JP2018125659A - Communication system, communication method, program, and non-temporary storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve communication system, communication method, program, and non-temporary recording medium which are difficult to analyze unauthorized access and authentication logic, have excellent expandability, and perform appropriate obfuscation in response to changes in circumstances. I will provide a. A communication system according to one aspect of the present disclosure is a communication system including a plurality of nodes connected to a network, and each node of the plurality of nodes is a message received from another node of the plurality of nodes. The authentication logic switching control unit that switches the authentication logic between multiple authentication logics so that the authentication logic used to authenticate the validity is the same among multiple nodes, and the legitimacy of the message using the authentication logic. A configuration is adopted in which a message authentication unit for authenticating sex is provided. [Selection diagram] Fig. 3

Description

  The present disclosure relates to a communication system, a communication method, a program, and a non-transitory recording medium.

  In recent years, the importance of communication using in-vehicle LANs such as CAN (Controller Area Network), LIN (Local Interconnect Network), FlexRay, Most (Media oriented systems transport) and the like has been increased along with the electrification of vehicles. Accordingly, there is an increasing need for a defense function against unauthorized access from the outside via a module connected to the in-vehicle LAN, and many in-vehicle LAN communication requirements with a protection function have been proposed (Patent Document 1, Patent Document 2).

JP2013-098719A JP 2016-158204 A

  However, the logic described in Patent Document 1 is simple, and there is a problem that authentication logic is easily analyzed and unauthorized access is likely to be caused by focusing on messages with fixed parameters. Moreover, in patent document 1 and patent document 2, each ECU needs to be provided with a counter for every CAN ID of ECU (Electronic Control Unit) connected to CAN which is vehicle-mounted LAN, management becomes complicated, and a system There is a problem that the extensibility of. In addition, as the number of counters increases, there is a problem that synchronization loss due to a communication error or the like increases, and the probability of successful authentication of illegal messages increases.

  Further, in Patent Document 1 and Patent Document 2, since the level of obfuscation is always constant, there is a problem that obfuscation more than necessary or insufficient obfuscation may occur.

  The purpose of this disclosure is an improved communication system, communication method, program, and non-temporary that is difficult to analyze unauthorized access and authentication logic, is highly scalable, and moderately obfuscates in response to changing circumstances Providing a static recording medium.

  A communication system according to an aspect of the present disclosure is a communication system including a plurality of nodes connected to a network, wherein each node of the plurality of nodes is valid of a message received from another node of the plurality of nodes. An authentication logic switching control unit that switches the authentication logic between the plurality of authentication logics so that the authentication logic used to authenticate the plurality of nodes is the same, and the message using the authentication logic And a message authenticating unit that authenticates the validity.

  A communication method according to an aspect of the present disclosure is a communication method in a communication system including a plurality of nodes connected to a network, and is used to authenticate the validity of a message received from another node of the plurality of nodes. Switching the authentication logic between a plurality of authentication logics, and authenticating the validity of the message using the authentication logic, such that the authentication logic to be used is the same between the plurality of nodes. The structure to be provided is taken.

  A program according to an aspect of the present disclosure authenticates validity of a message received from another node of the plurality of nodes in a computer provided in each of the plurality of nodes in a communication system including the plurality of nodes connected to the network. Switching the authentication logic between a plurality of authentication logics so that the authentication logic used to do the same among the plurality of nodes and authenticating the validity of the message using the authentication logic And a step is executed.

  A non-transitory recording medium according to an aspect of the present disclosure is a non-temporary recording medium that records a computer-readable program, and the communication system includes a plurality of nodes connected to a network. The plurality of authentication logics are configured so that authentication logic used to authenticate the validity of messages received from other nodes of the plurality of nodes is the same among the plurality of nodes. And a step of authenticating the validity of the message using the authentication logic and recording a program.

  According to the present disclosure, an improved communication system, communication method, program, and non-temporary that are difficult to analyze unauthorized access and authentication logic, have excellent scalability, and perform moderate obfuscation in response to changes in circumstances Recording medium can be provided.

