KR101979328B1 - Communication apparatus and communication method for free-space quantum key distribution - Google Patents

Abstract

The present invention relates to a communication apparatus for use in a communication system for distributing a wireless quantum cryptographic key, the apparatus comprising: a plurality of light sources for generating a quantum signal having different polarization information; A control unit for determining a specific light source to generate a quantum signal to be transmitted to another communication device among the plurality of light sources; A plurality of optical splitters for passing a quantum signal generated from a specific light source determined by the controller to the other communication device; And when a quantum signal is transmitted from another communication apparatus to obtain polarization information of the quantum signal transmitted and received between the communication apparatus and the other communication apparatus by making the wavelength of the quantum signal generated from each of the plurality of light sources different, And a photon detector for detecting whether a quantum signal transmitted from the other communication apparatus is incident on the plurality of light sources through the light splitters.

Description

[0001] COMMUNICATION APPARATUS AND COMMUNICATION METHOD FOR FREE-SPACE QUANTUM KEY DISTRIBUTION [0002]

The present invention relates to the field of wireless quantum cryptography and, more particularly, to a communication apparatus for wireless quantum cryptography key distribution that prevents eavesdropping (hacking) from an external eavesdropper that may occur in a wireless quantum cryptography key distribution system. will be.

The quantum key distribution system is a system in which two communication devices, that is, a transmitting device (Alice) and a receiving device (Bob) distribute a quantum cryptographic key using a photon as a communication medium. In such a QKD system, when an eavesdropper (Eve) tries to tap (e.g., tapping a photon in transit), returning the photons observed by Heisenberg's uncertainty principle to a pre-observed quantum state The statistical value of the received data detected by the receiving apparatus changes. Therefore, the receiving apparatus can detect the presence or absence of eavesdropping by detecting this change.

The QKD system transmits and receives quantum signals between a transmitting device and a receiving device through a quantum channel, while a wireless quantum key distribution system transmits and receives quantum signals between a transmitting device and a receiving device through a free space channel. Specifically, the transmitting apparatus of the wireless quantum key distribution system includes a plurality of light sources that generate quantum signals having different polarizations, respectively, and the transmitting apparatus transmits quantum signals generated from a specific one of the plurality of light sources to the receiving apparatus , The receiving apparatus detects the quantum signal according to the polarization information of the quantum signal and then exchanges basis information to generate a key for each of the transmitting apparatus and the receiving apparatus.

US registered patent US 6,289,104

It is an object of the present invention to provide a communication apparatus for preventing a hacking attack of an eavesdropper for obtaining polarization information of a quantum signal transmitted from a transmitting apparatus in a wireless quantum cryptography key distribution system.

According to a first aspect of the present invention, there is provided a communication apparatus for use in a communication system for distributing a wireless quantum cryptographic key, the apparatus comprising: A plurality of light sources; A control unit for determining a specific light source to generate a quantum signal to be transmitted to another communication device among the plurality of light sources; A plurality of optical splitters for passing a quantum signal generated from a specific light source determined by the controller to the other communication device; And when a quantum signal is transmitted from another communication apparatus to obtain polarization information of the quantum signal transmitted and received between the communication apparatus and the other communication apparatus by making the wavelength of the quantum signal generated from each of the plurality of light sources different, And a photon detector for detecting whether a quantum signal transmitted from the other communication apparatus is incident on the plurality of light sources through the light splitters.

Preferably, the plurality of light sources may correspond to four light sources having polarizers for generating quantum signals having respective polarization information corresponding to vertical, horizontal, diagonal, and reverse angles.

Preferably, the photon detector is provided in each of the plurality of light sources to monitor whether or not there is a quantum signal incident on each light source.

Preferably, when the photon detector detects a quantum signal incident on the light source, the control unit may stop generating the quantum signal and transmit the quantum signal to the other communication apparatus, Can be transmitted.

