On Tue, 23 Jul 1996, jim bell wrote:
At 03:20 AM 7/23/96 -0400, Rabid Wombat wrote:
Doesn't that make it vulnerable (detectable) to Tempest attacks?
No. Transmitting light via fiber doesn't emit EM. Anyway, the original post, as I recall, was about keeping sensitive data on a second hard drive, connected via (very thin, therefore harder to notice) fiber. Tempest monitoring was not a factor.
It occurs to me that a bare fiber could actually be (randomly) hung across treetops, roofs, power lines, and various other structures, over a many-block distance in suburban areas. Such a fiber wouldn't be protected very well, but it would probably last a few months. It would also be exceedingly hard to find its terminations, and tracing it would be a real pain. (It probably wouldn't be visible against a bright sky more than a meter or two away.)
It also would have little structural integrity - if you attached it to trees, which sway in the wind, you'd have a broken fiber in a short time. (The fiber doesn't even need to break, per se; microscopic cracking, usually at the cladding, will ruin your fiber) (bird strikes would also be a big problem, mostly for the bird) Fiber optic cable usually has a kevlar sheath, and exterior aerial grade fiber generally has a fiberglass rod inserted between the inner sheaths and the exterior jacket. Water is also a factor - fiber buried in areas where moisture is likely to be present (almost all applications) is usually installed with a silicon gel between the interior jackets and the exterior; water otherwise adheres to the exterior of the cladding, and expands due to freezing. This causes fine fractures in the cladding, which makes it more refractive - increasing chromatic dispersion, and therefore a higher db loss on the cable. :) ob crypto/privacy: Anybody have a good idea for detecting a tap on exterior fiber? I'd expect an attacker to have to interupt connectivity, terminate both ends of a break, and insert an active device. Thoughts?
Jim Bell jimbell@pacifier.com