KR102121027B1 - Apparatus and method for measurement immune quantum key distribution - Google Patents

Abstract

The measurement-independent quantum cryptographic key distribution apparatus and method according to the present invention generates and measures an encryption key using light as a light source based on respective phase modulators located in a transmitting unit and a receiving unit in a dual-Mach-Zehnder interferometer having a reciprocating path. Even though distribution is permitted, the encryption key cannot be distinguished according to the Mach-Zehnder interference path law, so it is established not only in quantized light, but also in classical light using a general laser light pulse as a light source. Under the influence of the environment, unconditional security can be guaranteed.

Description

Measurement related quantum cryptography key distribution device and method{APPARATUS AND METHOD FOR MEASUREMENT IMMUNE QUANTUM KEY DISTRIBUTION}

The present invention relates to an apparatus and method for measurement-related quantum cryptography key distribution.

Quantum cryptography is an unprecedented security measure based on the principles of quantum mechanics, and as a future measure for information protection, the first paper on the quantum cryptography key distribution in 1984, that is, the BB84 quantum cryptography key distribution protocol has been published. The theory and method of quantum cryptography key distribution have been proposed. On the other hand, when all cryptocurrencies currently in use except quantum cryptography are called classical cryptography, most cryptosystems follow the public key method. The public key cryptographic key distribution protocol is based on the NP (Nondeterministic Polynomial time) problem in the complexity of information theory, and NP is a domain that is currently difficult to perform with a computer and is representatively related to factor decomposition. That is, in the public key method, it is related to decryption by adopting one number multiplied by two prime factors as an encryption key and decomposing it into two prime factors. This public key cryptography is not an unconditionally secure cryptosystem because it depends on computer performance. In addition, since the problem of solving prime factorization does not belong to the NP complexity, it is very easy to decrypt the public key, and since the publication of the SHOR prime factorization quantum computer paper in 1994, countries have been competing for quantum cryptography. . In other words, the emergence of quantum computers defeats the current cryptosystem.

Published Patent: 10-2018-0025621, Published Date: March 9, 2018, Title: Quantum security direct communication device and method using path overlapping. Patent registration: 10-1767067, registration date: August 11, 2017, title: Quantum cryptographic key distribution method, apparatus and system.

An object of the present invention is to provide a measurement-independent quantum cryptographic key distribution device and method that guarantees the unconditional safety of the quantum mechanics despite the incomplete trap of the measuring device.

A key distribution method of a measurement-independent quantum encryption device according to an embodiment of the present invention includes: generating an encryption key; And sharing the encryption key using a DOUBLE-MAHAZENDER interferometer that satisfies unconditional security by using two different phase differences as the basis of each of the transmitter and the receiver.

In an embodiment, the method may further include configuring a reciprocating path configuring the dual Mach-Zehnder interferometer.

In an embodiment, it is characterized in that the coherent light incident on the dual Mach-Zehnder interferometer is used as a light source.

In an embodiment, it may include using a single photon incident on the dual Mach-Zehnder interferometer as a light source.

In an embodiment, it may include using a non-classical photon (entangled photon) incident on the dual Mach-Zehnder interferometer as a light source.

In an embodiment, the dual-Mahsendeh interferometer is characterized by extending N to N (N is a natural number) cryptographic key distribution.

In an embodiment, a phase base pair applying the phase difference to key distribution may be included.

In an embodiment, the key distribution is performed by the phase basis.

In an embodiment, the step of generating the phase basis may be further included.

In an embodiment, the step of measuring the phase basis may be further included.

In an embodiment, detecting an attacker may be further included by measuring the phase base pair.

In an embodiment, the method may further include generating a real-time two-dimensional quantum bit error rate (QBER) map by measuring the phase base pair.

Measurement independent quantum encryption key distribution device according to an embodiment of the present invention: a transmitter; Receiver; And two different phase differences as the basis of each of the transmitting unit and the receiving unit to satisfy unconditional security.

In an embodiment, the dual-Mach-Zehnder interferometer is characterized in that any one of single photon, entangled photon, and coherent light is used as a light source.

In an embodiment, the reciprocating path of the dual Mach-Zehnder interferometer may include a mirror.

In an embodiment, the reciprocating path of the dual-Mahsendeh interferometer may further include a phase conjugate mirror.

In an embodiment, N-to-N cryptographic key distribution is configured.

In an embodiment, each of the transmitting unit and the receiving unit may further include a phase basis generating device that generates any one of the different phases as a basis.

In an embodiment, each of the transmitting unit and the receiving unit may further include a phase basis measuring device that measures a phase basis transmitted through a corresponding transmission path.

In an embodiment, each of the transmitting unit and the receiving unit may further include a phase based distribution device that distributes a phase basis.

