Transmitting Data Through Steel
This is cool:
Tristan Lawry, doctoral candidate in electrical and computer engineering, has developed equipment which can transmit data at high rates through thick, solid steel or other barriers. Significantly, Lawry’s kit also transmits power. One obvious application here would be transmission through the steel pressure hull of a submarine: at the moment such hulls must have hundreds of penetrations for power and data cables, each one adding expense, weight and maintenance burden.
What’s interesting is that this technology can be used to transmit through TEMPEST shielding.
If you had the through-metal technology now reinvented by Lawry, however, your intruder—inside mole or cleaner or pizza delivery, whatever—could stick an unobtrusive device to a suitable bit of structure inside the Faraday cage of shielding where it would be unlikely to be found. A surveillance team outside the cage could stick the other half of the kit to the same piece of metal (perhaps a structural I-beam, for instance, or the hull of a ship) and they would then have an electronic ear inside the opposition’s unbreachable Faraday citadel, one which would need no battery changes and could potentially stay in operation for years.
Spooks might use such techniques even where there was no Faraday cage, simply to avoid the need for battery changes and detectable/jammable radio transmissions in ordinary audio or video bugs.
Naturally, if you knew how such equipment worked you might be able to detect or block it—hence the understandable plea from the British spooks to BAE to keep the details under wraps.
Unfortunately for the spooks, Lawry has now blown the gaff: his equipment works using ultrasound. His piezo-electric transducers send data at no less than 12 megabytes a second, plus 50 watts of power, through 2.5 inches of steel—and Lawry is confident that this could easily be improved upon. It seems certain that performance could be traded for range, to deal with the circumstances faced by surveillance operatives rather than submarine designers.