According to a second aspect of the present invention, there is provided a communication apparatus for use in a communication system for distributing wireless quantum cryptography keys, the apparatus comprising: A plurality of light sources; A control unit for determining a specific light source to generate a quantum signal to be transmitted to another communication device among the plurality of light sources; A plurality of optical splitters for passing a quantum signal generated from a specific light source determined by the controller to the other communication device; And a quantum signal generated from the plurality of light sources and transmitted through the plurality of optical splitters to be transmitted to the other communication device, and wavelengths of quantum signals generated from the plurality of light sources are made different And a control unit for controlling the plurality of optical splitters in a direction toward the plurality of light sources through the plurality of optical splitters when the quantum signal is transmitted from another communication apparatus to obtain polarization information of the quantum signal transmitted / And an isolator that reflects the quantum signal transmitted from the other communication device.

Preferably, the plurality of light sources may correspond to four light sources having polarizers for generating quantum signals having respective polarization information corresponding to vertical, horizontal, diagonal, and reverse angles.

Preferably, the isolator may be provided at a transmission end where quantum signals generated from the plurality of light sources are transmitted to another communication device.

According to a third aspect of the present invention, there is provided a communication apparatus for use in a communication system for distributing a wireless quantum cryptographic key, the apparatus comprising: A plurality of light sources; And a control unit for determining a specific light source to generate a quantum signal to be transmitted to another communication apparatus among the plurality of light sources and controlling a wavelength of a quantum signal generated from each of the plurality of light sources, The polarization information of the quantum signal transmitted and received between the communication device and the other communication device through different wavelengths of the quantum signals generated from each of the plurality of light sources is transmitted by another communication device Not acquired; And a plurality of optical splitters for passing the quantum signal generated from the specific light source determined by the controller to the other communication device.

Preferably, the plurality of light sources may correspond to four light sources having polarizers for generating quantum signals having respective polarization information corresponding to vertical, horizontal, diagonal, and reverse angles.

Preferably, the controller controls the temperature of each of the plurality of light sources to adjust the wavelength of the quantum signal generated from each of the plurality of light sources.

As described above, according to the present invention, it is possible to prevent a hacking attack of an eavesdropper for acquiring polarization information of a quantum signal transmitted from a transmitting apparatus to a receiving apparatus, thereby maintaining a high level of security.

1 is a configuration diagram illustrating a communication system for wireless quantum cryptography key distribution according to the present invention.
2 is a block diagram illustrating an attack method of an eavesdropper that can occur in the communication system of FIG.
3 is a configuration diagram illustrating a communication system according to an embodiment of the present invention.
4 is a configuration diagram illustrating a communication system according to an embodiment of the present invention.
5 is a configuration diagram illustrating a communication system according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will be more apparent from the following detailed description taken in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification. &Quot; and / or " include each and every combination of one or more of the mentioned items.

Although the first, second, etc. are used to describe various elements, components and / or sections, it is needless to say that these elements, components and / or sections are not limited by these terms. These terms are only used to distinguish one element, element or section from another element, element or section. Therefore, it goes without saying that the first element, the first element or the first section mentioned below may be the second element, the second element or the second section within the technical spirit of the present invention.

Also, in each step, the identification code (e.g., a, b, c, etc.) is used for convenience of explanation, and the identification code does not describe the order of each step, Unless the order is described, it may happen differently from the stated order. That is, each step may occur in the same order as described, may be performed substantially concurrently, or may be performed in reverse order.

The terminology used herein is for the purpose of illustrating embodiments and is not intended to be limiting of the present invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. It is noted that the terms "comprises" and / or "comprising" used in the specification are intended to be inclusive in a manner similar to the components, steps, operations, and / Or additions.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions in the embodiments of the present invention, which may vary depending on the intention of the user, the intention or the custom of the operator. Therefore, the definition should be based on the contents throughout this specification.

1 is a configuration diagram illustrating a communication system for wireless quantum cryptography key distribution according to the present invention.

1, the communication system includes a first communication device 100 which is a transmitting device (so-called Alice) and a second communication device 200 which is a receiving device (so-called Bob), and the first communication device 100 And the second communication device 200 are connected via a wireless channel.

