JP2017017615A - Communication apparatus and communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication apparatus capable of improving the security of an on-vehicle network, and a communication system.SOLUTION: The communication apparatus comprises: a transmission part which transmits a frame comprising plural bits to a cable network which is referred to by plural apparatuses for information; a reception part which receives the frame from the cable network; and a control part which rearranges the order of the bits of the frame to be transmitted by the transmission part in accordance with the number of times of transmitting the frame.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a communication device and a communication system.

  2. Description of the Related Art Conventionally, a communication system that detects or mediates a collision caused by simultaneous transmission information of a plurality of nodes in order to perform multiplex communication in an in-vehicle network is known (for example, see Patent Document 1). In this communication system, security information indicated by a sequence number is included in the communication frame portion together with the message type identifier. This security information is inserted at a fixed position in the communication frame.

JP 2014-183395 A

Communication data in an in-vehicle system exchanges information according to an agreement between nodes. Recently, however, an event has occurred in which internal information communicated between nodes of an automobile is read and altered. In an in-vehicle network using a conventional communication system, the arrangement of communication frames is fixed, and thus security may be deteriorated.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a communication device and a communication system that can improve the security of an in-vehicle network.

  According to the first aspect of the present invention, a transmission unit (52) that transmits a frame composed of a plurality of bits to a wired network (4) in which a plurality of devices refer to information, and receives the frame from the wired network. The communication device (10) includes a receiving unit (52) and a control unit (40, 44) that switches the order of bits of frames transmitted by the transmitting unit according to the number of times the frame is transmitted.

  The invention according to claim 2 is the communication apparatus according to claim 1, wherein the frame has a standard area defined by a communication protocol and an arbitrary area in which at least data contents are stored, and the control unit Replaces the bit order of the frames transmitted by the transmitting unit within the arbitrary area.

  The invention according to claim 3 is the communication apparatus according to claim 1 or 2, wherein the frame includes a plurality of data areas in which data contents are stored, and an alive counter area in which data identification information is included. The control unit changes the order of the bits by changing the positions of the data areas included in the plurality of data areas without changing the position of the alive counter area.

  According to a fourth aspect of the present invention, in the communication device according to the third aspect, the control unit determines positions of data areas included in the plurality of data areas based on information included in the alive counter area.

  The invention according to claim 5 is the communication apparatus according to claim 4, wherein the control unit associates information included in the alive counter area with positions of data areas included in the plurality of data areas. With reference to the correspondence information, the order of the positions of the data areas included in the plurality of data areas is changed in an order corresponding to the information included in the alive counter area.

  The invention according to claim 6 is the communication apparatus according to claim 1 or 2, wherein the frame includes a plurality of data areas in which data contents are stored, and an alive counter area in which data identification information is included. The control unit changes the order of the bits by interrupting the alive counter area between the plurality of data areas.

  A seventh aspect of the present invention is a communication system comprising the communication device according to any one of the first to sixth aspects and the wired network.

  According to the first, second, third, sixth, and seventh aspects of the invention, the control unit changes the order of the bits of the frame transmitted by the transmission unit according to the number of transmissions of the frame, thereby improving the security of the in-vehicle network. Can be improved.

  According to invention of Claim 4 and 5, the said control part determines the position of the data area contained in these data areas by the information contained in the said alive counter area | region, and is more security of vehicle-mounted network. Can be improved.

