Re: Tempest today

[<daylasoul () hush com>]

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On Sat, 19 Aug 2006 18:49:09 -0500 Bipin Gautam
<gautam.bipin () gmail com> wrote:
> Ok, here is something from the book that I was trying to
> assemble/write.
>
> Some Links: http://www.eskimo.com/~joelm/tempest.html
> http://www.erikyyy.de/tempest/
>
> Lets begin…
>
> Faraday cages may be used to provide protection from HERF and EMP
> effects.
>
> Countermeasures:
> It is easy to defeat ordinary audio eavesdropping, just by
> sound-proofing a room. And simply drawing the curtains or creating
> a
> specially crafted background noise or by using double glass with
> air
> gap in the middle can soundproof and can defeat newer systems,
> which
> shine a laser beam onto a glass window and decode any modulation of
> the reflected beam caused by sound vibrations in the room.
>
> Faraday's cage: The charge on a charged conductor resided only on
> its
> exterior, and had no influence on anything enclosed within it. To
> demonstrate this fact he built a room coated with metal foil, and
> allowed high-voltage discharges from an electrostatic generator to
> strike the outside of the room. He used an electroscope to show
> that
> there was no electric charge present on the inside of the room's
> walls. A Faraday cage is best understood as an approximation to an
> ideal hollow conductor. A round drum, sphere etc can act like a
> Faraday's Cage. Basically, the enclosure may be made of an unbroken
> conducting sheet, like the metal box surrounding a sensitive radio
> receiver, or a wire mesh, like that in the door of a microwave
> oven.
> Any holes in the box or mesh must be significantly smaller than the
> wavelength of the radiation that is being kept out, or the
> enclosure
> will not effectively approximate an unbroken conducting surface.
>
> This shielding effect is used to eliminate electric fields within a
> volume, for example to protect electronic equipment from lightning
> strikes and other electrostatic discharges (ESDs). Faraday cages
> are
> often put to a dual purpose: to block electric fields, as explained
> above, and to block electromagnetic radiation. The latter
> application
> is known as RF shielding.
>
> Some traditional architectural materials act as Faraday shields in
> practice. These include plaster with wire mesh, and rebar concrete.
> These will affect the use of cordless phones and wireless networks
> inside buildings and houses. While Some buildings have designs that
> block radio signals by accident due to thick concrete walls or a
> steel
> skeleton.
> RF and Magnetic shielding: Radio frequency (or RF) shielding is
> required when it is necessary to block high frequency - 100
> kilohertz
> and above - interference fields. These shields typically use
> copper,
> aluminum, galvanized steel, or conductive rubber, plastic or
> paints.
> These materials work at high frequencies by means of their high
> conductivity, and little or no magnetic permeability. Magnetic
> shields
> use their high permeability to attract magnetic fields and divert
> the
> magnetic energy through them. With proper construction, magnetic
> shielding alloys have the ability to function as broadband shields,
> shielding both rf and magnetic interference fields.
>
> Electromagnetic shielding: It is the process of limiting the
> coupling
> of an electromagnetic field between two locations. Typically it is
> applied to enclosures, separating electrical content from the
> outside
> world, and to cables, separating internal wires from the
> environment
> the cable runs through. The shielding is achieved using a
> conductive
> material as a barrier. Typical materials include sheet metal, metal
> mesh, ionized gas, plasma and aluminum foil. The shielding can
> reduce
> the coupling of radio waves, visible light, electromagnetic fields
> and
> electrostatic fields. The amount of reduction depends very much
> upon
> the material used, the method of connection of the shield (or
> screen)
> and the frequency of the fields of interest. One example is a
> coaxial
> cable, which has electromagnetic shielding in the form of a wire
> mesh
> surrounding an inner core conductor. The shielding impedes the
> escape
> of any signal from the core conductor, and also signals from being
> added to the core conductor.
>
> Though i have practically seen putting a dipole near the coaxial
> cable
> can sniff its signal within despite the sealing. The rf sealing
> strict
> depends on the quality which i've seen is rare in MOST commercial
> products for general uses.
>
> Shielded Tent: It Shielded enclosures, tempest equipment, shielded
> chambers Another way of making sure you are not being bugged is to
> use
> a shielded tent, which prevents radio waves entering or leaving.
> Though Mobile phone calls are impossible from inside the tent, but
> no-one will be able to listen to your conversations using bugs or
> radio wave listening devices. It will also prevent anyone
> intercepting
> radio emissions from computers, preventing them from seeing what
> you
> have on screen. A more sophisticated - and expensive - method is to
> build a "clean room", of the type used by the military, to shield
> radio waves and electromagnetic signals.
>
> Wireless Shielding Paint: A company, Force Field Wireless makes
> three
> products that it says can dramatically reduce the leakage of
> wireless
> signals from a room or building. The paint contains copper filings
> and
> an aluminum compound. When spread evenly on a wall, the paint
> reflects
> signals in frequencies from 100 MHz to 5 GHz. Paint four walls, a
> floor, and a ceiling, and you effectively have a Faraday cage,
> which
> is a specially constructed metal room that blocks all radio
> signals in
> or out. It also makes copper/aluminum powder that homeowners can
> add
> to their own paint. The company also makes a window film that cuts
> down on signal leakage. This product DefendAir would be an
> attractive
> option to
> protect an RFID-enabled warehouse.
> http://news.thomasnet.com/fullstory/459490/3280
>
> Critic: Though wireless signals are very hard to completely block.
> They will simply radiate over and around obstacles. Metallic paint
> might reduce the signal strength, but that's easily compensated
> for by
> an antenna. Further-more its drawbacks are like it could reduce
> cellular reception. Any such technology won't block all signal - it
> won't block signal eminating from windows, doors, and screw holes.
> What it will do is lower the range from which you can sniff or
> connect, with constant equipment, which is plenty to be useful for
> some cases. Like a building situated near the center of a military
> base. Up to a quarterkilometer away is secured area. But obviously
> it
> will help you lower the sniffable range of the radiation to
> within that security perimeter and it's possible to arrange any
> conductive medium to actually amplify RF signals in a given
> direction
> You are quite likely to find a spot where the signal is
> considerably
> stronger.

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