WO2014183158A1 - Génération de clés de cryptage sécurisées - Google Patents

Génération de clés de cryptage sécurisées Download PDF

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Publication number
WO2014183158A1
WO2014183158A1 PCT/AU2014/000515 AU2014000515W WO2014183158A1 WO 2014183158 A1 WO2014183158 A1 WO 2014183158A1 AU 2014000515 W AU2014000515 W AU 2014000515W WO 2014183158 A1 WO2014183158 A1 WO 2014183158A1
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WIPO (PCT)
Prior art keywords
photon
sequence
filters
filter sets
filter
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PCT/AU2014/000515
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English (en)
Inventor
Matthew John COLLINS
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The University Of Sydney
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Publication date
Priority claimed from AU2013901671A external-priority patent/AU2013901671A0/en
Application filed by The University Of Sydney filed Critical The University Of Sydney
Publication of WO2014183158A1 publication Critical patent/WO2014183158A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
    • H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
    • H04L9/0852—Quantum cryptography
    • H04L9/0858—Details about key distillation or coding, e.g. reconciliation, error correction, privacy amplification, polarisation coding or phase coding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/70—Photonic quantum communication

Definitions

  • the disclosure herein generally relates to a method and a system for generating a secure encryption key, and particularly but not exclusively to a method and a system for generating a secure encryption key using the spectral properties of photons.
  • Information security may be critically important. For example, national security, law enforcement, national defense, and intelligence services are heavily dependent on information security. Around 20% of companies reported information security incidents in 201 1 that resulted in a financial loss. Other undesirable consequences of an information security incident may include brand damage, loss of trust, and court action.
  • a method for securing a communication is by encrypting it.
  • AES advanced encryption standard
  • US government and other encryption techniques that employ a symmetric encryption algorithm, secures a communication using a secret encryption key ("the key") shared by the sender and the receiver of the communication. Only parties that have the key can easily decrypt the encrypted communication.
  • Information security may be compromised by the interception of the key during its distribution to at least one of the sender and receiver.
  • a key may be, notably, distributed with certainty that it was not intercepted using a quantum-key distribution technique, in which the key may be distributed using of a stream of photons of variable polarisation. Maintaining the polarisation of the photons during distribution may be, however, difficult or even impossible in some circumstances.
  • an optical fibre that forms part of a commercial network generally does not preserve the polarisation of photons transmitted thereon. Frequent mechanical and temperature changes to the optical fibre may generally alter its polarisation properties.
  • quantum-key distribution techniques may be bandwidth limited because they employ time- bin encoding, which may limit the speed at which a key may be distributed.
  • Some quantum-key distribution techniques require a frame of reference common to the sender and the receiver of the communication. This may be problematic when the sender or the receiver is moving, for example when the sender or the receiver is associated with a satellite or other moving vehicle.
  • the method comprises the step of receiving a sequence of photons each having a random frequency, the sequence of photons comprising a half of a sequence of photon pairs wherein each photon pair of the sequence of photon pairs comprises two photons of different frequencies.
  • the method comprises the step of selecting one of a plurality of filter sets for each photon of the sequence of photons, each of the plurality of filter sets comprising a plurality of filters having non-overlapping pass bands and wherein a pass band of one of the plurality of filters from one of the plurality of filter sets spectrally overlaps with a pass band of at least one of the plurality of filters from another one of the plurality of filter sets.
  • the method comprises the step of providing an optical path having a plurality of branches for each photon, each branch having one of the plurality of filters of the selected filter set.
  • the method comprises the step of determining which one of the plurality of filters of the selected filter set each photon of the sequence of photons passed and recording a symbol associated with the one of the plurality of filters so determined.
  • the method comprises the step of receiving from a system, the system having received another sequence of photons that are the other half of the sequence of photon pairs, filter sequence information indicative of the sequence in which another plurality of filter sets was used by the system to generate frequency information indicative of the frequencies of the other sequence of photons.
  • the method comprises the step of comparing the filter sequence information with information indicative of the sequence that the plurality of filter sets were selected to determine which of the recorded symbols to discard.
