Durden[SMTP:camera_lumina@hotmail.com] wrote:

I dunno...I'm thinking that optical tempest is probably bullshit 99% of the time, but what do I know? My Optical specialities are ultrafast and optical networking.

But I still don't believe that specular reflection of smallish type from a

monitor will have anything that is recoverable. Of course, this is going to be dependent on the quality of the wall material, but for most not-so-even

plaster/drywall painted surfaces, I just can't believe the appopriate spacial frequencies of the image are not scattered after that kind of reflection.

The conspiracy theorist is telling me there's some reason they floated the

optical tempest story, though I can't quite figure out what that reason is...

-TD

...

BTW, m-o-o-t uses a randomised virtual keyboard with TEMPEST (both EM and optical) resistant fonts. It's okay for inputting keys, but it's a hassle for inputting text.

Which means that your keys might be safe from keyloggers (both hardware

and

...

software), but your plaintext isn't. Sigh. I'm trying to improve it by putting the "senhorita" letters in one block and the rest elsewhere (not for key input obviously), and you do learn where the keys are after a while, but it's still a hassle.

Please don't top-post. Optical TEMPEST of the type we've been discussing has nothing to do with specular reflection. As your CRT screen is raster-scanned, the point at which the electron beam is pointing at any given moment is much brighter than the rest of the screen. That the screen seems uniformly illuminated is a result of your persistance of vision. Optical tempest records the brightness of the light reflecting off the wall behind the user as a function of time. This can be used to reconstruct the brightness of each pixel on the screen, since they are refreshed sequentially in raster order. Peter Trei