1 is a conceptual diagram of a communication system 1 including an ECU 10 (communication device) according to a first embodiment. 1 is a diagram showing a simplified configuration of a communication system 1. FIG. It is a figure which shows the structural example of ECU10. It is a format example of the frame which ECU10 transmits to a bus | bath. 5 is a flowchart showing a flow of transmission processing executed by a communication control unit 44. 4 is a flowchart showing a flow of reception processing executed by a communication control unit 44. It is a figure which shows a mode that the count value of alive counter AC is incremented by the communication control part 44, and the position of data is shifted. It is a figure which shows the structural example of ECU10A with which the communication system which concerns on 2nd Embodiment is provided. 5 is a diagram illustrating the contents of a data position table 38. FIG. It is a flowchart which shows the flow of the process performed by the communication control part 44 which concerns on 2nd Embodiment. It is a figure which shows a mode that the position of data is shifted while the count value of alive counter AC is incremented by the communication control part 44 of 2nd Embodiment. It is a flowchart which shows the flow of the transmission process performed by the communication control part 44 which concerns on 3rd Embodiment. It is a flowchart which shows the flow of the reception process performed by the communication control part 44 which concerns on 3rd Embodiment. It is a figure which shows typically a mode that the alive counter AC is shifted 1 each by the communication control part 44, and is inserted between data. It is a figure which shows the structural example of ECU10B with which the communication system which concerns on 4th Embodiment is provided. It is the figure which illustrated the contents of the alive counter position table. It is a flowchart which shows the flow of the process performed by the communication control part 44 which concerns on 4th Embodiment. It is a figure which shows a mode that alive counter AC is inserted in the position corresponding to the alive counter position table 39 by the communication control part 44. FIG.

  Hereinafter, embodiments of a communication device and a communication system according to the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a conceptual diagram of a communication system 1 including an ECU 10 (communication device) according to the first embodiment. The communication system 1 includes a bus 4 connected to the OBD connector 2, a sub communication bus 6 and a sub communication bus 8 connected to the bus 4. The bus 4, the sub communication bus 6, and the sub communication bus 8 are connected to a plurality of ECUs 10 for controlling the vehicle, detection sensors for detecting the state of the vehicle, and other devices mounted on the vehicle. Hereinafter, the bus 4, the sub-communication bus 6, and the sub-communication bus 8 are referred to as a bus n when not distinguished from each other. For example, communication based on CAN (Controller Area Network) is performed on the bus n. An OBD (On-board diagnostics) connector 2 acquires information on devices connected to the bus. The OBD connector 2 transmits diagnostic data to a device connected to the bus, and receives a response to the transmitted diagnostic data. The OBD connector 2 diagnoses whether or not a device connected to the bus n is operating normally based on a response to the received diagnostic data. In addition, when control data for controlling each device is transmitted to each device via the OBD connector 2, each device operates according to the transmitted control data. The ECU 10 is an engine ECU 9A that controls the engine, a seat belt ECU 9B that controls the seat belt, and the like. The detection sensor for detecting the state of the vehicle is, for example, a yaw rate sensor or an acceleration sensor.

  FIG. 2 is a diagram showing the configuration of the communication system 1 in a more simplified manner. The communication system 1 is connected to ECUs 10-1 to 10-3 connected to the bus 4-1, ECUs 10-4 to 10-6 connected to the bus 4-2, and buses 4-1 and 4-2. The gateway device 11 relays between the bus 4-1 and the bus 4-2. The configuration shown in FIG. 2 may be mounted on a vehicle similarly to the configuration shown in FIG. 1 or may be applied to other devices. In the bus 4-1 and the bus 4-2, for example, communication based on CAN is performed similarly to the bus n. Each ECU 10 can acquire data flowing through the bus 4-1 or 4-2. Hereinafter, when the ECUs 10-1 to 10-6 are not distinguished from each other, they are simply expressed as ECU10. The bus 4-1 and the bus 4-2 are, for example, twisted pair cables, and transmit signals by a differential voltage method.

  FIG. 3 is a diagram illustrating a configuration example of the ECU 10. The ECU 10 includes, for example, a storage unit 30, a control unit 40, a CAN controller 50, and a CAN transceiver 52. The control unit 40 includes a processor such as a CPU (Central Processing Unit), for example.

  The storage unit 30 includes, for example, a nonvolatile storage device such as a ROM (Read Only Memory), an EEPROM (Electrically Erasable and Programmable Read Only Memory), and an HDD (Hard Disk Drive), a RAM (Random Access Memory), a register, and the like. Realized by a volatile storage device. The storage unit 30 stores programs such as an application program 32 and a CAN driver 34. The storage unit 30 also has a temporary storage area 36 including a transmission buffer (not shown) and a reception buffer (not shown).