  • Embodiment are generally used in "quantum key distribution" techniques. Some embodiments may not suffer from polarisation distortions resulting from temperature or mechanical fluctuations in an optical fibre, for example. Any bandwidth limitations associated with embodiments may be reference frame independent, and may be suitable for free space implementations.
  • An embodiment comprises the step of discarding the recorded symbols determined to be discarded.
  • the remaining symbols may constitute the secure encryption key.
  • each photon of the photon pair is correlated to the other photon of the photon pair in time and energy.
  • Each photon of the photon pair may be quantum entangled with the other.
  • each photon of the photon pair may not be quantum entangled with the other.
  • the sequence of photons are those of a sequence of photon pairs that have a frequency that is one of less than and greater than the average frequency of the sequence of photon pairs.
  • the other sequence of photons may be those of the sequence of photon pairs that have the other one of less than and greater than the average frequency of the sequence of photon pairs.
  • the plurality of filter sets is constituted by two filter sets.
  • the plurality of filter sets may be constituted by more than two filter sets.
  • each of the plurality of filter sets is provided by a optical filtering device suitably configured.
  • the optical filtering device may comprise a liquid crystal optical filtering device.
  • the plurality of photon pairs are generated by spontaneous four wave mixing wherein an excitation light spontaneously interacts with a nonlinear optical medium.
  • the nonlinear medium comprises a nonlinear waveguide.
  • the nonlinear waveguide may comprise a photonic crystal waveguide.
  • the length of the nonlinear waveguide may be less than 1 mm.
  • a nonlinear parameter of the nonlinear waveguide may be greater than 1000 W/m.
  • the excitation light has a wavelength bandwidth and each of the plurality of filters of each of the plurality of filter sets comprise a plurality of wavelength pass-bands of width of at least the wavelength bandwidth.
  • determining which one of the plurality of filters each photon passed comprises detecting each photon with a photon detector associated with the one of the plurality of filters the photo passed.
  • the photon detector may be a single photon detector.
  • the system comprise a plurality of filter sets, each of the plurality of filter sets comprising a plurality of filters having non overlapping pass bands wherein the pass band of one of the plurality of filters from one of the plurality of filter sets overlaps with the pass band of at least one of the plurality of filters from another one of the plurality of filter sets.
  • the system comprises a filter set selector arranged to select one of the plurality of filter sets and provide an optical path having a plurality of branches for a photon when so received, each branch having one of the plurality of filters of the selected one of the plurality of filter sets when so selected.
  • the system comprises a photon passage determiner arranged to determine which one of the plurality of filters of the selected one of the plurality of filter sets the received photon passed and a symbol recorder arranged to record in memory a symbol associated with the one of the plurality of filters of the selected one of the plurality of filter sets that the received photon was determined to have passed.
  • the system comprises an information receiver arranged to receive information generated by another system, the other system having received another photon that is the received photon's pair, the received photon and the received other photon having different frequencies, the information being indicative of another filter set used by the other system to generate frequency information indicative of the frequency of the other photon.
  • the system comprises an information comparator arranged to compare the information indicative of the other filter set used by the other system and information indicative of the selected one of the plurality of filter sets to determine whether to discard the recorded symbol.
  • the information comparator is arranged to discard the recorded symbol if determined to be discarded.
  • An embodiment operates on each of a sequence of received photons to generate a sequence of symbols.
  • the received photon has a frequency that is one of less than and greater than the average frequency of the received photon.
  • the received other photon may have a frequency that that is the other one of less than and greater than the average frequency.
  • the received photon and the other photon are correlated in time and energy.
  • Each photon of the photon pair may be quantum entangled with the other. Alternatively, each photon of the photon pair may not be quantum entangled with the other.
  • the plurality of filter sets is two filter sets.
  • An embodiment comprises a reconfigurable optical filtering device. Each of the plurality of filter sets is provided by the reconfigurable optical filtering device when suitably configured.
  • the optical filtering device may comprise a liquid crystal optical filtering device.
  • An embodiment comprises a photon pair generator arranged to generate the received photon and the received other photon.
  • the generation of the received photon and the received other photon may be by spontaneous four wave mixing wherein excitation light spontaneously interacts with a nonlinear optical medium.
  • the nonlinear medium comprises a nonlinear waveguide.
