On Wed, 11 Oct 2000, jim bell wrote:
>> A popular, but false, myth. The video cards radiate more than the CRT's.
>> Laptops tend to be the worst offenders.
>>
>> --Lucky Green <[EMAIL PROTECTED]>
>
>As to the video cards...
>Sorry, Lucky, but you're going to have to support this a little better.
>Emissions are a function of the signal voltage in a conductor, and the
>extent that this conductor is free to emit.
Given that a laptop uses an LCD display, there's really no good
reason, electronically speaking, why its video hardware should
have to do the ((scan+horizontal_retrace)*+vertical_retrace)
sequence that the technology for getting a coherent signal
relies upon.
But the fact is, laptop hardware does write bits in a predefined
order, (in fact the same order as CRT-based machines) so it's a
worthwhile question whether anyone can figure the order and pick
up the emissions from the video hardware.
This looks like the sort of thing that can be resolved by experiment
though; Anybody got enough DSP smarts to put an induction coil next
to a laptop monitor and *see* whether they can read the darn thing?
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.
Bear
