Re: Soft Tempest

[David Honig <honig@otc.net>]

At 10:14 PM 2/8/98 -0800, Tim May wrote:
>At 9:19 PM -0800 2/8/98, Ryan Lackey wrote:
>
>
>The physics suggests just the opposite: the RF emissions from laptops are
>expected to be lower from first principles, and, I have heard, are
>measurably much lower. (I say "have heard" because I don't have any access
>to RF measurement equipment...I once spent many hours a day working inside
>a Faraday cage, but that was many years ago.)
...later...
>But before going this route, I'd want to see some measurements. Laptops
>might already be "quiet enough." (Measurements are needed to determine the
>effectiveness of any proposed RF shielding anyway, so....)

The interference that laptops can cause with avionics is 
prima facie evidence that laptops are not quiet.


>The first principles part is that the deflection yokes in a CRT are the
>largest radiated component of what got named "van Eck radiation." (I'd just
>call it RF, but whatever.)
>
>Laptops are missing this component. (It might be interesting to see the
>radiated RF numbers for various kinds of flat panel displays.)

They are not missing the periodic pixel clocking signals though.


...
>With some of these glasses, gargoyle-style, one could completely encase the
>laptop in a shielded case (like a Zero Haliburton) and then use a palm
>keypad...

Yes, but cables radiate.  Wires are antennae.  Used to be a big problem
when laptops had wired mice.

BTW, in van Eck's original paper, he gives a way to make screen spying
a little tougher: pick random raster-lines to draw instead of the usual
order.  This of course would not be a significant barrier to modern
interception.

------

Enrico Fermi used to tune a regular music radio to a cyclotron(?) so he
could tell
that it was working, I've read.






------------------------------------------------------------
      David Honig                   Orbit Technology
     honig@otc.net                  Intaanetto Jigyoubu

		Lewinsky for President '2012