Re: Question about 'TEMPEST': UPS
Now... Just curious, if I simply make my study into a faraday cage via use of fine (< 1/2 inch) chicken wire, and insulate my power system from the computer emenations, would that be enough? Chicken wire is not that expensive, and I think that I could make it look nice on walls.
The cages I've used were framed in wood and had several layers of copper screening. The mesh was like standard window screen, <.125". There were two, I think sometimes three, layers. The corners/joints were copper sheet. The screen was soldered to the corners. The doors were stepped or beveled and had several sets of fingers - indside edge, outside edge, perhaps one intermediate. Screen makes ventilation easier. Power should be brought in through a separate, partitioned, shielded box with filtering in each partition. Phone lines, same thing. You trust your apps, os and TCP/IP stack to not rat you out? If not, work off-line always. One cage I saw had ferrite tiles on the solid walls to minimize internal reflections which would cut down on leakage too. Al foil if it were thick enough would be OK but how do you reliably join edges? Al has a bad habit of oxidizing rapidly in air. I guess you could fold edges over several times - seems tacky. Converting your study is non-trivial. The door would look like crap. You would need the euivalent of a door over the window. Build one in your garage. Make it out of sections so you can move it. 6' x 8' seems about right for a couple computers and some lab equip. Is the cost justified? I wouldn't trust 1/2" galvanized chicken wire for containing anything but chickens or other non-gnawing furry woodland creatures. Mike
Michael Motyka wrote:
Now... Just curious, if I simply make my study into a faraday cage via use of fine (< 1/2 inch) chicken wire, and insulate my power system from the computer emenations, would that be enough? Chicken wire is not that expensive, and I think that I could make it look nice on walls.
The cages I've used were framed in wood and had several layers of copper screening. The mesh was like standard window screen, <.125". There were two, I think sometimes three, layers. The corners/joints were copper
Michael, Was the amount of work involved really necessary? What do three layers accomplish compared to just one?
sheet. The screen was soldered to the corners. The doors were stepped or beveled and had several sets of fingers - indside edge, outside edge, perhaps one intermediate. Screen makes ventilation easier. Power should be brought in through a separate, partitioned, shielded box with filtering in each partition. Phone lines, same thing. You trust your apps, os and TCP/IP stack to not rat you out? If not, work off-line always.
Right.
Al foil if it were thick enough would be OK but how do you reliably join edges?
Glue? Perhaps some weak glue that would not destroy the underlying paint.
Converting your study is non-trivial. The door would look like crap. You would need the euivalent of a door over the window.
My window has a mesh on it. Is that not enough?
I wouldn't trust 1/2" galvanized chicken wire for containing anything but chickens or other non-gnawing furry woodland creatures.
Is that confirmed by evidence? The reason for my question, I think that I somewhat value TEMPEST protection, but not enough as to cover my whole room with expensive and ugly looking copper or three layers of mesh and ferrite. I don't want all of it to be too conspicious. - Igor.
Igor, These were commercial cages used in the consumer products design business. Things like radios, TVs, 900MHz cordless phones etc...do I know for a fact that two or three layers of fine mesh copper ( BTW about an inch apart ) were necessary? No. I just took the word of the guys who had been doing the stuff for years. It wouldn't surprise me if the commercial cages were overkill. Neither would I be surprised if anything less leaked significantly. RFI is not an easy subject area. Find a commercial cage vendor and talk to an apps eng. Lacking an actual test facility, I suppose a really basic test would be to use a hand-held AM radio tuned to a space between stations and try out your PC with and without a chicken-wire cage. Sometimes a particular piece of SW will have a pattern that you can recognize, maybe following a keypress. I've been able to differentiate between button scan, watchdog, servos, processor etc... It's a relatively cheap, quick experiment. Try different frequencies and orientations of the ferrite loop antenna. For higher frequencies ( CPU clocks + other harmonics ) you'll need other methods. I've been meaning to take a look at a standard PC keyboard. Someday soon...if I do I'll let you know what I find. As for looks - tough - a PC generates lots of RFI, a partially functional cage is probably worse than none at all because of the false sense of security. Trying to shield the computer and the monitor is an entirely different can of worms. Probably an order of magnitude harder than making a good cage. Regards, Mike In real life even the easy things are not easy. Igor Chudov @ home wrote:
Michael Motyka wrote:
Now... Just curious, if I simply make my study into a faraday cage via use of fine (< 1/2 inch) chicken wire, and insulate my power system from the computer emenations, would that be enough? Chicken wire is not that expensive, and I think that I could make it look nice on walls.
