JP2018042168A - Data diode system and data transmission method for data diode system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To implement reliable data transmission using a data diode system.SOLUTION: A data diode system of the present invention is a data diode system comprising a data diode device and a transmission unit and reception unit that are arranged at stages prior and posterior to the data diode device, respectively. In the data diode system, the transmission unit grants a transfer code to a transfer data group transmitted from a transmission source and converts the transfer data group to one compliant to a communication protocol allowed to path through by the data diode device before transmitting the transfer data group. Through the data diode device, the reception unit receives the transfer data group transmitted from the transmission unit and converts the transfer data group to one compliant to a communication protocol of the transmission source before transmitting, for each transfer code, the transfer data group to the transmission source.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a data diode system and a data transmission method in the data diode system.

  In critical systems such as control systems that control equipment such as pumps and valves, medical systems, and local government systems, there is an increasing number of cases where data that is handled only in the critical system is used in cooperation with other systems. . When utilizing an important system in cooperation with another system, application of a data diode device that realizes one-way communication from the important system to the other system is progressing. Here, “one-way communication” means that data flows only in one direction from the important system to the other system, and prevents data flow in the reverse direction from the other system to the important system.

  Since the data diode device passes only a special communication protocol, a configuration in which protocol conversion devices are installed at both ends of the data diode device is generally used for practical application. Hereinafter, a configuration in which protocol conversion devices are installed at both ends of the data diode device is referred to as a data diode system. When applying this data diode system to an important system, when sending data from multiple senders, it is necessary to prevent inconsistencies when handling data as time-series data such as forms, etc. It is.

  In the field of data communication, a technique for assigning a unique key (for example, a time stamp) to a data group is known as a countermeasure against data inconsistency (for example, Patent Document 1). Patent Document 1 describes that “a packet recording support server asks a time stamp server to issue a time stamp for aggregate data and records it in a time stamp database together with a CRC code”.

JP 2007-096413 A

  However, the transmission order is not guaranteed when data is transmitted from the transmission source to the reception destination only by assigning a unique key to the data group at the transmission source as in the prior art. Therefore, since the occurrence of data mismatch cannot be prevented, there is a concern that the reliability of data transmission in the data diode system is lowered.

  An object of the present invention is to provide a data diode system capable of realizing highly reliable data transmission and a data transmission method in the data diode system.

In order to achieve the above object, the data diode system of the present invention comprises:
In a data diode system comprising a data diode device, and a transmission unit and a reception unit arranged in the front and rear stages of the data diode device,
The transmission unit assigns a transfer code to the transfer data group transmitted from the transmission source, converts the transmission code into a communication protocol that can be passed by the data diode device, and transmits it.
The reception unit receives the transfer data group transmitted from the transmission unit via the data diode device, converts the transmission data group into a communication protocol of the transmission source, and transmits the transmission data to the transmission destination for each transfer code.

Further, the data transmission method in the data diode system of the present invention,
A data transmission method in a data diode system comprising a data diode device, and a transmission unit and a reception unit arranged in front and rear stages of the data diode device,
A transfer code is given to the transfer data group transmitted from the transmission source by the transmission unit, and after conversion into a communication protocol that can be passed by the data diode device, the transmission unit transmits to the reception unit,
A transfer data group transmitted from a transmission unit is received via a data diode device, converted into a communication protocol of a transmission source, and then transmitted from the reception unit to a transmission destination for each transfer code.

  According to the present invention, highly reliable data transmission using a data diode system can be realized.