 Preferably, the first communication device 100 includes a first light source 111, a second light source 112, a third light source 113, and a fourth light source 114, a first light splitter 121, A light splitter 122, and a third light splitter 123. [ Here, the plurality of light sources 111 to 114 may be vertically (V), horizontally (H), diagonal (D), or diagonal through a polarizer (a structure shown by a black rectangle) (Hereinafter, referred to as a quantum signal) having a polarization of anti-diagonal (A), for example, the first light source 111 positions a polarizer perpendicular to the first polarizer, And the quantum signal generated from the light source 111 can have vertical polarization. The generated quantum signal is transmitted to the second communication device 200 through the third optical splitter 123 after passing through the first optical splitter 121 or the second optical splitter 122.

Preferably, the second communication device 200 includes a beam splitter (BS) 212, a first polarized beam splitter (PBS) 211, a second polarized beam splitter 213, (PC) 221 and 222, and a plurality of photodetectors (APDs) 231 to 234. The plurality of photodetectors (APD) Here, the optical splitter 212 separates the quantum signal received from the first communication device 100 into two paths, and the plurality of polarization beam splitters 211 and 213 are separated by the optical splitter 212 The movement path of the quantum signal is determined according to the polarization of the quantum signal so that the quantum signal is moved to the photodetector to be detected, and the polarization controllers 221 and 222 correct the changed polarization of the quantum signal. That is, the polarization of the quantum signal can be changed by an external environmental factor in the process of being transmitted from the first communication device 100 to the second communication device 200 through the wireless channel, and the polarization controllers 221 and 222 Thus, the polarization of the quantum signal changed in the transmission process is corrected. The plurality of photodetectors 231 to 234 can detect a quantum signal having polarized light corresponding to vertical (H), horizontal (V), diagonal (D), and reverse (A) directions, respectively. Further, the second communication device 200 can store and manage the information of each photodetector that detects the quantum signal, in association with the polarization information (H, V, D, A).

Hereinafter, with reference to FIG. 1, a process of distributing a quantum cryptographic key by a communication system for wireless quantum cryptography key distribution will be described.

The first communication apparatus 100 selects one of the light sources 111 to 114 and generates a quantum signal from the light source. More specifically, the control unit of the first communication device 100 is provided with a polarizer capable of generating polarized light to be transmitted to the second communication device 200 among the four polarized lights corresponding to V, H, D, and A A specific light source is operated, and a quantum signal generated from a specific light source has a specific polarization through a polarizer provided in front of the specific light source. That is, when it is desired to transmit the polarized light corresponding to D to the second communication device 200, the control unit operates the third light source 113, and the quantum signal generated from the third light source 113 transmits the polarizer So that the polarized light corresponding to D is obtained. Here, the control unit may be the main processor of the first communication device 100 that controls the operation of each configuration of the first communication device 100, or the first communication device 100 and the second communication device 200, (Or a computer) that controls the operations of the first and second communication devices 100 and 200, performs a protocol of cryptographic key distribution, and monitors eavesdropping by an eavesdropper .

The quantum signal generated by the specific light source is transmitted to the third optical splitter 123 through the first optical splitter 121 or the second optical splitter 122 and the quantum signal is transmitted through the third optical splitter 123 And then transmitted to the second communication device 200 through the wireless channel. That is, the quantum signals combined by the first through third optical splitters 121 through 123 are transmitted to the second communication device 200 through one wireless channel.

Next, the second communication device 200 detects the quantum signal to a specific one of the plurality of photodetectors 231 to 234 according to the polarization information of the quantum signal transmitted from the first communication device 100. [ Preferably, as a specific one of the first to fourth light sources 111 to 114 is operated in the first communication device 100, a quantum signal having a specific polarization is transmitted to the second communication device 200, When the detection of the quantum signal occurs in any one of the plurality of photodetectors 231 to 234 of the second communication device 200 according to the polarization of the second communication device 200, Based on the detected photodetector, it is possible to determine what polarization information the quantum signal transmitted from the first communication apparatus 100 has. Here, the control unit may be the main processor of the second communication device 100 that controls the operation of each configuration of the second communication device 200, or the first communication device 100 and the second communication device 200, (Or a computer) that is connected to the first communication device 100 and controls the operation of the first communication device 100 and the second communication device 200 and performs the protocol of encryption key distribution. Based on the result, a quantum cryptographic key can be shared between the first communication device 100 and the second communication device 200 by performing a predefined cryptographic key distribution protocol (e.g., BB84: Bennett Brassard 84) do.

