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TEMPEST
- To: [email protected]
- Subject: TEMPEST
- From: [email protected]
- Date: Wed, 19 May 93 21:12:43 EDT
- Original-From: anchor.ho.att.com!wcs (Bill_Stewart(HOY002)1305)
- Original-To: toad.com!cypherpunks
> Where can I find more info about tempest? Is it a roomwide thing, is it
> implemented in the cables and housings, or what? I understand that the
> purpose of Tempest is to prevent people from spying on you via electronic
> emissions detection. Is this just a glorified Faraday cage?
Both techniques are used. You can either buy TEMPEST-designed equipment,
which is designed for low emissions, separation of signals between classified
and unclassified components, shielded cables, etc., or you can build a
shielded box or room and use special filtered power supplies, fiber optics, etc.
The exact standards are classified, but they're a lot stricter than FCC Class A or B.
The shielded-room vendors out there also sell to the electromagnetic-compatibility-
testing market, who want to have nice quiet rooms to measure emissions from their
equipment in. Last time I saw one of these rooms built, about 5 years ago,
typical construction used plywood sheets with thick sheet metal
on each side, fancy connectors between plywoods, copper-wool crammed in any cracks,
and special waveguide meshes for air vents and fiber-optic communication cables,
and gives about 100-120 dB shielding for frequencies up to about 1-10GHz.
Twenty years ago, typical construction used copper screening and was good to ~60dB.
About 3-4 years ago, the typical cost for a TEMPEST PC was ~$4000 more than
the non-TEMPEST equivalent, and the equipment was maybe 1 year behind the
commercial models due to integration and testing time.
TEMPEST mini-computers, if they were small enough, generally took the approach of
putting the standard versions of the machine in a box built like the TEMPEST rooms;
TEMPEST PCs had a somewhat more integrated design, though they were starting to use
commercial motherboards.
Bill Stewart