It is an example of a block diagram which shows the whole structure at the time of applying with respect to an important system as an application example of the data diode system which concerns on embodiment of this invention. It is an example of the figure which shows the structure of the transmission screen of the transmitter in the application example of the data diode system which concerns on embodiment of this invention. It is an example of the flowchart which shows the flow of the file transfer by the transmission screen of a transmission device in the application example of the data diode system which concerns on embodiment of this invention. It is an example of a block diagram showing an example of composition of a data diode system concerning an embodiment of the present invention. 5 is an example of a flowchart showing a flow of processing until data is transmitted from a transmission device to a transmission unit of the data diode system in an application example of the data diode system according to the embodiment of the present invention. It is an example of the flowchart which shows the flow of a process until data are transmitted to a receiving part from the transmission part in the data diode system which concerns on embodiment of this invention. In the application example of the data diode system which concerns on embodiment of this invention, it is an example of the flowchart which shows the flow of a process until data are transmitted to a public server from a receiving part. It is an example of the flowchart which shows the flow of a process when a public server and a data reference apparatus exchange data in the application example of the data diode system which concerns on embodiment of this invention. It is an example of the figure which shows the structural example of the screen displayed with a data reference apparatus in the application example of the data diode system which concerns on embodiment of this invention.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings. The present invention is not limited to the embodiment, and various numerical values in the embodiment are examples. In the following description and each drawing, the same reference numerals are used for the same elements or elements having the same functions, and duplicate descriptions are omitted.

<Background of data diode system application to critical systems>
Critical systems such as control systems, medical systems, and municipal systems have been operated in closed networks. However, in recent years, there are increasing cases in which important systems cooperate with other systems via a network, such as O & M (Operation & Maintenance) in control systems and regional cooperation in medical / local government systems. For example, in a control system, new values such as realizing optimal operation of the control system by collecting and analyzing monitoring / operation data of the control system by the business system are being created.

  There is a possibility that important systems can create new values as described above by linking with other systems, but even for important systems that have been operated in a closed network and security measures are no longer needed, externally. It is becoming necessary to take measures against unauthorized access. In addition, virus infection due to targeted attacks for the purpose of fraud of personal information managed by an important system or a system linked to the important system (for example, a business system) is increasing.

  As countermeasures against unauthorized access from outside the critical system and targeted attacks on the critical system, a firewall device is installed at the connection point between the critical system and other systems to filter unauthorized access to the critical system. It is common. The firewall device prevents unauthorized access to an important system by comparing a predetermined permission list (IP (Internet Protocol) address, port number, protocol name, etc.) with an actual communication packet.

  However, there is a problem that unauthorized access to an important system cannot be completely prevented due to a definition error of the firewall device, a security vulnerability of the firewall device itself, and the like. In addition, the method of installing anti-virus software on each device included in an important system against targeted attacks means that the virus pattern file cannot be updated when necessary because the important system operates on a closed network. There are also challenges.

  In order to solve the above-mentioned problems, application of a data diode device that is installed at a connection point between an important system and another system and realizes one-way communication from the important system to the other system is proceeding in the same manner as the firewall device. Data diode devices only pass special communication protocols. Therefore, in actual application of the data diode device, a configuration of a data diode system in which a protocol conversion device is installed at both ends of the data diode device as a transmission unit and a reception unit is generally adopted.

  For example, when a file is transmitted from the transmission device by FTP (File Transfer Protocol), the file is transmitted from the transmission device to the transmission destination in the following steps. First, the transmission unit converts the FTP into a protocol that can be passed through the data diode device, and transmits it through the data diode device. Next, the reception unit converts the received data into FTP and transfers it to a transmission destination (for example, a public server). Finally, the data reference device refers to the data of the public server and outputs a form.

  When this data diode system is applied to an important system, when data is transmitted from a plurality of transmission sources, it is important not to mix the data. In addition, it is important to prevent incomplete data from being received by a destination device or system even when data loss due to communication abnormality occurs.

By the way, when data is transmitted from multiple transmission sources, if the data is mixed depending on the editing timing of the transmission unit and the reception unit, there is a possibility of inconsistency when handling it as time series data such as a form in a data reference device or the like. is there. This will be described below with a specific example. When sending the same data (for example, a file) from multiple sending devices,
For example, terminal 1: data A, data B, data C
Terminal 2: data A, data C, data D
Is assumed to be transmitted.