More specifically, the first communication device 100 transmits a quantum signal generated from a specific light source and having a specific polarization to the second communication device 200, and the second communication device 200 transmits a quantum signal having a specific polarization to the second communication device 200 according to the polarization of the quantum signal. When a quantum signal is detected through a specific photodetector, only what basis is used is shared between the first communication device 100 and the second communication device 200. Here, the polarized light corresponding to the vertical (H) and horizontal (V) corresponds to the vertical basis, and the polarized light corresponding to the diagonal (D) and reverse (A) corresponds to the horizontal basis. Accordingly, the first communication device 100 generates a key using the polarization information and the base information of the quantum signal transmitted to the second communication device 200, and the second communication device 200 generates the key using the base information and the quantum signal And generates the key using the information of the detected photodetector.

In this process, the external communication device, that is, the eavesdropper can not generally know the polarization information of the quantum signal generated in the first communication device 100, so that the first communication device 100 and the second communication device 200, Can not be predicted.

2 is a block diagram illustrating an attack method of an eavesdropper that can occur in the communication system of FIG.

As described with reference to Fig. 1, as long as the polarization information of the quantum signal generated by the first communication device 100 can not be known, the information communicated between the first communication device 100 and the second communication device 200 Although it is impossible to eavesdrop on the outside, according to the method described below, it becomes possible to acquire the polarization information of the quantum signal generated in the first communication device 100, so that the first communication device 100 and the second communication device The information transmitted / received between the base station 200 and the base station 200 can be released.

2, an external communication device 300 (hereinafter referred to as a "third communication device") in a communication system for distributing a wireless quantum cryptographic key includes a first communication device 100 and a second communication device 200, And the third communication device 300 can grasp the quantum signal generated in the first communication device 100 and transmitted to the second communication device 200 using a device such as a lens therebetween, And generates a quantum signal having the corresponding polarization information, and transmits the generated quantum signal to the second communication device 200.

Preferably, the third communication device 300 includes a light source 310, a wavelength divider 320, a polarization beam splitter 330, and first to fourth light sources 341 to 344. Hereinafter, a method for identifying the polarization of the quantum signal generated by the first communication device 100 by the third communication device 300 will be described in detail. The configuration in which the third communication device 300 finds the polarization information of the quantum signal generated in the first communication device 100 and then transmits the quantum signal to the second communication device 200 will now be described with reference to FIG. The description of the second communication device 200 is the same as that of the quantum signal transmission method between the first communication device 100 and the second communication device 200, The configuration of the communication device 200 is the same as that of the communication device 200, and a description thereof will be omitted.

First, the plurality of light sources 111 to 114 provided in the first communication apparatus 100 are always kept at the same wavelengths of the quantum signals generated therefrom, and the wavelengths of the quantum signals are transmitted to the plurality of light sources 111 to 114 The first communication apparatus 100 maintains the same temperature of the plurality of light sources 111 to 114 and keeps the wavelength of the quantum signal generated in each of them uniformly I suppose.

That is, if the temperature of each of the plurality of light sources 111 to 114 is different and the wavelength of the quantum signal generated in each of the plurality of light sources 111 to 114 is different, the third communication apparatus 300 may measure the polarization of the quantum signal based on the wavelength of the quantum signal Predictable. Therefore, the third communication device 300 can change the temperature of each of the plurality of light sources 111 to 114 of the first communication device 100, thereby changing the polarization information of the quantum signal generated in the first communication device 100 . ≪ / RTI >

First, in order to change the temperature of each of the plurality of light sources 111 to 114 of the first communication device 100, the light source 310 of the third communication device 300 transmits a strong laser pulse having a specific polarization to the first To the communication device (100). The laser pulse transmitted from the third communication device 300 passes through the third optical splitter 123 of the first communication device 100 and passes through the first optical splitter 121 or the second optical splitter 122 To reach the light sources 111 to 114, respectively. Here, the laser pulse reaching each of the plurality of light sources 111 to 114 is divided into a plurality of light sources 111 to 114 in accordance with the polarization information of the laser pulse itself and the polarization information of each of the plurality of light sources 111 to 114 114, respectively. The plurality of light sources 111 to 114 have different temperature changes depending on the amounts of laser pulses passing through the light sources 111 to 114, respectively.