  • the nonlinear waveguide may have a third order nonlinearity.
  • the nonlinear waveguide may comprise a photonic crystal waveguide.
  • the length of the nonlinear waveguide may be less than 1 mm.
  • a nonlinear parameter of the nonlinear waveguide may be greater than 1000 W/m.
  • the photon pair generator comprises an excitation light source arranged to generate the excitation light, and each of the plurality of filters of each of the plurality of filter sets comprise a plurality of frequency pass-bands of width of at least the wavelength bandwidth.
  • the plurality of frequency pass bands may be only within the phase matching band for the pair generation process.
  • the photon passage determiner comprises a plurality of detectors in optical communication which the plurality of filters of the selected one of the plurality of filter sets when so selected.
  • the plurality of detectors may comprise a plurality of single photon detectors in communication with the plurality of filters of the selected one of the plurality of filter sets.
  • Figure I is a schematic diagram of a system for generating a secure encryption key.
  • Figure 2 is a flow chart of an embodiment of a method that may be performed using the system of figure 1.
  • Figure 3 shows spectra of the pass bands of a plurality of alternative filter sets used by the system of figure 1.
  • Figure 4 is a schematic that diagrammatically shows the steps of a process for generating photon pairs that may be used by the system of figure 1.
  • Figure 5 shows a bi-photon spectrum of photon pairs generated using the process of figure 4.
  • Figure 1 is a schematic diagram of a system for generating a secure encryption key, the system being generally indicated by the numeral 10.
  • the system 10 may be used to perform the steps of an embodiment of a method 100 indicated by the flow chart of figure 2.
  • the method is used for "quantum key distribution".
  • the system 10 cooperates with another similar system 20 such that the secure encryption key is securely shared by the system and the other system.
  • the secure encryption key may be used by parties associated with the systems 10 and other system 20 to exchange messages encrypted with the secure encryption key over a non secured communications channel 41.
  • the system 10 receives a sequence of photons 1 1.
  • the sequence of photons 11 are half of a sequence of photon pairs, specifically those of a sequence of photon pairs 23 that have a frequency that is one of less than and greater than the average frequency of the sequence of photon pairs.
  • the system 20 receives another sequence of photons 13 that are those of the sequence of photon pairs that have the other one of less than and greater than the average frequency.
  • the photons of the photon pair are correlated in time and energy. In this but not necessarily all embodiment, the photons are correlated in time and energy because the photons in each pair are created simultaneously and the sum of the energy of the photons in each pair equals twice the energy of a pump photon.
  • Each photon of the photon pair is quantum entangled with the other. In some embodiments, however, each photon of the photon pair is not quantum entangled with the other.
  • the photon pairs are generated by a photon pair generator 15.
  • the photon pair generator may generate the photon pairs by spontaneous four wave mixing, wherein an excitation light spontaneously interacts with a third order nonlinear optical medium.
  • the photon pair generator may comprise an excitation light source arranged to generate the excitation light having, for example, a laser diode, fibre laser, or any other suitable source.
  • the nonlinear medium comprises a nonlinear waveguide in the form of a photonic crystal nonlinear waveguide.
  • the length of the nonlinear waveguide is length less than 1 mm, specifically 0.1 mm, and has a nonlinear parameter greater than 1000 W/m, specifically around 4000 W/m.
  • the sequence of photon pairs are split into the sequence of photons 11 and the other sequence of photons 13 by a wavelength division multiplexer 17 in the form of an array waveguide grating (AWG) or any suitable wavelength division de-multiplexer.
  • AWG array waveguide grating
  • the spectra 19, 21 and 23 are indicative of the frequency distribution of the photon pairs, the sequence of photons, and the other sequence of photons respectively.
  • the system 10 has a reconfigurable optical filtering device 12.
  • the reconfigurable optical filtering device 12 comprising a wavelength selective switch.
  • the wavelength selective switch may comprise liquid crystal on silicon.
  • An example of a suitable wavelength selective switch is the "Waveshaper" by FINISAR. Any suitable optical filtering device may be used, however, as described in detail below.
  • the optical filtering device 12 has an input port 26 that is in communication with an input port of the Waveshaper.
