New-Wave Spies --------------- Electronic eavesdropping is becoming mere child's play *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. Barry Fox From New Scientist, 6 November 1999