In an embodiment, the phase difference is applied to key distribution based on an encryption key distribution algorithm.

The apparatus and method for measurement independent quantum cryptography key distribution according to an embodiment of the present invention can guarantee unconditional security by sharing an encryption key using a dual-Mahagenter interferometer.

The accompanying drawings are provided to help understand the present embodiment, and provide embodiments with detailed description. However, the technical features of the present embodiment are not limited to specific drawings, and the features disclosed in each drawing may be combined with each other to form a new embodiment.
1 is a view showing an exemplary measurement independent quantum cryptography key distribution device of a phase-adjusted dual-Maha-Zehnder type according to an embodiment of the present invention.
2 is a detailed configuration diagram of a transmitter and a receiver illustrated in FIG. 1 for application to an optical communication network.
FIG. 3 is a general Mach-Zehnder interferometer shown in FIG. 1 and its calculation results.
FIG. 4 is an exploded view of the configuration of the dual-Maha-Zehnder interferometer shown in FIG. 1.
FIG. 5 is a detailed diagram of the dual Mach-Zehnder interferometer shown in FIG. 4.
FIG. 6 shows the automatic encryption key generation by unconditional security and measurement as the calculation result of FIG. 5.
7 is an N:N extension diagram of a 1:1 quantum key distribution configuration diagram of FIG. 1.
8 is a flowchart exemplarily showing a method of measuring and distributing quantum cryptography keys according to an embodiment of the present invention.

Hereinafter, the contents of the present invention will be described clearly and in detail so that those skilled in the art of the present invention can easily implement the drawings using the drawings.

The present invention can be applied to various changes and may have various forms, and specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosure form, and it should be understood that all modifications, equivalents, and substitutes included in the spirit and scope of the present invention are included. Terms such as first and second may be used to describe various components, but the components should not be limited by the terms.

The measurement independent quantum cryptography key distribution apparatus and method according to an embodiment of the present invention uses a light as a light source (quantum) based on the phase modulators located at a transmitter and a receiver in a dual-Maha-Zehnder interferometer having a reciprocating path. Even if the key is generated/measured/distributed and the measurement is allowed, it is impossible to distinguish the encryption key according to the Mach-Zehnder interference path law. Here, the Mach-Zehnder interference path law can be established not only in quantized light, but also in classical light using a general laser light pulse as a light source. The measurement independent quantum cryptography key distribution device light method of the present invention can guarantee unconditional security even under the influence of a general environment such as noise, vibration, or temperature change.

In general, quantum cryptography is based on the indeterminate principle of quantum mechanics and the principle of destructive measurement. The principle of uncertainty is that if one of the two conjugate variables, for example position and velocity or time and energy, is accurately known without error, the other variable becomes very inaccurate. It was discovered by Heisenberg in the early 20th century. Quantum cryptography is divided into several, the most common of which is BB84. The BB84 quantum cryptography key distribution method uses single photon polarization as a key, and uses vertical/horizontal polarization as one basis to rotate the base 45 degrees as another basis to distribute the keys. Here, the borrowing of the first uncertainty principle is that when trying to find out the polarization of an encrypted light using a single polarization base, if the polarization of the light is the same as the base used, it is perfectly decipherable, but otherwise it cannot be found at all.

Secondly, when measuring a single photon, that is, light in a quantum state, destructive measurement means that all measurement actions transform the original quantum state. Since measurement is a process of projecting to a reference coordinate, a quantum state having amplitude and phase naturally changes its original phase and amplitude in the measurement process. Therefore, it cannot be recovered again. The inability to recover again is based on the irreproducible principle of quantum mechanics. That is, no quantum state can be duplicated equally. Therefore, since quantized light cannot be measured without changing the original state, it is possible to know the presence or absence of an eavesdropper in quantum cryptography. This is the theoretically possible basis for unconditionally secure cryptographic key distribution in quantum cryptography.

However, in implementing the quantum cryptography system, practically, the principle of quantum mechanics is not purely achieved in the key distribution of quantum cryptography. For example, the incompleteness of the measuring device or the noise level of the medium through which light passes is not guaranteed to be an unconditionally safe quantum cryptography system. Currently, in the photodetector measuring the optical communication frequency, the light-to-electron conversion ratio is generally only 30%. Of course, 93% of light-to-electron conversion ratios using superconducting nanowires have been observed, and equipment with an efficiency of 80% or more has been sold, but measurement errors are inevitable unless complete conversion efficiency is allowed. This is called a loophole. As long as this trap exists, quantum attacks are possible and unconditional quantum cryptography is impossible.