  • the Waveshaper has a plurality of optical output ports 28.
  • a branched optical path connects the input port 26 to each of the plurality of optical output ports 28 of the Waveshaper.
  • Each branch of the optical path has a filter represented in figure 1 by their respective spectra 16, 18, 22, 24.
  • the filters 16, 18, 22, 24 are, in this but not necessarily in all embodiments, predetermined and programed into the Waveshaper.
  • the filters are grouped into a plurality of filter sets. In this embodiment there are two filter sets.
  • one of the filter sets comprises two filters.
  • the two filters have frequency pass bands indicated by numerals 16 and 18 (the ' ⁇ ' basis) in figure 1, where the shaded region is indicative of a pass band for light s
  • the other of the filter sets comprises two filters.
  • the other two filters have frequency pass band spectra indicated by numerals 22 and 24 (the ' ⁇ ' basis).
  • Each pass bands represents a frequency bin.
  • Each of the plurality of filter sets has a plurality of filters having non overlapping pass bands. The pass band of one of the plurality of filters from one of the plurality of filter sets overlaps with the pass band of at least one of the plurality of filters from another one of the plurality of filter sets.
  • the system 10 has a filter set selector 14, which comprises a plurality of optical switches in the form of optoelectronic switches 30, 32 and switching control system 24.
  • the filter set selector 14 may randomly choose the filter set selected for each photon of the sequence of photons.
  • the other system 20 may also have a filter set selector that randomly chooses the filter set for each photon of the other sequence of photons 13.
  • the optoelectronic switches 30, 32 couple each filter of the selected filter set to a passage determiner 34 arranged to determine which one of the plurality of filters of the selected plurality of filter sets the received photon passed.
  • the determiner comprises, in this but not all embodiments, a plurality of detectors in the form of photon detectors 36, 38.
  • Each of the photon detectors 36, 38 is coupled via the optoelectronic switches 30, 32 to one of the plurality of filters in the selected filter set. Consequently, each detector when so coupled is associated with one of the plurality of filters of the selected filter set, and when a detection event occurs, which filter the photon passed is determined. Detection event information may be communicated from the passage determiner to the switching control system 24.
  • the switching control system 24 also records in internal memory 40 a symbol associated with the one of the plurality of filters that the received photon was determined to have passed.
  • the detector 36 is associated with symbol '0' and the detector 38 is associated with the symbol T. Consequently, in this example a random string of bits is generated.
  • Other symbols may be used as appropriate. For example, if there where 16 filters in each filter set then each filter may be associated with a hexadecimal digit 0-9, A-F. In this example, a string of hexadecimal digits is generated.
  • the symbols may not be numeric. They may, as appropriate, be Roman letters, Chinese characters, or take any suitable form.
  • a sequence of photons is processed by the system 10
  • a sequence of symbols is recorded that when further processed as described below form the secure encryption key.
  • the system 10 and the other system 20 are in communication over a communication channel 41.
  • the channel 41 is a "classical channel", and may not be encrypted.
  • the channel 41 may comprise an optical fibre, for example or free space optics carrying messages using a suitable protocol(s), for example TCP/IP over Ethernet.
  • the system comprises an information transceiver 42 in communication with the communication channel 41 and arranged to receive information generated by the other system 20 and may be arranged to send information to the other system.
  • the other system when cooperating with the system 10, receives another photon that is the pair of the photon received by the system 10.
  • the received photon and the other photon having different frequencies.
  • the information is indicative of another filter set 20 used by the other system to generate frequency information indicative of the frequency of the other photon.
  • the system 20 comprises an information comparator 44 arranged to compare the information indicative of the other filter set used by the other system and information indicative of the selected one of the plurality of filter sets to determine whether to discard the recorded symbol. If the filter set used at the system 10 and the other system 20 for each photon pair have spectra that are mirror images of each other, around the photon pair average frequency, then the symbol is retained. Otherwise the symbol is to be discarded.
  • the information comparator 44 is arranged to remove from the memory the recorded symbols determined to be discarded. In other embodiments, however, another module may discarded the recorded symbols determined to be discarded. Once the determined symbols are discarded the remaining sequence of symbols constitute the secure encryption key.