  The application program 32 is a program for performing information processing assigned to the ECU 10. The CAN driver 34 mediates between the application program 32 and the CAN controller 50.

  The control unit 40 includes a central control unit 42 and a communication control unit 44. The central control unit 42 functions by executing the application program 32 and executes control given to the ECU 10.

  The communication control unit 44 refers to information (ID) included in the frame received by the CAN transceiver 52, and determines whether the frame includes information used by the own device. When the information used by the own device is included in the frame, the communication control unit 44 acquires the information included in the frame and stores it in the temporary storage area 36 of the storage unit 30.

  The communication control unit 44 causes the CAN transceiver 52 to transmit a frame. In this embodiment, the communication control unit 44 changes the order of the bits of the frames transmitted by the CAN transceiver 52 according to the number of frame transmissions.

  The CAN controller 50 transmits / receives various data to / from the bus 4-1 or 4-2 (hereinafter referred to as the bus 4) via the CAN transceiver 52. When transmitting a frame to the bus 4, the CAN controller 50 converts the frame stored in the transmission buffer of the temporary storage area 36 into a serial transmission signal by, for example, the NRZ (Non-Return-to-Zero) method. And output to the CAN transceiver 52. The CAN controller 50 outputs a voltage having a low logic level to a bit whose converted signal is “0” (dominant), and outputs a voltage having a high logic level to a bit having “1” (recessive). Further, when receiving data (frame) from the CAN transceiver 52, the CAN controller 50 converts the received frame into information that can be analyzed by the control unit 40 from, for example, a serial transmission signal, and passes through the CAN controller 50. Store in the reception buffer of the temporary storage area 36.

  The CAN transceiver 52 functions as a transmission unit that transmits a frame or a reception unit that receives a frame. The CAN transceiver 52 converts the transmission signal acquired from the CAN controller 50 into a differential voltage and transmits it to the bus 4. Further, when acquiring data from the bus 4, the CAN transceiver 52 reads the differential voltage of the bus 4 and transmits a reception signal shaped to be included in a predetermined voltage range to the CAN controller 50. A comparator is attached to the reception terminal Rx of the CAN controller 50, and digital data “1” and “0” are generated and stored by comparing a predetermined threshold voltage with a reception signal from the CAN transceiver 52. Store in the unit 30.

  FIG. 4 is a format example of a frame transmitted from the ECU 10 to the bus. A frame transmitted in one transmission includes a start of frame (SOF) indicating the start of the frame, an ID as a data identifier, a remote transmission request (RTR) for identifying the data frame and the remote frame, and a data byte. A control field representing the number, a data field that is the substance of the data to be transferred, an alive counter AC to which identification information is added, a CRC sequence to which a CRC for checking a frame error is added, a unit from which the correct message is received An ACK slot and an ACK delimiter for receiving a notification (ACK), an end-of-frame (EOF) indicating the end of the frame, and the like are included. In the frame, the data field is an example of a “data area”. The area including the data field and the alive counter AC is an example of “arbitrary area”, and the other area is an example of “standard area defined by the communication protocol”.

  In the bus 4, communication arbitration based on the priority represented by the ID and RTR is performed. When frames are transmitted simultaneously from a plurality of ECUs 10, each ECU 10 compares the data transmitted by itself with the result of monitoring the bus state. Here, when recessive and dominant are transmitted simultaneously from different ECUs 10, dominant is given priority and the bus state becomes dominant. At this time, the node that transmitted the recessive determines that the node has lost communication arbitration due to the difference in the bus state from the node that transmitted the recessive and stops transmission. According to such a principle, when a frame is started to be transmitted from a plurality of ECUs 10 at the same time, the node that transmitted the dominant wins communication arbitration when other nodes are performing recessive transmission. This means that the priority is high.

  Hereinafter, the flow of processing executed by the communication control unit 44 will be described with reference to flowcharts. FIG. 5 is a flowchart showing a flow of transmission processing executed by the communication control unit 44.

