WO2013175633A1

WO2013175633A1 - Communication device, communication system and communication method

Info

Publication number: WO2013175633A1
Application number: PCT/JP2012/063532
Authority: WO
Inventors: 充啓馬渕
Original assignee: トヨタ自動車株式会社
Priority date: 2012-05-25
Filing date: 2012-05-25
Publication date: 2013-11-28

Abstract

In this communication device, which improves the reliability of messages to be communicated, a plurality of electronic control units (ECUs) is connected to a communication bus that enables communication messages to be communicated. In each ECU, check values (302) used for authenticating communication messages are set. Each ECU has a check value (CV) generation unit (32) for updating the check values (302) according to check value updating conditions. The check value updating conditions are synchronized between the plurality of ECUs on the basis of a single communication message that includes content indicating that the check values (302) are to be updated. An ECU that is to transmit a message includes, in the communication message to be transmitted, a message authentication code (MAC) (311) generated from a check value (302) that has been set. An ECU that us to receive the message determines whether or not the received communication message is authentic by comparing a regenerated value (341) regenerated from the MAC (311) included in the received communication message, and the check value (302) that has been set.

Description

COMMUNICATION DEVICE, COMMUNICATION SYSTEM, AND COMMUNICATION METHOD

The present invention relates to a communication device that is network-connected in a vehicle or the like, a communication system in which a plurality of communication devices are network-connected, and a communication method.

As is well known, a plurality of electronic control units (ECUs) mounted on a vehicle are connected to each other via a network so that information (vehicle information) of the electronic control units can be communicated with each other. Often configured. That is, such a communication system is configured as a vehicle network system using an ECU as a communication device. One such vehicle network system is a controller area network (CAN).

In CAN, each ECU that shares a bus, which is a communication line, can send a message on the bus according to each judgment. Therefore, transmission of a message from each ECU to the bus is easy. Therefore, for example, it is possible to connect an unauthorized ECU to a CAN bus and transmit an unauthorized message to the bus. When such an unauthorized message is transmitted, the ECU receiving the unauthorized message There is a risk of processing the message in the same way as a regular message.

Therefore, a technique for preventing communication by an unauthorized message has been proposed, and an example thereof is described in Non-Patent Document 1.

The communication system described in Non-Patent Document 1 is an in-vehicle CAN network including a plurality of ECUs connected to a CAN bus. The ECU that transmits the communication message among the plurality of ECUs generates a test code (MAC) that is a 64-bit message authentication code based on the four communication messages communicated first. The generated MAC is divided into four to generate four 16-bit codes, and these four codes are sequentially added to four communication messages communicated thereafter. The ECU that receives the communication message generates a 64-bit MAC based on the previously received four communication messages, and combines the four codes obtained from the four communication messages received thereafter to combine the 64-bit MAC. Reconfigure. The receiving ECU compares the generated MAC with the reconfigured MAC, and determines that the communication message is correct if the two MACs are the same, while the communication message is determined if the two MACs are different. It is determined to be illegal. Thereby, in this communication system, the correctness / incorrectness of the communication message is verified based on the highly confidential 64-bit MAC.

According to the communication system described in Non-Patent Document 1, the correctness / incorrectness of the four communication messages communicated first is reconstructed from the codes added by dividing the four communication messages communicated thereafter. It is verified based on the MAC. That is, based on the verification result, communication using an unauthorized communication message in the communication system is prevented. However, since the correct / incorrect determination of the communication message is performed based on the four communication messages communicated first and the four communication messages transmitted thereafter, at least the communication message It will take more than 8 minutes. For this reason, in this communication system, the delay required for correct / incorrect determination cannot be ignored, and it is difficult to adopt it for applications that require highly reliable processing in real time.

The present invention has been made in view of such circumstances, and its purpose is to prevent unauthorized communication through real-time processing, that is, to improve the reliability of a message to be communicated, and communication A method and a communication apparatus used in the communication system are provided.

Hereinafter, means for solving the above-mentioned problems and their effects will be described.

In order to achieve the above object, a communication system provided by the present invention is a communication system in which a plurality of communication devices are connected to a communication line so that communication messages can be communicated. An inspection code used for message authentication is set, and an inspection code update unit that executes the update of the inspection code in accordance with the inspection code update condition is provided. The inspection code update condition is synchronized based on one communication message including the content for instructing the update of the inspection code, and the communication device that transmits the communication message uses the assigned code generated from the set inspection code as described above. The communication device that is included in the communication message to be transmitted and receives the communication message is included in the received communication message. Determining positive / bad of the communication the received message based on a comparison of the test code check code that the set reproduced from the grant codes that.

In order to achieve the above object, a communication method provided by the present invention is a communication method in which a plurality of communication devices communicate communication messages via a communication line, and is used for authentication of communication messages to the plurality of communication devices. A step in which the inspection code update unit executes the update of the set inspection code according to the inspection code update condition, and instructs the update of the inspection code between the plurality of communication devices with the inspection code update condition Synchronizing based on one communication message including the contents, and including a step of including the grant code generated from the set inspection code in the communication message and transmitting the communication message.

In order to achieve the above object, a communication method provided by the present invention is a communication method in which a plurality of communication devices communicate communication messages via a communication line, and is used for authentication of communication messages to the plurality of communication devices. A step in which the inspection code update unit executes the update of the set inspection code according to the inspection code update condition, and instructs the update of the inspection code between the plurality of communication devices with the inspection code update condition A step of synchronizing based on one communication message including the content, a step of receiving a communication message including a grant code generated from the set inspection code, and a grant code included in the received communication message And the received communication based on the step of reproducing the inspection code from a comparison between the reproduced inspection code and the set inspection code. And a step of determining positive / incorrect message.

In order to achieve the above object, a communication apparatus provided by the present invention is a communication apparatus that is connected to a communication line and performs communication using a communication message with another communication apparatus connected to the communication line. In the communication device, an inspection code used for authentication of a communication message is set, and an inspection code update unit that executes update of the inspection code according to an inspection code update condition is provided. The inspection code update condition is synchronized with another communication device based on one communication message including contents instructing to update the inspection code, and is generated from the set inspection code. Send the grant code in the communication message.

