Communication system, transmitting device, receiving device, processing method, and program

Abstract

To provide a communication system that can provide secure communication as optical communication.SOLUTION: A communication system comprises a transmission device and a reception device. The transmission device comprises: synchronization means for synchronizing the reception device with the time; control means for controlling encryption of a light signal based upon a protocol set for every plurality of periods that the time indicates; generation means for generating a light signal, encrypted in every plurality of periods, under the control of the control means; and transmission means for transmitting the light signal, encrypted in one of the plurality of periods, to the reception device in the one period. The reception device comprises: synchronization means for synchronizing the transmission device with the time; reception means for receiving the light signal, encrypted in the one period, in the one period; conversion means for converting the encrypted light signal received by the reception means into an electric signal; and decryption means for decrypting the electric signal based upon a protocol set in every plurality of periods.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a communication system, a transmitting device, a receiving device, a processing method, and a program. [Background technology]

[0002] With the spread of computers and networks, communications are becoming more prevalent in a variety of fields. The data handled in such communications is often large, and high-speed communications are desired. For this reason, optical communications are increasingly being used in, for example, submarine cables and inter-satellite communications. Patent Document 1 discloses a related technology, which is an optical communications system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-136489 Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, cyber attacks have been increasing, and there is a demand for secure communications. This demand is also growing for optical communications, which are capable of high-speed communications. Therefore, there is a demand for technology that enables secure communication in optical communications.

[0005] Each aspect of the present disclosure aims to provide a communication system, a transmitting device, a receiving device, a processing method, and a program that can solve the above-mentioned problems. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, according to one aspect of the present disclosure, a communication system is a communication system comprising a transmitting device and a receiving device, wherein the transmitting device comprises a synchronization means for synchronizing time with the receiving device, a control means for controlling encryption of an optical signal based on rules set for each of a plurality of periods indicated by the time, a generation means for generating an encrypted optical signal for each of the plurality of periods based on control by the control means, and a transmitting means for transmitting the encrypted optical signal to the receiving device during one of the plurality of periods, and the receiving device comprises a synchronization means for synchronizing time with the transmitting device, a receiving means for receiving the encrypted optical signal during the one period, a conversion means for converting the encrypted optical signal received by the receiving means into an electrical signal, and a decryption means for decrypting the electrical signal based on rules set for each of the plurality of periods.

[0007] In order to achieve the above object, according to another aspect of the present disclosure, a processing method is a processing method executed by a communication system including a transmitting device and a receiving device, wherein the transmitting device performs the following: synchronizes time with the receiving device; controls encryption of an optical signal based on rules set for each of a plurality of periods indicated by the time; generates an encrypted optical signal for each of the plurality of periods based on the control; and transmits the encrypted optical signal to the receiving device in one of the plurality of periods; and the receiving device performs the following: synchronizes time with the transmitting device; receives the encrypted optical signal in the one period; converts the received encrypted optical signal into an electrical signal; and decrypts the electrical signal based on rules set for each of the plurality of periods.

[0008] In order to achieve the above object, according to another aspect of the present disclosure, a transmitting device comprises a synchronization means for synchronizing time with a receiving device with which communication is to be performed, a control means for controlling encryption of an optical signal based on rules set for each of a plurality of periods indicated by the time, a generation means for generating an encrypted optical signal for each of the plurality of periods based on control by the control means, and a transmission means for transmitting the encrypted optical signal to the receiving device during one of the plurality of periods.

[0009] In order to achieve the above object, according to another aspect of the present disclosure, a processing method includes synchronizing time with a receiving device that is a communication target, controlling encryption of an optical signal based on rules set for each of a plurality of periods indicated by the time, generating an encrypted optical signal for each of the plurality of periods based on the control, and transmitting the encrypted optical signal to the receiving device during one of the plurality of periods.

[0010] In order to achieve the above object, according to another aspect of the present disclosure, a program causes a computer to synchronize time with a receiving device with which communication is to be performed, control encryption of an optical signal based on rules set for each of multiple periods indicated by the time, generate an encrypted optical signal for each of the multiple periods based on the control, and transmit the encrypted optical signal to the receiving device during one of the multiple periods.

[0011] In order to achieve the above object, according to another aspect of the present disclosure, a receiving device includes a synchronization means for synchronizing time with a transmitting device with which the receiving device is communicating, a receiving means for receiving an optical signal encrypted by the transmitting device during one of a plurality of periods indicated by the time, a conversion means for converting the encrypted optical signal received by the receiving means into an electrical signal, and a decoding means for decrypting the electrical signal based on rules set for each of the plurality of periods.

[0012] In order to achieve the above object, according to another aspect of the present disclosure, a processing method includes synchronizing time with a transmitting device with which communication is to be performed, receiving an optical signal encrypted by the transmitting device during one of a plurality of periods indicated by the time, converting the received encrypted optical signal into an electrical signal, and decrypting the electrical signal based on rules set for each of the plurality of periods.