  • the other system 20 receives from the system 10 information indicative of the sequence that the plurality of filter sets were used to similarly construct the secure encryption key. In another embodiment, the determination regarding a symbol may be made prior to recording in memory.
  • the secure encryption key may be, for example, a string of bits, a string of hexadecimal digits, or generally any suitable form.
  • Each of the plurality of filters of each of the plurality of filter sets may have a plurality of frequency pass-bands of width of at least the bandwidth of the excitation light.
  • the pass bands of the filters are at least 0.5 nm, which is approximately the photon coherence length of the generated photons. If the widths of the pass bands were less, then there is a risk of correlations between non corresponding pass bands which would result in symbol determination errors.
  • Each of the plurality of frequency pass bands may be within the phase matching band for the photon pair generation process.
  • Figure 3 shows spectra of the pass bands of a plurality of alternative filter sets. The pass bands to the left of the vertical axis are used by one of the system and pass bands to the right of the vertical axis are used by the other system. This may be reversed in some systems.
  • the system 10 and the other system 20 may cooperate to correlate respective photon detection events. Each may have a clock synchronised to the other. A symbol may be recorded and/or retained only when a photon detection events at the system 10 and other system 20 are correlated. Photon detection event timing information may be exchanged via communication channel 41 between the system 10 and the other system 20 for correlation. Detection events may be time stamped by field programmable gate array interval analyser , for example, of each of the system 10 and other system 20. Photon generator
  • FIG. 4 is a schematic that
  • a picosecond pulsed laser centred in the telecommunication C-band of wavelengths generates an excitation light ("pump light").
  • the laser is a C-band erbium doped fibre laser, with a output having a spectral bandwidth of approximately 0.5 nm and pulses having a temporal length less than 10 ps.
  • the repetition rate is 50 MHz with average powers of around 1 mW and peak powers generally but not necessarily less than a 3 W.
  • the laser pulses are coupled to a nonlinear waveguide 54, for example a photonic crystal waveguide of length 100 ⁇ , nonlinear parameter ⁇ ⁇ 4000 W/m, coupling loss of 4 dB per facet and a typical chip size of 1-2 mm square.
  • a nonlinear waveguide 54 for example a photonic crystal waveguide of length 100 ⁇ , nonlinear parameter ⁇ ⁇ 4000 W/m, coupling loss of 4 dB per facet and a typical chip size of 1-2 mm square.
  • Slow-light photonic crystals are used as the enhancement to the nonlinearity allows highly compact devices.
  • the slow-light region has a flat dispersion over a 15nm bandwidth. Over this region, the phase matching band for the photon pair generation process, the spontaneous four wave mixing generating the photon pairs occurs efficiently with an almost flat spectral distribution, i.e. the pair generation bandwidth is 15 nm.
  • An integrated arrayed waveguide grating separates the photon pair output into 50 GHz ( ⁇ 0.4 nm) channels, which are roughly matched to the pump (optimum).
  • the pump channel is dumped and the idler and signal photons, the "blue and red photon" in the pair respectively, may optionally be directed to single photon detectors for characterisation.
  • the difference in arrival times at the idler and signal detectors may be histogrammed, with a sharp peak the signature of correlated photon pair generation.
  • the wavelength selective switch may replace the AWG.
  • the phase matching band is the frequency band for which the phase mismatch is small. Far enough away from the pump there is no spontaneous four-wave mixing (SFWM) to generate the photon pairs.
  • the phase matching bandwidth will determine the maximum possible number of frequency pass bands ("bins") in say a fiber-based source. In a photonic crystal device this phase matching bandwidth may be broader than the slow-light band. Therefore only weak SFWM outside the slow light band is observed, because without the enhancement the power is too low.
  • the photon pairs of the sequence of photon pairs may be correlated in energy and time.
  • the energy-time correlated photon pair may, but not necessarily, be energy-time entangled (that is, be an "entangled pair" of photons). Entanglement requires uncertainty in one measurable quantity - we do not know which pass band the photons are generated within until we measure it.
  • the photon passage determiner Before an entangled photon goes through the photon passage determiner, which makes a measurement and provides photon frequency information, it existed in a superposition of multiple pass bands.