In order to achieve the above object, a communication apparatus provided by the present invention is a communication apparatus that is connected to a communication line and performs communication using a communication message with another communication apparatus connected to the communication line. In the communication device, an inspection code used for authentication of a communication message is set, and an inspection code update unit that executes update of the inspection code according to an inspection code update condition is provided. The inspection code update condition is synchronized with another communication device based on one communication message including contents instructing the update of the inspection code, and is generated from the set inspection code. Receiving a communication message transmitted from the other communication device including the assigned code, and obtaining an inspection code from the assigned code included in the communication message. No, it determines a positive / incorrect communication the received message based on a comparison of the test code is the set inspection code this play.

According to such a configuration or method, the inspection code used to determine whether the communication message is correct / incorrect is updated in real time between a plurality of communication devices connected to the communication system according to the synchronized inspection code update conditions. The As a result, even if a correct inspection code is obtained from a communication message illegally obtained from the network, whether the inspection code is used or not is determined in real time by updating the inspection code. That is, the reliability of communication messages communicated in the network is naturally improved.

Also, by including an inspection code update instruction in the communication message, the execution of the inspection code and the update condition are synchronized among a plurality of communication devices that communicate (transmit or receive) one communication message. The That is, the inspection codes of a plurality of communication devices are synchronized with a simple mechanism.

This makes it possible to eliminate communication from unauthorized communication messages from unauthorized ECUs or external devices from the communication system. Further, since it becomes difficult to forge the validity of the communication message, security can be improved.

As a preferred configuration, the communication device is set with a conversion code used when generating a provision code from the inspection code and reproducing the inspection code from the provision code. There is provided a conversion code update unit that executes an update according to the conversion code update condition, and the conversion code update condition includes a content that instructs updating of the conversion code between the plurality of communication devices. Synchronized based on the communication message.

In order to achieve the above object, a communication system provided by the present invention is a communication system in which a plurality of communication devices are connected to a communication line so that communication messages can be communicated. An inspection code used for authentication of a message, a conversion code used when generating an assignment code from the inspection code and reproducing the inspection code from the assignment code are set, and the conversion code A conversion code update unit is provided for executing the update according to the conversion code update condition. Among the plurality of communication devices, the conversion code update condition includes a content for instructing the update of the conversion code 1 A communication device that is synchronized based on two communication messages and transmits the communication message transmits the conversion code to the inspection code. And the communication device that receives the communication message is reproduced by using the conversion code with respect to the grant code included in the received communication message. Whether the received communication message is correct / incorrect is determined based on a comparison between the inspection code and the set inspection code.

According to such a configuration, a conversion code used for conversion / reconversion (encryption / decryption) to the inspection code is exchanged between a plurality of communication devices connected to the communication system in real time according to the synchronized conversion code update conditions. Updated. As a result, it is difficult to obtain a correct inspection code from a communication message that is illegally acquired from the network, and it is also difficult to estimate a correct conversion code, thereby preventing an inspection code from being obtained from an assigned code. That is, since the communication device that is illegally connected cannot use the correct conversion code and the correct inspection code, communication using an illegal communication message is prevented.

Also, the grant code generated from the inspection code is changed by changing the conversion code. As described above, the inspection code and the conversion code are updated in accordance with the change of the assigned code, so that communication by an unauthorized communication message is prevented and the reliability of the communication message is further improved.

As a preferred configuration, the transmitting communication device generates the assignment code by encrypting the inspection code based on the conversion code, and the receiving communication device uses the conversion code based on the conversion code. The inspection code is reproduced by decoding.

According to such a configuration, since the inspection code to be updated becomes a grant code that is further converted by the conversion code and encrypted, the confidentiality of the generated grant code can be improved. This makes it difficult to reproduce the inspection code from the assigned code, thereby preventing communication using an unauthorized communication message and improving the reliability of the communication message.

As a preferred configuration, the inspection code is a value set in the communication device,
The conversion code is an encryption key set in the communication device.

According to such a configuration, since the grant code included in the communication message is encrypted with the encryption key, the secrecy of the grant code is ensured. As a result, it becomes more difficult to reproduce the inspection code from the assigned code, so communication by an unauthorized communication message is prevented, and the reliability of the communication message is improved.

As a preferred configuration, the inspection code update condition is a condition determined based on the content of the assigned code.

According to such a configuration, the inspection code update condition is determined based on the content of the assigned code. That is, since the inspection code update condition is determined according to the assigned code, it is difficult to guess the inspection code update condition, and it becomes difficult for an unauthorized communication device to assign an appropriate assigned code to the communication message. Thereby, the reliability of the communication message in the communication system is improved.

As a preferred configuration, the conversion code update condition is a condition determined based on the content of the assigned code.

According to such a configuration, the conversion code update condition is determined based on the content of the assigned code. That is, since the conversion code update condition is determined according to the assignment code, it is difficult to guess the conversion code update condition, and it becomes difficult for an unauthorized communication device to assign an appropriate assignment code to the communication message. Thereby, the reliability of the communication message in the communication system is improved.

As a preferred configuration, the communication message is a message according to a CAN protocol, and the grant code is stored in an extended ID area secured in the communication message.

According to such a configuration, since the assigned code is stored in the extended ID area defined by the CAN protocol, there is no influence on the data area in which the communication data to be transferred is stored. Can be maintained. In the CAN protocol, it is not assumed that data other than the extended ID is stored in the extended ID area. However, if the extended ID is not used for determination of whether or not a communication message can be received (filtering), the extended ID area is not used. Can be extracted.

As a preferred configuration, the communication message is a message according to a CAN protocol, and the grant code is stored in a data area secured in the communication message.

According to such a configuration, since the grant code is stored in the data storage area defined by the CAN protocol, it is easy to give the grant code to the CAN protocol. Further, even if the number of bits of the assigned code is reduced, confidentiality is ensured even by the high update frequency. For this reason, it is possible to reduce the number of assigned codes occupied in the data area for storing the communication data to be transferred, and to suppress the reduction in the transfer amount of the communication data.