[0013] In order to achieve the above object, according to another aspect of the present disclosure, a program causes a computer to synchronize time with a transmitting device with which communication is to be performed, receive an optical signal encrypted by the transmitting device during one of multiple periods indicated by the time, convert the received encrypted optical signal into an electrical signal, and decrypt the electrical signal based on rules set for each of the multiple periods. [Effects of the Invention]

[0014] According to each aspect of the present disclosure, secure communication can be achieved in optical communication. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of a communication system according to an embodiment of the present disclosure. [Figure 2] FIG. 10 is a diagram illustrating an example of a rule according to an embodiment of the present disclosure. [Figure 3] 10A and 10B are diagrams illustrating an example of a multi-bit signal for each unit time output by a light source device according to another embodiment of the present disclosure. [Figure 4] FIG. 10 is a diagram illustrating an example of a communication processing flow according to an embodiment of the present disclosure. [Figure 5] FIG. 1 is a diagram illustrating an example of a minimum configuration of a communication system according to an embodiment of the present disclosure. [Figure 6] FIG. 10 is a diagram illustrating an example of a processing flow of a communication system with a minimum configuration according to an embodiment of the present disclosure. [Figure 7]FIG. 1 is a schematic block diagram illustrating the configuration of a computer according to at least one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, the embodiments will be described in detail with reference to the drawings. <Embodiment> (Communication System Configuration) A communication system 1 according to an embodiment of the present disclosure will be described with reference to the drawings. The communication system 1 is a system that encrypts an optical signal of plaintext (original data) to be transmitted and decrypts an optical signal of received data into plaintext based on a predetermined protocol. An example of communication modulation in the communication system 1 is binary intensity modulation.

[0017] Fig. 1 is a diagram illustrating an example of a configuration of a communication system 1 according to an embodiment of the present disclosure. As shown in Fig. 1, the communication system 1 includes a transmitting device 10, a receiving device 20, and a transmission path 30. The transmitting device 10 and the receiving device 20 are connected to each other via the transmission path 30 so that they can communicate with each other. An example of the transmission path 30 is an optical fiber.

[0018] The transmitting device 10 is a device that generates an optical signal in which plaintext is encrypted, and transmits the generated optical signal to the receiving device 20 via a transmission path 30. As shown in Fig. 1, the transmitting device 10 includes a synchronizing device 101 (an example of a synchronizing means), a memory device 102, an input device 103, a processing device 104 (an example of a control means), a light source device 105 (an example of a generating means), and a multiplexer 106 (an example of a transmitting means).

[0019] The synchronization device 101 synchronizes the time at the transmitting device 10 with the time at the receiving device 20. For example, the synchronization device 101 receives radio waves indicating the time generated based on the time of an atomic clock, and synchronizes its own time to the time indicated by the received radio waves. Furthermore, the synchronization device 201 (described later) provided in the receiving device 20 receives radio waves indicating the time generated based on the time of an atomic clock, and synchronizes its own time to the time indicated by the received radio waves. In this way, the time at the transmitting device 10 and the time at the receiving device 20 can be synchronized.

[0020] The storage device 102 stores various information necessary for the processing performed by the transmitting device 10. FIG. 2 is a diagram illustrating an example of the protocol TBL1 according to an embodiment of the present disclosure. For example, the storage device 102 stores the protocol TBL1 indicating the relationship between each unit time, which is indicated as the time from one time to another, and the frequency of the optical signal used in each unit time. In the example of the protocol TBL1 illustrated in FIG. 2, the storage device 102 stores the protocol TBL1 including the relationship between each unit time and the frequency of the optical signal used in each unit time, as well as the light source and light receiving element corresponding to that frequency. In the protocol TBL1 illustrated in FIG. 2, each unit time is associated with the frequency of the optical signal, the light source, and the light receiving element.

[0021] The input device 103 receives information to be transmitted from the transmitting device 10 to the receiving device 20. Examples of the input device 103 include a keyboard, a mouse, and a touch panel.

[0022] The processing device 104 controls the light emission of the light source device 105 based on the protocol TBL1 to generate an encrypted optical signal, which is an optical signal corresponding to the information received by the input device 103. For example, the processing device 104 acquires information indicating the protocol TBL1 from the storage device 102. The processing device 104 also acquires information indicating a time from the synchronization device 101. The processing device 104 identifies the time in the information acquired from the synchronization device 101. The processing device 104 identifies which unit of time the identified time is included in the acquired protocol TBL1, and identifies the frequency of the optical signal to be used in that unit of time. The processing device 104 then controls the light emission of light sources 105a1, 105a2, 105a3, ..., 105an in the light source device 105, which will be described later, so that the information received by the input device 103 is output as an optical signal with the identified frequency. Hereinafter, the light sources 105a1, 105a2, 105a3, ..., 105an will be collectively referred to as light source 105a.

