Christian E. Lysel wrote:
> Morton P. Christiansen wrote:
>
>> Hvor let er det at udføre elektromagnetisk aflytning af kabler el.
>> skærme?
>> Hvor mange resourcer må en aflytter forventes at skulle benytte?
Jeg har fundet en række andre gode link, her er et udpluk:
http://www.sans.org/infosecFAQ/encryption/TEMPEST.htm
http://archive.newscientist.com/archive.jsp?id=22111400
Ovenstående kræver man er registeret, søg efter "From New Scientist
magazine, vol 164 issue 2211, 06/11/1999, page 11". Det korte af det
lange er at det i 1999 kostede 30.000 pund at købe udstyr til aflysning
og de regner med at prisen i 2004 er nede på 1.000 pund.
Her er et citat:
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In a conventional PC, the magnetic heads of the hard disc drive rest
over the data tracks that were last accessed. The drive keeps spinning,
the heads keep reading and the readout amplifier keeps repeating the
data-which provides a perfect signal for an eavesdropper's tuner to lock
onto. The inventors say the answer is to load software into the PC that
ensures that the drive heads are always "parked" over a safe area of the
disc which contains no data.
But the monitor also transmits signals, which depend on the text
displayed. An ordinary TV receiver can display on-screen documents on a
remote screen, which can then be video-recorded and transcribed at the
spy's leisure. So Anderson and Kuhn suggest using a text font with
softened edges. This limits high-frequency emissions-radiation which
beams farthest afield from the computer. Sharp-edged fonts need fast
signal "rise times", which demand high-frequency harmonics.
And keyboards are also troublesome. They rely on a scanning signal,
which radiates the pattern of keys being pressed. So the patent suggests
using a random number generator to continually distort the scanning signal.