For example, when the light source 310 of the third communication device 330 transmits a laser pulse having vertical (H) polarization to the first communication device 100, the first light source 310 of the first communication device 100 The second light source 112 can pass the horizontal polarized light so that the laser light having the vertical polarized light is allowed to pass through 0% Since the three light sources 113 can pass the diagonal polarized light through 50% of the laser pulse having the vertically polarized light and the fourth light source 114 can pass the backward polarized light, it passes the laser pulse having the vertical polarized light 50% . Accordingly, the first light source 111 having passed the laser pulse 100% has the highest temperature, the third and fourth light sources 113 and 114 have the next highest temperature, and the second light source 112 ) Does not pass the laser pulse at all and therefore the temperature does not change.

According to the temperature change of each of the plurality of light sources 111 to 114, the plurality of light sources 111 to 114 generate quantum signals having different wavelengths. For example, the first light source 111 generates a quantum signal having a wavelength of 782 nm because the temperature is the highest, and the second light source 112 generates a quantum signal having a wavelength of 780 nm because there is no temperature change, And the four light sources 113 and 114 pass only 50% of the laser pulses, and thus can generate a quantum signal having a wavelength of 781 nm.

The quantum signal generated from the first communication device 100 is transmitted to the third communication device 300 and then divided into wavelengths by the wavelength divider 320. Then, the third communication device 300 can predict the polarization information based on the wavelength of the quantum signal transmitted from the first communication device 100, so that the quantum signal divided according to the wavelength is divided into the angular To the light source. Here, since the quantum signals generated from the third and fourth light sources 113 and 114 have the same wavelength, the quantum signals generated from the third and fourth light sources 113 and 114 are separated by the wavelength divider 320 The polarized beam splitter 330 is used to provide a quantum signal to each light source according to the polarization, that is, whether it is a diagonal polarization or a backward polarization. The quantum signal generated by the third light source 113 and having the diagonal polarization is reflected without being transmitted through the polarization beam splitter 330 and the quantum signal generated by the fourth light source 114, It can pass through the beam splitter 330, so that the polarization information of each quantum signal can be distinguished.

After that, the third communication device 300 acquires the polarization information of the quantum signal generated by the first communication device 100, and then transmits the quantum signal to the second communication device 100. [ That is, the third communication device 300 generates a quantum signal from any one of the first to fourth light sources 341 to 344 in accordance with the polarization information of the quantum signal generated in the first communication device 100 To the second communication device 200 through which the third communication device 300 can attempt to intercept the first communication device 100 and the second communication device 200. [

Therefore, when the third communication apparatus 300 transmits a laser pulse having a specific polarization to the first communication apparatus 100, the amount of laser pulses passing through each of the plurality of light sources 111 to 114 is different according to the polarization, The temperature difference of the plurality of light sources 111 to 114 is generated. That is, the third communication apparatus 300 can predict the polarization of the quantum signal generated from the first communication apparatus 100 by using the characteristic of the wavelength change according to the temperature change of the plurality of light sources 111 to 114 .

3 is a configuration diagram illustrating a communication system according to an embodiment of the present invention.

Referring to FIG. 3, a communication system for wireless quantum cryptography key distribution for preventing an eavesdropping method that can be performed by the third communication device 300 illustrated in FIG. 2, includes a first communication device 100, The second light source 112, the third light source 113, the fourth light source 114, the first light splitter 121, the second light splitter 122, the third light splitter 123, A plurality of circulators C, a plurality of photon detectors 131 to 134, and a control unit (not shown). Here, the plurality of circulators C are devices for separating the ports through which the signals pass. The quantum signals generated by the plurality of light sources 111 to 114 are transmitted through the circulator C in the direction of the light splitters And the laser pulses generated in the light source 310 of the third communication device 300 can move in the direction of the detectors through the circulator C. [ The configuration of the second communication device 200 is the same as that of the second communication device 200 shown in Fig. The process of distributing the quantum cryptography key performed in the communication system of FIG. 3 is the same as or similar to the process of distributing the quantum cryptography key described with reference to FIG. 1, and therefore, detailed description of the same or similar parts as those described in FIGS. The description is omitted. Hereinafter, a process of defending an eavesdropper's attack for acquiring polarization information of a quantum signal generated in the first communication apparatus 100 performed in the communication system of FIG. 3 will be described.