  • the photon passage determiner makes a measurement of one of the photons, projects it into a definite pass band, takes away the uncertainty and the photons are no longer entangled. While there is entanglement in this example, it may be difficult to show experimentally, and is not required for security.
  • the photons in each pair correspond to frequencies equidistant from the photon pair's centre (average) frequency, which it the frequency of the excitation light.
  • the photons having one of greater than and less than the frequency of the excitation light are isolated to constitute the sequence of photons, and the remaining photons constitute the other sequence of photons.
  • the generator may exploit spontaneous parametric down-conversion (SPDC) using a nonlinear optical medium , for example a beta-BaB 2 0 ("BBO") crystal.
  • SPDC is a process used to generate photon pairs from a strong pump beam. On entering the optical nonlinear medium, one photon from the pump is annihilated to generate signal and idler daughter photons which must obey energy and momentum conservation, such that the daughter photons are at half the frequency of the pump.
  • SPDC is seeded by quantum vacuum fluctuations the emission of photons is random and has a low conversion efficiency of ⁇ 10 12 per pump photon.
  • There are a number of forms of SPDC the most common being Type-I and Type-II.
  • Type-I SPDC the generated photons have the same polarisation.
  • the generated photons are orthogonally polarised. This difference is the key behind how in Type-II SPDC the phase matching can be rotated and used for "correlated" photon pair generation.
  • the photons there may be an energy conservation relation between the photons (the idler and signal photons) within each photon pair, with a bi-photon spectrum shown in figure 5.
  • the photons are generally but not necessarily generated simultaneously, and are equally spaced in frequency from the pump frequency.
  • the photon pairs having the relationship shown in figure 5 are said to be "frequency anti-correlated".
  • the phase matching can be rotated through dispersion engineering of a material with second order optical nonlinearity, which manifests by a rotation of the diagonal line in figure 5 by 90 degrees anti-clock wise. This may allow a frequency correlated photon pair to be generated.
  • An example of this is type II spontaneous parametric down conversion (SPDC).
  • Type-II SPDC takes a pump photon at a frequency co pump polarised in the TE mode and generates signal and idler photons at frequency C0pump/2 polarised in the TE and T modes respectively (that is the signal and idler are orthogonally polarized).
  • the two photons generated are in different polarisation, their group velocities are independent, which may be achieved by cutting the nonlinear crystals along different axis, changing the pump wavelength, or poling. This may be harder to achieve in Type- I SPDC where both the signal and idler are co- polarised. This will allow a frequency correlated spectrum to be generated.
  • the group velocity condition idler photon frequency > pump photon frequency > signal photon frequency or signal photon frequency ⁇ pump photon frequency ⁇ signal photon frequency must be held, in addition to the requirement of a broad (say femto second) pump.
  • the above dispersion condition could be realised with say a Bragg reflection waveguide.
  • Single photon detection may be performed by super conducting single photon detectors.
  • Single photon detection may also be performed using a single-photon avalanche diode (SPAD) (also known as a Geiger-mode APD or G-APD).
  • SPAD single-photon avalanche diode
  • This is a of solid-state photodetector based on a reverse biased p-n junction in which a photo-generated carrier can trigger an avalanche current due to an impact ionization mechanism.
  • a SPAD may be used to determine the arrival times of the photons with a jitter of a few tens of picoseconds.
  • a relatively robust and field deployable option may be an InGaAs based avalanche photodiode, purchasable from Id-Quantique, model ID210 for the lab and ID220 for the field.
  • the branches of the optical path may be formed using an appropriately configured fused tapered coupler and an appropriately configured Bragg fibre grating filter or dielectric stack filter at each branch of the coupler.
  • the filter set may be implemented using a network of fused couplers and at least one array waveguide device.
  • an optical beam splitting cube may be used to create two branches, and filter sets comprising dielectric stacks on glass substrates may be selectively inserted into the branches.
  • any suitable implementation of the filter sets may be used.
  • optical switches are switches that enables signals in optical fibres, integrated optical circuits (IOCs), or free space optical systems, to be selectively switched from one circuit to another.
  • IOCs integrated optical circuits
  • An optical switch may operate by mechanical means, such as physically shifting an optical fibre to drive one or more alternative fibres, or by electro-optic / opto-electronic effects, magneto-optic effects, or other methods.
