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`