Irrespective of the process of distributing the quantum cryptographic keys performed between the first communication device 100 and the second communication device 200, the plurality of photon detectors 131-134 of the first communication device 100 may comprise a plurality of And detects a quantum signal incident in the direction of the plurality of light sources 111 to 114 through the light dividers 121 to 123. Preferably, the photon detector is provided in each of the plurality of light sources 111 to 114 together with the circulator C, and when there is a quantum signal incident in the direction of each light source, the quantum signal is transmitted to the circulator C The photon detector can monitor in real time whether there is a quantum signal incident on each light source.

Preferably, the light source 310 of the third communication system 300 transmits a strong laser pulse having a specific polarization to the first communication device 100 so that the plurality of light sources 111 to 114 A plurality of photon detectors 131 to 134 provided in each of the plurality of light sources 111 to 114 of the first communication apparatus 100 is incident on the plurality of light sources 111 to 114 The first communication device 100 immediately stops transmitting the quantum signal to the second communication device 200 and the second communication device 200 detects the presence of the third communication device (eavesdropper) And the like. That is, when a laser pulse is detected through any one of the photodetectors 131 to 134, the quantum key distribution between the first communication device 100 and the second communication device 200 is immediately stopped, The interruption of distribution of the quantum key is maintained until a communication device (eavesdropper) is not present.

That is, the communication system shown in Fig. 3 detects whether or not the laser pulse generated from the eavesdropper's third communication system is transmitted to the first communication apparatus 100, and then passes through each of the plurality of light sources 111 to 114 And monitors whether or not a temperature change of a plurality of light sources 111 to 114 by the eavesdropper occurs.

4 is a configuration diagram illustrating a communication system according to an embodiment of the present invention.

Referring to FIG. 4, a communication system for wireless quantum cryptography key distribution for preventing an eavesdropping method that can be performed by the third communication apparatus 300 described in FIG. 2, the first communication apparatus 100 includes a first The second light source 112, the third light source 113, the fourth light source 114, the first light splitter 121, the second light splitter 122, the third light splitter 123, An isolator 140, and a control unit (not shown in the figure). The configuration of the second communication device 200 is the same as that of the second communication device 200 shown in Fig. The process of distributing the quantum cryptography key performed in the communication system of FIG. 4 is the same as or similar to the process of distributing the quantum cryptography key described with reference to FIG. 1, and therefore, a detailed description of the same or similar parts The description is omitted. Hereinafter, a process of defending an eavesdropper's attack for acquiring polarization information of a quantum signal generated in the first communication apparatus 100 performed in the communication system of FIG. 4 will be described.

Preferably, the isolator 140 is configured to transmit signals only in one direction, and is generated by the plurality of light sources 111 to 114 of the first communication apparatus 100, 123 to the second communication device 200 and transmits the signal in the opposite direction to the first communication device 100 through the plurality of optical dividers 121 to 123 and the plurality of A signal incident in the direction toward the light sources 111 to 114 can be reflected without passing through. That is, the light is generated from any one of the plurality of light sources 111 to 114 of the first communication device 100 and is transmitted to the second communication device 200 through the plurality of light dividers 121 to 123 The signal is transmitted from the transmitting end of the first communication device 100 to the second communication device 200 through the isolator 140.

Preferably, regardless of the process of distributing the quantum cryptographic keys performed between the first communication device 100 and the second communication device 200, the isolator 140 of the first communication device 100 may communicate with the first communication device 100 100 and the quantum signal is incident on the plurality of light sources 111 to 114 through the plurality of light splitters 121 to 123, And reflects the signal.