In addition, there is no device capable of definitively generating a single photon used for quantum cryptography. Therefore, key distribution is performed in a purely stochastic manner. Finally, the quantum bit rate (QBR; QUANTUM BIT RATE) reached per unit distance is very low. The best quantum cryptography key distribution method to prevent this is the E91, which was invented by EKERT of England in 1991, which uses the same single photon, but uses a quantum entanglement between photons to measure the path in different paths. It is the application of the EPR principle, which leads to errors, to the unconditional incompleteness of quantum cryptography. However, an entanglement photon pair must be used in this method. However, definitive entanglement photon pairing is a challenge. It is also a limitation that two photons reaching the light splitter cannot be reliably measured.

The measurement-independent quantum cryptographic key distribution device and method according to an embodiment of the present invention can ensure the unconditional safety of the quantum mechanics in spite of the incomplete trap of the measurement device in the quantum cryptographic key distribution method.

The measurement independent quantum cryptography key distribution device and method according to an embodiment of the present invention is a new quantum completely different from the existing method to overcome the limitations of the quantum attack based on the trap of the measurement device in the existing quantum cryptography and to ensure unconditional security It can be implemented on the principle of cryptographic key distribution. In addition, despite using a classic laser light, the measurement-independent quantum cryptography key distribution apparatus and method according to an embodiment of the present invention may satisfy the quantum cryptography principle based on the uncertainty principle.

The measurement independent quantum cryptography key distribution apparatus and method according to an embodiment of the present invention avoids the use of quantized light or quantum entangled light, which is very difficult to implement, and can use laser pulses belonging to the classical region as cryptographic bits. In addition, the measurement independent quantum cryptography key distribution apparatus and method according to an embodiment of the present invention may use definite path selection by a superposition principle and phase difference of a Mach-Zehnder interferometer to satisfy the uncertainty principle. In addition, the measurement-independent quantum cryptography key distribution device and method according to an embodiment of the present invention, by employing a dual-Mach-Zehnder interferometer as a core device, reveals whether or not wiretap is revealed due to an attack signal change in key distribution based on two phase bases A quantum key distribution (QKD) can be initiated.

1 is a view showing an exemplary measurement independent quantum cryptography key distribution device of a phase-adjusted dual-Maha-Zehnder type according to an embodiment of the present invention. Referring to FIG. 1, the measurement independent quantum cryptography key distribution device 10 may include two transmission paths 109 of a transmitter 100, a receiver 120, and a Mach-Zehnder type.

Each of the transmitter 100 and the receiver 120 may include phase adjusters 106 and 113. The phase adjusters 106 and 113 may serve to determine an exit path of light according to the phase setting of light. On the other hand, the role sharing between the receiver and the sender may be changed.

The current RSA method of classical encryption and all proposed quantum encryption key distribution methods require only one path. Of course, classical passwords cannot be secured because unconditional security is impossible. Although quantum cryptography satisfies unconditional security in principle, it has already been proved in various quantum attack experiments that unconditional security is impossible due to the incompleteness of the photodetector. The only way to prevent this is to set the quantum bit error rate (QBER) low to ensure relative safety. However, since this is only due to the incompleteness of the detector, it is inevitably neutralized in front of a better attack method.

The measurement independent quantum encryption key distribution device 10 according to an embodiment of the present invention can achieve unconditional security even under all existing realistic conditions by using two transmission paths 109. These two transmission paths 109 are a core principle and an essential device. The physical laws for this are as follows.

The well-known Mach-Zehnder interferometer is identical to the double slit experiment conducted by Young in 1801. In this double slit experiment, the interference fringe is caused by two path differences and the basis is the coherence of the two lights. However, in this double slit experiment, the same interference pattern has been demonstrated by a single photon, a single atom, or a single molecule, and the physical interpretation of this is the inability to distinguish paths. That is, since one light grain cannot be divided into two, it is the essence of quantum optics that it is impossible to know which path it has followed. This applies not only to a single light grain, but also to a light bundle.

In FIG. 1, when one phase of '0'and'π' is applied to the phase adjuster (Z or Ψ) by Bob or Alice between the two transmission paths 109, this causes the two transmission paths 109 to be The passing light must have one of the phase differences of '0'or'π'. As will be described in detail below, the light passing through the Mach-Zehnder by this path difference selects one of two traveling directions, that is, E ₅ or E ₆ in FIG. 1, so that the receiver simply determines the phase of the transmitter by measurement. You can see if you have set

Now suppose an attacker can measure both paths unnoticed. As will be described below, it cannot be measured without being noticed by the laws of physics, but even so, it has no significant meaning in the present invention. In FIG. 1, since the light (E ₃ and E ₄ ) passing through the two paths 109 are originally split by the light shield 104 in one light (E ₁ ), the intensity is the same, but the phase is 90 degrees difference. Have Therefore, the determinant for the light shield (50/50 non-polarization, lossless) for the outputs (E ₅ , E ₆ ) and the inputs (E ₁ , 0) is as follows ([Output]=[BS][Input ]):

However, measuring the absolute phase of the light (E3, E4) on the path is not only possible without the reference light (E1), but also has no effect on the measurement intensity according to the phase, so the two attackers secretly measured The light intensity is always the same in all cases. That is, the attacker cannot know the phase of light set by the sender or receiver at all. This principle is a physical principle that appears when measuring in two transmission paths 109 of Mach-Zehnner implied by the measurement officer in the present invention.