The block diagram which shows the schematic structure about one Embodiment which actualized the vehicle carrying the communication system which concerns on this invention. The schematic diagram which shows typically the structure of the communication message transmitted / received in the communication system shown in FIG. The block diagram which shows schematic structure of the information processing part shown in FIG. FIG. 2 is a schematic diagram schematically illustrating a message inspection code (MAC) included in a communication message transmitted and received by the communication system illustrated in FIG. 1, and (a) is a schematic diagram illustrating a case where the lower first bit is “1”. FIG. 4B is a schematic diagram illustrating a case where the lower first bit is “0” and the lower second bit is “1”. The flowchart which shows the procedure which concerns on the transmission process of the communication message in ECU shown in FIG. 6 is a flowchart showing a procedure related to parameter update processing shown in FIG. 5. The flowchart which shows the procedure which concerns on the reception process of the communication message in ECU shown in FIG. The schematic diagram which shows typically the other example which actualized the communication message communicated in the communication system which concerns on this invention. The schematic diagram which shows typically the other example which actualized the communication message communicated in the communication system which concerns on this invention. The schematic diagram which shows typically the communication message transmitted / received in the conventional communication system.

A first embodiment embodying a communication system according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, the vehicle 10 includes an in-vehicle network system as a communication system. The in-vehicle network system includes first to third electronic control units (ECUs) 11 to 13 as communication devices and a communication bus 15 to which the first to third ECUs 11 to 13 are connected. Accordingly, the first to third ECUs 11 to 13 can exchange (transmit / receive) various information used for control and the like via the communication bus 15. The in-vehicle network system is configured as a CAN network to which a CAN (Controller Area Network) protocol is applied as a communication protocol. The communication bus 15 is, for example, a twisted pair cable. This makes it easy to add other ECUs to the communication bus 15 and allows the added other ECUs to easily transmit and receive communication messages. That is, the first to third ECUs 11 to 13 transmit various communication messages MS1 to MS3 to the communication bus 15, respectively, so that various types of information are communicated with other ECUs connected to the communication bus 15. Can give and receive. In the present embodiment, for convenience of explanation, the first and

second ECUs

11 and 12 are regular ECUs, while the third ECU 13 is an illegally connected ECU.

As shown in FIG. 2, the communication messages MS1 and MS2 transmitted from the first and

second ECUs

11 and 12 include “ID region”, “extended ID region”, and “data region” in the data frame constituting the communication message. Is defined. The “ID area” stores “message ID”, the “extended ID area” stores “embedded” “message check code” (MAC), and the “data area” stores “embedded”. Communication data "is stored. In the CAN protocol, an “extended ID area” is provided for a communication message set as an extended frame, but only an “ID area” is provided for a communication message set as a standard frame. That is, each communication message MS1, MS2 is set as an extended frame. When the MAC is stored (embedded) in the “extended ID area”, the MAC is also used for arbitration, but a communication message can be communicated. That is, if the first and

second ECUs

11 and 12 do not use the MAC in the “extended ID area” for filtering that restricts reception, the “extended ID area” of the communication message set in the extended frame is used. MAC can be transmitted and received.

On the other hand, as shown in FIG. 10, since the communication message MS3 transmitted from the third ECU 13 is set to, for example, a normal frame, an “ID region” and a “data region” are included in the data frame constituting the communication message. Is stipulated. The “ID area” stores “message ID”, and the “data area” stores “communication data”. That is, the “extended ID area” is not provided and “MAC” is not stored anywhere. That is, the third ECU 13 does not support “MAC”.

In addition, the communication bus 15 is provided with a data link connector (DLC) 16 which is a connection terminal capable of connecting an external device so as to be communicable. The DLC 16 connects a diagnostic device or the like as a regular communication device prepared by a manufacturer or a card dealer to the communication bus 15 so as to be communicable. Furthermore, the DLC 16 can be connected to a user tool 17 that is an unauthorized communication device prepared by the user.

By the way, if other ECUs or user tools 17 that are not sufficiently verified when connected to the network are connected to the communication bus 15, communication messages transmitted from those devices will adversely affect communication on the communication bus 15. There is also a risk of giving. In particular, the user tool 17 such as an unauthorized tester or a smartphone may cause a communication message transmission operation that adversely affects communication in the communication bus 15 when inappropriate software or a virus is executed. . Further, an unauthorized ECU may be connected to the communication bus 15 with the intention of disturbing communication. Therefore, it is necessary for the communication system to prevent communication using a communication message that may affect the communication on the communication bus 15. That is, in this embodiment, it is necessary to prevent the influence of an unauthorized communication message transmitted from the third ECU 13 that is illegally connected.

Each of the first and

second ECUs

11 and 12 is a control device that is used for various controls of the vehicle 10. For example, an ECU that controls a drive system, a traveling system, a vehicle body system, an information equipment system, and the like. It is. For example, an ECU for a drive system is an ECU for an engine, an ECU for a travel system is an ECU for a steering or a brake ECU, and an ECU for controlling a vehicle body system An ECU for a light and an ECU for a window can be mentioned, and an ECU for controlling an information device system includes an ECU for car navigation. The number of ECUs connected to the communication bus 15 is not limited to two, and may be one or three or more. Since the first and

second ECUs

11 and 12 have the same structure, the structure of the first ECU 11 will be described below, and for the sake of convenience of explanation, the same numbers are assigned to the same components. Thus, the detailed description of the structure of the second ECU 12 is omitted.

As shown in FIG. 1, the first ECU 11 includes a CAN between an information processing unit 20 that performs processing required for various controls using various information, and another ECU via a communication bus 15. There is provided a CAN controller 21 for performing communication using a communication message based on the protocol and for exchanging data related to the communication message with the information processing unit 20.

The CAN controller 21 analyzes a communication message received from the communication bus 15 and acquires a message ID included in the communication message, communication data that is a data body to be transferred, and the acquired message ID and communication. Data and the like are provided to the information processing unit 20. The CAN controller 21 generates a communication message including the message ID and communication data based on the message ID and communication data input from the information processing unit 20, and sends the generated communication message to the communication bus 15. Send.

Therefore, in the first ECU 11, a communication message (such as MS2) transmitted (flowed) to the communication bus 15 is received by the CAN controller 21, and the communication data included in the received communication message. Are provided from the CAN controller 21 to the information processing unit 20. In the first ECU 11, communication data or the like to be transmitted is given from the information processing unit 20 to the CAN controller 21, and a communication message MS 1 including the given communication data or the like is sent from the CAN controller 21 to the communication bus 15. (Flowed).