4, when the light source 310 of the third communication system 300 generates and transmits a strong laser pulse to the first communication device 100, the transmission of the first communication device 100 And corresponds to a method of reflecting the laser pulse at the transmission end of the first communication device 100 so that the laser pulse can not be received by the first communication device 100 by the isolator 140 provided at the first communication device 100. [ That is, the laser pulse transmitted from the third communication system 300 does not reach the plurality of light sources 111 to 114, so that no temperature change occurs.

5 is a configuration diagram illustrating a communication system according to an embodiment of the present invention.

Referring to FIG. 5, a communication system for wireless quantum cryptography key distribution for preventing an eavesdropping method that can be performed by the third communication apparatus 300 illustrated in FIG. 2 includes a first communication device 100, A first light splitter 111, a second light source 112, a third light source 113 and a fourth light source 114, a first light splitter 121, a second light splitter 122, a third light splitter 123, And a control unit (not shown in the figure). The configuration of the second communication device 200 is the same as that of the second communication device 200 shown in Fig. Since the process of distributing the quantum cryptography key performed in the communication system of FIG. 5 is the same as or similar to the process of distributing the quantum cryptography key described with reference to FIG. 1, detailed description of the same or similar parts as those described in FIGS. The description is omitted. Hereinafter, a process of defending an attack by an eavesdropper for acquiring polarization information of a quantum signal generated in the first communication apparatus 100 performed in the communication system of FIG. 5 will be described.

Preferably, the control unit of the first communication device 100 can select a particular light source to generate the quantum signal transmitted to the second communication device 200 of the plurality of light sources 111 to 114, The wavelength can be controlled. Here, the function of selecting a specific light source and the function of controlling the wavelength may be separated, and the function of controlling the wavelength may be performed through a separate wavelength controller. Hereinafter, the case where the wavelength of the quantum signal generated in the specific light source is controlled through the wavelength controller will be described.

The control unit of the first communication system 100 selects a specific light source to generate a quantum signal to be transmitted to the second communication device 200 out of the plurality of light sources 111 to 114 that generate quantum signals having different polarization information When a specific light source is determined, the wavelength control unit controls the wavelength of the quantum signal generated from the specific light source. Alternatively, the wavelength controller can maintain a state in which the wavelength of the quantum signal generated from each light source is randomly changed, and in this state, a specific light source can be selected through the control unit. Here, the method of changing the wavelength of the quantum signal at random is not limited to the embodiment described below, and various methods can be applied.

In one embodiment, the wavelength controller may adjust the wavelength of the quantum signal by controlling the temperature of the particular light source. That is, the quantum signals generated in the first communication system 100 do not have the same wavelength but have different wavelengths from generation. That is, the third communication device 300 transmits laser pulses to the first communication device 100 to change the temperature of the plurality of light sources 111 to 114, and then changes the wavelength of the quantum signal generated in each light source Even if the wavelengths of the quantum signals themselves generated from the original plurality of light sources 111 to 114 are different from each other, it is difficult for the third communication apparatus 300 to predict the polarization information according to the change in wavelength.

In other words, since the communication system shown in FIG. 5 generates a quantum signal having a different wavelength from the beginning, even if the laser pulse generated from the third communication system 300 of the eavesdropper is transmitted to the first communication apparatus 100, It is a way to prevent eavesdroppers from acquiring polarization information because the change can not be predicted.

Such a communication method for a wireless quantum cryptography key distribution system may be implemented in an application or may be implemented in the form of program instructions that may be executed through various computer components and recorded on a computer readable recording medium. The computer-readable recording medium may include program instructions, data files, data structures, and the like, alone or in combination. Program instructions that are recorded on a computer-readable recording medium may be those that are specially designed and constructed for the present invention and are known and available to those skilled in the art of computer software.

Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tape, optical recording media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those generated by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. A hardware device may be configured to operate as one or more software modules to perform processing in accordance with the present invention, and vice versa.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It should be understood that various modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention.

In this specification, both the invention and the method invention are explained, and the description of both inventions can be supplemented as necessary.

