Monday

Reading displays at a distance.

Well, I knew that CRT's are susceptible to an eavesdropping attack called Van Eck phreaking. A small explanation from wikipedia:

The electron beam is deflected by several electromagnetic coils. The voltage in the coils is modulated at a high frequency and contains information related to the video image. These high frequency, high voltage signals create electromagnetic radiation that has, according to van Eck, "a remarkable resemblance to a broadcast TV signal".

So you could capture this broadcast and replay it on another screen. One way to protect from this was TEMPEST. One possibility was shielding the signal.
Well, a TFT/LCD screen works in quite a different way. Does this makes you safe from interception? According to Markus Khun apperently not:

With a flat panel display the aim is to tune into the radio emissions produced by the cables sending a signal to the monitor. The on-screen image is fed through the cable one pixel at a time.

Makes you think not using shielding for your network cabling alone. I first read about Van Eck phreaking in Neal Stephenson's novel Cryptonomicon. It's a nice book to read and you pick up some stuff about cryptography on top of it!

No comments: