CN114221758A - Round-trip double-phase modulation quantum key sharing system and method - Google Patents
Round-trip double-phase modulation quantum key sharing system and method Download PDFInfo
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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
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- 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
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/548—Phase or frequency modulation
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- 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
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- 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
- H04B10/80—Optical aspects relating to the use of optical transmission for specific applications, not provided for in groups H04B10/03 - H04B10/70, e.g. optical power feeding or optical transmission through water
- H04B10/85—Protection from unauthorised access, e.g. eavesdrop protection
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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
- H04L9/085—Secret sharing or secret splitting, e.g. threshold schemes
Abstract
The invention discloses a quantum key sharing system and method of reciprocating bi-phase modulation, wherein the system comprises a signal sending module of a trusted terminal, a remote user side and a signal receiving module of the trusted terminal; the method includes that a signal sending module generates a light source and modulates signal light to send the signal light to a remote user side; all remote user terminals carry out double-phase modulation on the received signals and then send the signals to a signal receiving module; the trusted terminal measures signals and obtains a measurement result; repeating the above steps; calculating the transmissivity between each remote user side and the trusted terminal; the trusted terminal recalculates the measurement result and calculates the security key rate of the link; the trusted terminal selects and judges the final security key rate; and the trusted terminal uses the new secret key encryption information to complete secret key sharing with a plurality of remote user terminals. The method can be used for immunizing local oscillator light attack, reducing the deployment cost of the system and solving the problem of signal synchronization of the traditional system, and has high actual safety.
Description
Technical Field
The invention relates to a quantum key distribution system combining a round-trip architecture, a bi-phase modulation technology and a quantum key sharing protocol, in particular to a quantum key sharing method for transmitting signal light of a trusted terminal to a plurality of remote user sides, and transmitting the received signal light back to the trusted terminal after the remote user sides perform bi-phase modulation.
Background
With the rapid development of computer technology, the network environment is increasingly complex, the traditional information security technology is impacted in different degrees, and the information security is also widely concerned by researchers. In recent years, a quantum key distribution technology supported by uncertainty of quantum physics and non-clonality theorem realizes unconditional theoretical security, and becomes a great research hotspot in the field of secure communication.
The quantum key distribution technology is mainly divided into continuous variable quantum key distribution and discrete variable quantum key distribution, and the continuous variable quantum key distribution is one of the main research directions in the field of quantum secret communication because of the advantages of low detection cost, easy compatibility with a classical communication system and the like. Generally, continuous variable quantum key distribution generally only comprises two users, but in a complex network environment, a demand scenario that multiple users share a key exists, but the continuous variable quantum key distribution technology of two users cannot meet the situation.
In order to solve the complex scene, a quantum key sharing protocol is provided. In a quantum key sharing system, each user needs to be equipped with a laser to generate a coherent state, and then the coherent state is sent to the next user, where it interferes with the coherent state prepared by the local user through a beam splitter. However, in the actual deployment and transmission process of the system, several problems are worth paying attention, firstly, the high cost of deployment of each user end is caused by the high price of the laser, and the problem is particularly prominent in the case of a large number of users. A second problem is that the problem of synchronization of the signals becomes very complex and troublesome when the lasers of all users work together. Still another problem is that the transmitted local oscillator light is vulnerable to eavesdroppers, the transmitted information may be leaked, and the security of the system is greatly threatened.
Disclosure of Invention
Aiming at the defects of the existing system, the invention aims to combine the anti-attack capability of a round-trip architecture and the characteristic of stable polarization of dual-phase modulation in the round-trip architecture, thereby realizing a round-trip dual-phase modulation quantum key sharing system and method, which are easy to deploy, have lower cost, can improve the anti-attack capability of the system and have practical application value.
The invention provides a quantum key sharing system of reciprocating bi-phase modulation, comprising:
the signal sending module of the trusted terminal: the system is used for generating a coherent light source, dividing the coherent light source into local oscillator light and signal light, sending the signal light to a remote user end through an unsafe optical fiber quantum channel, and keeping the local oscillator light in a signal sending module.
Remote user end: the system is used for receiving the signal light, modulating the signal light into a dual-phase modulation coherent state by using dual-phase modulation, and sending the modulated quantum state to the next remote user end closest to the user end. The quantum key sharing system is provided with a plurality of remote user ends.
The signal receiving module of the trusted terminal: the signal receiving module is arranged in the credible terminal, receives the quantum signal transmitted by the last remote user side, and interferes and detects the received quantum signal and the local oscillator light transmitted from the signal sending module.
Further, the signal sending module of the trusted terminal includes:
a continuous laser: for generating a coherent light source;
a beam splitter: the system is used for separating the coherent light source into signal light and local oscillator light, the local oscillator light is left at a signal sending end locally, and the signal light continues to be transmitted forwards;
an intensity modulator: the intensity modulator is used for modulating the separated signal light into pulse signal light and transmitting the pulse signal light to the signal modulation end through a quantum optical fiber channel;
attenuator: attenuating the pulsed signal light to a quantum level;
an optical isolator: for preventing attacks by potential eavesdroppers.
Further, the remote user terminal includes:
wavelength filter: for resisting trojan horse attacks;
a first beam splitter: the system comprises a remote user end, a photoelectric detector, a phase remapping attack detector and a control module, wherein the remote user end is used for receiving signals;
variable attenuator: a modulation variance for adjusting the signal light to achieve a target;
a second beam splitter: the device is used for splitting the transmitted signal light into two beams, the two beams of signal light are respectively modulated by different phase modulators, the modulated signal light is reflected by a Faraday mirror on a corresponding line, and the two beams of light generate interference on the beam splitter to complete the modulation operation. The modulated signal light is sent to the next remote user end by the system;
a phase modulator: the Faraday mirror is used for carrying out phase modulation on the signal light transmitted by the second beam splitter and sending the modulated signal light to the Faraday mirror;
a Faraday mirror: the Faraday rotator is used for generating a 90-degree polarization rotation for a signal transmitted to the Faraday mirror and reflecting the signal;
adjustable delay line: used for controlling the time delay between the pulse signals of the two modulation light paths.
Further, the signal receiving module of the trusted terminal includes:
90-degree optical mixer: the device is used for quantum signal light to interfere with local oscillator light transmitted by a trusted terminal sending module, and four outputs of the quantum signal light are received by two balanced homodyne detectors;
heterodyne detector: the device consists of two balanced homodyne detectors and is used for detecting received quantum signal light;
a data processing center: for sampling the analog signal, detecting the presence of an attack, and extracting the original key.
Further, a beam splitter in the signal sending module of the trusted terminal separates the coherent light source into signal light and local oscillation light by adopting an intensity ratio of 99: 1.
Furthermore, the adjustable attenuator of the remote user end obtains the optimal biphase modulation variance by controlling the attenuation coefficient, thereby improving the key rate.
The invention also provides a quantum key sharing method of the round-trip type bi-phase modulation, which comprises the following specific steps:
s1: the continuous laser of the signal sending module of the trusted terminal outputs a pulse light source, which is divided by the beam splitter into 99: the intensity ratio of 1 is divided into local oscillator light and signal light, the local oscillator is reserved in the local of the credible terminal, and the signal light is modulated into pulse signal light through an amplitude modulator, the pulse signal light is attenuated to the quantum level through an attenuator, and then the pulse signal light is transmitted to the farthest user side through an isolator.
S2: after receiving quantum signal pulses sent by a trusted terminal, a farthest user end transmits signals to a wavelength filter to limit Trojan horse attack, then transmits the signals to a beam splitter, and is divided into two beams by the beam splitter, one beam is sent to a photoelectric detector to monitor other attacks, the other beam is subjected to Gaussian modulation by phase modulators in two optical paths after passing through an attenuator, then the signals in the two optical paths are respectively reflected to the beam splitter by a Faraday mirror to perform interference to complete dual-phase modulation, and finally the dual-phase modulation coherent state is sent to the next nearest remote user end.
S3: after the next remote user end receives the quantum signal, the received quantum signal is modulated according to the step described in S2, and the modulated mixed quantum state is continuously sent to the next remote user end closest to the next remote user end.
S4: and repeating the step S3 until all the remote user terminals complete the bi-phase modulation on the received quantum signals. And the last remote user side sends the final mixed quantum state back to the signal receiving module of the trusted terminal.
S5: the signal receiving module of the trusted terminal receives the mixed quantum state sent by the last remote user side, firstly, an optical mixer is used for interfering local oscillation light and quantum signal light of the trusted terminal, and then the output result of the mixer is sent to two balanced homodyne detectors to measure the phase and amplitude of the quantum signal light, so that the measurement result is obtained.
S6: repeating steps S3-S5 for a plurality of times until the trusted terminal obtains enough continuously correlated measurements, at which time all remote user terminals also hold as much mixed data as the trusted terminal.
S7: as a result of a portion of the measurements made in the trusted terminal disclosure S6, the remote user terminals also disclose a mix of data of equal length corresponding to the published data of the trusted terminal, from which the transmittance experienced by the signal from each remote user terminal to the trusted terminal is determined.
S8: the trusted terminal firstly selects any one remote user side, prepares to establish a point-to-point quantum key distribution link with the selected remote user side, selects any part of undisclosed measurement result data, and requires that all other remote user sides except the selected remote user side disclose corresponding mixed data.
S9: and the trusted terminal recalculates the measurement result and obtains the final measurement result. And according to the measurement result of the trusted terminal and the relevant data of the selected remote user, after the trusted terminal and the selected remote user perform a post-processing process of classical quantum key distribution, calculating to obtain a security key rate, and establishing a quantum key distribution link.
S10: the steps S8 and S9 are repeated many times, and each operation selects a different remote user side until all remote user sides establish a quantum key distribution link with the trusted terminal.
S11: and selecting the minimum security key rate from all the security key rates obtained in the step S10 as the final security key rate in the quantum key sharing system, and then judging the minimum key rate by the trusted terminal according to the actual operation condition, so that the trusted terminal completes the operation of sharing the key with the multi-party remote user side.
S12: the trusted terminal obtains key data from different remote user sides, forms a string of new keys, encrypts the target information by using the keys, and then discloses the encrypted information to all the remote user sides, so that the target information is shared among all the remote user sides.
Furthermore, in the above steps, the public data of the remote user terminal and the trusted terminal must be discarded, so as to improve the security of the system.
Further, the bi-phase modulation coherent state described in the above step S2 is represented as | x1+ip1>。
Further, the mixed quantum state described in the above step S3 is represented as
N, T, wherein m is 2jRepresenting the channel transmittance experienced by the signal of the remote user j to the trusted terminal.
Further, the signal receiving module of the trusted terminal in step S5 receives the mixed quantum state sent by the last remote user end, and after an optical mixer is used to interfere the local oscillator light and the quantum signal light of the trusted terminal, the output result of the mixer is sent to two balanced homodyne detectors to measure the phase and amplitude of the quantum signal light, so as to obtain the measurement result. In particular the received mixed quantum states as
The measurement result is represented by (x)d,pd)。
Further, the trusted terminal described in the above S9 recalculates the measurement result and obtains the final measurement result. And according to the measurement result of the trusted terminal and the relevant data of the selected remote user side, after the trusted terminal and the selected remote user side perform a post-processing process of classical quantum key distribution, calculating to obtain a security key rate, and establishing a quantum key distribution link. In particular using the formula for trusted terminals
The measurement results are recalculated, where s is 1, 2. The final measurement is expressed as (x)r,pr) The security key rate is calculated according to the following formula:
Kj＝βIAB-χBE
wherein KjIndicating trusted terminal and jA secure key rate for each remote user; β is the efficiency of the reverse negotiation; i isABIs the mutual information quantity of the trusted terminal and the selected remote user terminal, and is expressed as
Wherein A and B represent a trusted terminal and a selected remote user terminal respectively, and V represents the variance of EPR state in an entanglement scheme of continuous variable quantum key distribution, ξsRepresenting noise caused by an attacker interfering with the light source; chi shapetotRepresents the total noise of the channel; chi shapeBERepresents the maximum value of information stolen by an attacker from a remote user side, wherein E represents the attacker, and
wherein λjJ 1.. 5 denotes an eigenvalue of a covariance matrix of continuous variable quantum key distribution, and has
λ5＝1
Wherein A, B, C and D are both intermediate parameters, respectively
A＝V2-2T1(V2-1)+T1 2(V+ξs+χline)2
B＝T1 2[1+V(ξs+χline)]2
Wherein T isjRepresents the channel transmittance from the jth remote user terminal to the trusted terminal, expressed as
Alpha represents a fiber loss factor of 0.2dB/km,
representing the channel distance between the trusted terminal and the jth remote user terminal, wherein n represents the number of the remote user terminals; chi shapelineAdditive noise representing the channel, denoted as
Wherein
And xi0Representing the excess noise introduced by each remote user end; chi shapehIs additive noise to heterodyne detection, andh＝[(2-η)+2υel]eta, eta is the detection efficiency of the heterodyne detector; chi shapetotIs the total noise of the channel, and χtot＝χline+χh/T1。
Further, in S11, the minimum security key rate is selected from all the security key rates obtained in S10 as the final security key rate in the quantum key sharing system, and then the trusted terminal determines the minimum key rate according to the actual operating condition, where the specific determination method is as follows:
if the final security key rate R is greater than 0, the trusted terminal forms a new key using the unpublished key data in the measurement and encrypts the information, as described in step S12. Otherwise, if the final security key rate R is less than or equal to 0, it indicates that the security key cannot be established in the current link, and the key sharing operation of the system fails.
Further, the trusted terminal described in S12The key data from different remote user ends are obtained, a string of new keys is formed by the key data, and after the target information is encrypted by using the key, the encrypted information is disclosed to all the remote user ends, so that the target information is shared among all the remote user ends. In particular trusted terminal usage formula
Generating a new key and publishing the encrypted information to all remote clients
Where M denotes target information and K denotes an encryption key.
The quantum key sharing method of the round-trip bi-phase modulation has the advantages that the round-trip architecture is adopted for communication, so that the attack of local oscillator light is avoided, the signal synchronization problem in the traditional quantum key sharing system is solved, the deployment cost of a user side is reduced, and the actual safety of the system is improved.
Drawings
FIG. 1 is a schematic flow diagram of the process of the present invention.
FIG. 2 is a diagram of an experimental configuration of the system of the present invention.
Detailed Description
The present invention will be further described with reference to the drawings in the examples, which will help the researchers in this field to better understand the present invention. It is to be noted that all relevant modifications and variations of the present invention are covered by the protection scope of the present invention.
The experimental configuration diagram of the system of the invention is shown in fig. 1: the invention provides a round-trip bi-phase modulation quantum key sharing system, which specifically comprises:
the signal sending module of the trusted terminal: the system is used for generating a coherent light source, dividing the coherent light source into local oscillator light and signal light according to the intensity ratio of 99:1, sending the signal light to a remote user end through an unsafe optical fiber quantum channel, and keeping the local oscillator light in a signal sending module.
Remote user end: the system is used for receiving the signal light, modulating the signal light into a dual-phase modulation coherent state by using dual-phase modulation, and sending the modulated quantum state to the next remote user end closest to the user end. The quantum key sharing system is provided with a plurality of remote user ends.
The signal receiving module of the trusted terminal: the signal receiving module is arranged in the credible terminal, receives the quantum signal transmitted by the last remote user side, and interferes and detects the received quantum signal and the local oscillator light transmitted from the signal sending module.
The signal sending module of the trusted terminal comprises:
a continuous laser: for generating a coherent light source;
a beam splitter: the system is used for separating a coherent light source into signal light and local oscillator light according to the intensity ratio of 99:1, the local oscillator light is left at a signal sending end locally, and the signal light continues to be transmitted forwards;
an intensity modulator: the intensity modulator is used for modulating the separated signal light into pulse signal light and transmitting the pulse signal light to the signal modulation end through a quantum optical fiber channel;
attenuator: attenuating the pulsed signal light to a quantum level;
an optical isolator: for preventing attacks by potential eavesdroppers.
The remote user side comprises:
wavelength filter: for resisting trojan horse attacks;
a first beam splitter: the system comprises a remote user end, a photoelectric detector, a phase remapping attack detector and a control module, wherein the remote user end is used for receiving signals;
variable attenuator: a modulation variance for adjusting the signal light to achieve a target;
a second beam splitter: the device is used for splitting the transmitted signal light into two beams, the two beams of signal light are respectively modulated by different phase modulators, the modulated signal light is reflected by a Faraday mirror on a corresponding line, and the two beams of light generate interference on the beam splitter to complete the modulation operation. The modulated signal light is sent to the next remote user end by the system;
a phase modulator: the Faraday mirror is used for carrying out phase modulation on the signal light transmitted by the second beam splitter and sending the modulated signal light to the Faraday mirror;
a Faraday mirror: the Faraday rotator is used for generating a 90-degree polarization rotation for a signal transmitted to the Faraday mirror and reflecting the signal;
adjustable delay line: used for controlling the time delay between the pulse signals of the two modulation light paths.
The signal receiving module of the trusted terminal comprises:
90-degree optical mixer: the device is used for quantum signal light to interfere with local oscillator light transmitted by a trusted terminal sending module, and four outputs of the quantum signal light are received by two balanced homodyne detectors;
heterodyne detector: the device consists of two balanced homodyne detectors and is used for detecting received quantum signal light;
a data processing center: for sampling the analog signal, detecting the presence of an attack, and extracting the original key.
The adjustable attenuator of the remote user side obtains the optimal biphase modulation variance by controlling the attenuation coefficient, so that the key rate is improved.
The flow diagram of the system of the invention is shown in FIG. 2: the embodiment of the invention discloses a quantum key sharing method for reciprocating bi-phase modulation, which comprises the following specific steps:
s1: the continuous laser of the signal sending module of the trusted terminal outputs a pulse light source, which is divided by the beam splitter into 99: the intensity ratio of 1 is divided into local oscillator light and signal light, the local oscillator is reserved in the local of the credible terminal, and the signal light is modulated into pulse signal light through an intensity modulator, the pulse signal light is attenuated to the quantum level through an attenuator, and then the pulse signal light is transmitted to the farthest user side through an isolator.
S2: after receiving quantum signal pulses sent by a trusted terminal, a remote user side transmits signals to a wavelength filter to limit Trojan horse attacks, then transmits the signals to a beam splitter, and is split into two beams by the beam splitter, wherein one beam is delivered to a photoelectric beamThe detector monitors other attacks, the other beam passes through the attenuator and is subjected to Gaussian modulation by the phase modulators in the two light paths, then signals in the two light paths are respectively reflected by the Faraday mirror to the beam splitter for interference to complete dual-phase modulation, and finally the dual-phase modulation coherent state | x1+ip1>And sending the data to the next remote user end closest to the user.
S3: after the next remote user end receives the quantum signal, the received quantum signal is modulated according to the same procedure as the step described in S2, and the modulated mixed quantum state is obtained
N is sent to the next nearest remote user, where T is 2jRepresenting the channel transmittance experienced by the signal of the remote user j to the trusted terminal.
S4: and repeating the step S3 until all the remote user terminals complete the bi-phase modulation on the received quantum signals. The last remote user end will finally mix the quantum state
And sending the signal back to the signal receiving module of the trusted terminal.
S5: the signal receiving module of the trusted terminal receives the mixed quantum state sent by the last remote user end, firstly, an optical mixer is used for interfering local oscillation light and quantum signal light of the trusted terminal, and then the output result of the mixer is sent to two balanced homodyne detectors to measure the phase and amplitude of the quantum signal light to obtain a measurement result (x)d,pd)。
S6: repeating S3-S5 for a plurality of times until the trusted terminal obtains enough continuously correlated measurements, at which time all remote clients also hold as much mixed data as the trusted terminal.
S7: as a result of a portion of the measurements made in the trusted terminal disclosure S6, the remote user terminals also disclose a mix of data of equal length corresponding to the published data of the trusted terminal, from which the transmittance experienced by the signal from each remote user terminal to the trusted terminal is determined.
