huridocs-tech Electronic eavesdropping becoming child's play

FYI
Harsh Kapoor
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From: New Scientist, 6 November 1999

New-wave spies
Electronic eavesdropping is becoming mere child's play
by Barry Fox

 SOFTWARE that allows a computer to receive radio signals could make spying
on other computers all too simple, according to two scientists at the
University of Cambridge. Such are the dangers that they are patenting
countermeasures that computer manufacturers can take to foil any electronic
eavesdroppers.

 Spies can already read documents written on computers by intercepting the
radio-frequency emissions from their electronics, but the tuning and
antenna equipment needed to do this is not available off-the-shelf and is
very expensive. But a new breed of "software radio", designed to let
computers tune in to radio signals in any waveband, promises to make this
type of eavesdropping simple and cheap. A PC circuit board with a plug-in
aerial does all the tuning under software control and has a digital signal
processor chip to cut noise.

 "Equipment to do this [spying] would now cost at least £30 000, but in
five years it will cost less than £1000, and it's hackers who will be
writing the software," predicts Markus Kuhn, a research student who has
filed the patent with Cambridge cryptographic expert Ross Anderson (see
interview this issue, p 48).

 The late Peter Wright, who worked for British intelligence, was the first
to blow the whistle on electronic eavesdropping. His 1986 book, Spycatcher,
revealed how he had spied on messages sent by the French during Britain's
negotiations to join the European Economic Community-electromagnetic
emissions from the input of the French encoding machine allowed plain text
to be received and read. (See diagram)

 Insulating computers in metal jackets to prevent these telltale emissions
is difficult, expensive and ugly. Modern offices want stylish PCs-but their
plastic cabinets emit radiation. So, in patent application GB 2 333 883,
Kuhn and Anderson detail how PC makers can foil spies without fitting PCs
with metal enclosures.

 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.



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