Thereby, the information processing unit 20 of the first ECU 11 can acquire various data necessary for the control function transmitted from the second ECU 12 or the like from the communication message (MS2 or the like) flowing through the communication bus 15. Further, the information processing unit 20 of the first ECU 11 can transmit a communication message MS1 including various data to be transmitted to the second ECU 12 or the like to the communication bus 15.

The third ECU 13 is provided with an information processing unit 20A and a CAN controller 21. The information processing unit 20A has the same configuration as the information processing unit 20 of the first ECU 11 except that it does not support MAC, and the CAN controller 21 has the same configuration as the CAN controller 21 of the first ECU 11. Therefore, the detailed explanation is omitted.

The information processing unit 20 is configured to include a microcomputer, and includes a computing device that performs various processes, and a storage device that holds computation results and programs that provide various control functions. The information processing unit 20 provides the predetermined control function by executing a program that provides the predetermined control function on the arithmetic device. In the present embodiment, the information processing unit 20 performs a generation process for generating a MAC from authentication data and a reproduction process for reproducing the authentication data from the MAC. The information processing unit 20 is provided with a function of executing a program corresponding to the generation process and the reproduction process held in the storage device by executing each program on the arithmetic device.

As shown in FIG. 3, the information processing unit 20 is provided with a storage unit 30 for storing parameters used for generation processing and reproduction processing.

The storage unit 30 uses the storage device of the information processing unit 20 as a storage medium. The storage device used for the storage unit 30 may be another storage device. The storage unit 30 stores, as parameters, a key 301 as a conversion code used for data encryption / decryption and a check value 302 as an inspection code that is authentication data used for ECU authentication. The initial value of the key 301 and the initial value of the check value 302 are set in the storage unit 30 at the time of factory shipment.

The key 301 is used when generating the MAC (311) from the check value 302 and when reproducing the check value 302 from the MAC (311). The key 301 is a so-called common key (common encryption key), and the same key 301 is held in each of the first and

second ECUs

11 and 12.

The check value 302 is a value used to authenticate a normal ECU, and the same check value 302 is held in each of the first and

second ECUs

11 and 12.

As illustrated in FIG. 3, the information processing unit 20 includes a MAC generation unit 31 that generates a MAC 311 from a check value, a CV generation unit 32 as a check code update unit that generates a new check value (CV), and a new And a key generation unit 33 as a conversion code update unit for generating a simple key. Further, the information processing unit 20 determines whether or not the reproduction unit 34 that reproduces CV from the MAC, the check value 302 stored in the storage unit 30, and the reproduction value 341 reproduced by the reproduction unit 34 are the same. A determination unit 35 for determination is provided.

The MAC generation unit 31 receives the check value 302 and the key 301 and outputs the MAC 311, and generates the MAC 311 based on the input check value 302 and the key 301. More specifically, the MAC generation unit 31 generates the MAC 311 by encrypting (encoding, encoding) the input check value 302 with the key 301. This encryption may be a conversion that can convert the check value 302 into a specific value using the key 301. For example, the conversion may be a conversion in which a logical operation such as logical sum (AND) or exclusive logical sum (XOR) is applied between the check value 302 and the key 301, or various functions such as a hash function are applied. Conversion is also possible. Thus, the MAC 311 generated by converting the check value 302 with the key 301 is output from the MAC generation unit 31. In the present embodiment, the MAC generation unit 31 generates an 18-bit MAC 311. Since the calculation for generating the 18-bit MAC 311 is simpler than the calculation for generating the 64-bit MAC used in the communication system of Non-Patent Document 1, the load that the MAC generation processing gives to the information processing unit 20 Can be kept small. Then, the generated MAC 311 is stored in an 18-bit “extended ID area” defined in the data frame of the CAN protocol, and transmitted in a communication message. By storing the check value 302 in one communication message in this way, it is possible to perform verification of the correctness / incorrectness of the communication message every time the communication message is communicated, that is, in real time.

The CV generation unit 32 causes the check value 302 stored in the storage unit 30 to be input to the CV generation unit 32 and outputs a new check value to update the check value 302 stored in the storage unit 30. . More specifically, the CV generation unit 32 acquires the value of the check value 302 stored in the storage unit 30 when the check value update condition as the inspection code update condition, which is a condition for updating the check value, is established. A predetermined calculation is performed on the acquired check value 302 to calculate a new check value. This predetermined operation is not limited as long as a new check value can be calculated from the check value 302, and may be an operation using a logical operation such as logical sum (AND) or exclusive logical sum (XOR). An operation using various functions such as a pseudo-random number or a hash function may be performed, or an arithmetic operation may be performed. Note that the new check value is calculated as a value different from the previous check value 302. Then, the CV generation unit 32 stores the new check value in the storage unit 30 as the check value 302. That is, the check value 302 stored in the storage unit 30 is updated to a new check value.

The key generation unit 33 inputs the key 301 stored in the storage unit 30 to the key generation unit 33 and outputs a new key to update the key 301 stored in the storage unit 30. More specifically, when a key update condition as a conversion code update condition that is a condition for updating a key is satisfied, the key generation unit 33 performs a predetermined operation on the value of the key 301 stored in the storage unit 30 to newly Key is calculated. This predetermined operation is not limited as long as a new key can be calculated from the key 301, and may be an operation using a logical operation such as logical sum (AND) or exclusive logical sum (XOR), or pseudo-operation. An operation using various functions such as a random number or a hash function may be performed, or an arithmetic operation may be performed. Note that the new key is calculated as a value different from the immediately preceding key 301. The key generation unit 33 stores the new key as the key 301 in the storage unit 30. That is, the key 301 stored in the storage unit 30 is updated with a new key.

By the way, the 18-bit MAC 311 generated by the MAC generation unit 31 has a smaller number of bits than the 64-bit MAC generated by the communication system described in Non-Patent Document 1, so that the analysis is easy and the security is low. However, in this embodiment, since the check value 302 and the key 301 used by the MAC generation unit 31 for generating the MAC 311 are changed as described above, even the MAC 311 with a small number of bits is difficult to analyze, and security is improved. Highly maintained.