If transmission is performed in the order of terminal 1 and terminal 2, data may be mixed at the transmission destination as follows depending on the editing timing. Assuming that the transmission time of terminal 1 is T1, the transmission time of terminal 2 is T2, and T1 <T2, for example,
T1: Data A (terminal 1), data C (terminal 2)
T2: Data A (terminal 2), data B (terminal 1), data C (terminal 1), data D (terminal 2)
There are cases where

  Further, in the data diode system, when data loss occurs due to communication abnormality, incomplete data is received by the transmission destination public server or the linkage system. In the data diode system, since only one-way communication from the transmission source to the transmission destination can be performed, a retransmission request cannot be made from the transmission destination to the transmission source when communication is abnormal. In addition, since monitoring and operation data handled by important systems, especially control systems, are constantly updated, if there is no transmission error at the transmitting device, but an error occurs at a later step, a retransmission request is received by another means. Even so, there is a possibility that the transmission data does not already exist in the transmission device.

<Embodiment of the present invention>
Therefore, in the embodiment of the present invention, in consideration of the above points, a data diode system that enables data held in an important system to be transmitted to other devices and other systems while maintaining the security level of the important system. To construct.

  FIG. 1 is an example of a block diagram showing an overall configuration when applied to an important system as an application example of a data diode system according to an embodiment of the present invention. In this application example, the important system 10, the plurality of public servers 30, and the abnormality notification device 40 are connected by the data diode system 20. In addition, a plurality of public servers 30, a plurality of data reference devices 60, and a cooperation system 70 are connected via the Internet 50. Here, the important system 10 is a data transmission source, and the public server 30 is a data transmission destination.

  The important system 10 includes a plurality of transmission devices 11 and an important device 12 that manages important data 121 such as control / operation data and personal information. The plurality of transmission devices 11 and the important device 12 are connected via a network 13. Are connected to the data diode system 20. The data diode system 20 includes a transmission unit 21, a data diode device 22 that realizes one-way communication, and a reception unit 23. The transmission unit 21 and the reception unit 23 include a gateway (GW) having a protocol conversion function.

  The important data 121 managed by the important device 12 is transmitted by the transmission device 11 via the transmission unit 21, the data diode device 22, and the reception unit 23 of the data diode system 20 under the operation of the transmission source user U1. The data is transmitted to the public server 30 and stored in the public server 30. The important data 121 stored in the public server 30 is referred to and utilized via the Internet 50 by the data reference device 60 under the operation of the destination user U2.

  The abnormality notification device 40 includes a mail server or the like, and is a device that receives an abnormality notification such as data loss from the reception unit 23 when the reception unit 23 of the data diode system 20 detects a communication abnormality. When receiving the abnormality notification, the abnormality notification device 40 notifies the plurality of transmission devices 11 of the important system 10 that a communication abnormality such as data loss has occurred via a communication line (not shown).

  The linkage system 70 is another important system 10 or a business system, and uses a linkage server 71, a data reference device 72, and a printer 73 for utilizing the important data 121 stored in the public server 30 in the form data format. Etc. The cooperation server 71 periodically collects important data 121 stored in the public server 30, converts it into form data or the like, and stores it in the cooperation server 71. The data reference device 72 displays the data stored in the cooperation server 71 under the operation of the transmission destination user U3. The printer 73 prints the data stored in the cooperation server 71 under the operation of the transmission destination user U3.

  Thereafter, the monitoring control system is taken as an example of the important system 10, and monitoring data of the monitoring control system is transmitted to the public server 30 as the important data 121 transmitted from the transmission device 11, and is disclosed as form data by the public server 30. An explanation will be given assuming this.

  FIG. 2 is an example of a diagram illustrating a configuration of a transmission screen of the transmission device 11 in an application example of the data diode system 20 according to the embodiment of the present invention. The transmission screen in FIG. 2A shows an example of the display contents of the file registration screen 3100. The transmission screen of FIG. 2B shows an example of the display contents of the file selection screen 3110.

[Example of file transfer by sending screen of sending device]
FIG. 3 is an example of a flowchart showing the flow of file transfer on the transmission screen of the transmission apparatus 11 in an application example of the data diode system 20 according to the embodiment of the present invention. This series of processing is executed under the control of a control unit (not shown) of the transmission device 11.