  First, the communication control unit 44 determines whether or not the number of times of transmission / reception is the first time (step S100). The first time means, for example, the first time after the ECU 10 is turned on. The ECU 10 performs a process of setting the count value of the alive counter AC to zero as an initialization process when the power is turned on. Also, when the count value of the alive counter AC reaches the upper limit value and overflows, the count value of the alive counter AC is returned to zero and is treated as the first time in a pseudo manner.

  If it is determined in step S100 that the number of times of frame transmission / reception is the first time, the communication control unit 44 causes the CAN transceiver 52 to transmit a frame including the alive counter AC whose count value is set to zero (step S102). In this case, a process for shifting data, which will be described later, is not performed.

  If it is determined in step S100 that the number of times of frame transmission / reception is not the first time, the communication control unit 44 increments the count value of the alive counter AC by one (step S104). Next, the communication control unit 44 shifts the data in the data field as described later (see FIG. 7) (step S106). Next, the communication control unit 44 sets the count value of the alive counter AC in step S104, and transmits a frame in which data is shifted in step S106 (step S108). Thereby, the process of one routine of this flowchart is completed.

  FIG. 6 is a flowchart showing a flow of reception processing executed by the communication control unit 44. First, the communication control unit 44 acquires the count value of the alive counter AC included in the received frame (step S150). Next, the communication control unit 44 specifies the position of the shifted data based on the count value acquired in step S150 (step S152). Next, the communication control unit 44 restores the frame (arbitrary area) based on the position of the data specified in step S152, and stores at least a part of the frame in the temporary storage area 36 as received data (step S154). . Thereby, the process of one routine of this flowchart is completed.

  FIG. 7 is a diagram illustrating how the communication control unit 44 increments the count value of the alive counter AC and shifts the data position. In the figure, only data D1 to D4, alive counter AC, and CRC sequence included in the data field of the frame are shown. Further, the description will be made assuming that the initial position of data is arranged in the order of data D1, D2, D3, and D4 from the beginning of the data (on the opposite side to the CRC sequence).

  In the first transmission of the frame, the data D1 to D4 are arranged at the initial position. At this time, the count value of the alive counter AC is set to zero. In the second transmission of the frame, the communication control unit 44 increments the count value of the alive counter AC by one and transmits the positions of the data D1 to D4 cyclically shifted backward. That is, in the second transmission of the frame, the data D4 is transmitted at the head, and the data D1, D2, and D3 are arranged in this order. In the third transmission of the frame, the communication control unit 44 increments the count value of the alive counter AC by one and transmits the positions of the data D1 to D4 cyclically shifted backward. As a result, in the third transmission of the frame, the data D3 is transmitted at the head and the data D4, D1, and D2 are arranged in this order.

  In the ECU 10 that receives the frame, the communication control unit 44 determines the positions of the data D1 to D4 by the process of FIG. 6 described above. In the first reception of the frame, since the count value of the alive counter AC is 0, the communication control unit 44 determines that the positions of the data D1 to D4 are the initial positions. In the second reception of the frame, since the count value of the alive counter AC is 1, the communication control unit 44 sets the data D4, D1, D2 in which the order of the data D1 to D4 of the previously transmitted frame is shifted by one. , D3 is determined to be transmitted in the order. In the third reception of the frame, since the count value of the alive counter AC is 2, the communication control unit 44 performs data D3 in which the order of the data D4, D1, D2, and D3 of the previously transmitted frame is shifted by one. , D4, D1, and D2.

  The communication control unit 44 of the ECU 10 on the receiving side stores the data in the temporary storage area 36 in a state where the order of the data included in the frame is rearranged in the original data order. As a result, the application program 32 (central control unit 42) of the ECU 10 on the receiving side can receive the content of data intended by the transmission source.

  In addition, according to the ECU 10 and the communication system 1 of the present embodiment, the arrangement of data is not fixed, but is changed according to the number of transmissions. Therefore, it is inappropriate to access communication from outside and analyze communication data. Interference can be prevented. As a result, security can be improved.

