CDR: Re: Burglar Politics, Tempesting PC's that watch TV and DVD

[Sean Roach]

At 10:31 AM 10/11/2000, Ray Dillinger wrote:
...
>Also, it looks like the sort of thing that could be designed around.
>If someone were building a "secure laptop" they could make a video
>system and drivers that wrote the bits in a different, randomized
>order each time, and which only wrote the changed bits.  If anybody
>is actually making a product like this, it would be a strong
>indication that *somebody* with money to spend on R&D considers
>it a valid threat model, because nobody makes products without a
>market.

This could easily be the recipe for a flickering monitor.  First of all, 
the refresh rate needs to be probably in excess of twice what the human eye 
can see, just so a random signal can be detected before the old signal has 
expired.

if you can count to 4 in n length of time, then you can only reliably 
provide all the information in that time by keeping to the same order.
1,2,3,4. or 4,3,2,1 or 1,3,2,4, etc.  But not 1,2,3,4,3,2,4,1.  By the time 
it rewrote 1, the old 1 would be out of date, and it would appear that you 
had video problems, (shortly followed by a headache).

If you can count to 16, but only need to count to 4, then your options are 
tremendous.
1,2,3,4,3,4,2,4,2,3,1,2,4,  11 commands from 1 to the next 1 in this 
example.  from line to that same line.  This would allow for a secure 
monitor that didn't invite eyestrain.

Good luck,

Sean