The playback unit 34 receives the MAC 311 and the key 301 and outputs the playback value 341. The playback unit 34 generates the playback value 341 based on the input MAC 311 and the key 301. More specifically, the reproduction unit 34 obtains a reproduction value 341 reproduced from the MAC by decoding (decoding and reconverting) the 18-bit MAC generated by the MAC generation unit 31 using the key 301. Normally, the MAC 311 generated from the check value 302 by encryption based on the key 301 is decrypted (re-converted) based on the key 301 used to generate the MAC 311, thereby reproducing the check value 302. The That is, the reproduction value 341 is a check value, and if it is normal, it is the same value as the check value 302.

The determination unit 35 receives the value of the check value 302 stored in the storage unit 30 and the reproduction value 341 reproduced from the MAC by the reproduction unit 34, and outputs a comparison result between the check value 302 and the reproduction value 341. . More specifically, the determination unit 35 compares the value of the check value 302 with the reproduction value 341 to determine whether or not the check value 302 and the reproduction value 341 are the same. When the check value 302 and the reproduction value 341 are the same, since the MAC is confirmed to be a code generated from the check value 302, the ECU or the like that generated the MAC holds the correct check value 302. Is confirmed. That is, it is determined that the communication message is a message transmitted from a correct ECU or the like. On the other hand, if the check value 302 and the reproduction value 341 are different, it is determined that the MAC is not a code generated based on the check value 302 and the key 301. It is confirmed that the value 302 and the key 301 are not held. That is, it is determined that the communication message is a message transmitted from an unauthorized ECU or the like.

Next, the check value update condition and key update condition will be described.

In this embodiment, the success or failure of the check value update condition or key update condition is determined based on the MAC 311. Since the MAC 311 is included in the communication message, each ECU connected to the communication bus 15 determines success or failure of the check value update condition and the key update condition based on the MAC 311 obtained from the same communication message. That is, each ECU connected to the communication bus 15 obtains the same result as success or failure of the check value update condition or success or failure of the key update condition based on the same communication message.

As shown in FIG. 4A, for example, when the lower first bit of the MAC 311 is 1, the CV generation unit 32 determines that the check value update condition is satisfied. For example, when the lower 1st bit of the MAC 311 is 0 and the lower 2nd bit of the MAC 311 is 0, it is determined that the check value update condition is satisfied. On the other hand, for example, in other cases, that is, when the lower first bit of the MAC 311 is 0 and the lower second bit of the MAC 311 is 1, it is determined that the check value update condition is not satisfied.

As shown in FIG. 4B, for example, when the lower first bit of the MAC 311 is 0, the key generation unit 33 determines that the key value update condition is satisfied. On the other hand, for example, when the lower first bit is 1, it is determined that the key update condition is not satisfied.

That is, when the combination of the lower 1st bit and the lower 2nd bit of the MAC 311 is “1, 1” and “1, 0”, the check value update condition is satisfied, and when the same combination is “0, 1”, When the key update condition is satisfied and the combination is “0, 0”, the check value update condition and the key update condition are satisfied. In other words, the check value update condition is satisfied when the combination of the lower first bit and the lower second bit of the MAC 311 is “1, 1”, “1, 0”, and “0, 0”, and the key update condition is This is true when the combination of the lower 1st bit and the lower 2nd bit of the MAC 311 is “0, 1” and “0, 0”. Thereby, based on the MAC 311, when only the check value update condition is satisfied (“1, 1”, “1, 0”), when only the key update condition is satisfied (“0, 1”), the check value is updated. There are three states when the condition and the key update condition are both satisfied (“0, 0”). In addition, by providing a plurality of combinations that satisfy the conditions in this way, it becomes more difficult to analyze the MAC 311 included in the communication message received illegally.

Subsequently, the operation of the communication system of the present embodiment will be described with reference to FIGS. In the present embodiment, a case where the communication message MS1 transmitted from the first ECU 11 is received by the second ECU 12 will be described. However, the combination of the ECU that transmits the communication message and the ECU that receives the communication message is not limited thereto. I can't.

First, a case where a communication message is transmitted from the first ECU 11 will be described with reference to FIGS. When communication data to be transferred is prepared in the first ECU 11, a communication message transmission process is started.

As shown in FIG. 5, when the communication message transmission process is started, the first ECU 11 generates a MAC (step S10 in FIG. 5). In generating the MAC, the information processing unit 20 converts the check value 302 in the storage unit 30 based on the key 301 to generate an 18-bit MAC 311. When the MAC 311 is generated, the first ECU 11 creates a communication message (step S11 in FIG. 5). In creating a communication message, communication data, message ID, and MAC 311 are transmitted from the information processing unit 20 to the CAN controller 21, where the message ID is stored in the “ID area” of the data frame, and the “data area” The communication data is stored in, and the MAC 311 is stored in the “extended ID area”. Note that the communication data and the message ID may be transmitted from a device other than the information processing unit 20 provided in the first ECU 11 as long as it is transmitted to the CAN controller 21.

When the communication message is created, the first ECU 11 transmits the communication message (step S12 in FIG. 5). In the transmission of the communication message, the communication message created by the CAN controller 21 is transmitted to the communication bus 15. If a communication error occurs when transmission is performed, a communication message retransmission process is performed based on the CAN protocol. Furthermore, if the retransmission process cannot be performed, the transmission of the communication message is stopped, and the information processing unit 20 is notified that there is a transmission error. On the other hand, when the transmission of the communication message is normally completed, the information processing unit 20 is notified that there is no transmission error.

Then, when there is no transmission error, that is, when transmission of the communication message is normally completed, the first ECU 11 executes a parameter update process (step S13 in FIG. 5).

As shown in FIG. 6, when the parameter update process is executed, the first ECU 11 determines whether or not the lower first bit of the MAC 311 is “1” (step S20 in FIG. 6). When it is determined that the lower 1st bit of the MAC 311 is “1” (YES in step S20 in FIG. 6), the first ECU 11 generates a new check value (step S21 in FIG. 6). The check value is stored in the storage unit 30 (step S22 in FIG. 6). Then, returning to FIG. 5, the communication message transmission process is terminated. That is, in this case, only the check value 302 is updated.