  According to the communication system 1 of the first embodiment described above, the communication control unit 44 on the frame transmission side increments the count value of the alive counter AC by 1 and cyclically moves the position of each data backward. To send. The communication control unit 44 on the frame receiving side determines the order of the data included in the frame based on the count value of the alive counter AC included in the received frame, and switches the position of the data based on the determination result. . As a result, the communication system 1 can improve the security of the in-vehicle network.

  In the present embodiment, each ECU 10 of the communication system 1 is described as including the communication control unit 44. However, even if the OBD connector 2 illustrated in FIG. 1 has the same function as that of the communication control unit 44 of the ECU 10. Good. In this case, the data for diagnosis transmitted from the OBDA connector 2 or the data transmitted from each ECU 10 is shifted based on the count value of the alive counter AC.

<Second Embodiment>
The communication system according to the second embodiment will be described below with reference to the drawings. FIG. 8 is a diagram illustrating a configuration example of the ECU 10A included in the communication system according to the second embodiment. The second embodiment is different from the first embodiment in that the ECU 10A includes a data position table 38, and the communication control unit 44 refers to the data position table 38 to replace the data position. Below, it demonstrates centering on the difference which concerns.

  FIG. 9 is a diagram illustrating the contents of the data position table 38. The data position table 38 is information (corresponding information) indicating the correspondence between the count value of the alive counter AC and the position of the data included in the frame. In the illustrated example, the count value of the alive counter AC is associated with the position of the data D1. For example, when the count value of the alive counter AC is 0, the position of the alive counter AC is No. 1 (the head of the transmitted data), and when the count value of the alive counter AC is 1, the position of the alive counter AC is the data to be transmitted. When the count value of the alive counter AC is 2, the position of the alive counter AC is second,..., When the count value of the alive counter AC is N, the position of the alive counter AC is third. It is shown that.

  Hereinafter, processing of the communication control unit 44 using the data position table 38 will be described with reference to a flowchart. FIG. 10 is a flowchart showing a flow of processing executed by the communication control unit 44 according to the second embodiment. First, the communication control unit 44 acquires the count value of the alive counter AC (step S200). Next, the communication control unit 44 refers to the data position table 38, and specifies the position of data corresponding to the count value of the alive counter AC acquired in step S200 (step S202). Next, the communication control unit 44 replaces the data at the data position specified in step S202 (step S204), and transmits a frame including the replaced data (step S206). Thereby, the process of one routine of this flowchart is completed.

  The communication control unit 44 on the side receiving the frame transmitted in step S206 obtains the count value of the alive counter AC included in the received frame. The communication control unit 44 refers to the data position table 38 and specifies the position of data corresponding to the count value of the alive counter AC. The communication control unit 44 restores the frame (arbitrary area) based on the specified position, and stores at least a part of the frame in the temporary storage area 36 as received data.

  FIG. 11 is a diagram illustrating a state in which the count value of the alive counter AC is incremented and the data position is shifted by the communication control unit 44 according to the second embodiment. In the figure, only data D1 to D4, alive counter AC, and CRC sequence included in the data field of the frame are shown. Further, the description will be made assuming that the initial position of data is arranged in the order of data D1, D2, D3, and D4 from the beginning of the data (on the opposite side to the CRC sequence).

  In the first transmission of the frame, the count value of the alive counter AC is zero. The communication control unit 44 refers to the data position table 38 and transmits the data so as to correspond to the count value zero of the alive counter AC. The position corresponding to the count value zero of the alive counter AC is a position where the data D1 to D4 are arranged at the initial position. In the second transmission of the frame, the count value of the alive counter AC is 1. The communication control unit 44 refers to the data position table 38 and exchanges data so as to correspond to the count value 1 of the alive counter AC and transmits the data. The position corresponding to the count value 1 of the alive counter AC is a position where the data D1 is replaced fourth. In the second transmission of the frame, data 4 is transmitted first, and then data D2, D3, and D1 are transmitted in this order. In the third transmission of the frame, the count value of the alive counter AC is 2. The communication control unit 44 refers to the data position table 38, exchanges data so as to correspond to the count value 2 of the alive counter AC, and transmits the data. The position corresponding to the count value 2 of the alive counter AC is a position where the data D1 is replaced second. In the third transmission of the frame, data 2 is transmitted at the head, and then data D1, D3, and D4 are transmitted in this order.