[0023] For example, if the rule TBL1 is the rule shown in FIG. 2 and the time indicated by the information acquired by the processing device 104 from the synchronizer 101 is equal to or greater than time t1 and less than time t2, the processing device 104 specifies unit time T1 in rule TBL1 shown in FIG. 2 and specifies frequency 1 of the optical signal associated with the specified unit time T1. The processing device 104 then controls the light emission of the light source 105a1 capable of outputting light of the specified frequency 1 so that an optical signal of that frequency is output. Furthermore, if the time indicated by the information acquired by the processing device 104 from the synchronizer 101 is equal to or greater than time t2 and less than time t3, the processing device 104 specifies unit time T2 in rule TBL1 shown in FIG. 2 and specifies frequencies 2 and n of the optical signal associated with the specified unit time T2. The processing device 104 then controls the light emission of the light sources 105a2 and 105an capable of outputting light of that frequency so that an optical signal of the specified frequency 2 and n is output. Furthermore, if the time indicated by the information acquired by the processing device 104 from the synchronization device 101 is equal to or greater than time t3 and less than time t4, the processing device 104 specifies unit time T3 in accordance with rule TBL1 shown in FIG. 2 and specifies frequencies 2 and 3 of the optical signal associated with the specified unit time T3. The processing device 104 then controls the light emission of light sources 105a2 and 105a3 capable of outputting light of the specified frequencies 2 and 3 so that optical signals of those frequencies are output. Furthermore, if the time indicated by the information acquired by the processing device 104 from the synchronization device 101 is equal to or greater than time t4 and less than time t5, the processing device 104 specifies unit time T4 in accordance with rule TBL1 shown in FIG. 2 and specifies frequency n of the optical signal associated with the specified unit time T4. The processing device 104 then controls the light emission of light source 105an capable of outputting light of that frequency so that an optical signal of the specified frequency n is output. Furthermore, if the time indicated by the information acquired by the processing device 104 from the synchronization device 101 is equal to or greater than time t5 and less than time t6, the processing device 104 identifies the unit time T5 in the rule TBL1 shown in Fig. 2 and identifies the frequencies 1, 2, and n of the optical signal associated with the identified unit time T5. Then, the processing device 104 controls the light emission of the light sources 105a1, 105a2, and 105an that can output light of the identified frequencies 1, 2, and n so that the optical signals of the identified frequencies 1, 2, and n are output.

[0024] The processing device 104 may control the light sources 105a corresponding to the frequencies of the optical signals not used in that unit time to emit light randomly (i.e., emit light as a dummy signal). For example, in the example shown here, the processing device 104 may randomly emit light from light sources other than light source 105a1 during unit time T1, randomly emit light from light sources other than light sources 105a2 and 105an during unit time T2, randomly emit light from light sources other than light sources 105a2 and 105a3 during unit time T3, randomly emit light from light sources other than light source 105an during unit time T4, and randomly emit light from light sources other than light sources 105a1, 105a2, and 105an during unit time T5. In the example shown in FIG. 1, the dashed line portion of the signal output by the light source device 105 is an encrypted signal, and the solid line portion is a dummy signal. The output signal of the light source device 105 shown in FIG. 1 is an example in which the light source device 105 outputs a 1-bit signal per unit time. In other embodiments, the light source device 105 may output a multi-bit signal per unit time. FIG. 3 is a diagram illustrating an example of a multi-bit signal per unit time output by the light source device 105 according to another embodiment of the present disclosure. The light source device 105 according to another embodiment of the present disclosure may transmit, for example, three bits of data per unit time, as shown in FIG. 3. In this case, encrypted signals and dummy signals can be arbitrarily combined per unit time. This enables more secure communication than when either a one-bit encrypted signal or a one-bit dummy signal is transmitted per unit time. Furthermore, increasing the proportion of encrypted signals can increase communication capacity.

[0025] The light source device 105 generates an optical signal generated (i.e., encrypted) based on protocol TBL1 under the control of the processing device 104. As shown in FIG. 1, the light source device 105 includes light sources 105a1, 105a2, 105a3, . . . , 105an. Each of the light sources 105a emits light at one of the multiple frequencies specified in protocol TBL1. Before starting communication between the transmitting device 10 and the receiving device 20, the transmitting device 10 and the receiving device 20 share common information including protocol TBL1 that enables decryption of encrypted signals, such as whether to output a 1-bit signal or a multi-bit signal in each unit time of communication at each time point, and, if a 1-bit signal is output, what logic, such as logical sum, exclusive logical sum, or logical product, the signal should be expressed according to. This information is determined in advance by some means (for example, by using another highly confidential communication device or exchanging information via mail such as paper). The timing at which each of the light sources 105a emits light is controlled by the processing device 104 in accordance with the common information.

[0026] In addition, when transmitting a multi-bit signal within each unit time, the rule TBL1 may include information indicating which of the multi-bit signals within each unit time should be encrypted signals and which should be dummy signals.

[0027] The multiplexer 106 multiplexes a plurality of optical signals with different wavelengths output from the light source device 105. The multiplexer 106 transmits the multiplexed optical signal to the receiving device 20 via the transmission path 30.

[0028] The receiving device 20 is a device that generates plaintext by decrypting an encrypted optical signal based on the protocol TBL1. As shown in Fig. 1, the receiving device 20 includes a synchronization device 201 (an example of a synchronization means), a storage device 202, an output device 203, a processing device 204 (an example of a decryption means), a light receiving device 205 (an example of a conversion means), and a demultiplexer 206 (an example of a receiving means).