When it is determined that the lower 1st bit of the MAC 311 is not “1” (NO in step S20 in FIG. 6), the first ECU 11 generates a new key (step S23 in FIG. 6), and the generated key Is stored in the storage unit 30 (step S24 in FIG. 6). Then, the first ECU 11 determines whether or not the lower 2nd bit of the MAC 311 is “1” (step S25 in FIG. 6). When it is determined that the lower 2nd bit of the MAC 311 is not “1” (NO in step S25 of FIG. 6), the first ECU 11 generates a new check value and stores it in the storage unit 30 (FIG. 6). Steps S21 and S22), the process returns to FIG. 5 and the communication message transmission process is terminated. That is, in this case, the key 301 and the check value 302 are updated.

On the other hand, when it is determined that the lower 2nd bit of the MAC 311 is “1” (YES in step S25 in FIG. 6), the first ECU 11 returns to FIG. 5 and ends the communication message transmission process. That is, in this case, only the key 301 is updated.

When there is a communication error, that is, when transmission of the communication message is not normally terminated, the first ECU 11 temporarily terminates the communication message transmission process without performing the parameter update process. When the transmission of the communication message is not normally terminated, other ECUs including the second ECU 12 have not been able to receive this communication message, or have not been normally received. For this reason, the first ECU 11 does not perform parameter update processing based on this communication message. If the first ECU 11 performs a parameter update process based on this communication message, a device that executes the parameter update process, such as the first ECU 11, and the second ECU 12 in the communication system. Thus, there is a mixture of apparatuses that do not execute parameter update processing, and the update of each parameter is not synchronized. That is, if the communication of the communication message is normal, the regular ECU (first ECU 11) that transmits the communication message updates at least one of the key 301 and the check value 302 each time the communication message is communicated.

Next, the case where the second ECU 12 receives a communication message will be described with reference to FIG. When the communication message is transmitted to the CAN controller 21, the second ECU 12 starts a communication message reception process.

As shown in FIG. 7, in the communication message reception process, the CAN controller 21 analyzes the communication message, acquires the message ID from the “ID area” of the data frame, acquires the communication data from the “data area”, The MAC 311 is acquired from the “extended ID area” (step S30 in FIG. 7).

When the communication message is analyzed, the second ECU 12 decodes the MAC 311 in the information processing unit 20 (step S31 in FIG. 7). In the decryption of the MAC 311, the reproduction value 341 is obtained by decrypting the MAC 311 with the key 301. When the reproduction value 341 is obtained by decoding the MAC 311, the determination unit 35 of the second ECU 12 determines whether or not the check value is correct (step S <b> 32 in FIG. 7). That is, the determination unit 35 determines that the check value is correct when the reproduction value 341 and the check value 302 stored in the storage unit 30 match, and when the reproduction value 341 and the check value 302 are different, the check value Is determined to be incorrect. When it is determined that the check value is not correct (NO in step S32 in FIG. 7), the second ECU 12 does not process the communication message, that is, does not use the communication data included in the communication message. Then, the communication message reception process is terminated.

On the other hand, when it is determined that the check value is correct (YES in step S32 in FIG. 7), the communication message is processed (step S33 in FIG. 7). In the processing of the communication message, the type of communication data is specified based on the message ID, and the value of the specified type of variable is rewritten to the value obtained from the communication data. For example, when it is specified from the message ID that the type of communication data is vehicle speed, the value of the variable assigned to the vehicle speed in the second ECU 12 is rewritten based on the value stored in the communication data, Various controls on the vehicle are performed based on the rewritten speed value.

When the communication message processing is normally completed, the second ECU 12 executes a parameter update process (step S34 in FIG. 7). In this parameter update process, at least one of the check value and the key is updated. This parameter update process is the same as the parameter update process (step S13 in FIG. 5) of the communication message transmission process described above. That is, since it is the same as the processing of step S20 to step S25 shown in FIG. 6, its detailed description is omitted. Therefore, in the parameter update process, the parameter update process is performed based on the MAC 311 having the same value as the MAC 311 used by the first ECU 11 for the parameter update process. Therefore, when only the check value 302 is updated in the first ECU 11, only the check value 302 is updated in the second ECU 12, and when only the key 301 is updated in the first ECU 11, the second ECU 12 is updated. However, only the key 301 is updated. Further, when the key 301 and the check value 302 are updated in the first ECU 11, the key 301 and the check value 302 are also updated in the second ECU 12.

Thereby, the update of the key 301 of the first ECU 11 and the update of the key 301 of the second ECU 12 are executed in synchronization. Further, the update of the check value 302 of the first ECU 11 and the update of the check value 302 of the second ECU 12 are executed in synchronization. Furthermore, the first ECU 11 and the second ECU 12 are initially set with the same content key 301 and the same content check value 302. Further, since the first ECU 11 and the second ECU 12 update the key 301 by the key generation unit 33 having the same configuration, the updated keys become the same key, so that the identity of each key is maintained. . Similarly, since the first ECU 11 and the second ECU 12 update the check value 302 by the CV generation unit 32 having the same configuration, the updated check values become the same check value, so that the check values are identical. Is maintained.

That is, in the normal ECU (second ECU 12) that receives the communication message, if communication of the communication message is normal, the key in the ECU (first ECU 11) that transmits the communication message each time the communication message is communicated. The key 301 and the check value 302 are updated in synchronization with the update of the check value.

This makes it possible to prevent unauthorized communication, that is, to improve the reliability of a message to be communicated, by determining the validity of the check value in real time. Further, communication by an unauthorized communication message from an unauthorized ECU or external device can be excluded from the communication system. Furthermore, it is possible to prevent an unauthorized ECU or the like from impersonating a regular ECU. Further, since it becomes difficult to forge (disguise) the correctness of the communication message, the security of the communication system is improved.

As described above, the communication system according to the present embodiment has the effects listed below.

(1) The check value 302 used for determining whether the communication message is correct / incorrect is updated in real time between the first and

second ECUs

11 and 12 connected to the communication system in accordance with the synchronized check value update conditions. The As a result, even if a correct check value 302 is obtained from a communication message illegally acquired from the network, the check value 302 is updated to determine whether the check value 302 is correct / incorrect in real time. Is done. That is, the reliability of communication messages communicated in the network is naturally improved.

Further, by making the update instruction of the check value 302 in accordance with the contents of the MAC 311 included in the communication message, the execution of the update of the check value 302 and the update condition are communicated (transmitted or transmitted). It is synchronized between the first and

second ECUs

11 and 12 that are received. That is, the check values 302 of the first and

second ECUs

11 and 12 are synchronized with a simple mechanism.