The cages I've used were framed in wood and had several layers of copper screening. The mesh was like standard window screen, <.125". There were two, I think sometimes three, layers. The corners/joints were copper
Michael,
Was the amount of work involved really necessary? What do three layers accomplish compared to just one?
sheet. The screen was soldered to the corners. The doors were stepped or beveled and had several sets of fingers - indside edge, outside edge, perhaps one intermediate. Screen makes ventilation easier. Power should be brought in through a separate, partitioned, shielded box with filtering in each partition. Phone lines, same thing. You trust your apps, os and TCP/IP stack to not rat you out? If not, work off-line always.
Right.
Al foil if it were thick enough would be OK but how do you reliably join edges?
Glue? Perhaps some weak glue that would not destroy the underlying paint.
Converting your study is non-trivial. The door would look like crap. You would need the euivalent of a door over the window.
My window has a mesh on it. Is that not enough?
I wouldn't trust 1/2" galvanized chicken wire for containing anything but chickens or other non-gnawing furry woodland creatures.
Is that confirmed by evidence?
The reason for my question, I think that I somewhat value TEMPEST protection, but not enough as to cover my whole room with expensive and ugly looking copper or three layers of mesh and ferrite. I don't want all of it to be too conspicious.
- Igor.
For a new type of RF shielding consider "Flectron" a metallized fabric that allegedly shields up to 100db. Originally developed by Monsanto it has recently been bought by Advanced Performance Materials (which also makes a range of EMI-related products): http://www.apm-emi.com/ Another company, BEMA, Inc. offers portable enclosures made mostly of Flectron for TEMPEST protection, with RF-protected doors, vents, and electrical and cable connections. One is a walk-in, 6 x 6 x 7, weighs 125 lbs. and fits in two suitcases for transport. And there's a desktop version. These are reportedly in use by NSA, other TLAs, the military and corporations. There's a brief description at: http://www.martykaiser.com/bema1.htm The market in TEMPEST-related products is rapidly growing. Check AltaVista under that term or, say, NSA 65-6 and MIL-STD-285. There's more material appearing all the time as the word gets out on the need for RF-protection. We've heard from manufacturers that the demand for their shielding products is increasing for medical purposes -- some related to those dreaded signals being received by teeth and brain. Flectron clothing and bed shrouding are in the works. To be sure, Joel McNamara's TEMPEST Web site remains the best of all unclassified sources: http://www.eskimo.com/~joelm/tempest.html
John Young wrote:
We've heard from manufacturers that the demand for their shielding products is increasing for medical purposes -- some related to those dreaded signals being received by teeth and brain. Flectron clothing and bed shrouding are in the works.
Something akin to the mosquito netting draped over beds in the tropics? I live in a mountain valley. Once mined for iron ore, compasses are unreliable here. TV reception was limited to watching the ant races. Radio was squelchy and drift prone. Signals could not bore through the mountain's heart of iron. The voices went away. The sky was a vacuum, pressure was relieved. But lately rf has been falling from the sky, the heavy signal moisture causes fungi, slate-grey disks, to sprout from the roofs and sides of homes. The conditions have caused a fungal bloom. Spores rain down into the valley, collide, bounce and ricochet into a storm. The disease pressure is high. My head's a sensurround, Imax theater of voices and images that never fucking stop. Surely some protective prophylaxis is called for, maybe something as cheap as a plastic grocery bag, but this is no guaranty. Coffins manufactured to the highest Tempest standard may attenuate the signal strength enough to prevent reanimation of the corpses. Bodies are sealed in composite fiber radomes, designed to reflect and absorb the offensive radiation. Some choose incineration to escape the influx, mixing incinerate with powdered ferrite to achieve some measure of final rest.
participants (4)
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Frederick Burroughs -
ichudov＠Algebra.COM -
John Young -
Michael Motyka