[0029] The synchronization device 201 matches the time at the receiving device 20 with the time at the transmitting device 10. For example, the synchronization device 201 receives radio waves indicating the time generated based on the time of an atomic clock, and synchronizes its own time to the time indicated by the received radio waves. As described above, the synchronization device 101 provided in the transmitting device 10 receives radio waves indicating the time generated based on the time of an atomic clock, and synchronizes its own time to the time indicated by the received radio waves, so that the time at the receiving device 20 and the time at the transmitting device 10 can be matched.

[0030] The storage device 202 stores various information necessary for the processing performed by the receiving device 20. For example, the storage device 202 stores a rule TBL1 that indicates the relationship between each unit time, which is indicated as the time from one time to another, and the frequency of the optical signal used in each unit time.

[0031] The demultiplexer 206 demultiplexes a plurality of optical signals having different wavelengths that have propagated through the transmission line 30 into optical signals having a plurality of wavelengths. The demultiplexer 206 outputs the demultiplexed optical signals to the photodetector 205.

[0032] The light receiving device 205 is a device that converts an optical signal into an electrical signal. As shown in FIG. 1 , the light receiving device 205 includes light receiving elements 205a1, 205a2, 205a3, ..., 205an. Hereinafter, the light receiving elements 205a1, 205a2, 205a3, ..., 205an will be collectively referred to as light receiving element 205a. An example of the light receiving element 205a is a PIN photodiode. Each light receiving element 205a is provided for each spectrally separated optical signal. Upon receiving an optical signal, each light receiving element 205a converts the received optical signal into an electrical signal corresponding to the optical signal (i.e., an electrical signal that differs depending on the frequency of the optical signal), and outputs the converted electrical signal to the processing device 204.

[0033] The processing device 204 generates a decrypted electrical signal by extracting an electrical signal identified based on protocol TBL1 from the electrical signals output by the optical receiving device 205. For example, the processing device 204 identifies the time at which the electrical signal was received from the optical receiving device 205 based on the time in the synchronizer 201. The processing device 204 identifies a unit time including the time at which the electrical signal was received in protocol TBL1 stored in the storage device 202, and identifies the frequency of the optical signal to be used in that unit time. Identifying the frequency of the optical signal corresponds to identifying which of the optical receiving elements 205a will receive the encrypted optical signal. The processing device 204 then decrypts the electrical signal output by the optical receiving element that received the optical signal of the identified frequency based on protocol TBL1.

[0034] Here, a process of the transmitting device 10 in which the transmitting device 10 transmits data 0, 1, 0, 0, 1 to the receiving device 20 using the signal shown in FIG. 1 will be described. In this case, protocol TBL1 allows the transmitting device 10 and the receiving device 20 to share information that the dashed line portions of the signal output by the light source device 105 shown in FIG. 1 are encrypted signals and the solid line portions are dummy signals. Protocol TBL1 also allows the transmitting device 10 and the receiving device 20 to share information that the logical sum (OR) of the encrypted signals is calculated at each unit time (i.e., in the example shown in FIG. 1, at each of unit times T1, T2, T3, T4, and T5). This allows the transmitting device 10 to transmit data of 0 at unit time T1, 1 at unit time T2, 0 at unit time T3, 0 at unit time T4, and 1 at unit time T5 to the receiving device 20. In this case, the receiving device 20 includes a logic circuit that implements the logical sum (OR). Then, for each of unit times T1, T2, T3, T4, and T5, the logic circuit performs a logical OR operation on the encrypted signals received by the receiving device 20, thereby enabling the receiving device 20 to decrypt the encrypted signals. As a result, the receiving device 20 can obtain the data 0, 1, 0, 0, 1 transmitted by the transmitting device 10.