(2) The key 301 used for conversion / reconversion (encryption / decryption) with respect to the check value 302 is real-time in accordance with the synchronized key update conditions between the first and

second ECUs

11 and 12 connected to the communication system. Updated to This makes it difficult to obtain the correct check value 302 from a communication message that is illegally acquired from the network, and it is also difficult to estimate the correct key 301, so that obtaining the check value 302 from the MAC 311 is also prevented. That is, since an illegally connected ECU cannot use the correct key 301 and the correct check value 302, communication using an unauthorized communication message is prevented.

Also, by changing the key 301, the MAC 311 generated from the check value 302 is also changed. As described above, the check value 302 and the key 301 are updated in accordance with the change of the MAC 311, thereby preventing communication by an unauthorized communication message and further improving the reliability of the communication message.

(3) Since the updated check value 302 is further converted by the key 301 and encrypted to become the MAC 311, the confidentiality of the generated MAC 311 can be improved. This makes it difficult to reproduce the check value 302 from the MAC 311, thereby preventing communication using an unauthorized communication message and improving the reliability of the communication message.

(4) Since the MAC 311 included in the communication message is encrypted by the key 301, the confidentiality of the MAC 311 is ensured. As a result, it becomes more difficult to reproduce the check value 302 from the MAC 311. Therefore, communication by an unauthorized communication message is prevented, and the reliability of the communication message is improved.

(5) Check value update conditions are determined based on the contents of the MAC 311. That is, since the check value update condition is determined according to the MAC 311, it is difficult to guess the check value update condition, and it becomes difficult for an unauthorized communication device to assign an appropriate MAC 311 to a communication message. Thereby, the reliability of the communication message in the communication system is improved.

(6) The key update condition is determined based on the contents of the MAC 311. That is, since the key update condition is determined according to the MAC 311, it is difficult to guess the key update condition, and it becomes difficult for an unauthorized communication device to assign an appropriate MAC 311 to a communication message. Thereby, the reliability of the communication message in the communication system is improved.

(7) Since the MAC 311 is stored in the “extended ID area” defined by the CAN protocol, there is no influence on the data area in which the communication data to be transferred is stored. Can do. In the CAN protocol, it is not assumed that data other than the extended ID is stored in the “extended ID area”. However, if the extended ID is not used for determining whether or not a communication message can be received (filtering), reception is possible. The side can take out the MAC 311 stored in the “extended ID area”.

(Other embodiments)
In addition, the said embodiment can also be implemented with the following aspects.

In the above embodiment, the case where the key 301 is a common encryption key has been exemplified, but the key strength is not particularly limited, and thus a key generated by an advanced encryption algorithm or a key consisting of a random numerical value is appropriate. It may be a key consisting of a value defined in As a result, the degree of freedom in designing the communication system can be improved.

In the above embodiment, the case where the CV generation unit 32 and the key generation unit 33 are provided is illustrated. However, the present invention is not limited thereto, and only one of the CV generation unit and the key generation unit may be provided in the information processing unit. This also updates the check value or key, thereby improving the MAC security and simplifying the communication system.

In the above embodiment, the case where the MAC is stored in the “extended ID area” is exemplified. However, the present invention is not limited to this, and the MAC may be stored in another area such as a “data area”.

As shown in FIGS. 8 and 9, the MAC may be stored in the “data area”. For example, FIG. 8 shows a case where the MAC is arranged on the ID area side (front side) of the “data area” with respect to the communication data, and FIG. The case where it is arranged on the ID area side (front side) of the “data area” is shown. According to this, since the MAC is stored in a data area defined by the CAN protocol, it is easy to assign the MAC to the CAN protocol.

Note that since the size of the “data area” is limited in the CAN protocol, when the MAC is stored in the data area, the communication data to be transferred that can be stored in the “data area” decreases. However, by frequently updating check values and keys, this communication system can minimize the number of MAC bits while maintaining communication message security. For this reason, even when the MAC is stored in the data area, the number of occupied MACs in the “data area” is reduced to suppress the decrease in communication data, and the communication message is verified for real / incorrect in real time. Can do.

In the above embodiment, the case where the MAC 311 is 18 bits is exemplified. However, the present invention is not limited to this, and the MAC may be smaller than 18 bits or larger than 18 bits. As a result, it is possible to adjust the MAC security strength and the load on the arithmetic processing.

In the above embodiment, the case where the check value update condition and the key update condition are determined by the lower first bit and second bit values of the MAC is illustrated. However, the present invention is not limited to this, and if the check value update condition and the key update condition are data included in one communication message, the data other than the MAC that changes irregularly, such as the contents of communication data or the contents of CRC data, can be used. Success or failure may be determined based on the result.

In the above embodiment, the case where at least one of the check value 302 and the key 301 is updated each time a communication message is communicated is illustrated. However, the present invention is not limited to this, and if the required security is ensured, both the check value and the key may not be updated even if the communication message is communicated. At this time, it is preferable to use data other than the MAC as the update condition. Thereby, the improvement of the design freedom of a communication system comes to be aimed at.

・ If the required security is ensured, the check value and key may be updated according to the number of communication messages. Thereby, the improvement of the design freedom of a communication system comes to be aimed at.

In the above embodiment, the case where the initial value of the key 301 and the initial value of the check value 302 are set at the time of shipment from the factory is illustrated. However, the present invention is not limited to this, and each initial value can be used if security can be ensured. May be set by communication with a card dealer or an external center. Each initial value may be set only with the initial value or may be set with reprogramming of the ECU. Thereby, the improvement of the design freedom of such a communication system comes to be aimed at.

In the above embodiment, the case where the CV generation unit 32 and the key generation unit 33 are provided is illustrated. However, the present invention is not limited to this, and the CV generation unit and the key generation unit may be combined into one generation unit by applying the same arithmetic processing to the generation of the key and the generation of the check value. Thereby, the structure of the communication system can be simplified.

In the above embodiment, the case where an external device is wired to the DLC 16 is illustrated. However, the present invention is not limited to this, and an external device may be connected to the DLC via wireless communication. For example, a wireless communication terminal may be connected to the DLC, and another wireless communication device may be provided in the external device so that the DLC and the external device communicate wirelessly. This makes it possible to prevent unauthorized communication regardless of the connection mode of the external device to the DLC.