As described above, the two phases 0 and can be replaced with digital encryption keys 0 and 1. This is used as a phase basis for distribution of cryptographic keys. In other words, it is impossible to distinguish between the set encryption keys 0 and 1 without measuring the phase in the path, so even if the measurement is perfectly possible, the attacker cannot distinguish the set phase. Therefore, unconditional security is guaranteed.

)에 의해 구해진다. 위상(

)에 따라 두 개의 출력경로 중 반드시 하나가 선택된다 (

).Lastly, being able to know the presence of an attacker by the laws of physics does not constitute the measurement itself without changing the phase of the measurement object, so any measurement attempt will affect the Mach gender or double slit interference pattern. At 1, the Mach-Zehnder output stage affects the measurement results of the two lights (E5, E6). Therefore, it is possible to know whether an attacker exists. The two lights at the Mach-Zehnder output using Equation 1 are as follows:

). Phase(

), one of the two output paths must be selected (

).

According to an embodiment of the present invention, an unconditional security of quantum cryptographic key distribution guaranteed in principle by quantum mechanics may allow an attacker to intervene due to realistic limitations, i.e., measurement errors due to incompleteness of the detector. Therefore, in all existing quantum cryptographic key distribution methods that cannot guarantee unconditional security, its practical limitations such as very low quantum bit rate, limited transmission distance, and conditional security, use the double paths Mach-Zehnder of the present invention. Can completely overcome. In addition, the measurement independent quantum cryptographic key distribution according to an embodiment of the present invention can provide an innovative principle, method, and apparatus configuration to achieve unconditional security under the same error condition. This is a limitation even for classical cryptography, where unconditional security is impossible in principle (for example, in the public key method), i.e., waste of computer resources that require hundreds of cryptographic bits to be difficult to decompose and difficult to process. To overcome with simple quantum optical laws and devices. Modern cryptography based on prime factor decomposition is helpless in quantum computers, but the present invention is irrelevant. In addition, since the coherent light is used as an encryption key, it can be applied to all classic paths such as satellites and wireless communication as well as existing optical communication lines, thus causing a revolutionary revolution in security that replaces not only classical cryptography but also conventional quantum cryptography.

2 is a detailed configuration diagram of a transmitting unit 100 and a receiving unit Alice 120 shown in FIG. 1 for application to an optical communication network. The transmitter (Bob) 100 may include a light source 101, a pulse device 102, a light shield 104, a photodetector 103, 105, 108, and a light phase modulator 106.

면 E6로

면 E5로 진행하게 된다. 따라서 수신부는 두 경로(A1, A2)에서 빛의 세기를 측정하는 것만으로도 송신부의 위상 설정 상태를 알 수 있다.3 is a general Mach-Zehnder interferometer of FIG. 1 and its calculation results. 3A is a diagram exemplarily showing calculation results of interference and visibility of a Mach-Zehnder interferometer. The two lights arriving at the receiver are already routed according to the phase setting.

With cotton E6

If you go to E5. Therefore, the receiving unit can know the phase setting state of the transmitting unit only by measuring the light intensity in the two paths A1 and A2.

Ei represents the amplitude of light i, and the square of the absolute value of the amplitude is the measurement by the detector. Example I0=|E1|2.

가 0과 에서 가시성(V5,6)은 각각 1과 -1의 최대/최소값을 각각 나타내어 최대 구분성을 보여준다. 여기서 가시성에 대한 정의는 E6의 측정값에서 E5의 측정값을 뺀 값을 그 두 합으로 나눈 값이다.

. 다시 말하면, 위상이

이면 E6만 살아남고,

면 E5만 살아남게 된다. 마하젠더 간섭계의 첫 번째 핵심원리를 보여준다(수학식 2 참조). 한편, 간섭에 있어서는 구분성이 없다(파선 참조). 측정은 수신부 광검출기 A1과 A2에 의해 수행될 수 있다.FIG. 3B is for visibility measured by an output terminal, that is, a receiver photodetector in FIG. 1. Phase modulator value of phase modulator

The visibility (V5,6) in A and 0 shows the maximum/minimum value of 1 and -1, respectively, to show the maximum distinction. Here, the definition of visibility is the value obtained by subtracting the measured value of E5 from the measured value of E6 divided by the sum of the two.

. In other words, the phase

If only E6 survives,

If only E5 will survive. Shows the first key principle of the Mach-Zehnder interferometer (see Equation 2). On the other hand, there is no distinction in interference (see broken lines). Measurement can be performed by the receiver photodetectors A1 and A2.

3C is a calculation result showing the second key principle of the Mach-Zehnder interferometer. By showing the same value in both phase-dependent interference and visibility, the inability to discriminate the measurement appears. This is the same as the historic Young's double slit experiment conducted in 1801, and the difference between the two paths creates an interference pattern. The key principle is that the light moving along the two paths cannot be distinguished from each other. This has already been demonstrated experimentally using single photons. In addition, the interference pattern disappears only by measuring either path of Mach-Zehnder (or Young's double slit), which is a key principle that characterizes the unconditional security of the present invention.

FIG. 4 is a diagram exemplarily showing the dual-Mach-Zehnder configuration shown in FIG. 1. Referring to FIG. 4, the transmitter (Bob) 110 may include a phase adjuster 106, and the receiver (Alice; 120) may include a phase adjuster 108.

FIG. 5 is a diagram embodying key distribution of measurement independent quantum cryptography according to an embodiment of the present invention. 5, B ₁ ~ B ₄ is a photodetector of the transmitter, A ₁ ~ A ₄ is a photodetector of the receiver. The M of the receiving unit Alice is a mirror, and the key transmitted by the transmitting unit Bob is automatically reflected to construct a dual Mach-Zehnder interferometer. In order to satisfy the dual-Mahzen gender configuration, the phase adjuster Ψ for the light reflected from the receiver is in the common Mach-Zehnder path, Ψ for the light transmitted from Alice to Bob, and Ζ for the light reflected by Bob. It can be adjusted to not apply. Here, the mirror M of the receiver may be replaced with a phase conjugate mirror. In a general environment, light traveling along two paths may have different phases added depending on the surrounding environment such as vibration, air flow, or temperature, and the phase conjugate mirror acts to compensate for the phase difference in light traveling in reverse.

를 선택하여 위상 조절기(106)에 인가하면, 마하젠더 간섭계로 들어온 레이저빛 펄스는 위상 조절되어 Alice로 전송될 수 있다. 도 3에서 설명했듯이, 이 위상 설정된 빛은 둘 중 하나의 방향으로만 출력되는데, 어느 쪽 경로든 수신된 빛은 각 경로의 끝에 있는 거울에 반사해 다시 Bob으로 향한다. 이제 Alice는 Bob이 했던 것처럼 반사된 빛에 무작위적으로 0과 π중 하나의 위상

를 선택하여 위상 조절기(108)를 통해 인가할 수 있다. 이렇게 두 개의 조합으로 Alice와 Bob에 의해 위상 설정된 빛은 위상이 동일하면, B₃(103)로 서로 반대면 B₄(107)에 의해 검출될 수 있다. 이에 대한 이중-마하젠더 행렬식은 다음과 같다.

.As described in FIG. 3, Bob is one of 0 and p arbitrarily

If selected and applied to the phase adjuster 106, the laser light pulse entering the Mach-Zehnder interferometer can be phase-adjusted and transmitted to Alice. As illustrated in FIG. 3, this phased light is output only in one of the two directions, and the received light in either path reflects in the mirror at the end of each path and goes back to Bob. Now Alice phases one of 0 and π randomly on the reflected light as Bob did.

It can be selected and applied through the phase adjuster 108. The light set in phase by Alice and Bob in the two combinations can be detected by B ₃ (103) and B ₄ (107) if they are opposite phases. The dual-Maha-Zehnder determinant is as follows.

.

From Equation 4, the results for each phase base combination are as follows. The result of this is the same matrix (B ₃ ) or inverse matrix (B ₄ ), which provides a theoretical framework for distinct and clear visibility to be described in FIG. 6.

. 숫자는 E_i에서 i. 여기서 동일행렬은

이고 역행렬은

이다.Accordingly, the distribution of measurement-independent quantum cryptographic cryptographic keys based on visibility according to the phase-base combination is summarized in the table below.

. The numbers are from E _i to i. Where the same matrix is

And the inverse matrix is

to be.

양자키로 설정될 수 있다. 그러므로, 도청자가 없다면 추가적인 경로 차가 발생하지 않기에 Bob과 Alice는 별다른 조치 없이 측정만으로 양자키를 분배할 수 있다. 한편, 기존 양자암호 키분배 방법들에서는 반드시 일반 경로(예를 들어 전화나 인터넷)를 통해 서로 어떠한 기저빛(키를 이루는 편광이나 위상)을 사용했는지 주고 받아야만 하는데, 이를 시프팅(sifting; 혹은 handshake)이라 부른다.As a result, Alice and Bob can only know what phase setting they have made with their own measurement results. Only for the same phase with each other (

Can be set with a quantum key. Therefore, without an eavesdropper, there is no additional path difference, so Bob and Alice can distribute the quantum key by measurement only without any action. On the other hand, in the existing quantum cryptography key distribution methods, it is necessary to send and receive what kind of base light (polarization or phase that forms a key) to each other through a general path (for example, a telephone or the Internet). ).

If an eavesdropper exists on the path, a measurement error occurs in both Alice and Bob according to the principle of quantum mechanics, and the measurement value is different. Accordingly, it is possible to know whether the wiretap exists. Although the eavesdropper has no way of knowing information about the key (phase) by measurement, it is meaningless, but in case of unknown information, bits due to errors are excluded from the key.

FIG. 6 shows the automatic encryption key generation by unconditional security and measurement as the calculation result of FIG. 5. First, FIGS. 6A and 6B are calculation results of interference and visibility measured in the Mach-Zehnder path 109 of FIG. 5. As already mentioned in Fig. 3c, it shows the inability to distinguish the phase basis in both interference and visibility.

Figure 6a is the result of the interference (I _7,8 ) for the combination of all phase values that can be modulated in the phase controller (Z) of the transmitter Bob and the phase controller (Ψ) of Alice, the phase basis (0,π) The combination of shows the same values for all four cases (indicated by dots, see Figure 6b). It is completely indistinguishable for visibility V _7,8 (see FIG. 6B ). This shows that it is not possible to distinguish the base value by measurement in the Mach-Zehnder interference path, which satisfies the unconditional security that is impossible in existing quantum codes due to detector measurement error. Of course, the Mach-Zehnder interferometer is a physical theory established in classical optics, so whether the light source is a single photon having a particle or a laser light having a wave nature is applied.

값에 대한

값은 0과 π 모든 조합에 있어

이면 V_B=-1을

면 V_B=+1을 나타내어 구분이 명료하고, 따라서, 측정만으로도 Alice는 Bob이 어떤 위상기저를 사용했는지, 그의 최초 설정된

위상에 의거 자동적으로 알 수 있다(도 8 참조).6C and 6D show interference and visibility of the measurement values of the photodetectors B ₃ (103) and B ₄ (107) after the optical signal modulated by Alice of the receiver reaches the transmitter Bob again. Unlike Figure 6a, the base

For value

The value is in any combination of 0 and π

V _B =-1

The face V _B =+1, so the distinction is clear, so even with the measurement alone, Alice used Bob's initial phase set

It can be determined automatically based on the phase (see Fig. 8).

If an attacker attempts to measure, in any case it affects the measure. The point in all cases of FIGS. 6A and 6C is, paradoxically, a measure of whether or not there is an attacker on the path. And its distinct clarity only depends on the sensitivity of the meter. Since the sensitivity of the current measuring instrument is sufficient to enable a measurement limit of 10 ^-12 W and a 10 ⁷ V/W photoelectric conversion efficiency, even a very small measurement displacement difference can be sufficiently detected. Incidentally, the quality of the base light E ₁ (temporal instability in intensity, phase, line width, etc.) used in the calculations of visibility measurement in FIGS. 3 and 6 is not a problem at all. The reason is the characteristics of the Mach-Zehnder interferometer. On the first path 109, the two lights E ₃ and E ₄ maintain perfect coherence regardless of laser quality, and the visibility at the output stage depends only on the relative intensity difference. Of course, this assumption is a condition that both Mach-Zehnder pathways are independent of the environment. This was successfully demonstrated in the 2017 Nobel Prize in Physics, LIGO gravitational field detection. Above all, it can be more fully guaranteed in the future multi-core fiber for implementing FIG. 2. For reference, the current optical fiber is a single core, but it is inevitable to switch to a multi-core optical fiber since it reaches saturation within several years. Lastly, the combination of the phase bases of Figs. 6A and 6C is not a measurement error of the transmitter or the receiver, but a measurement displacement that appears as an attempt to measure an attacker who has entered the path.