[0035] Specifically, for example, rule TBL1 is a rule including the information shown in FIG. 2 and information that the logical sum (OR) of the encrypted signals is taken for each unit time to obtain data. When the time indicated by the information acquired by the processing device 204 from the synchronizer 201 is equal to or greater than time t1 and less than time t2, the processing device 204 identifies the unit time T1 in rule TBL1 shown in FIG. 2 and identifies frequency 1 of the optical signal associated with the identified unit time T1. The processing device 204 identifies the photodetector 205a1 that received the optical signal with the identified frequency 1. The processing device 204 then calculates the logical sum (OR) of the electrical signals output by the identified photodetector 205a1 (in this case, since there is only one input, the result is actually the logic indicated by the electrical signal). The result of this calculation becomes the decoded signal for unit time T1. Furthermore, if the time indicated by the information acquired by the processing device 204 from the synchronizer 201 is equal to or greater than time t2 and less than time t3, the processing device 204 identifies the unit time T2 in accordance with the rule TBL1 shown in FIG. 2 and identifies the frequencies 2 and n of the optical signal associated with the identified unit time T2. The processing device 204 identifies the photodetectors 205a2 and 205a3 that received the optical signals of the identified frequencies 2 and n. The processing device 204 then performs a logical sum (OR) operation on the electrical signals output by the identified photodetectors 205a2 and 205a3. The result of this operation is the decoded signal for the unit time T2. Furthermore, if the time indicated by the information acquired by the processing device 204 from the synchronizer 201 is equal to or greater than time t3 and less than time t4, the processing device 204 identifies the unit time T3 in accordance with the rule TBL1 shown in FIG. 2 and identifies the frequencies 2 and 3 of the optical signal associated with the identified unit time T3. The processing device 204 identifies the photodetectors 205a2 and 205a3 that received the optical signals of the identified frequencies 2 and 3. Then, the processing device 204 calculates the logical sum (OR) of the electrical signals output by the identified light receiving elements 205a2 and 205a3. The result of this calculation becomes the decoded signal for unit time T3. Furthermore, if the time indicated by the information acquired by the processing device 204 from the synchronization device 201 is equal to or greater than time t4 and less than time t5, the processing device 204 identifies unit time T4 in the rule TBL1 shown in FIG. 2, and identifies the frequency n of the optical signal associated with the identified unit time T4.The processing device 204 identifies the photodetector elements 205an that received the optical signal of the identified frequency n. The processing device 204 then calculates the logical sum (OR) of the electrical signals output by the identified photodetector elements 205an (in this case, since there is only one input, the result is actually the logic indicated by the electrical signal). The result of this calculation becomes the decoded signal for unit time T4. Furthermore, if the time indicated by the information acquired by the processing device 204 from the synchronization device 201 is equal to or greater than time t5 and less than time t6, the processing device 204 identifies unit time T5 in the rule TBL1 shown in FIG. 2 and identifies frequencies 1, 2, and n of the optical signal associated with the identified unit time T5. The processing device 204 identifies the photodetectors 205a1, 205a2, and 205an that received the optical signals of the identified frequencies 1, 2, and n. The processing device 204 then calculates the logical sum (OR) of the electrical signals output by the identified photodetectors 205a1, 205a2, and 205an. The result of this calculation is the decoded signal for unit time T5. Then, the processing device 204 outputs the results of the calculations performed for each of unit times T1, T2, T3, T4, and T5, i.e., the decoded signals, to the output device 203.

[0036] 1, the transmitting device 10 can also transmit data, for example, 0, 1, 1, 0, 0, 0, 1, 0, 1 to the receiving device 20. In this case, protocol TBL1 allows the transmitting device 10 and the receiving device 20 to share information that, of the signals output by the light source device 105 shown in FIG. 1, the dashed line portions are encrypted signals and the solid line portions are dummy signals. Protocol TBL1 also allows the transmitting device 10 and the receiving device 20 to share information that encrypted signals are transmitted as data in sequence at each unit time (i.e., in the example shown in FIG. 1, at each of unit times T1, T2, T3, T4, and T5). In this way, the transmitting device 10 can transmit data of 0 at unit time T1, 1, 1 at unit time T2, 0, 0 at unit time T3, 0 at unit time T4, and 1, 0, 1 at unit time T5 to the receiving device 20. In this case, the receiving device 20 can decrypt the encrypted signal by sequentially assembling the encrypted signal received by the receiving device 20 in each of the unit times T1, T2, T3, T4, and T5. As a result, the receiving device 20 can obtain the data 0, 1, 1, 0, 0, 0, 1, 0, 1 transmitted by the transmitting device 10.

[0037] Specifically, for example, the rule TBL1 includes the information shown in FIG. 2 and information that the encrypted signal for each unit time is treated as data as is. When the time indicated by the information acquired by the processing device 204 from the synchronizer 201 is equal to or greater than time t1 and less than time t2, the processing device 204 identifies the unit time T1 in the rule TBL1 shown in FIG. 2 and identifies the frequency 1 of the optical signal associated with the identified unit time T1. The processing device 204 identifies the light-receiving element 205a1 that received the optical signal with the identified frequency 1. The processing device 204 then regards the electrical signal output by the identified light-receiving element 205a1 as the decoded signal for the unit time T1. Furthermore, when the time indicated by the information acquired by the processing device 204 from the synchronizer 201 is equal to or greater than time t2 and less than time t3, the processing device 204 identifies the unit time T2 in the rule TBL1 shown in FIG. 2 and identifies the frequencies 2 and n of the optical signal associated with the identified unit time T2. The processing device 204 identifies the photodetectors 205a2 and 205a3 that received the identified optical signals of frequencies 2 and n. Then, the processing device 204 regards the electrical signals output by the identified photodetectors 205a2 and 205a3 as the decoded signals for unit time T2. Furthermore, if the time indicated by the information acquired by the processing device 204 from the synchronizer 201 is equal to or greater than time t3 and less than time t4, the processing device 204 identifies the unit time T3 in the rule TBL1 shown in FIG. 2 and identifies the frequencies 2 and 3 of the optical signals associated with the identified unit time T3. The processing device 204 identifies the photodetectors 205a2 and 205a3 that received the identified optical signals of frequencies 2 and 3. Then, the processing device 204 regards the electrical signals output by the identified photodetectors 205a2 and 205a3 as the decoded signals for unit time T3. Furthermore, if the time indicated by the information acquired by the processing device 204 from the synchronizer 201 is equal to or greater than time t4 and less than time t5, the processing device 204 identifies the unit time T4 in the rule TBL1 shown in Fig. 2 and identifies the frequency n of the optical signal associated with the identified unit time T4. The processing device 204 identifies the photodetector 205an that received the optical signal with the identified frequency n. The processing device 204 then regards the electrical signal output by the identified photodetector 205an itself as the decoded signal for the unit time T4.Furthermore, if the time indicated by the information acquired by the processing device 204 from the synchronizer 201 is equal to or greater than time t5 and less than time t6, the processing device 204 identifies the unit time T5 in the rule TBL1 shown in FIG. 2 and identifies the frequencies 1, 2, and n of the optical signals associated with the identified unit time T5. The processing device 204 then identifies the photodetectors 205a1, 205a2, and 205an that received the optical signals with the identified frequencies 1, 2, and n. The processing device 204 then determines that the electrical signals output by the identified photodetectors 205a1, 205a2, and 205an are the decoded signals for the unit time T5. The processing device 204 then outputs the decoded signals for each of the unit times T1, T2, T3, T4, and T5 to the output device 203.