100: first communication device
111: first light source 112: second light source
113: third light source 114: fourth light source
121: first optical splitter 122: second optical splitter
123: third optical splitter 131, 132, 133, 134: detector
140: Isolator 150: Wavelength controller
200: second communication device
211: first polarization beam splitter 212:
213: Second polarized beam splitter 221, 222: Polarization controller
231: first photodetector 232: second photodetector
233: third photodetector 234: fourth photodetector
300: third communication device
310: light source 320: wavelength splitter
341: first light source 342: second light source
343: third light source 344: fourth light source

Claims (10)

A communication device connected to another communication device via a wireless channel, the communication device being used in a communication system for distributing a wireless quantum cryptographic key,
A plurality of light sources for generating quantum signals having different polarization information;
A control unit for determining a specific light source to generate a quantum signal to be transmitted to another communication device among the plurality of light sources;
A plurality of optical splitters for passing a quantum signal generated from a specific light source determined by the controller to the other communication device; And
When a quantum signal is input by an external communication device attempting to intercept, the amount of light passing through each of the plurality of light sources varies according to polarization, and polarization information of the quantum signal is obtained using the characteristic of the wavelength Wherein the photon detectors are provided in each of the plurality of light sources so as to detect whether a quantum signal transmitted from an external communication apparatus is incident on the plurality of light sources through the light splitters, And monitors whether or not there is a quantum signal incident on each of the light sources from the external communication apparatus.
2. The apparatus of claim 1, wherein the plurality of light sources
And a polarizer for generating a quantum signal having respective polarization information corresponding to vertical, horizontal, diagonal, and reverse angles, respectively.
delete The apparatus of claim 1,
When the photon detector detects a quantum signal incident on the light source from the external communication device, generates a quantum signal and stops transmitting the quantum signal to the other communication device, and informs the other communication device of information To the communication device.
A communication device connected to another communication device via a wireless channel, the communication device being used in a communication system for distributing a wireless quantum cryptographic key,
A plurality of light sources for generating quantum signals having different polarization information;
A control unit for determining a specific light source to generate a quantum signal to be transmitted to another communication device among the plurality of light sources;
A plurality of optical splitters for passing a quantum signal generated from a specific light source determined by the controller to the other communication device; And
A quantum signal generated from the plurality of light sources and transmitted through the plurality of optical splitters is transmitted to the other communication device, and a wavelength of a quantum signal generated from each of the plurality of light sources is made different When a quantum signal is transmitted from an external communication device to acquire polarization information of a quantum signal transmitted and received between the communication device and another communication device and attempts to intercept it, And an isolator that reflects the quantum signal transmitted from the external communication device.
6. The apparatus of claim 5, wherein the plurality of light sources
And a polarizer for generating a quantum signal having respective polarization information corresponding to vertical, horizontal, diagonal, and reverse angles, respectively.
6. The apparatus of claim 5, wherein the isolator
And a quantum signal generated from the plurality of light sources is provided to a transmission terminal through which the quantum signal is transmitted to another communication apparatus.
A communication device connected to another communication device via a wireless channel, the communication device being used in a communication system for distributing a wireless quantum cryptographic key,
A plurality of light sources for generating quantum signals having different polarization information;
A control unit for determining a specific light source to generate a quantum signal to be transmitted to another communication apparatus among the plurality of light sources and controlling a wavelength of a quantum signal generated from each of the plurality of light sources; And
And a plurality of optical splitters for passing a quantum signal generated from the specific light source determined by the controller to the other communication device,
When a quantum signal is input by an external communication device attempting to intercept, the amount of light passing through each of the plurality of light sources varies according to polarization, and polarization information of the quantum signal is obtained using the characteristic of the wavelength The control unit controls the other wavelength values to be random at the time of generation of the quantum signal so that the quantum signal from the external communication apparatus is different from the quantum signal generated from each of the plurality of light sources The wavelength change can not be predicted even when the wavelength characteristic of the incident light is utilized, thereby preventing the eavesdropper from acquiring the polarization information.
9. The apparatus of claim 8, wherein the plurality of light sources
And a polarizer for generating a quantum signal having respective polarization information corresponding to vertical, horizontal, diagonal, and reverse angles, respectively.
9. The apparatus of claim 8, wherein the control unit
Wherein the wavelength of the quantum signal generated from each of the plurality of light sources is controlled by controlling the temperature of each of the plurality of light sources.

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