unintended consequences?

[Ed Gerck]

Steven M. Bellovin wrote:
> Does that mean that the new fiber is less tappable?

No change, notwithstanding anecdotal references on fiber bending
as used for tapping.

Tapping a fiber can be done without much notice by matching the
index of refraction outside the outer fiber layer, after abrasion
and etching to reach that layer. There is no need for bending,
which might not be physically possible (eg, in a thick cable bundle),
would increase propagation losses beyond that caused by the tapped
signal power itself, and might create detectable backward
propagating waves (BPWs are monitored to detect fiber breach).

Low-loss taps are essential. A tap must extract a portion of
the through-signal. This, however, should not have the effect of
significantly reducing the level of the remaining signal. For
example, if one-quarter of the incident signal is extracted, then
there is a 1.25 db loss in the remaining through-signal, which
can easily be detected.

Cheers,
Ed Gerck

---------------------------------------------------------------------
The Cryptography Mailing List
Unsubscribe by sending "unsubscribe cryptography" to majordomo at metzdowd.com