On Fri, 19 Sep 2003, martin f krafft wrote:

> But Newton gets more wrong the faster you go. So it's not F = m.a,
> that theory was only a good approximation, nothing more.

Actually it still is F = m.a, but the numbers depend on the observer.

F=m.a is a fundamental consequence of the conservation of momentum, which
in turn is equivalent to the isotropy of inertial reference frames. This
fundamental princinple was reinforced by Einstein's relativity which made
conservation of momentum work accross a much larger range of physical
phenomena (classical dynamics + electromagnetism + gravity).

Quantum mechanics introduces into our understanding not only new
"approximate truths", which are subject to later revisions, but also some
fundamental concepts, that will be features of all future theories.

I am not necessarily claiming that the non-cloning theorems are on as
solid a footing as conservation of momentum and energy, but it is
quite plausible that while quantum *dynamics* will continue to be
refined by future theories, that quantum statistics is fundamental.

This still does not mean that QKD is commercially useful, but what it does
mean is that there is little reason to believe that the physics will be
found wrong. QKD *is* good and interesting physics. QKD is not
commercially sound security technology for terrestrial fibre optics.

Out in space, with line of sight communications, two infosec minded
starship captains might engage in QKD secured crypto some day :-) They
will still face the black box problem, and need to secure the channel
between the person and the device (internal security). It seems unlikely
that they will not have any simpler (easier to trust and verify, closer to
the endpoints of communication) technology available.


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