Re: [Discuss-gnuradio] "Tempest" for LCD displays?

[John Gilmore]

> I'm actually interested in detecting LCD and CRT leakage, and decoding 
> the picture display from both LCDs and CRTs with a remote USRP, as a 
> useful hack for determining what TV channels people are watching nearby  
> (I know you can also listen for the local oscillator in the tuner, but 
> the tube probably leaks more energy, and gives you more information.

Ross Anderson and Markus Kuhn did some work on this.  In fact, they
designed a font that makes it hard to see the text on a computer
screen when monitoring via Tempest emissions.  And they have a great
way of optical eavesdropping, based on watching a CRT's phosphor light
vary over small increments of time (e.g. watching a wall that the CRT
is illuminating).  The USRP may be fast enough to capture such light
from slow monitors, though the USB bottleneck gets in the way.  See:

  http://www.cl.cam.ac.uk/Research/Security/tamper/

        John