At 01:33 PM 7/17/03 -0700, Meyer Wolfsheim wrote:

For what it's worth, a "secure viewer" that displayed text in red on a black background should make an optical tempest attack much more difficult.

Why? On a black background you have higher contrast, which you don't want here. The eye is most sensitive to greenish, so if you are trying to reduce the signal, use barely visible green. On a nearly-same-luminance green background. Green on green or gray on gray is *low contrast*. That's what you want. (You may as well use gray on gray, assume the adversary has color vision, and might even have the CIE chart on your monitor phosphor. The different RGB phosphors also have different decay times, which smears the signal if the adversary has no color vision) Possibly dither the text. You might also have brighter lines or areas on the screen to obscure the signal from the less-bright e-beamed text areas. Actual distribution should depend on the decay over time of the phosphor (you want the bright "distractors" to be as bright as the text-pixel even though the distractor is no longer illuminated by the e beam). You also want some incandescants and fluorescant lights, the latter running off batteries (with switching converters) so they run out of phase and frequency with the ones on wall current. Optical jamming. Or just close the windowshade and put a towel under the door gap. (Others may think you're [sm|t]oking, however.. and with the multiple, multitinted fluorescants, they'll think you're growing too) Or use a box. (I once did med-imaging related vision experiments... the setup was a Sun with a calibrated greyscale monitor, in a medical office, behind the receptionists until we got more space... we had a giant cardboard box over the monitor & subject to control ambient light.. which stayed while I was programming it too.. it amused the patients who came in to see their cardiologist to see a guy working with his head in a big box.. probably would have been more disconcerting if the MD was a psychiatrist :-)