FIG. 7 is a diagram illustrating a configuration in which the general one-to-one encryption key distribution diagram of FIG. 1 is expanded from N to N. Unlike all quantum cryptography key distribution methods limited to one-to-one, the present invention is limited to wavelength converters (MUX/DeMUX), optical switches, optical amplifiers, etc. currently used in optical communication networks to utilize coherent light sources such as lasers as phase bases. Do not receive The reason is that the absolute phase changes naturally due to various optical components on the optical network, but the relative phase of the light passing through the two paths is constant. In particular, the use of optical amplifiers is strictly prohibited in the existing quantum cryptography key distribution method according to the principle of non-reproduction of quantum mechanics. Currently, there is no quantum repeater, so existing quantum cryptographic key distribution is vulnerable to long distance transmission over 100km.

8 is a flowchart exemplarily showing a key distribution algorithm for measurement-related quantum cryptography key distribution according to an embodiment of the present invention. 1 to 8, a measurement independent quantum cryptography key distribution method may be performed as follows.

Bob may select an arbitrary phase basis (φ {0, ð}) and transmit a phase-adjusted light pulse according to the selected phase basis to Alice (S110). Bob may convert the selected phase basis into a key and store the converted key in {x} (S120). For example, x {0, 1}, x = 0, if φ = 0; x = 1, if φ = ð.

Alice may store the visibility VA output from the photodetectors A1 and A2 in {y} (S130). For example, y = 0 if VA = 1; y = 1, if VA =-1; y = VA if VA ≠ ±1; {y} = {x}, except for VA ≠ ±1.

Alice selects an arbitrary phase basis (φ {0, ð}), is phase adjusted to the reflected light according to the selected phase basis, and can be automatically transmitted to Bob (S140).

Alice may convert the selected phase base into a key and store the converted key in {z} (S150). For example, z {0, 1}, z = 0, if φ = 0; z = 1, if φ = ð.

Alice may perform shifting to use the same thing as Bob as a key and store the result in {a} (S160). For example, a = y 0 if y-z = 0; a = D of y-z ≠0.

Bob may store the selected key in {w} based on the visibility VB detected from the photodetectors B3 and B4 (S170). For example, w = x if VB = -1; w = D if VB = 1; w = VB if VB ≠ ±1. At this time, {w} is effectively equal to {a}.

Bob may perform shifting to remove the error key and store the result in {b} (S180). For example, b = w 0 if w-x = 0; b = D of w-y ≠ 0; {w} = {a}, except for VB ≠ ±1.

S110 to S180 described above may be repeated N times. Thereafter, Alice and Bob disclose their error key (visibility is not ±1), and can remove the opposite error machine from their lists {a} and {b}. Thus, the final encryption key can be shared between Alice and Bob (S190).

The phase basis according to an embodiment of the present invention is the same for both Alice and Bob. The phase basis values are 0 and π. That is, since the key distribution is established for only two of the four combinations of these two values (see FIG. 6), the quantum bit rate (QBR) is 50%. On the other hand, for an attacker, the probability of guessing in each path is 50%, and the probability of guessing for the dual path is 25%, which is the same as that of BB84, a representative quantum cryptographic protocol. However, the attacker cannot determine the phase base value set by the measurement in any way, and since the measurement action itself leads to a change in visibility by the photodetector, the key distribution method of the present invention is the best in the existing quantum cryptographic key distribution method. The pitfalls of vulnerable photodetector imperfections can be completely overcome, and the quantum cryptographic key distribution, which was limited to quantized light, can be extended with a general laser. Therefore, since the quantum cryptographic key distribution method of the present invention can be applied to an existing optical communication network as it is, it can bring a revolutionary turning point to replace the classic cryptosystem, which is weak in security, at once. Finally, the table below describes an example of the algorithm for FIG. 8.

Party Order
Sequence One 2 3 4 5 6 7 8 9 10 set Alice 3 VA One -One -One One -One One One -0.5 ^* One -One Copy x: y 0 One One 0 One 0 0 -0.5 0 One

4

0 0 π π π 0 π π π 0 5

0 0 One One One 0 One One One 0

6 Sifting y: a 0 D One D One 0 D D D D

9 Final key 0 D One D One D ^** D D D D

Bob One

0 π π 0 π 0 0 π 0 π 2 Prepared key:

0 One One 0 One 0 0 One 0 One

7 VB -One One -One One -One -0.8 ^* One -One One One Copy A: w 0 D One D One -0.8 D One D D

8 Sifting w: b 0 D One D One D D One D D

9 Final key 0 D One D One D D D ^** D D

^* The red numbers may be caused by network errors or eavesdropping.

. Here D represents an error bit. D can be set to any different number, e.g., D=9 for a computing algorithm. ^** Only error bits are announced publically to discard the corresponding bit from the final key set

. Here D represents an error bit. D can be set to any different number, eg, D=9 for a computing algorithm.

참조).The above table is a case where n=10 is repeated in FIG. 8, a bold number is a measurement error due to an eavesdropper (FIG. 6C), and a bold D indicates that an error is extracted and removed in the last step of the algorithm. The length of the quantum key distributed between the final Alice and Bob is equal to 3 out of 10. If the eavesdropper is not involved, the maximum length is 50% of N (

Reference).