S8: the trusted terminal firstly selects any one remote user side, prepares to establish a point-to-point quantum key distribution link with the selected remote user side, selects any part of undisclosed measurement result data, and requires that all other remote user sides except the selected remote user side disclose corresponding mixed data.
S9: formula for trusted terminal
Recalculating the measurement and obtaining the final measurement (x)r,pr). And according to the measurement result of the trusted terminal and the relevant data of the selected remote user side, after the trusted terminal and the selected remote user side perform a post-processing process of classical quantum key distribution, calculating to obtain a security key rate, and establishing a quantum key distribution link.
In specific implementation, for a continuous variable quantum key sub-link established by the trusted terminal and the selected remote user side, the trusted terminal calculates the security key rate by adopting the following formula:
Kj＝βIAB-χBE
wherein KjRepresenting the security key rate of the trusted terminal and the jth remote user terminal; β is the efficiency of the reverse negotiation; i isABIs the mutual information quantity of the trusted terminal and the selected remote user terminal, and is expressed as
A and B respectively represent a trusted terminal and a selected remote user side, and V represents the variance of an EPR state in an entanglement scheme of continuous variable quantum key distribution; xisRepresenting noise caused by an Eve interfering light source; chi shapetotRepresents the total noise of the channel; chi shapeBERepresents the maximum value of information stolen by an attacker from a remote user side, wherein E represents the attacker, and
wherein λjJ 1.. 5 denotes an eigenvalue of a covariance matrix of continuous variable quantum key distribution, and has
λ5＝1
Wherein A, B, C and D are both intermediate parameters, respectively
A＝V2-2T1(V2-1)+T1 2(V+ξs+χline)2
B＝T1 2[1+V(ξs+χline)]2
Wherein T isjRepresents the channel transmittance from the jth remote user terminal to the trusted terminal, expressed as
Where alpha represents a fiber loss factor of 0.2dB/km,
representing the channel distance between the trusted terminal and the jth remote user terminal; n represents the number of remote user ends; chi shapelineAdditive noise representing the channel, denoted as
Wherein
And xi0Representing the excess noise introduced by each remote user end; chi shapehIs additive noise to heterodyne detection, andh＝[(2-η)+2υel]eta, eta is the detection efficiency of the heterodyne detector; chi shapetotIs the total noise of the channel, and χtot＝χline+χh/T1。
S10: s8 and S9 are repeated a plurality of times, each run selecting a different remote user terminal until all remote user terminals establish a quantum key distribution link with the trusted endpoint.
S11: selecting the minimum security key rate from all the security key rates obtained in the step S10 as the final security key rate in the quantum key sharing system, and then determining the minimum key rate by the trusted terminal according to the actual operating condition: if the final security key rate R is greater than 0, the trusted terminal can share the quantum key with the multi-party remote user side. Otherwise, if the final security key rate R is less than or equal to 0, it indicates that the security key cannot be established in the current link, and the key sharing operation of the system fails.
S12: the trusted terminal obtains key data from different remote user terminals by using a formula
Forming a new key string, encrypting the target information M with the key, and encrypting the encrypted information
The target information is shared among all the remote user terminals.
After the operation of the data disclosed by the remote user side and the trusted terminal for estimating the key rate and establishing the quantum key distribution link is finished, all the remote user side and the trusted terminal need to be deleted from the original data, so that the safety of the system is improved.
The system adopts a reciprocating type framework, the trusted terminal firstly divides the coherent light source into local oscillator light and signal light, then the local oscillator light is left in the trusted terminal, and the local oscillator light and the quantum signal do not need to be transmitted in a quantum channel at the same time, so that the attack of the local oscillator light initiated by an eavesdropper is avoided, and the actual safety of the system is improved. The signal light is transmitted in the quantum channel and received by each remote user terminal, the remote user terminals encode information on the regular components of the signal light, and then the modulated signal light is sent to the next remote user terminal again through the quantum channel, each remote user terminal only needs to modulate the signal light, and the modulation operation does not need the existence of a laser. Therefore, compared with the traditional quantum key sharing system, the system does not have a plurality of lasers to run synchronously any more, the problem of complex signal synchronization is solved easily, and the configuration and experiment cost is greatly reduced.
