P(t) - photons transmitted
P(l) - photons lost ( by absorption in space or by transparency / inefficiency
of optical fibre )
P(r) - photons received
The future of secure quantum cryptography is dependent upon the following :
Condition ( a) : Development of a super efficient optical fibre such that P(t)
= P(r) whereby if P(t)>P(r) or P(t)<P(r) the system automatically shuts down.
Problem - material sciences and detector efficiency are still not up to that
standard.
Condition (b) : Development of a super efficient optical fibre such that P(l)
in any surface area of the fibre accessible to the hacker do not comprise a
statistically complete quantum key or quantum message.
Problem - as in (a) but is easier to achieve than Condition (a).
Condition (c) : For satellite routed quantum messages, before routing a message
from a transmitter to a receiver - a very high resolution intelligent
space-based synthetic aperture radar coupled with scanning of SAR imagery by
supercomputers would be used to locate a receiver antennae ( i.e. resolution of
SAR approx. 1cm ). A transponder would be used to probe and identify the laser
receiver antennae of mobile unit. This would allow the satellites to route the
laser beam / quantum key directly to the laser antennae thereby eliminating
P(l) to the background - e.g enemies in a battle-space.
Problem - a directed beam would be good for civilian networks and surface naval
vessels, but a disadvantage to submarines as they could be located by enemies.
This would minimize the usage of this technology in submarines to quantum key
reception mode only before reverting to broad undirected beam reception mode.
Problem - this mode of prioritized satcoms would be too expensive.
Optionally : Ships / vehicles and submarines i.e. would have a Galileo tracking
on their laser antennae.
Problem - enemies could abuse tracking signals from antennae.
Field units could also originate quantum keys!
Nyagudi Musandu
tel.: 254-722-484730 ( CAUTION : this line is not secure )
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