Steps and/or operations according to an embodiment of the present invention may be understood by one of ordinary skill in the art, in other order, or in parallel, or other embodiments for other epochs, etc. Can happen at the same time.

Depending on the embodiment, some or all of the steps and/or actions drive instructions, programs, interactive data structures, clients and/or servers stored in one or more non-transitory computer-readable media. At least some may be implemented or performed using one or more processors. The one or more non-transitory computer-readable media may illustratively be software, firmware, hardware, and/or any combination thereof. Also, the functionality of the "module" discussed herein may be implemented in software, firmware, hardware, and/or any combination thereof.

One or more non-transitory computer-readable media and/or means for implementing/performing one or more operations/steps/modules of embodiments of the present invention include application-specific integrated circuits (ASICs), standard integrated circuits, Controllers that perform appropriate instructions, including microcontrollers, and/or embedded controllers, field-programmable gate arrays (FPGAs), complex programmable logic devices (CPLDs), and the like. Does not.

Meanwhile, the above-described contents of the present invention are only specific embodiments for carrying out the invention. The present invention will include technical ideas that are abstract and conceptual ideas that can be utilized as future technologies, as well as the concrete and practical means available.

100: transmitting unit (Bob)
120: receiving unit (Alice)
101: light source (cw)
102: optical modulator
103: photodetector (B ₃ )
104: Light shield (non-polarized 50/50)
105: photodetector (B ₁ )
106: phase modulator (Ζ)
107: photodetector (B ₄ )
108: phase modulator (Ψ)
109: Mach gender path (optical fiber, free space, etc.)
110: photodetector (A ₄ )
111: photodetector (A ₂ )
112: photodetector (A ₁ )
113: photodetector (A ₃ )
M: Mirror
BS: Light shield (non-polarized 50/50)
I ₀ : Intensity of E ₁

Claims (18)

In the key distribution method of the measurement independent quantum cryptography device:
Generating an encryption key; And
And sharing the encryption key using a DOUBLE-Maha-Zehnder interferometer that satisfies unconditional security by using two different phase differences as the basis of each of the transmitter and receiver.
Further comprising the step of configuring the reciprocating path constituting the dual- Mach-Zehnder interferometer,
The dual Mach-Zehnder interferometer represents a dual path consisting of a Mach-Zehnder interferometer between the transmitter and the receiver,
The reciprocating path represents the dual path through which light comes and goes according to the encryption key generation. delete According to claim 1,
The method of claim 1, wherein any one of a single photon, entangled photon, and coherent light incident on the dual Mach-Zehnder interferometer is used as a light source. According to claim 1,
The method of claim 2, wherein the dual-Mach-Zehnder interferometer is extended with an encryption key distribution of N to N (N is a natural number). According to claim 1,
And a phase base pair applying the phase difference to key distribution. The method of claim 5,
Method characterized in that the key distribution is made by the phase basis. The method of claim 5,
And generating the phase basis. The method of claim 5,
And measuring the phase basis. The method of claim 8,
And detecting an attacker by measuring the phase base pair. The method of claim 8,
And generating a real-time two-dimensional quantum bit error rate (QBER) map by measuring the phase base pair. For measurement independent quantum cryptography key distribution devices:
Transmitter;
Receiver; And
A two-phase difference between the transmitter and the receiver includes a dual (DOUBLE) Mach-Zehnder interferometer that satisfies unconditional security.
Further comprising a reciprocating path constituting the dual- Mach-Zehnder interferometer,
The dual Mach-Zehnder interferometer represents a dual path consisting of a Mach-Zehnder interferometer between the transmitter and the receiver,
The reciprocating path is a device representing the dual path through which light is reciprocated according to the encryption key generation. The method of claim 11,
The dual-Mach-Zehnder interferometer is a device characterized in that any one of a single photon, entangled photons, and coherent light as a light source. The method of claim 11,
The dual-Mach-Zehnder interferometer further comprises a phase conjugate mirror. The method of claim 11,
Device characterized in that N to N cryptographic key distribution is configured. The method of claim 11,
Each of the transmitter and the receiver,
And a phase basis generator for generating any one of the different phases as a basis. The method of claim 15,
Each of the transmitter and the receiver,
And a phase basis measurement device for measuring the phase basis transmitted through the corresponding transmission path. The method of claim 16,
Each of the transmitter and the receiver,
And further comprising a phase basis distribution device for distributing the phase basis. The method of claim 17,
Apparatus characterized in that the phase difference is applied to key distribution based on an encryption key distribution algorithm.

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