Apparatus and method for secure space communication
View Patent ↗Free-Space quantum keyless private communication method according to a communication protocol comprising exchanging information between an emitter ( 100 ) and a receiver ( 200 ) through a main quantum-classical channel and with an eavesdropper tapping said main channel through a wiretap channel, based on the wiretap channel model, wherein the overall degradation of the wiretap channel is superior than that of the main channel, comprising the steps of preparing, at the emitter ( 100 ), a message M composed of classical bits, coding said message M so as to transform it into a coded message X, practical modulating the amplitude and/or the phase of the optical pulses of the coded classical bits, sending the encoded message to the receiver ( 200 ) through a classical-quantum channel ( 500 ), such that an eavesdropper ( 300 ) tapping said channel is provided with partial information about the said states only, detecting and decoding the received message through quantum security analysis.
1 . Free-Space quantum keyless private communication method according to a communication protocol comprising exchanging information between an emitter ( 100 ) and a receiver ( 200 ) through a main-classical-quantum channel and with an eavesdropper tapping said main-classical-quantum channel through a wiretap channel, based on the wiretap channel model, wherein an overall degradation of the wiretap channel is superior than that of the main channel, comprising the steps of
defining an exclusion radius r e surrounding the receiver ( 200 ) and computing a degradation parameter γ based on said exclusion radius r e wherein the degradation parameter γ permits that the overall degradation of the wiretap channel is superior to that of the main channel and a wiretap channel degrading step based on the degradation parameter,
preparing, at the emitter ( 100 ), a message M composed of classical bits,
coding said message M so as to transform it into a coded message X,
converting the classical bits of the coded message into a signal to be sent to Bob by modulating an amplitude and/or a phase of coherent states,
sending the signal comprising the coded message to the receiver ( 200 ) through a quantum-classical channel ( 500 ), such that an eavesdropper ( 300 ) tapping said channel is provided with partial information about the said states only, and
detecting and decoding the received message.
2 . Free-Space key distribution method according to claim 1 , characterized in that said transformation step is a stochastic coding step.
3 . Free-Space key distribution method according to claim 2 , characterized in that the communication protocol is a one-way communication protocol.
4 . Free-Space key distribution method according to claim 1 , characterized in that the classical bits modulate a coherent state which is modeled with quantum electrodynamics.
5 . Free-Space key distribution method according to claim 1 , characterized in that the degradation parameter γ calculation step depends on the receiver's parameter, such that:
γ
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d
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=
1
η
b
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d
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d
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2
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D
R
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D
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-
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where d B is a distance between the emitter and the receiver, d E is the distance between the emitter and the eavesdropper, D E R is a diameter of the of an antenna of the eavesdropper, D B R is a diameter of an antenna of the receiver, η B is the (additional) loss of the receiver such as atmospheric, pointing, optic circuits, and detector efficiency, θ div is a far field divergence, and θ E is Eve's angle to a satellite where θ E =r E /d E .
6 . Free-Space key distribution method according to claim 5 , characterized in that exclusion surrounding the receiver ( 200 ) is defined such that the degradation parameter γ is lower than a given value smaller than 1.
7 . Free-Space key distribution method according to claim 6 , characterized in that the exclusion surrounding the receiver ( 200 ) is defined such that the degradation parameter γ is lower than 0.1.
8 . Free-Space key distribution method according to claim 1 , characterized in that the signal is an optical signal.
9 . Free-Space quantum keyless private communication system comprising an emitter ( 100 ) and a receiver ( 200 ) adapted to exchange information through a main classical-quantum channel and with an eavesdropper tapping said main channel through a wiretap channel, based on the wiretap channel model, wherein the overall degradation of the wiretap channel is superior than that of the main channel, adapted to carry out the method of claim 1 .
10 . Free-Space quantum keyless private communication method according to a communication protocol comprising exchanging information between an emitter ( 100 ) and a receiver ( 200 ) through a main-classical-quantum channel and with an eavesdropper tapping said main-classical-quantum channel through a wiretap channel, based on the wiretap channel model, wherein an overall degradation of the wiretap channel is superior than that of the main channel, comprising the steps of:
calculating a degradation parameter γ depending on a receiver's parameter, such that
γ
(
d
B
,
d
E
,
η
b
,
θ
E
,
θ
div
)
=
1
η
b
(
d
B
d
E
)
2
(
D
R
E
D
R
B
)
2
e
-
2
(
2
θ
E
θ
div
)
2
where d B is a distance between the emitter and the receiver, d E is the Distance Between the emitter and the eavesdropper, D E R is a diameter of the of an antenna of the eavesdropper, D B R is a diameter of the antenna of the receiver, η B is a (additional) loss of the receiver, θ div is a far field divergence, and θ E is Eve's angle to a satellite;
defining an exclusion surrounding the receiver ( 200 ) based on the degradation parameter γ;
preparing, at the emitter ( 100 ), a message M composed of classical bits;
coding said message M so as to transform it into a coded message X;
converting the classical bits of the coded message into a signal to be sent to Bob by modulating an amplitude and/or a phase of the coherent states;
sending the signal comprising the encoded message to the receiver ( 200 ) through a quantum-classical channel ( 500 ), such that an eavesdropper ( 300 ) tapping said channel is provided with partial information about the said states only; and
detecting and decoding the received message.
11 . Free-Space key distribution method according to claim 10 , characterized in that said converting step is by stochastic coding.
12 . Free-Space key distribution method according to claim 11 , characterized in that the communication protocol is a one-way communication protocol.
13 . Free-Space key distribution method according to claim 10 , characterized in that the classical bits modulate a coherent state which is modeled with quantum electrodynamics.
14 . Free-Space key distribution method according to claim 13 , characterized in that exclusion surrounding the receiver ( 200 ) is defined such that the degradation parameter γ is lower than a given value smaller than 1.
15 . Free-Space key distribution method according to claim 14 , characterized in that the exclusion surrounding the receiver ( 200 ) is defined such that the degradation parameter γ is lower than 0.1.
16 . Free-Space key distribution method according to claim 10 , characterized in that the signal is an optical signal.