It is explanatory drawing of the communication system which concerns on this indication. FIG. 3 is a configuration diagram of a master node according to the present disclosure. It is a lineblock diagram of a slave node concerning this indication. It is a flowchart which shows the operation | movement flow of the master node with respect to the security risk which concerns on this indication. It is explanatory drawing of the relationship between the risk level of a security risk, and an authentication logic. It is a flowchart which shows the operation | movement flow of the master node with respect to the change of the vehicle state which concerns on this indication. It is explanatory drawing of the relationship between the risk level of a vehicle state, and authentication logic. It is a figure which shows an example of the hardware constitutions of a computer.

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is an explanatory diagram of a communication system 1000 according to the present disclosure. FIG. 2 is a configuration diagram of the master node 100A according to the present disclosure. FIG. 3 is a configuration diagram of the slave node 100B according to the present disclosure. In FIG. 1 to FIG. 3, components having the same reference numerals represent the same components.

  The communication system 1000 includes a plurality of nodes 100 (100-1, 100-2,..., 100-n) and a network 200. The plurality of nodes 100 are connected to the network 200 via transceivers 110 (110-1, 110-2,..., 110-n) included in each of the nodes 100.

  The communication system 1000 is a LAN (in-vehicle LAN) provided in a vehicle. The in-vehicle LAN is, for example, CAN, LIN, FlexRay, Most. The node 100 is, for example, an ECU. In one example, the network 200 is, for example, a bus network such as a CAN bus or a LIN bus as shown in FIG. In another example, the network 200 is a star network such as a FlexRay network or a ring network such as a Most network.

  In one example, the plurality of nodes 100 are all master nodes 100 </ b> A that monitor vehicle conditions such as vehicle speed and security risks such as security breaches in the communication system 1000. In this case, the plurality of nodes 100 have a multi-master configuration. In this case, the master node 100A does not need to instruct the other node 100 to switch the operation.

  In another example, any of the plurality of nodes 100 is the master node 100A, and the nodes other than the master node 100A are slave nodes 100B that switch operations in accordance with instructions from the master node 100A.

  In yet another example, two or more nodes 100 of the plurality of nodes 100 are the master nodes 100A and other than the master node 100A as long as the consistency with respect to the operation for the instructions from the two or more nodes 100 is ensured. The node 100 is the slave node 100B. In this case, a configuration in which roles are shared between two or more master nodes 100A may be employed. For example, the master node 100A that monitors the vehicle state such as the vehicle speed and the master node 100A that monitors the security risk may be two master nodes 100A.

  First, components that the master node 100A and the slave node 100B have in common as the node 100 will be described.

  Each of the nodes 100 includes a transceiver 110, a message control unit 120, a calculation logic storage device 130, an authentication key storage device 140, and an authentication logic switching control unit 150. In one example, each of the nodes 100 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. For example, the CPU reads out a program corresponding to the processing content from the ROM, expands it in the RAM, and centrally controls the operations of the message control unit 120 and the authentication logic switching control unit 150 in cooperation with the expanded program.

  The transceiver 110 includes a receiver 111 and a transmitter 112.

  The message control unit 120 functions as a transmission data input unit 121, a message generation unit 122, a message verification unit 123, a reception data output unit 124, and a MAC value generation unit 125.

  The transmission data input unit 121 inputs data (transmission data) that the node 100 should transmit to other nodes from other components (not shown) included in the node 100.

  The MAC value generation unit 125 calculates a message authentication code value for transmission data using an authentication key and a message authentication code value calculation logic (hereinafter simply referred to as calculation logic).

  The authentication key is a value having a predetermined bit length that is shared and concealed among the plurality of nodes 100 and is unknown to a third party. In one example, the authentication key is an encryption key.

  As will be described later, the message authentication code value is a value used by the message verification unit 123 to generate a message authentication code value for insertion used for verifying the validity of the received data.