[0038] The output device 203 notifies the decoded signal. Examples of the output device 203 include a device such as a display that displays the decoded signal, a printing device that prints the decoded signal, and a communication device that transmits the decoded signal to the outside of the receiving device 20.

[0039] Next, a process performed by the communication system 1 according to an embodiment of the present disclosure will be described. Fig. 4 is a diagram showing an example of a process flow of the communication system 1 according to an embodiment of the present disclosure. Here, the encryption and decryption processes performed by the communication system 1 will be described assuming that the protocol TBL1 is the protocol shown in Fig. 2. It is assumed that the time indicated by the synchronization device 101 included in the transmitting device 10 and the time indicated by the synchronization device 201 included in the receiving device 20 are the same.

[0040] The input device 103 receives information to be transmitted from the transmitting device 10 to the receiving device 20 (step S1).

[0041] The processing device 104 controls the light emission of the light source device 105 based on the protocol TBL1 to generate an encrypted optical signal that corresponds to the information received by the input device 103 (step S2). For example, the processing device 104 acquires information indicating the protocol TBL1 from the storage device 102. The processing device 104 also acquires information indicating a time from the synchronization device 101. The processing device 104 identifies the time in the information acquired from the synchronization device 101. The processing device 104 identifies which unit of time the identified time is included in the acquired protocol TBL1, and identifies the frequency of the optical signal to be used in that unit of time. The processing device 104 then controls the light emission of the light sources 105a1, 105a2, 105a3, ..., 105an in the light source device 105 so that the information received by the input device 103 is output as an optical signal of the identified frequency.

[0042] For example, if the rule TBL1 is the rule shown in FIG. 2 and the time indicated by the information acquired by the processing device 104 from the synchronizer 101 is equal to or greater than time t1 and less than time t2, the processing device 104 identifies the unit time T1 in the rule TBL1 shown in FIG. 2 and identifies the frequency 1 of the optical signal associated with the identified unit time T1. The processing device 104 then controls the light emission of the light source 105a1 capable of outputting light of the identified frequency 1 so that an optical signal of that frequency is output. The processing device 104 also controls light sources other than the light source 105a1 during the unit time T1 to output a dummy signal. The processing device 104 also controls the light emission of the light source 105a in the same manner during each of the unit times T2, T3, T4, and T5.

[0043] The light source device 105, under the control of the processing device 104, generates an optical signal that is generated (that is, encrypted) based on the protocol TBL1.

[0044] The multiplexer 106 multiplexes a plurality of optical signals with different wavelengths output from the light source device 105 (step S3). The multiplexer 106 transmits the multiplexed optical signal to the receiving device 20 via the transmission path 30.

[0045] The demultiplexer 206 demultiplexes (disperses) the multiple optical signals with different wavelengths that have propagated through the transmission line 30 into optical signals with multiple wavelengths (step S4). The demultiplexer 206 outputs the demultiplexed optical signals to the photodetector 205.

[0046] When each of the photodetectors 205a included in the photodetector device 205 receives an optical signal, it converts the received optical signal into an electrical signal corresponding to the optical signal (i.e., an electrical signal that differs depending on the frequency of the optical signal), and outputs the converted electrical signal to the processing device 204 (step S5).

[0047] The processing device 204 generates a decoded electrical signal by extracting an electrical signal identified based on protocol TBL1 from the electrical signals output by the light receiving device 205 (step S6). For example, the processing device 204 identifies the time at which the electrical signal was received from the light receiving device 205 based on the time in the synchronizer 201. The processing device 204 identifies a unit time including the time at which the electrical signal was received in protocol TBL1 stored in the storage device 202, and identifies the frequency of the optical signal to be used in that unit time. Then, the processing device 204 decodes the electrical signal output by the light receiving element that received the optical signal of the identified frequency based on protocol TBL1.

[0048] Then, the processing device 204 outputs the decoded signals for each unit time T1, T2, T3, T4, and T5 to the output device 203. The output device 203 broadcasts the decoded signals (step S7).