  The communication control unit 44 that has received the transmitted frame refers to the data position table 38 to restore the frame (arbitrary area) based on the count value of the alive counter AC included in the received frame and receive the frame. At least a part of the frame is stored in the temporary storage area 36 as data. As shown in FIG. 11, when the communication control unit 44 receives a frame including an alive counter whose count value is set to 2, the communication control unit 44 refers to the data position table 38 and refers to the position of the data D1. Is replaced from the top to the second. The communication control unit 44 restores the frame (arbitrary area) based on the determination result, and stores at least a part of the frame in the temporary storage area 36 as received data.

  According to the communication system 1 of the second embodiment described above, the communication control unit 44 refers to the data position table 38 and transmits the data by changing the order of data to be transmitted based on the count value of the alive counter AC. Further, the communication control unit 44 refers to the data position table 38 and restores the data based on the count value of the alive counter AC included in the received frame. As a result, the communication system 1 can achieve the effects of the first embodiment and can change the order of data irregularly.

<Third Embodiment>
The communication system according to the third embodiment will be described below with reference to the drawings. In the first embodiment and the second embodiment, the communication control unit 44 switches the position of the data of the frame to be transmitted. However, in the communication system 300 of the third embodiment, the communication control unit 44 transmits the frame. Based on the number of times, the position of the alive counter AC is switched. Below, it demonstrates centering on the difference which concerns.

  FIG. 12 is a flowchart illustrating a flow of transmission processing executed by the communication control unit 44 according to the third embodiment. First, the communication control unit 44 refers to the frame transmission / reception result stored in the storage unit 30 and specifies the number of times of frame transmission / reception in the communication system 1 so far (step S300). Next, the communication control unit 44 determines whether or not the number of times of transmission / reception of the frame specified in step S300 is the first time (step S302). When the number of transmission / reception times of the frame specified in step S300 is the first time, the communication control unit 44 causes the CAN transceiver 52 to transmit the frame while maintaining the position of the alive counter AC inserted in the initial position (step S300). S304). Note that when the alive counter AC is not inserted in the initial position in advance, the communication control unit 44 may insert the alive counter AC in the initial position and transmit the frame to the CAN transceiver 52.

  If the transmission / reception frequency of the frame specified in step S300 is not the first time, the communication control unit 44 inserts the alive counter AC at a position shifted by one from the previous position (step S306). The position where the position of the alive counter AC is shifted by one is, for example, a position shifted by one to the head side or the rear side of the data in the frame. In the present embodiment, the “position shifted by one” is used, but the present invention is not limited to this. The processing in step S306 may be, for example, “position shifted by N (N is an arbitrary natural number)”. Next, the communication control unit 44 causes the CAN transceiver 52 to transmit the frame that has been processed in step S306 (step S308). Thereby, the process of one routine of this flowchart is completed.

  FIG. 13 is a flowchart illustrating a flow of reception processing executed by the communication control unit 44 according to the third embodiment. First, the communication control unit 44 refers to the frame transmission / reception result stored in the storage unit 30 and identifies the number of times of frame transmission / reception in the communication system 1 so far (step S350). Next, the communication control unit 44 determines whether or not the number of times of transmission / reception of the frame specified in step S350 is the first time (step S352). When the number of transmission / reception times of the frame specified in step S350 is the first time, the communication control unit 44 considers the position of the alive counter AC to be the initial position, restores the frame, and receives at least a part of the frame as received data. Store in the temporary storage area 36 (step S354). If the transmission / reception frequency of the frame specified in step S350 is not the first time, the communication control unit 44 restores the frame by regarding the position of the alive counter AC as being shifted from the previous alive counter AC position by one. Then, at least a part of the frame is stored in the temporary storage area 36 as received data (step S356). Thereby, one routine of this flowchart is completed.