Claims (8)
1. A quantum key sharing system of a round-trip double-phase modulation is characterized by comprising a signal sending module of a trusted terminal, a remote user side and a signal receiving module of the trusted terminal;
the signal sending module of the trusted terminal comprises:
a continuous laser: for generating a coherent light source;
a beam splitter: the system is used for separating the coherent light source into signal light and local oscillator light, the local oscillator light is left at a signal sending end locally, and the signal light continues to be transmitted forwards;
an intensity modulator: the intensity modulator is used for modulating the separated signal light into pulse signal light and transmitting the pulse signal light to the signal modulation end through a quantum optical fiber channel;
attenuator: attenuating the pulsed signal light to a quantum level;
an optical isolator: for preventing attacks by potential eavesdroppers;
the remote user side comprises:
wavelength filter: for resisting trojan horse attacks;
a first beam splitter: the system comprises a remote user end, a photoelectric detector, a phase remapping attack detector and a control module, wherein the remote user end is used for receiving signals;
variable attenuator: a modulation variance for adjusting the signal light to achieve a target;
a second beam splitter: the optical fiber modulator is used for dividing the transmitted signal light into two beams and respectively transmitting the two beams of signal light to two modulation optical paths for modulation;
a phase modulator: the Faraday mirror is used for carrying out phase modulation on the signal light transmitted by the second beam splitter and sending the modulated signal light to the Faraday mirror;
a Faraday mirror: the Faraday rotator is used for generating a 90-degree polarization rotation for a signal transmitted to the Faraday mirror and reflecting the signal;
adjustable delay line: the time delay control circuit is used for controlling the time delay between pulse signals of the two modulation light paths;
the signal receiving module of the trusted terminal comprises:
90-degree optical mixer: the device is used for quantum signal light to interfere with local oscillator light transmitted by a trusted terminal sending module, and four outputs of the quantum signal light are received by two balanced homodyne detectors;
heterodyne detector: the device consists of two balanced homodyne detectors and is used for detecting received quantum signal light;
a data processing center: for sampling the analog signal, detecting the presence of an attack, and extracting the original key.
2. The round-trip bi-phase modulated quantum key sharing system according to claim 1, wherein the coherent light source is separated into a local oscillator light and a signal light by a 99:1 beam splitter, the signal light is transmitted to the remote user end through a quantum channel for modulation, and the local oscillator light is locally retained by the trusted terminal for performing interferometry with the signal light received by the trusted terminal.
3. The system of claim 1, wherein the remote clients comprise a plurality of remote clients, and after a remote client performs bi-phase modulation on the signal light, the modulated signal light reflected by the faraday mirror is continuously transmitted to the next closest remote client through the quantum channel until all remote clients have modulated the quantum signal.
4. A method for realizing quantum key sharing of a round-trip bi-phase modulation is characterized in that the method is carried out according to the following steps:
s1: and a signal sending module of the trusted terminal sends a coherent light source and divides the coherent light source into local oscillation light and signal light according to the intensity ratio of 99:1, the signal light is modulated into pulse signal light and then sent to a farthest user side through attenuation, and the local oscillation light is left locally.
S2: and after receiving the quantum signal pulse sent by the trusted terminal, the most remote user side carries out bi-phase modulation on the signal and sends the modulated bi-phase coherent state to the next remote user side closest to the user side.
S3: after the next remote user end receives the quantum signal, the received quantum signal is modulated according to the step described in S2, and the modulated mixed quantum state is continuously sent to the next remote user end closest to the next remote user end.
S4: and repeating the step S3 until all the remote user terminals complete the bi-phase modulation on the received quantum signals. And the last remote user side sends the final mixed quantum state back to the signal receiving module of the trusted terminal.
S5: and a signal receiving module of the trusted terminal receives the mixed quantum state sent by the last remote user side, and a heterodyne detector is used for measuring the phase and amplitude of the quantum signal light to obtain a measurement result.
S6: repeating steps S3-S6 for a plurality of times until the trusted terminal obtains enough continuously correlated measurements, at which time all remote user terminals also hold as much mixed data as the trusted terminal.
