Re: Bomb Law Reporter - special edition
At 10:43 AM 8/23/01 +0200, Eugene Leitl wrote:
Using cast aluminum cases, copper foil shielding, tight glands which
Just because you're German doesn't mean you can say 'tight glands' without a snicker. 'Highly conductive gaskets' is perhaps less likely to amuse the more adolescent among us. Faustine, look up Faraday cages, TEMPEST, and search the archives. As if you didn't know. Succinctly, the electron gas in metals shields you from the electromagnetic antics of distant, radiating electrons, by shorting the ripples in the aether they make -and this shielding makes it harder to listen to your emissions, too. The problem is that cables and ventilation vents are antennae, for sending and receiving both. Testing is key. If you don't measure, you don't know.
At 04:45 AM 08/23/2001 -0700, David Honig wrote:
Faustine, look up Faraday cages, TEMPEST, and search the archives. As if you didn't know. Succinctly, the electron gas in metals shields you from the electromagnetic antics of distant, radiating electrons, by shorting the ripples in the aether they make -and this shielding makes it harder to listen to your emissions, too. The problem is that cables and ventilation vents are antennae, for sending and receiving both.
Testing is key. If you don't measure, you don't know.
This stuff was a *lot* easier when computers were slower. I used to test my TEMPEST room at 450MHz, since that was high enough frequency to cover any realistic level of emissions from the upper harmonics from the VAX, and it was also a short enough wavelength that leaks were pretty detectable. It doesn't take much to get a leak - copper foil on a joint wearing out, or the copper mesh we'd stuff inside gaskets getting set unevenly. The waveguides we used for fiber or air vents were typically 1/8 inch wide and an inch or two deep - and if you pushed a paperclip halfway through you'd twang the leak meter. Well, that was fine for computers that were around 10MHz. These days, when 1GHz is slow, there's tons of stray energy above that, and that stuff is much more penetrating, plus you've got all the 100 and 133MHz memory and disk bus stuff. Fortunately, the equipment runs at much lower power levels; you can run on batteries instead of 208-volt 3-phase (:-), but I'm still glad I don't have to design a room or even a box for that level of tightness. That room was still in active use with a VAX 8650; we retired it about when we put in the Sparcstation 1 or 1+ - were those 25MHz?
On Thu, 23 Aug 2001, David Honig wrote:
Just because you're German doesn't mean you can say 'tight glands' without a snicker. 'Highly conductive gaskets' is perhaps less likely
Um, how do you know I wrote it without a snicker? ;) Actually, I was referring to cable ducts which can act as a waveguide. Of course, a fiber is rather thin, and it can be wrapped with adhesive copper strips, so that it wouldn't be just a hole.
to amuse the more adolescent among us.
Testing is key. If you don't measure, you don't know.
Renting time in HF testing facilities is expensive. Do you have suggestions for a simple sniffer type of instrument, that detects the amplitude of a radiated field? Do FETs pick up HF fine? I intend to build me a wearable based on a LART type of board http://www.lart.tudelft.nl/ which will also house the crypto setup. Tempest proofing the rig will be definitely part of the considerations. I see most problems with the twiddler and the hud. -- Eugen* Leitl <a href="http://www.lrz.de/~ui22204/">leitl</a> ______________________________________________________________ ICBMTO : N48 10'07'' E011 33'53'' http://www.lrz.de/~ui22204 57F9CFD3: ED90 0433 EB74 E4A9 537F CFF5 86E7 629B 57F9 CFD3
david wrote:
Faustine, look up Faraday cages, TEMPEST, and search the archives. As if you didn't know.
I know, I was just hoping for a few meaningful shortcuts to achieving the full combination of "do-it-yourself" (because tinkering is more satisfying than COTS), "cheap"(limited funds; low on my priority list), "effective"(too much hokum floating around the subject), and "portable" (obvious). It's still a tall order, but I've found the discussion so far quite helpful. There you go! ~Faustine.
participants (4)
-
Bill Stewart -
David Honig -
Eugene Leitl -
Faustine