Re: [Fonts] filtered Tempest fonts

2003-03-04 Thread GSO
On 03 Mar 2003 22:21:43 -0500
James H. Cloos Jr. [EMAIL PROTECTED] wrote:
 Essentially a steg technique, yes?

The image transmitted with radio frequencies is different (how exactly?)
to that transmitted optically, the image transmitted optically being the
decoded text, with the coded image being derived from the message. 
Now there's a thought (I've just used the word 'message' instead of
character).  Markus is talking about varying the image for each usage of
a character:

On Mon, 03 Mar 2003 14:32:28 +
Markus Kuhn [EMAIL PROTECTED] wrote:
 The X11 font system is in addition at present not capable to vary each
 useage of a glyph, as it would be essential to make sure the filtering
 does not actually leak more information on digital video links.

Why not vary character usage by varying the transmitted image of a word
(phrase, paragraph, entire message) as a whole.  Might be easier to do
and more effective than attempting to vary the usage of individual
characters. Not sure if you could do this with Freetype2.  Then again
adding more to the coded message (radio frequency image) other than
recoding an individual character might not be necessary.

GSO

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Re: [Fonts] filtered Tempest fonts

2003-03-04 Thread Markus Kuhn
Juliusz Chroboczek wrote on 2003-03-03 22:56 UTC:
 MK Putting an anti-tempest filter into freetype2 has been on my todo list
 MK for a long time
 
 Could you guys be so kind as to tell us mere mortals what you're
 speaking about?

Compromising emanations of video display systems. Low-cost software-only
countermeasures. Modifying the font renderer so as to minimize
information-carrying radio frequency signals generated by the graphics
adapter, video cable and display. This involves primarily two
techniques:

  - Lowpass filtering the glyphs in horizontal direction (removing everything
above 70% of the Nyquist limit (half pixel clock) is in practice a good
compromise between readability on the screen and unreadability with
with radio receiver).

  - Replace the least few significant bits with pseudo-random bits for each
usage of a glyph on the screen. This causes frame-rate correlated
noise that eavesdroppers cannot eliminate by periodic averaging. This
technique is in particular useful for jamming emissions of VGA cards
and digital video cables such as NEC's FPD-Link (used in many laptops)
and DVI (used in recent desktop flat-panel displays).

Optionally you can also generate glyph variants by slightly offsetting
the Bezier control points (hinting is switched off in this anyway), and
then randomly pick one of the glyph variants to make radio character
recognition slightly more challenging.

Results, see pages 31-44 of

  http://www.cl.cam.ac.uk/~mgk25/em-eaves.pdf

I have already written a new techreport with all the gory details on
this, which I hope to get around to finalise and publish in a few weeks.

[The UK patent office was even so kind to grant me GB2333883 on this
stuff. I'd be happy of course to grant XFree86 a free licence.]

 It's got something to do with deploying XFree86 in the American
 embassy in Moscow, right?

No, these folks put their computers inside 100 dB shielding instead. It
is more for people who can neither afford the £5 for an NSA-94-106
certified shielded room (say, the embassy of Lower Slovbodia in Paris),
nor the £500 that an intitial psychiatric treatment course for mild
paranoia costs.

CRT and LCD eavesdropping is for much target equipment quite feasible
within around 10-30 meters, in rurals areas sometimes even in the 100
meter range. However, I don't think it is actually done frequently,
because there aren't many situations where you know in advance, which
screen is going to display something so interesting that it is worth
setting up all the fancy equipment necessary to do it. People who should
worry about such things seriously usually have already taken care of
voice eavesdropping, a in comparison far more significant threat.

And once you believe that you have taken care of RF shielding, you can
start to worry about optical VHF leaks from CRTs:

  http://www.cl.cam.ac.uk/~mgk25/emsec/optical-faq.html

The fun never ends.

Markus

-- 
Markus Kuhn, Computer Lab, Univ of Cambridge, GB
http://www.cl.cam.ac.uk/~mgk25/ | __oo_O..O_oo__

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[Fonts] ABD'nin Kuzey Cephesi Yalanýný Belgesiyle Kanýtlýyoruz

2003-03-04 Thread Turkiye2023




   
 
  
 
  
   

   
 
  
 
   
 
   

   
 
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  ABD daha fazla asker kaybeder ve bizi sorumlu 
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  <%Call Create_Bottom()%> 
  







Re: [Fonts] filtered Tempest fonts

2003-03-04 Thread G S Osler
 Anti-aliasing, also the psychological principle that we can recognize
 a letter of the alphabet from a partial or distorted representation
 (given the context - i.e. if you know what your're looking for).

EM radiation measures, but also radio Optical Character Recognition and
varying each use of a character/glyth to counter this.
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Re: [Fonts] filtered Tempest fonts

2003-03-04 Thread Juliusz Chroboczek
GSO PS A quick plug for the other item on my 'OpenSource the computing
GSO environment for Legal work' wish list.  A document processor that
GSO numbers paragraphs

That's a question for comp.text.tex.

Juliusz

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Re: [Fonts] filtered Tempest fonts

2003-03-04 Thread Markus Kuhn
Juliusz Chroboczek wrote on 2003-03-04 12:16 UTC:
 MK   - Lowpass filtering the glyphs in horizontal direction
 
 Why the glyphs?  Wouldn't you want to do that for everything that's
 displayed?