[0049] The communication system 1 according to an embodiment of the present disclosure has been described above. The communication system 1 includes a transmitting device 10 and a receiving device 20. The transmitting device 10 includes a synchronizing device 101 (an example of a synchronizing means) that synchronizes time with the receiving device 20, a processing device 104 (an example of a control means) that controls encryption of an optical signal based on a rule set for each of a plurality of periods indicated by the time, a light source device 105 (an example of a generating means) that generates an encrypted optical signal for each of the plurality of periods based on control by the processing device 104, and a multiplexer 106 (an example of a transmitting means) that transmits the encrypted optical signal during one of the plurality of periods to the receiving device 20 during that one period. The receiving device 20 includes a synchronizing device 201 (an example of a synchronizing means) that synchronizes time with the transmitting device 10, a demultiplexer 206 (an example of a receiving means) that receives the encrypted optical signal during the one period, an optical receiving device 205 (an example of a converting means) that converts the encrypted optical signal received by the demultiplexer 206 into an electrical signal, and a processing device 204 (an example of a decrypting means) that decrypts the electrical signal based on a protocol set for each of the multiple periods. This enables secure communication in optical communication.

[0050] 5 is a diagram showing a minimum configuration of a communication system 1 according to an embodiment of the present disclosure. The communication system 1 is a communication system including a transmitting device 10 and a receiving device 20.

[0051] The transmission device 10 includes a synchronization unit 1001 (an example of a synchronization means), a control unit 1002 (an example of a control means), a generation unit 1003 (an example of a generation means), and a transmission unit 1004 (an example of a transmission means).

[0052] A synchronization unit 1001 synchronizes time with the receiving device 20. A control unit 1002 controls encryption of an optical signal based on rules set for each of a plurality of periods indicated by the time. A generation unit 1003 generates an encrypted optical signal for each of the plurality of periods based on control by the control unit 1002. A transmission unit 1004 transmits the encrypted optical signal to the receiving device 20 during one of the plurality of periods.

[0053] The receiving device 20 includes a synchronizing unit 2001 (an example of a synchronizing means), a receiving unit 2002 (an example of a receiving means), a converting unit 2003 (an example of a converting means), and a decoding unit 2004 (an example of a decoding means).

[0054] A synchronization unit 2001 synchronizes time with the transmitting device 10. A receiving unit 2002 receives the encrypted optical signal during the one period. A conversion unit 2003 converts the encrypted optical signal received by the receiving unit 2002 into an electrical signal. A decryption unit 2004 decrypts the electrical signal based on a rule set for each of the multiple periods.

[0055] 6 is a diagram illustrating an example of a processing flow of the communication system 1 having a minimum configuration according to an embodiment of the present disclosure. Next, processing of the communication system 1 having a minimum configuration according to an embodiment of the present disclosure will be described with reference to FIG.

[0056] The synchronization unit 1001 synchronizes time with the receiving device 20 (step S101). The control unit 1002 controls encryption of the optical signal based on a rule set for each of a plurality of periods indicated by the time (step S102). The generation unit 1003 generates an encrypted optical signal for each of the plurality of periods based on the control of the control unit 1002 (step S103). The transmission unit 1004 transmits the encrypted optical signal for one of the plurality of periods to the receiving device 20 for that one period (step S104).

[0057] The synchronization unit 2001 synchronizes time with the transmitting device 10 (step S105). The receiving unit 2002 receives the encrypted optical signal during the one period (step S106). The conversion unit 2003 converts the encrypted optical signal received by the receiving unit 2002 into an electrical signal (step S107). The decryption unit 2004 decrypts the electrical signal based on a rule set for each of the multiple periods (step S108).

[0058] The communication system 1 with the minimum configuration according to an embodiment of the present disclosure has been described above. This communication system 1 enables secure optical communication.

[0059] The order of the processes in the embodiments of the present disclosure may be changed as long as the processes are performed appropriately.

[0060] Although the embodiments of the present disclosure have been described, the above-mentioned communication system 1, transmitting device 10, receiving device 20, synchronizing device 101, 201, input device 103, processing device 104, 204, output device 203, and other control devices may have a computer system therein. The above-mentioned processing steps are stored in the form of a program on a computer-readable recording medium, and the above processing is performed by reading and executing this program by a computer. Specific examples of computers are shown below.

[0061] 7 is a schematic block diagram showing the configuration of a computer according to at least one embodiment. As shown in FIG. 7, the computer 5 includes a CPU 6, a main memory 7, a storage 8, and an interface 9.

[0062] For example, the above-described communication system 1, transmitting device 10, receiving device 20, synchronizing devices 101 and 201, input device 103, processing devices 104 and 204, output device 203, and other control devices are each implemented in a computer 5. The operations of each of the above-described processing units are stored in the form of a program in storage 8. CPU 6 reads the program from storage 8, loads it into main memory 7, and executes the above-described processing in accordance with the program. Furthermore, CPU 6 allocates storage areas in main memory 7 corresponding to each of the above-described storage units in accordance with the program.