  First, the control unit of the transmission apparatus 11 activates the file registration screen 3100 under the operation of the transmission source user U1 (step S301), and displays the file registration screen 3100 shown in FIG. 2A (step S302). Next, the control unit of the transmission device 11 determines whether or not the user U1 has clicked the file addition button 3101 on the file registration screen 3100 (step S303). When the file addition button 3101 is clicked (YES in S303), the control unit of the transmission apparatus 11 displays the file selection screen 3110 shown in FIG. 2B (step S304), and the file addition button 3101 is not clicked. (NO in S303), the process returns to step S302.

  In the file selection screen 3110, the user U 1 clicks an open button 3112 after selecting a file to be transmitted from the file list 3111 when transmitting the file. Further, the user U1 clicks a cancel button 3113 when not transmitting a file.

  Therefore, the control unit of the transmission apparatus 11 determines whether or not the user U1 has clicked the open button 3112 after selecting the file to be transmitted from the file list 3111 on the file selection screen 3110 (step S305). When the open button 3112 is clicked (YES in S305), the control unit of the transmission device 11 returns the display screen to the file registration screen 3100, and the file that the user U1 wants to transmit to the registered file list 3102 on the file registration screen 3100. Are displayed together with related information (file name, update date, capacity) (step S306).

  On the file registration screen 3100, the user U1 selects the transfer destination public server from the public server list 3103 and clicks the transfer button 3104 when transmitting the selected file. Therefore, the control unit of the transmission device 11 determines whether or not the user U1 has clicked the transfer button 3104 on the file registration screen 3100 (step S307). Then, when the transfer button 3104 is clicked (YES in S307), the control unit of the transmission device 11 transmits the selected file (step S308), ends a series of file transfer processes on the transmission screen, and transfers the transfer button. If 3104 is not clicked (NO in S307), the process returns to step S306.

  In step S305, when the open button 3112 is not clicked (NO in S305), the control unit of the transmission device 11 determines whether or not the cancel button 3113 is clicked (step S309). When the cancel button 3113 is not clicked (NO in S309), the control unit of the transmission device 11 returns to step S304, and when the cancel button 3113 is clicked (YES in S309), the file selection screen 3110 shown in FIG. 2B. Is closed (step S310).

[Configuration example of data diode system]
FIG. 4 is an example of a block diagram showing a configuration example of the data diode system 20 according to the embodiment of the present invention.

  In the data diode system 20, the transmission unit 21 includes a communication unit 211, a storage unit 212, and a control unit 213. The storage unit 212 stores reception data 2121 received from the transmission device 11, a reception file 2122 generated by the control unit 213, and a transmission file 2123 to be transmitted to the transmission destination. The transmission file 2123 is saved for each transfer code as a file to be transmitted to the transmission destination from the reception file 2122 under the control of the control unit 213.

  The control unit 213 of the transmission unit 21 includes functional units such as a reception file generation unit 2131, a transfer code acquisition unit 2132, a transmission file generation unit 2133, a file transmission unit 2134, and a file deletion unit 2135. The reception file generation unit 2131 generates a reception file based on the reception data 2121 and stores it in the storage unit 212 as the reception file 2122.

  The transfer code acquisition unit 2132 generates (acquires) a new transfer code based on the transfer code assigned to the latest file of the transmission file 2123, for example. The transmission file generation unit 2133 adds the transfer code acquired by the transfer code acquisition unit 2132 and generates a transmission file. The file transmission unit 2134 converts the transmission file generated by the transmission file generation unit 2133 into a communication protocol that can be passed by the data diode device 22 and transmits the communication protocol. The file deletion unit 2135 deletes files as appropriate.

  In the data diode system 20, the reception unit 23 includes a communication unit 231, a storage unit 232, and a control unit 233. The storage unit 232 stores reception data 2321 received from the transmission unit 21 via the data diode device 22, a reception file 2322 generated by the control unit 233, and an abnormality log 2323.

  The control unit 233 of the reception unit 23 includes functional units such as a reception packet check unit 2331, a reception file generation unit 2332, a file transmission unit 2333, and an abnormality notification unit 2334. The reception packet check unit 2331 checks the reception data 2321 for data loss due to communication abnormality using a known check method, and if it detects data loss, records that fact in the abnormality log 2323.