Sure, if that's feasible to implement. Text is just the most interesting
and most radio-readable part of the screen, because of its
high-frequency content. You can also do the filtering in analog right
after the DAC on the card of course. I connected a spectrum analyser to
a couple of graphics cards and found significant differences in their
harmonics output. VGA outputs of some Toshiba laptops go well above 1
GHz with their harmonics, whereas a Matrox cards that I tested seemed to
filter quite properly. I personally believe that careful selection of
the graphics cards adds far more protection than the font filtering
along could ever provide. And if you want to make a PC easy to eavesdrop
(sabotage), then just short-circuit the output filters after the DAC.
The user might even thank you for sharper pixels ... at the cost of more
radio/TV interference.

 MK   - Replace the least few significant bits with pseudo-random bits for each
 MK usage of a glyph on the screen.
 
 Are you implying that what the eavesdroppers get is the derivative of
 the signal rather than the signal itself?

Not quite, but something similar. For analog displays (CRTs), they get a
high-pass filtered version of the video signal, replicated throughout
the spectrum by the discrete sampling. If you have a 100 MHz pixel
clock, then any arbitrary 50 MHz band in the upper VHF or lower UHF
range will contain a complete copy of a high-pass filtered version of
the full pixel information. Therefore, continuous-tone images (JPEG
photos, etc.) are practically impossible to see for an eavesdropper,
unless they are dithered significantly.

Markus

-- 
Markus Kuhn, Computer Lab, Univ of Cambridge, GB
http://www.cl.cam.ac.uk/~mgk25/ | __oo_O..O_oo__

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Re: [Fonts] filtered Tempest fonts [OT]

2003-03-04 Thread Juliusz Chroboczek
That's fun.

MK Sure, if that's feasible to implement.

Yes, it's easy.  And it doesn't break the protocol.

Shadowfb, you introduce noise upon blasting to the real framebuffer.
Because, GetImage and friends work from the shadowfb, you're not
breaking the protocol.

You might actually end up with an implementation that is not
measurably slower than stock shadowfb.

(That's my interpretation of the protocol: an X server that produces a
black screen does respect the protocol, as long as GetImage returns
the right data.  Your interpretation may differ.)

Now of course you need to look out for your shadowfb RAM broadcasting ;-)

Juliusz
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Re: [Fonts] filtered Tempest fonts

2003-03-04 Thread Markus Kuhn
G S Osler wrote on 2003-03-04 13:23 UTC:
 The question is how feasible is it for an average electronics engineer
 to install the basics needed.  Slashdot Nov 99:
 
 New Scientist has an interesting article about a new toy we will all
 want. It's a card that plugs in one of your PCI slots and allows you to
 scan the EMF spectrum and read your neighbours terminal. In about 5
 years you might be able to get one for just under £1000. (Modern Tempest
 Hardware costs about £3)  
 http://slashdot.org/yro/99/11/08/093250.shtml

Slashdot is not very good in quoting, otherwise you would have noticed
that your interlocutor made that quick remark when a New Scientist
reporter rang him up sometimes in November 1999. But we are actually
getting there, with Analog Devices now shipping an 8-bit 1.5 Gsample/s
ADC for under 500 USD and companies such as Echotek starting to produce
first affordable data-acquisition boards where that chip is surrounded
by a couple of high-end FPGAs to do the interpolating and periodic
averaging necessary to lift the compromising emanations out of the
noise. Combine that with a decent analog RF preselector front-end and a
set of broadband antennas, and you too could be in the Tempest business.
Tedious in practice, but not unfeasible.

 For myself the paranoia set in when I began to use my computer for a
 £30,000+ legal claim.

I probabaly wouldn't start to worry much about compromising emanations
of a single device unless  £1e6 were involved. Burglary risks might be
a far more important concern (as a friend of mine learned painfully
recently, when he finally realized the difference between a realdog and
a robodog after burglars took his Aibo).

Markus

-- 
Markus Kuhn, Computer Lab, Univ of Cambridge, GB
http://www.cl.cam.ac.uk/~mgk25/ | __oo_O..O_oo__

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Re: [Fonts] filtered Tempest fonts

2003-03-04 Thread G S Osler
It won't do any harm to start looking at this now.  Am not a C
programmer as a matter of routine but can handle it if needed so will
take a look at freetype2.

Cheers,


GSO
opensource project: http://sourceforge.net/projects/money-go-round
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[Fonts] weird font spacing

2003-03-04 Thread Maxwell Bottiger
Hello,
I recently installed Xfree 4.2.x on my redhat linux system.  I needed
to upgrade because I purchased an Nvidia GeForce4 MX card, and the
version of Xfree shipped with RH 8.0 doesn't support that card.
I downloaded binary packages from the Xfree site, and the installation
went very well.  Eventually I moved to the nvidia driver, but I am still
very pleased with X.
The only problem I'm having is with the fonts in word processors.  For
some reason the lettering has really big spaces between each character. 
Generally the space between each letter is 2x the size of the letter
itself.  I've seen this behavior in Abiword, OpenOffice Writer, and
Ghostscript.
I don't really know where to start on this.  All the application and
console fonts look great, but anything that deals with page layout draws
a really strangely shaped page with all the lettering bent out of
shape.  Has anyone else run into this?
-- 
Maxwell Bottiger [EMAIL PROTECTED]

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