S7: as a result of the part of the results measured in the trusted terminal publishing step S6, the remote user terminals also publish the mixed data of the same length corresponding to the published data of the trusted terminal, and accordingly determine the transmittance experienced by the signal from each remote user terminal to the trusted terminal.
S8: the trusted terminal firstly selects any one remote user side, prepares to establish a point-to-point quantum key distribution link with the selected remote user side, selects any part of undisclosed measurement result data, and requires that all other remote user sides except the selected remote user side disclose corresponding mixed data.
S9: and the trusted terminal recalculates the measurement result and obtains the final measurement result. And according to the measurement result of the trusted terminal and the relevant data of the selected remote user, after the trusted terminal and the selected remote user perform a post-processing process of classical quantum key distribution, calculating to obtain a security key rate, and establishing a quantum key distribution link.
S10: the steps S8 and S9 are repeated many times, and each operation selects a different remote user side until all remote user sides establish a quantum key distribution link with the trusted terminal.
S11: from all the security key rates obtained in step S10, the final security key rate in the quantum key sharing system is selected and determined. And the trusted terminal completes the operation of sharing the key with the multi-party remote user side.
S12: the trusted terminal obtains key data from different remote user sides, forms a string of new keys, encrypts the target information by using the keys, and then discloses the encrypted information to all the remote user sides, so that the target information is shared among all the remote user sides.
5. The method as claimed in claim 4, wherein the modulated biphase coherent state in step S2 is represented by | x |1+ip1>。
6. A round-trip bi-phase modulated quantum according to claim 4The method for realizing key sharing is characterized in that the modulated mixed quantum state in the step of S3 is
N, T, wherein m is 2jRepresents the channel transmittance experienced by the signal of the jth remote user terminal to the trusted terminal, and n represents the number of remote user terminals.
7. The method as claimed in claim 4, wherein the trusted terminal recalculates the measurement result and calculates the security key rate, specifically to a secure key rate used by the trusted terminal
The measurement results are recalculated, where s is 1, 2. The final measurement is expressed as (x)r,pr) The secure key rate is:
Kj＝βIAB-χBE
wherein KjRepresenting the security key rate of the trusted terminal and the jth remote user terminal; β is the efficiency of the reverse negotiation; i isABIs the mutual information quantity of the trusted terminal and the selected remote user terminal, and is expressed as
Wherein A and B represent a trusted terminal and a selected remote user terminal, respectively; v represents the variance of EPR state in the entanglement scheme of continuous variable quantum key distribution; xisRepresenting noise caused by an attacker interfering with the light source; chi shapetotRepresents the total noise of the channel; chi shapeBERepresents the maximum value of information stolen by an attacker from a remote user side, wherein E represents the attacker, and
wherein λjJ 1.. 5 denotes an eigenvalue of a covariance matrix of continuous variable quantum key distribution, and has
λ5＝1
Wherein A, B, C and D are both intermediate parameters, respectively
A＝V2-2T1(V2-1)+T1 2(V+ξs+χline)2
B＝T1 2[1+V(ξs+χline)]2
Wherein T isjRepresents the channel transmittance from the jth remote user terminal to the trusted terminal, expressed as
Where alpha represents a fiber loss factor of 0.2dB/km,
representing the channel distance between the trusted terminal and the jth remote user terminal, wherein n represents the number of the remote user terminals; chi shapelineAdditive noise representing the channel, denoted as
Wherein
And xi0Representing the excess noise introduced by each remote user end; chi shapehIs additive noise to heterodyne detection, andh＝[(2-η)+2υel]eta, eta is the detection efficiency of the heterodyne detector; chi shapetotIs the total noise of the channel, and χtot＝χline+χh/T1。
8. The method as claimed in claim 4, wherein the trusted terminal forms the obtained keys of all remote clients into a string of new keys, encrypts the target information using the new keys, and then discloses the encrypted information to all remote clients, specifically, the trusted terminal uses a formula
Generating a new key and applying a formula to the target information M
And encrypting, and then sharing the encrypted information E to all remote user terminals.
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