  FIG. 14 is a diagram schematically illustrating how the alive counter AC is shifted by one by the communication control unit 44 and inserted between data. In the figure, only data D1 to D4, alive counter AC, and CRC sequence included in the data field of the frame are shown. In addition, it is assumed that the initial position of the alive counter AC is after the data 4.

  In the first transmission of the frame, the communication control unit 44 transmits the alive counter AC to the bus 4 with the alive counter AC placed at the initial position. In the second transmission of the frame, the communication control unit 44 transmits the alive counter AC to the bus 4 while shifting the alive counter AC from the initial position to one head side. In the second transmission of the frame, the alive counter AC is inserted between D3 and D4 and transmitted to the bus. Further, in the third transmission of the frame, the communication control unit 44 transmits the alive counter AC to the bus while shifting the alive counter AC from the second transmission position to the first head side. In the third transmission of the frame, the alive counter AC is inserted between D2 and D3 and transmitted.

  In the ECU 10 that receives the frame, the communication control unit 44 specifies the position of the alive counter AC by the process of FIG. 13 described above. In the first reception of the frame, the position of the alive counter AC is regarded as the initial position, and the frame is restored. In the second reception of the frame, the communication control unit 44 determines that the position of the alive counter AC is shifted by one from the previous alive counter AC position, that is, a frame inserted between D3 and D4. Restore. In the third reception of the frame, the communication control unit 44 assumes that the position of the alive counter AC is shifted by one from the position of the previous alive counter AC, that is, a frame inserted between D2 and D3. Restore.

  According to the communication system 1 of the third embodiment described above, the frame transmitting side inserts the alive counter AC in the frame in accordance with the set standard, so that the set standard is not stored. It is possible to prevent the position of the alive counter AC included in the frame from being specified. On the other hand, on the receiving side in which the set reference is stored, the position of the alive counter AC included in the frame can be specified. As a result, the communication system 1 can improve the security of the in-vehicle network.

<Fourth embodiment>
FIG. 15 is a diagram illustrating a configuration example of the ECU 10B included in the communication system according to the fourth embodiment. The fourth embodiment is different from the third embodiment in that the ECU 10B includes an alive counter position table 39, and the communication control unit 44 refers to the alive counter position table 39 to replace the data position. Below, it demonstrates centering on the difference which concerns.

  FIG. 16 is a diagram illustrating the contents of the alive counter position table 39. The alive counter position table 39 is information indicating the correspondence between the number of frame transmissions in the entire communication system 1 and the position of the alive counter AC. In the illustrated example, for example, the position of the alive counter AC is 5 in the first transmission, the position of the alive counter AC is 3 in the second transmission, and the position of the alive counter AC is 4 in the third transmission. In addition, the number of frame transmissions is associated with the position of the alive counter AC. The alive counter position table 39 is stored in the storage unit 30 of each ECU 10 constituting the communication system 1.

  FIG. 17 is a flowchart showing a flow of processing executed by the communication control unit 44 according to the fourth embodiment. First, the communication control unit 44 refers to the frame transmission / reception result stored in the storage unit 30 and specifies the number of times of frame transmission / reception so far in the communication system 1 (step S400). Next, the communication control unit 44 refers to the alive counter position table 39 (step S402), and inserts the alive counter AC at a position corresponding to the number of times of frame transmission / reception specified in step S400 (step S404). Next, the communication control unit 44 causes the CAN transceiver 52 to transmit the frame in which the alive counter AC is inserted by the process of step S404 (step S406). Thereby, the process of one routine of this flowchart is completed.

  The communication control unit 44 on the side receiving the frame transmitted in step S406 refers to the alive counter position table 39 and specifies the position of the alive counter AC included in the received frame. The communication control unit 44 restores the frame based on the position of the alive counter AC, and stores at least a part of the frame in the temporary storage area 36 as received data. For example, the communication control unit 44 treats the information of the alive counter AC at the specified position as invalid and restores the data.

