's Law. One of the corollaries is:
-- If you want the signal to be strong, it will fade.
-- If you want the signal to be contained, it will leak.
Murphy's law is sometimes stated in facetious terms, but it has
a solid foundation in engineering principles. The situation is
very asymmetric:
-- When a wireless widget is supposed to work, you expect it
to work everywhere in the home / office / whatever. So you
care about the weakest signal.
-- The attacker, Eve, does not need to succeed everywhere; she
only needs to succeed somewhere. So she cares about the
strongest leak.
Security is hard, and will always be hard. It requires tremendous
attention to detail.
On 02/28/2017 08:05 AM, Henry Baker wrote:
> When I lived in Los Angeles in the early 1980's, I met someone whose
> business was building Faraday Cage rooms for several million dollars
> a pop.
Try building one sometime. One that works when there is a strong
source on one side and a delicate receiver on the other side. One
that works across a wide range of frequencies.
Most people have no idea how to begin. Even if you know, it's still
a lot of work.
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