In the above embodiment, the case where the communication system is mounted on the vehicle 10 is illustrated. However, the present invention is not limited to this, and a part or all of the communication system may be provided other than the vehicle. As a result, it is possible to determine whether the communication message is correct / incorrect even for a communication system including a CAN that is used outside the vehicle, so that the applicability of the communication system can be improved.

In the above embodiment, the case where the communication system is a system based on the CAN protocol has been exemplified. However, the communication protocol applied to the communication system is, for example, Ethernet (registered trademark) or FlexRay (registered trademark), as long as the communication message is verified for correctness / incorrectness using a check value, a key, or the like. The communication protocol may be other than the CAN protocol. Thereby, the applicability of such a communication system can be improved.

In the above embodiment, the case where the communication system is mounted on the vehicle 10 is illustrated. However, the present invention is not limited to this, and the communication system may be provided in a moving body other than a vehicle, such as a ship, a railway, an industrial machine, or a robot.

DESCRIPTION OF SYMBOLS 10 ... Vehicle, 11 ... 1st ECU, 12 ... 2nd ECU, 13 ... 3rd ECU, 15 ... Communication bus, 16 ... Data link connector (DLC), 17 ... User tool, 20, 20A ... Information Processing unit, 21 ... CAN controller, 30 ... storage unit, 31 ... MAC generation unit, 32 ... CV generation unit, 33 ... key generation unit, 34 ... reproduction unit, 35 ... determination unit, 301 ... key, 302 ... check value, 311 ... MAC, 341 ... reproduction value.

Claims

A communication system in which a plurality of communication devices are connected to a communication line so that communication messages can be communicated,
Each of the plurality of communication devices is provided with a test code update unit configured to perform a test code update according to a test code update condition, and a test code used for authentication of a communication message is set.
Among the plurality of communication devices, the inspection code update condition is synchronized based on one communication message including content instructing to update the inspection code,
The communication device that transmits the communication message includes the grant code generated from the set inspection code in the communication message to be transmitted,
The communication device that receives the communication message determines whether the received communication message is correct or incorrect based on a comparison between the inspection code reproduced from the assigned code included in the received communication message and the set inspection code. A communication system characterized by:
The communication device is set with a conversion code that is used when generating a provision code from the inspection code and when reproducing the inspection code from the provision code. A conversion code update unit is provided to execute according to the update conditions.
The communication system according to claim 1, wherein the conversion code update condition is synchronized between the plurality of communication devices based on one communication message including content instructing to update the conversion code.
The transmitting communication device generates the grant code by encrypting the inspection code based on the conversion code,
The communication system according to claim 2, wherein the receiving communication device reproduces the inspection code by decoding the grant code based on the conversion code.
The inspection code is a value set in the communication device,
The communication system according to claim 2, wherein the conversion code is an encryption key set in the communication device.
The communication system according to any one of claims 1 to 4, wherein the inspection code update condition is a condition determined based on a content of the assigned code.
The communication system according to any one of claims 2 to 4, wherein the conversion code update condition is a condition determined based on a content of the assigned code.
The communication message is a message according to a CAN protocol,
The communication system according to any one of claims 1 to 6, wherein the assignment code is stored in an extended ID area secured in a communication message.
The communication message is a message according to a CAN protocol,
The communication system according to any one of claims 1 to 6, wherein the assignment code is stored in a data area secured in a communication message.
A communication system in which a plurality of communication devices are connected to a communication line so that communication messages can be communicated,
In each of the plurality of communication devices, an inspection code used for authentication of a communication message, a conversion code used when generating an assignment code from the inspection code, and reproducing the inspection code from the assignment code, Is provided, and a conversion code update unit that executes the update of the conversion code according to the conversion code update condition is provided,
Between the plurality of communication devices, the conversion code update condition is synchronized based on one communication message including content instructing the update of the conversion code,
The communication device that transmits the communication message includes the grant code generated by using the conversion code for the inspection code in the communication message to be transmitted,
The communication device that receives the communication message, based on the comparison between the inspection code reproduced by using the conversion code with respect to the grant code included in the received communication message, and the set inspection code A communication system, characterized by determining whether a received communication message is correct or incorrect.
A communication method in which a plurality of communication devices communicate communication messages via a communication line,
A step in which an inspection code update unit updates an inspection code set for use in authentication of communication messages in the plurality of communication devices according to an inspection code update condition, and the inspection code update condition is transmitted to the plurality of communication Synchronizing between apparatuses based on one communication message including contents for instructing update of the inspection code, and including a grant code generated from the set inspection code in the communication message, and the communication message And a step of transmitting the communication method.
A communication method in which a plurality of communication devices communicate communication messages via a communication line,
A step in which an inspection code update unit updates an inspection code set for use in authentication of communication messages in the plurality of communication devices according to an inspection code update condition, and the inspection code update condition is transmitted to the plurality of communication Synchronizing between apparatuses based on one communication message including contents for instructing to update the inspection code; and receiving a communication message including a grant code generated from the set inspection code; , Reproducing the inspection code from the assigned code included in the received communication message, and whether the received communication message is correct / incorrect based on a comparison between the reproduced inspection code and the set inspection code And a step of determining the communication method.
A communication device that is connected to a communication line and performs communication using a communication message with another communication device connected to the communication line,
In the communication device, an inspection code used for authentication of a communication message is set, and an inspection code update unit that executes update of the inspection code according to an inspection code update condition is provided,
The communication device is synchronized with another communication device based on a single communication message including the contents for instructing the update of the inspection code and the inspection code update condition. A communication apparatus comprising: a transmission message including an addition code generated from a code.
A communication device that is connected to a communication line and performs communication using a communication message with another communication device connected to the communication line,
In the communication device, an inspection code used for authentication of a communication message is set, and an inspection code update unit that executes update of the inspection code according to an inspection code update condition is provided,
The communication device is synchronized with another communication device based on a single communication message including the contents instructing the update of the inspection code and the inspection code update condition. The communication message transmitted from the other communication device including the grant code generated from the code is received, the test code is reproduced from the grant code included in the communication message, and the reproduced test code and the set are set. A communication device that determines whether the received communication message is correct or incorrect based on a comparison with a check code.