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: Sun, 20 Feb 2005 16:07:15 +0100 (CET)
  • Message-id: <Pine.LNX.4.58.0502201558120.7132@xxxxxxxxxxxxxxxx>

The Saturday 2005-02-19 at 18:11 -0800, Randall R Schulz wrote:

> > It must be a special watermark designed to interfere with the scanner
> > matrix. The document can be scanned, but the quality is bad, and OCR
> > does not work. The design is most probably proprietary.
>
> Yes, I was wondering if that was the intent. It's common nowadays (at
> least here in the States) for financial institutions to issue checks
> that have include in their background some text (typically the words
> "VOID" or some such) delineated in varying halftone patterns that are
> virtually invisible to the human eye but that become quite stark when
> reproduced by a photocopier.

¬°Ah! Here there has been cases with paer money, you know, Euros, Dollars,
etc. Well, euros I don't know, but the one we had before, pesetas,
certainly.


> > There are also some special fonts designed so that the human eye can
> > read it, but they can't be read by scanning the radio waves emitted
> > by the CRT monitor - believe me, there are businesses very paranoid
> > about such things. For example, PGP for windows support it:
>
> 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 :-?


> > Secure Viewer. Select this option to protect the data from TEMPEST
> > attacks upon decryption. If you select this option, the decrypted
> > data is displayed in a special TEMPEST attack prevention font that
> > is unreadable to radiation capturing equipment, and cannot be
> > saved in decrypted format. For more information about TEMPEST
> > attacks, see the section on vulnerabilities in An Introduction to
> > Cryptography.
>
> 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.

>
> C'es la vie. Let the better party win. Either that, or off with their
> heads...

:-)

--
Cheers,
Carlos Robinson

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