WLAN shielding

Howard C. Berkowitz hcb at gettcomm.com
Tue Dec 2 21:54:32 UTC 2003

At 9:06 PM -0500 11/26/03, David Lesher wrote:
>Speaking on Deep Background, the Press Secretary whispered:
>>  My company is investigating the use of wireless in a couple of our
>>  conference rooms.  Aside from limiting the scope of reception with various
>>  directional antennae, does anyone have any suggestions or pointers for
>>  other ways to limit the propagation of signals (i.e. special shielding
>>  paint, panels or other wall coatings)?
>As I told Andy, you need a "RayProof" or similar brand shielded
>conference room. This is Faraday Cage, with a tight-fighting door,
>I don't know what they cost, but I've installed one or 2. Outside
>of labor, I suppose they might be in the $50-500K range or so,
>for small (12'x6') ones.
>Note it's a PITA to keep tight; as the door needs very
>tight-fitting gaskets.
>You'll need to bring phone/Ethernet in over fiber,
>but that's not hard.

If you do put one in, and your local laws don't prevent smoking, make 
it an absolutely no-smoking area. Ventilation tends not to be 

I was once attending a Federal Telecommunications Standards Committee 
meeting, where we were displaced from our regular conference room and 
given a SCIF vault/conference room.  It was stuffy enough as we met 
for a couple of hours, but as we adjourned, the NSA representative 
lit a cigar.

That's when we found out that the vault door was jammed.

No simple cipherlock. Full combination lock.  Trust me. Do not ever 
get in a mostly-sealed room with a dead cigar and some smoke 
remnants.  When we got out, maybe two hours later, our faces matched 
the government green [1] walls. If this hadn't been in the 
then-Defense Communications Agency headquarters with resident 
locksmiths, I don't know how long we'd have been there!

Seriously, give ventilation a lot of thought. You'll need ducts with 
grounded screening and lots of 90-degree bends.

Also, consider having a kick-out panel for emergency escape.  Even 
without high-security locks, I've seen the gasketed doors get stuck 
just in shielded labs.  Think of fire protection -- you really don't 
want a fire suppression gas release in a vault.

[1] I believe the proper descriptor for that shade of green is "gang".

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