  • Semiconductor optical amplifiers which are optoelectronic devices, may be operated as optical switches and may be integrated with discrete or integrated microelectronic circuits.
  • Communication of the filter set information and/or detection event time stamp information may be performed using any suitable physical medium using and any suitable protocol(s).
  • the physical medium may be a plain old telephone (POTS) network, free space electromagnetic waves at optical frequencies, radio frequencies or microwave frequencies, a fibre network, an electrical network, or any suitable combination of these and other networks.
  • POTS plain old telephone
  • an optical Ethernet network supporting an IP network layer and a TCP transport layer may be used.
  • the system 10 and other system 20 may comprise optical Ethernet transceivers to which fibre cabling is coupled.
  • the information may be sent over, for example, a point-to-point connection.
  • the information may be sent as symbols of paper.
  • any suitable communication channel may be used.
  • the communication of the information need not be secure.
  • the impossibility of cloning a photon (the quantum "no cloning theorem") of the photon pairs provides security. If either one of the sequence of photons and the other sequence of photons is intercepted by an eavesdropper, then by the Heisenberg uncertainty principle the eavesdropper modifies the sequence. This increases the number of errors, notifying the systems 10,20 of the eavesdropper. Consequently, the encryption key is secured. While the pair of photons may be entangled, this is not a necessity for the security. The pair of photons may not be entangled.
  • Processor Figure 6 shows a schematic diagram of the architecture of a processor 140 of the systems 10,20.
  • the processor incorporates the switching control logic, the internal memory 40, the information transceiver 42, and the information comparator.
  • the processor controls the execution of the steps of the method of figure 2.
  • the method may be coded in a program for instructing the processor.
  • the program is, in this embodiment stored in nonvolatile memory 148 in the form of a hard disk drive, but could be stored in FLASH, EPROM or any other form of tangible media within or external of the processor.
  • the program generally, but not necessarily, comprises a plurality of software modules that cooperate when installed on the processor so that the steps of the method is performed.
  • the software modules at least in part, correspond to the steps of the method or components of the system described above.
  • the functions or components may be compartmentalised into modules or may be fragmented across several software modules.
  • the software modules may be formed using any suitable language, examples of which include C++ and assembly.
  • the program may take the form of an application program interface or any other suitable software structure.
  • the processor 140 includes a suitable micro processor 142 such as, or similar to, the INTEL XEON or AMD OPTERON micro processor connected over a bus 144 to a random access memory 146 (incorporating memory 40) of around 1GB and a non- volatile memory such as a hard disk drive 148 or solid state non-volatile memory having a capacity of around 1 Gb.
  • Alternative logic devices may be used in place of the microprocessor 142.
  • the processor 140 has input/output interfaces 150 which may include one or more network interfaces, and a universal serial bus.
  • the processor may support a human machine interface 152 e.g. mouse, keyboard, display etc.
  • This partite space Fi (3 ⁇ 4 Fs is the tensor product of the two individual photon state spaces, with the state vector described by some orthonormal basis set
  • the wavelength of the photons used to generate the secure encryption key may be

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Abstract

L'invention concerne de manière générale un procédé et un système de génération d'une clé de cryptage sécurisée. Une séquence de photons est reçue et un ensemble de filtres est choisi pour chaque photon dans la séquence de photons. Un trajet optique se ramifie pour chaque photon, et chaque ramification comprend un des filtres de l'ensemble de filtres choisi. Le procédé détermine lequel des filtres de l'ensemble de filtres choisi a été traversé par chaque photon et enregistre un symbole associé au filtre ainsi déterminé. Un système reçoit une autre séquence de photons constitutant l'autre moitié de la séquence de paires de photons. Les informations de séquence de filtres reçues du système indiquent la séquence dans laquelle d'autres ensembles de filtres ont été utilisés par le système. Les informations de séquence de filtres sont comparées aux informations indiquant la séquence afin de déterminer lequel des symboles enregistrés doit être rejeté.
PCT/AU2014/000515 2013-05-13 2014-05-12 Génération de clés de cryptage sécurisées WO2014183158A1 (fr)

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