  The reception file generation unit 2332 generates reception data 2321 as a reception file with a transfer code when the reception packet check unit 2331 detects no data loss. The file transmission unit 2333 converts the reception file with the transfer code generated by the reception file generation unit 2332 into the communication protocol of the transmission destination (public server 30) and transmits the transmission code to the transmission destination for each transfer code. The abnormality notification unit 2334 refers to the abnormality log 2323 and notifies the abnormality notification device 40 of the presence or absence of abnormality.

[Communication between transmitter and transmitter]
FIG. 5 is a flowchart showing a flow of processing until data is transmitted from the transmission device 11 to the transmission unit (GW) 21 of the data diode system 20 in the application example of the data diode system 20 according to the embodiment of the present invention. It is an example. This series of processing is executed under the control of the control unit (not shown) of the transmission device 11 and the control unit 213 of the transmission unit 21.

  When file transmission including monitoring data is started under the control of the control unit of the transmission device 11 on the file registration screen 3100 (see FIG. 2A) of the transmission device 11, the transmission device 11 and the transmission unit 21 may The following processing is executed.

  First, when starting the file transmission (step S501), the control unit of the transmission device 11 transmits a data transmission start message to the transmission unit 21 (step S502). Then, the control part 213 of the transmission part 21 receives a data transmission start message via the communication part 211, and stores it in the memory | storage part 212 (step S511).

  Next, after completing the transmission of the data transmission start message, the control unit of the transmission device 11 transmits the number of file transfers to the transmission unit 21 (step S503). Then, the control part 213 of the transmission part 21 receives the number of file transfers via the communication part 211, and stores it in the memory | storage part 212 (step S512).

  Next, the control unit of the transmission device 11 transmits data to the transmission unit 21 (step S504), and then determines whether the file transfer is completed (step S505), and the file transfer must be completed. If (NO in S505), the process returns to step S504 to continue the file transmission. When the file transfer is completed (YES in S505), the control unit of the transmission device 11 transmits a data transmission end message to the transmission unit 21 (step S506), and ends a series of processes for data transmission. .

  On the other hand, in the transmission unit 21, the control unit 213 receives the data via the communication unit 211, subtracts the file transfer remaining number in the storage unit 212 (step S 513), and then in the calculation result of this file transfer remaining number Then, it is determined whether or not the remaining file transfer number is 0, that is, whether or not the reception of all the files has been completed (step S514). If the remaining file transfer number is not 0, that is, if reception of all files is not completed (NO in S514), the control unit 213 returns to step S512, and if the remaining file transfer number is 0 (S514). YES), it is determined whether or not a data transmission end message has been received from the transmitter 11 within a predetermined time (step S515).

  If the data transmission end message has not been received within a certain time (NO in S515), the control unit 213 discards the received file from the storage unit 212 as a timeout (step S516), and a series of processes for data transmission Exit. If the data transmission end message is received within a predetermined time (YES in S515), the control unit 213 compresses the transferred files upon completion of file transfer, and combines them into one file to form a transfer data group (step S517), the next data reception is awaited.

[Communication between transmitter, data diode device, and receiver]
FIG. 6 is an example of a flowchart showing a processing flow until data is transmitted from the transmission unit (GW) 21 to the reception unit (GW) 23 in the data diode system 20 according to the embodiment of the present invention. This series of processing is executed under the control of the control unit 213 of the transmission unit 21 and the control unit 233 of the reception unit 23.

  A unique transfer code is assigned to a transfer data group transmitted from the transmission unit 21 to the reception unit 23. Further, the transfer data group is accumulated in the storage unit 212 of the transmission unit 21 for a certain period in order to enable execution of retransmission. The transfer code is specified by the file name when the transfer data group is accumulated in the storage unit 212 of the transmission unit 21. For example, when the file name of the transfer data group is “010_201607131715.zip”, this indicates that the transfer code is “010” and the transmission date and time is “2016/07/13 17:15”.