[0063] Examples of storage 8 include a hard disk drive (HDD), a solid state drive (SSD), a magnetic disk, a magneto-optical disk, a compact disc read-only memory (CD-ROM), a digital versatile disc read-only memory (DVD-ROM), and a semiconductor memory. Storage 8 may be an internal medium directly connected to the bus of computer 5, or an external medium connected to computer 5 via interface 9 or a communication line. In addition, when this program is distributed to computer 5 via a communication line, computer 5 that receives the program may load the program into main memory 7 and execute the above-mentioned processing. In at least one embodiment, storage 8 is a non-transitory tangible storage medium.

[0064] The program may also implement some of the functions described above. Furthermore, the program may be a file that can implement the functions described above in combination with a program already recorded in the computer system, a so-called differential file (differential program).

[0065] Although several embodiments of the present disclosure have been described, these embodiments are merely examples and do not limit the scope of the disclosure. Various additions, omissions, substitutions, and modifications may be made to these embodiments without departing from the spirit of the disclosure. [Explanation of symbols]

[0066] 1. Communication Systems 5. Computer 6 CPU 7. Main memory 8. Storage 9. Interface 10. Transmitting device 20. Receiving device 101, 201...Synchronization device 102, 202...Storage device 103 Input device 104, 204 Processing device 105...Light source device 105a...Light source 106...Multiplexer 203 Output device 205...Light receiving device 205a···Photodetector 206...brancher TBL1...Terms

Claims

1. A communication system including a transmitting device and a receiving device, The transmitting device a synchronization means for synchronizing the time with the receiving device; a control means for controlling encryption of an optical signal based on a rule set for each of a plurality of periods indicated by the time; a generating means for generating an encrypted optical signal for each of the plurality of periods under control of the control means; a transmitting means for transmitting the encrypted optical signal to the receiving device during one of the plurality of periods; Equipped with The receiving device a synchronization means for synchronizing the time with the transmitting device; a receiving means for receiving the encrypted optical signal during the one period; a conversion means for converting the encrypted optical signal received by the receiving means into an electrical signal; a decoding means for decoding the electrical signal based on a rule set for each of the plurality of periods; A communication system comprising:

2. the rules define a combination of optical signal frequencies to be used for encryption for each of the plurality of time periods, The control means controlling encryption of the optical signal based on a combination of frequencies of the optical signal used for encryption for each of the plurality of periods; The decoding means decrypting the electrical signal based on a combination of frequencies of optical signals used for encryption for each of the plurality of periods; The communication system of claim 1 .

3. the optical signal includes a dummy signal having a random light emission timing; 3. The communication system according to claim 1 or 2.

4. the optical signal is a binary intensity modulated signal; A communication system according to any one of claims 1 to 3.

5. A processing method executed by a communication system including a transmitting device and a receiving device, The transmitting device Synchronizing the time with the receiving device; Controlling encryption of optical signals based on rules set for each of a plurality of periods indicated by the time; generating an encrypted optical signal for each of the plurality of time periods based on the control; transmitting the encrypted optical signal to the receiving device during one of the plurality of time periods; Run The receiving device Synchronizing the time with the transmitting device; receiving the encrypted optical signal during the one period of time; converting the received encrypted optical signal into an electrical signal; decoding the electrical signal based on a rule set for each of the plurality of periods; To execute Processing method.

6. a synchronization means for synchronizing the time with a receiving device of a communication target; a control means for controlling encryption of an optical signal based on a rule set for each of a plurality of periods indicated by the time; a generating means for generating an encrypted optical signal for each of the plurality of periods under control of the control means; a transmitting means for transmitting the encrypted optical signal to the receiving device during one of the plurality of periods; A transmitting device comprising:

7. Synchronizing the time with a receiving device that is a communication target; Controlling encryption of optical signals based on rules set for each of a plurality of periods indicated by the time; generating an encrypted optical signal for each of the plurality of time periods based on the control; transmitting the encrypted optical signal to the receiving device during one of the plurality of time periods; A processing method comprising:

8. On the computer, Synchronizing the time with a receiving device that is a communication target; Controlling encryption of optical signals based on rules set for each of a plurality of periods indicated by the time; generating an encrypted optical signal for each of the plurality of time periods based on the control; transmitting the encrypted optical signal to the receiving device during one of the plurality of time periods; A program that executes the following.

9. a synchronization means for synchronizing the time with a transmitting device as a communication target; a receiving means for receiving, during one period of a plurality of periods indicated by the time, an optical signal encrypted by the transmitting device; a conversion means for converting the encrypted optical signal received by the receiving means into an electrical signal; a decoding means for decoding the electrical signal based on a rule set for each of the plurality of periods; A receiving device comprising:

10. Synchronizing the time with a transmitting device to be communicated with; receiving, during one period of a plurality of periods indicated by the time, an optical signal encrypted by the transmitting device during the one period; converting the received encrypted optical signal into an electrical signal; decoding the electrical signal based on a rule set for each of the plurality of periods; A processing method comprising:

11. On the computer, Synchronizing the time with a transmitting device to be communicated with; receiving, during one period of a plurality of periods indicated by the time, an optical signal encrypted by the transmitting device during the one period; converting the received encrypted optical signal into an electrical signal; decoding the electrical signal based on a rule set for each of the plurality of periods; A program that executes the following.

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