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.