  First, after the file transmission from the transmission device 11 to the transmission unit 21 is completed, in the transmission unit 21, the control unit 213 acquires the current transfer code (step S611) and sets the transfer code of the transmission file (step S612). . Next, in the transmission unit 21, the control unit 213 converts the transfer data group into a protocol that can be passed by the data diode device 22, and transmits the protocol to the reception unit 23 (step S613).

  When data is transmitted from the transmission unit 21 to the reception unit 23, the data diode device 22 relays the data (step S621).

  On the other hand, in the receiving unit 23, the control unit 233 first sets the file transfer mode (step S631), and then receives the transfer data group via the communication unit 231 (step S632). Next, the control unit 233 checks whether there is a communication abnormality (step S633). If there is no communication abnormality (NO in S633), the control unit 233 generates a file assuming that the received data is normal (step S634). .

  On the other hand, if there is a communication abnormality (YES in S633), the control unit 233 records that there was a communication abnormality in the abnormality log 2323 (step S635), and then discards the received data (step S636). A communication abnormality is notified to the abnormality notification device 40 (see FIG. 1) (step S637).

  The abnormality notification device 40 that has received the notification of the communication abnormality notifies the transmission device 11 of the important system 10 together with the transfer code that data loss or the like has occurred due to the communication abnormality. Upon receiving this notification, the transmission device 11 requests the retransmission of the data by designating the transfer code to the transmission unit 21. The transmission unit 21 accumulates (holds) the transmitted files in the transmission file (save) 2123 of the storage unit 212 together with the transfer code. Therefore, when the transmission device 11 designates a transfer code from the transmission device 11 and receives a data retransmission request, the transmission device 11 transmits the transmission file of the transfer code again.

  In this way, when a communication error is detected, the received data is discarded, so that even if there is a data loss in the received data due to the communication error, the data is lost at the destination due to the data discard. No data is sent. In addition, since the transmission unit 21 holds the transmission file together with the transfer code, the transmission unit 21 transmits the transmission file again even when data loss or the like due to communication abnormality occurs.

  In the transmission unit 21, the control unit 213 determines whether or not the data transmission is successful after the data transmission in step S613 (step S614). If the data transmission is successful (YES in S614), the file with the transfer code (transfer) The data group is saved (step S615), and the file transmission is terminated (step S616). When the data transmission has failed (NO in S614), the control unit 213 notifies the transmission device 11 that the data transmission has failed (step S617), and returns to step S501 in FIG. retry).

  As described above, by assigning a transfer code to a transfer data group that is a data unit to be transmitted and transmitting the data with the transfer code from the transmission unit 21 to the reception unit 23, the transmission unit 21 and the reception unit 23 Data will not be mixed depending on the editing timing. Therefore, inconsistency can be prevented from occurring when the destination such as the data reference device 60 is handled as time-series data such as a form.

[Communication between receiver and public server]
FIG. 7 is an example of a flowchart showing a processing flow until data is transmitted from the receiving unit 23 to the public server 30 in the application example of the data diode system 20 according to the embodiment of the present invention. This series of processing is executed under the control of the control unit 233 of the receiving unit 23 and the control unit (not shown) of the public server 30.

  First, in the receiving unit 23, the control unit 233 determines whether or not the file transfer mode is overwrite (step S701). If the file transfer mode is not overwrite (NO in S701), the transmission given to the transfer file A date / time directory is created and transferred to the public server 30 (step S702).

  Next, the control unit 233 transfers the file to the public server 30 (step S703). If the file transfer mode is overwrite (YES in S701), the control unit 233 proceeds directly to step S703 and transfers the file to the public server 30. Finally, the control unit 233 deletes the transferred file from the storage unit 232 (step S704).

  On the other hand, the control unit of the public server 30 creates a transmission date / time directory based on the reception information from the reception unit 23 (step S711), and then receives the file transferred from the reception unit 23 (step S712). ).

[Communication between public server and data reference device]
FIG. 8 is an example of a flowchart showing a flow of processing when the public server 30 and the data reference device 60 exchange data in the application example of the data diode system 20 according to the embodiment of the present invention. This series of processing is executed under the control of a control unit (not shown) of the public server 30 and a control unit (not shown) of the data reference device 60.

