Laptops and TEMPEST

>Not to mention the point that an external attacker--say, the NSA van parked
>across the street--will under no circumstances be able to measure "the"
>spectrum: his antennas cannot possibly measure the signals (at the lower
>bits) seen by the FM receiver, noise source local to the computer, whatever.

Tim was talking about the Bad Guys setting your radio noise generator,
but the other side of the coin is TEMPEST - making sure your computers
don't emit enough radiation for Bad Guys to read it.  CRTs are well known
as emitters of easily decoded signal, but people have occasionally suggested
on this list that laptop LCD screens are much quieter.  I now have a data
point on this one, and basically, it ain't so.

Take a basic television with big rabbit-ear antennas.
Tune to the football game on Channel 6.
Take your AT&T Globalyst 250P (which is a gray NEC Versa with a Death Star),
with the 16-million-color 640x480 screen in 65536-color mode, 
and pop up a DOS command window in white-on-black.
Type a few lines of text, then look at the TV.

The sync wasn't quite right, but there were about three copies of
my DOS window.  It may have been scrolling slowly vertically or horizontally,
but it was relatively readable given the lack of resolution of the screen.
A good receiver run by a Bad Guy ought to be able to set its scan rates
correctly to pick up the screen at better resolution.
There are obviously more variables to be explored, but other people
who were present at the time considered the football game to be
more important :-)

#			Thanks;  Bill
# Bill Stewart, +1-415-442-2215 stewarts@ix.netcom.com
# You can get PGP outside the US at ftp.ox.ac.uk
#     (If this is posted to cypherpunks, I'm currently lurking from fcpunx,
#     so please Cc: me on replies.  Thanks.)

On Thu, 5 Dec 1996 stewarts@ix.netcom.com wrote:

> don't emit enough radiation for Bad Guys to read it.  CRTs are well known
> as emitters of easily decoded signal, but people have occasionally suggested
> on this list that laptop LCD screens are much quieter.  I now have a data
> point on this one, and basically, it ain't so.
> 
> Take a basic television with big rabbit-ear antennas.
> Tune to the football game on Channel 6.
> Take your AT&T Globalyst 250P (which is a gray NEC Versa with a Death Star),
> with the 16-million-color 640x480 screen in 65536-color mode, 
> and pop up a DOS command window in white-on-black.
> Type a few lines of text, then look at the TV.

 [snip]

Here's some more about that.  I use both the Texas Instruments ti85 and
Hewlett Packard HP48 graphics calculators.  I was playing tetris on my ti85
one day and had the radio on.  every now and then this funny noise would
come out of my radio.  After a while I noticed it was sync'ed with a
keypress on my calc.  So I tried some experiments, and I found that doing 
just about anything would emit a detectable signal.  Keep in mind that I was
using a cheap radio, tuned to a 100kW radio stn and still could tune in a
calc.  I tried 

indiviual keystrokes.........yup
individual pixel changes.....yup
idling.......................yup
printing to screen...........yup
"For" loop...................yup
NOP's........................yup

and they all sound different.  My favorite was the for loop.... sounds like
a diesel engine.  Maybe that's why my calc is running so slow.  it's only
going at 1500 RPM (revolutions per minute) The hamster inside must be
getting tired. 

I guess that's why there's that crap like this that's printed in the manual
of everything electronic...

	This equipment generates and uses radio frequency energy 
	may interfere with radio and television reception.  This
	device complies with the limits for a class B computing
	device as specified in part 15 of the FCC Rules for radio
	frequency emission and SIGINT operations pursuant to the
	interests of national security and inter-departmental
	funnies and scandals.  In the unlikely event that there
	is no interference, please call your local spook-funded
	telco and the will be more than happy to remedy this 
	situation. 

I think it was "Lucky Green" whose friend saw the little TEMPEST demo.
Perhaps this friend might care to elaborate on this issue.  I almost wonder
if there is some kind of order from on high (NSA, [A-Za-z0-0]1,5) <--regexp
to include other agencies like CSIS, MI5, Mafia, etc... -- to make "leaky"
computers. So now we have to have thermite wired onto our HD's and Noise
generators on the board. :) ICK.

--
Chris Kuethe <ckuethe@gpu.srv.ualberta.ca> LPGV Electronics and Controls
http://www.ualberta.ca/~ckuethe/
RSA in 2 lines of PERL lives at http://www.dcs.ex.ac.uk/~aba/rsa/
print pack"C*",split/\D+/,`echo "16iII*o\U@{$/=$z;[(pop,pop,unpack"H*",<>
)]}\EsMsKsN0[lN*1lK[d2%Sa2/d0<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<J]dsJxp"|dc`

At 2:03 PM -0700 12/5/96, C. Kuethe wrote:

>Here's some more about that.  I use both the Texas Instruments ti85 and
>Hewlett Packard HP48 graphics calculators.  I was playing tetris on my ti85
>one day and had the radio on.  every now and then this funny noise would
>come out of my radio.  After a while I noticed it was sync'ed with a
>keypress on my calc.  So I tried some experiments, and I found that doing
>just about anything would emit a detectable signal.  Keep in mind that I was
>using a cheap radio, tuned to a 100kW radio stn and still could tune in a
>calc.  I tried
...
>and they all sound different.  My favorite was the for loop.... sounds like
>a diesel engine.  Maybe that's why my calc is running so slow.  it's only
...

Back in the Olden Days, we used to use these signals as sound output for
our computers. For example, on my Sol 20 computer (bought and soldered
together in 1978, in case anyone's interested).

There were various BASIC programs that ran various loops, thus generating
crude tones on nearby radios. And the games that were available had
routines which used radios as crude sound devices.

(None of which could hold a candle to my 1968 "amateur transmitters": neon
sign transformers, sending Morse code to my friend a mile or so away...it
was detectable on all AM bands! I never got a visit from the FCC, but I
only "transmitted" a few times.)

--Tim



Just say "No" to "Big Brother Inside"
We got computers, we're tapping phone lines, I know that that ain't allowed.
---------:---------:---------:---------:---------:---------:---------:----
Timothy C. May              | Crypto Anarchy: encryption, digital money,
tcmay@got.net  408-728-0152 | anonymous networks, digital pseudonyms, zero
W.A.S.T.E.: Corralitos, CA  | knowledge, reputations, information markets,
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