Mailinglist Archive: opensuse (2912 mails)

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Re: [SLE] How to avoid copying/scanning printed paper ?
  • From: "Carlos E. R." <robin1.listas@xxxxxxxxxx>
  • Date: Mon, 21 Feb 2005 03:01:53 +0100 (CET)
  • Message-id: <Pine.LNX.4.58.0502210242550.7859@xxxxxxxxxxxxxxxx>

The Sunday 2005-02-20 at 12:08 -0800, Randall R Schulz wrote:

> If this stuff intrigues you, check out
> <http://www.moneyfactory.com/newmoney/main.cfm/currency/new20> and
> <http://www.moneyfactory.com/newmoney/main.cfm/currency/new50>.

Yep, I'm intrigued. I'll have a look. :-)


> > > Yup. I've heard of this as well. However, in this case the point is
> > > to make it difficult to "view" a CRT display by detecting its
> > > radio-frequency emissions.
> >
> > Correct. I wonder if TFT displays are vulnerable :-?
>
> Probably not. The reason the technique can be applied to CRTs is that
> they are particle accelerators and the energy levels they employ are
> very much higher. They operate by modulating the electron beam at radio
> frequencies. This in turn produces radio frequency emissions which, if
> not shielded, are quite easy to detect at a distance and use to
> reconstruct the display. In comparison, LCD displays are solid state
> devices operating with low current and low voltage. The illumination
> source is the highest-power component in those devices and even it
> consumes far less power than a comparable sized CRT.

I know :-) But the vga cable is still the same as for a CRT, and perhaps
it can be detectable. Much less power, and mixed signals, but perhaps
usable.


> > > It's an arms race. Every attempt to obscure information is met with
> > > a counter-measure to assist its detection. And vice versa.
> >
> > Offices can have a grounded wire mesh inside walls, and glass windows
> > a thin metalissed film, to stop radiation going out - or in. I know
> > they had such a thing, because mobile phones - I think you call them
> > something different, what was it... ah, cellulars - did not work
> > inside.
>
> That's called a Faraday cage.

Heh, I knew that before I was 14 year old :-p

The neat thing about it is that we knew not that they had it installed, it
was disguised. We learnt about it when we noticed the "side" effects, like
cellulars not working inside - till they installed repeaters inside,
because the company issued cellulars to us.

--
Cheers,
Carlos Robinson

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