  FIG. 9 is an example of a diagram illustrating a configuration example of a screen displayed on the data reference device 60 in an application example of the data diode system 20 according to the embodiment of the present invention. The display screen of FIG. 9A shows an example of the display content of the display screen 9001 for data display (current value). The display screen in FIG. 9B shows an example of the display contents of the data display (history value) display screen 9002.

  First, the control unit of the data reference device 60 activates a screen in response to a display request from the destination user U2 (step S801), and then issues a data acquisition request to the public server 30 (step S802). . In response to the data acquisition request from the data reference device 60, the control unit of the public server 30 transfers the data to the data reference device 60 (step S811).

  The control unit of the data reference device 60 displays a screen for data display based on the data acquired from the public server 30 (step S803). In this screen display, on the current value display screen 9001 in FIG. 9A, the data items are displayed by the latest acquired data. In the history value display screen 9002 of FIG. 9B, the acquired data is displayed in time series. Data that could not be acquired is displayed as “−”.

  The control unit of the data reference device 60 determines whether or not a certain period has elapsed after displaying the data (step S804). If the certain time has passed (YES in S804), the process returns to step S802 to reacquire the data. And update the display. When the predetermined period has not elapsed (NO in S804), the control unit of the data reference device 60 ends the screen display in response to the display end request from the user U2 as the transmission destination (step S805).

  As described above, the data diode system 20 according to the embodiment of the present invention can prevent data from being mixed even when data is transmitted from a plurality of transmission sources. More specifically, since a transmission code is assigned to the data unit (transfer data group) to be transmitted, data is not mixed at the transmission destination, and inconsistency occurs at the transmission destination. Never do.

  Further, according to the data diode system 20 according to the embodiment of the present invention, it is important to prevent incomplete data from being received by the destination device or system even when data loss due to communication abnormality occurs. is there. More specifically, when a communication abnormality is detected, the received data is discarded and the transmission file is retransmitted from the transmission unit 21, so that incomplete data lacking data is transmitted to the transmission destination. There is nothing.

<Modification>
As mentioned above, although this invention was demonstrated using embodiment, this invention is not limited to embodiment mentioned above, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described. In the above-described embodiment, the monitoring control system is taken as an example of the important system 10. However, the present invention is not limited to the monitoring control system, and the present invention is linked to other systems such as a control system, a medical system, and a local government system. It can be applied to all systems that utilize data.

  DESCRIPTION OF SYMBOLS 10 ... Important system, 11 ... Transmission apparatus, 20 ... Data diode system, 21 ... Transmission part, 22 ... Data diode apparatus, 23 ... Reception part, 30 ... Public server, 40 ... Abnormality notification apparatus, 50 ... Internet, 60 ... Data Reference device, 70 ... cooperation system

Claims (4)

In a data diode system comprising a data diode device, and a transmission unit and a reception unit arranged in the front and rear stages of the data diode device,
The transmission unit assigns a transfer code to the transfer data group transmitted from the transmission source, converts the transmission code into a communication protocol that can be passed by the data diode device, and transmits.
The reception unit receives the transfer data group transmitted from the transmission unit via the data diode device, converts the transmission data group into a communication protocol of a transmission source, and transmits the transmission code to the transmission destination for each transfer code. Characteristic data diode system. The data diode system according to claim 1, wherein the transmission unit accumulates the transfer data group for each transfer code. The data diode system according to claim 1, wherein the receiving unit discards the received data when a communication abnormality is detected during reception of the transfer data group. A data transmission method in a data diode system comprising: a data diode device; and a transmission unit and a reception unit arranged in front and rear stages of the data diode device,
A transfer code is given to the transfer data group transmitted from the transmission source by the transmission unit, and after conversion to a communication protocol that can be passed by the data diode device, the transmission unit transmits to the reception unit,
The transfer data group transmitted from the transmission unit is received via the data diode device, converted into a communication protocol of a transmission source, and then transmitted from the reception unit to a transmission destination for each transfer code. A data transmission method in a data diode system.

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