  FIG. 18 is a diagram illustrating a state in which the alive counter AC is inserted at a position corresponding to the alive counter position table 39 by the communication control unit 44. In the figure, only data D1 to D4, alive counter AC, and CRC sequence included in the data field of the frame are shown. In addition, it is assumed that the initial position of the alive counter AC is after the data 4.

  In the first transmission of the frame, the communication control unit 44 refers to the alive counter position table 39 and specifies the position where the alive counter AC corresponding to the first transmission count is inserted. When the position of the alive counter AC corresponding to the first transmission is fifth, the alive counter AC is inserted fifth from the top data, and the frame is transmitted. In the second transmission of the frame, the communication control unit 44 refers to the alive counter position table 39 and specifies the position where the alive counter AC corresponding to the second transmission count is inserted. If the position of the alive counter AC corresponding to the second transmission count is the third position, the alive counter AC is inserted third from the top data, and the frame is transmitted. In the third transmission of the frame, the communication control unit 44 refers to the alive counter position table 39 and specifies the position where the alive counter AC corresponding to the third transmission count is inserted. When the position of the alive counter AC corresponding to the third transmission is fourth, the alive counter AC is inserted fourth from the top data, and the frame is transmitted.

  The communication control unit 44 that has received the transmitted frame refers to the alive counter position table 39 to restore the frame (arbitrary area) based on the number of transmissions of the received frame, and receives at least the frame as received data. A part is stored in the temporary storage area 36. As shown in FIG. 17, when receiving a frame including the alive counter AC with the third transmission count, the communication control unit 44 refers to the alive counter position table 39 and inserts the alive counter AC fourth from the top. Judge that it was done. The communication control unit 44 restores the frame (arbitrary area) based on the determination result, and stores at least a part of the frame in the temporary storage area 36 as received data.

  According to the communication system 1 of the fourth embodiment described above, the communication control unit 44 refers to the alive counter position table 39, determines the position of the alive counter AC included in the data to be transmitted, and based on the determined result. A frame including data in which the alive counter AC is inserted at the position is transmitted. Further, the communication control unit 44 refers to the alive counter position table 39 and specifies the position of the alive counter AC included in the received frame. As a result, the communication system 1 has the effects of the third embodiment, and can irregularly insert the alive counter AC into the frame.

  As mentioned above, although the form for implementing this invention was demonstrated using embodiment, this invention is not limited to such embodiment at all, In the range which does not deviate from the summary of this invention, various deformation | transformation and substitution Can be added.

DESCRIPTION OF SYMBOLS 1 ... Communication system 10 ... ECU, 30 ... Memory | storage part, 40 ... Control part, 44 ... Communication control part,
AC alive counter

Claims (7)

A transmission unit that transmits a frame composed of a plurality of bits to a wired network in which a plurality of devices refer to information;
A receiving unit for receiving the frame from the wired network;
A control unit for changing the order of bits of the frame transmitted by the transmission unit according to the number of transmissions of the frame;
A communication device comprising: The frame has a standard area defined by a communication protocol and an arbitrary area in which at least the content of data is stored,
The control unit replaces the order of the bits of the frame transmitted by the transmission unit within the arbitrary region.
The communication apparatus according to claim 1. The frame has a plurality of data areas in which data contents are stored, and an alive counter area in which data identification information is included.
The control unit changes the order of the bits by changing the position of the data area included in the plurality of data areas without changing the position of the alive counter area.
The communication device according to claim 1 or 2. The control unit determines positions of data areas included in the plurality of data areas according to information included in the alive counter area;
The communication apparatus according to claim 3. The control unit refers to correspondence information in which information included in the alive counter area is associated with positions of data areas included in the plurality of data areas, and an order corresponding to the information included in the alive counter area And changing the order of the positions of the data areas included in the plurality of data areas,
The communication apparatus according to claim 4. The frame has a plurality of data areas in which data contents are stored, and an alive counter area in which data identification information is included.
The control unit changes the order of the bits by interrupting the alive counter area between the plurality of data areas.
The communication device according to claim 1 or 2. A communication device according to any one of claims 1 to 6;
The wired network;
A communication system comprising:

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