A TEMPEST in a ... wall outlet?

[unixronin]

Bruce Schneier points to a paper on keyboard sniffing by detecting crosstalk between poorly shielded keyboard cables and power lines.  He also observes that the NSA has known about this principle for decades.

What I want to know is, why haven’t we switched to optical interconnect cables yet?  Component-stereo CD changers have had digital-optical outputs for over ten years now, and the home audio industry is hardly known for leading the field in interconnect technology.  Mice, keyboards — heck, ALL HIDs — monitors, external disks, even powered computer speakers:  they could all easily use optical-fiber data connections.  Many devices would still need power, of course, but the low levels of power required by devices that don’t already have their own separate power supply could be carried on a braid layer around the fiber.  Most speeds of what we’re still calling Ethernet can already run over fiber.  There’s no technical reason why we should be using copper cables any more for anything except supplying power — and copper is becoming expensive enough that it was actually cost-effective for thieves to steal 45km of undersea Internet cable from the seabed off Korea in order to sell it as scrap.  Even telephony devices run over copper only because telephones have historically been line-powered devices and the installed base is too huge to easily change.

Make sure computer cases are properly shielded and power supplies back-filtered to prevent feeding RFI back into their own power lines, and we could probably virtually eliminate RFI emissions from computers except for the display — and as a bonus, it would reduce their susceptibility to RFI and crosstalk.  (Even with magnetically-shielded computer speakers, I’ve had crosstalk issues when a monitor cable passes a few inches too close to a powerful speaker.)

Reason says it ought to be possible to RFI-shield flat-panel displays too.  (Perhaps a transparent conductive coating on one of the face layers?)

Comments

[montieth.livejournal.com]

Tactically secure under field conditions. Ie a radio will be easily DF'd and intercepted if it's regular voice. Basically a LOT of field manuals state to use wired commo lines.