  The calculation logic is logic for calculating the same message authentication code value for a plurality of data having the same authentication key and the same content. Furthermore, the original transmission data cannot be restored from the calculated message authentication code value. That is, the calculation logic has irreversibility. In one example, the calculation logic is an HMAC algorithm that calculates using a hash function such as SHA-256. In one example, the calculation logic is a CMAC algorithm that is a message authentication code algorithm based on a block cipher.

  In one example, the calculation logic also depends on parameters such as an identification number (ID) of the node 100 and a CRC (Cyclic Redundancy Check) value of transmission data. In this case, the calculation logic is a logic for calculating the same message authentication code value for a plurality of data having the same contents with the same authentication key and parameter.

  The MAC value generation unit 125 generates a message authentication code value for insertion from the calculated message authentication code value. In one example, the MAC value generation unit 125 sets a part of the message authentication code value as an insertion message authentication code value. For example, the MAC value generation unit 125 generates a message authentication code value for insertion by cutting out a bit string included in a window at a specific offset position of the message authentication code value. For example, the offset position may be a predetermined position shared as a parameter of the entire communication system 1000.

  The message generator 122 generates a message (main message) including transmission data in the data field. Further, the message generator 122 generates a message (MAC message) including the message authentication code value for insertion generated by the MAC value generator 125 in the data field for the transmission data. In one example, the main message and the MAC message are unified messages.

  In one example, the message generation unit 122 encrypts the main message and the MAC message using a public key cryptosystem.

  The transmitter 112 sends the message generated by the message generation unit 122 to the network 200.

  The receiver 111 acquires a message (main message and MAC message) addressed to itself from the network 200.

  When the main message and the MAC message are encrypted using a public key cryptosystem, the message verification unit 123 decrypts the main message and the MAC message using a secret key corresponding to the public key.

  The message verification unit 123 extracts data (received data) included in the data field of the message from the main message received by the receiver 111. Further, the message verification unit 123 extracts a message authentication code value included in the data field of the message from the MAC message received by the receiver 111.

  The MAC value generation unit 125 calculates the message authentication code value for the received data using the same authentication key, calculation logic, and parameters used to calculate the message authentication code value for the transmission data. The message authentication code value for insertion is generated from the calculated message authentication code value.

  The message verification unit 123 receives the message by determining whether the message authentication code value for insertion extracted from the received MAC message matches the message authentication code value for insertion generated for the received data. Verify the validity of the data. Here, the validity of data means that the data is not created or altered by an entity other than the original transmission source. For example, even if the calculation logic and parameters are known, the message authentication code value for insertion cannot be generated unless the authentication key is known. It is also impossible or extremely difficult to estimate the authentication key used for calculating the message authentication code value from the received data and the message authentication code value for insertion. Using these properties, the message verification unit 123 can verify the validity of the received data.

  The reception data output unit 124 outputs the reception data whose validity has been verified to another component (not shown) included in the node 100.

  The calculation logic storage device 130 stores a plurality of calculation logics. Since all the calculation logic storage devices 130 of the plurality of nodes 100 store the same plurality of calculation logics, the plurality of nodes 100 share the plurality of calculation logics. For example, the calculation logic storage device 130 includes a nonvolatile storage medium such as a flash memory, and stores a plurality of calculation logics as programs in the storage medium.

  In one example, the plurality of calculation logics are different in complexity (calculation cost) and safety. For example, the plurality of calculation logics include those using hash functions MD5, SHA-1, SHA-256, SHA-384, and SHA-512.

  In one example, the calculation logic storage device 130 further stores a plurality of calculation logic identifiers, each associated with one calculation logic. For example, the calculation logic storage device 130 stores the calculation logic and the calculation logic identifier in the form of a table. In this case, all the calculation logic storage devices 130 of the plurality of nodes 100 store the same table. In one example, the calculation logic storage device 130 stores the calculation logic complexity in association with the calculation logic identifier for each calculation logic.

  The authentication key storage device 140 stores a plurality of authentication keys. Since all the authentication key storage devices 140 of the plurality of nodes 100 store the same plurality of authentication keys, the plurality of nodes 100 share the plurality of authentication keys. In one example, the authentication key is an encryption key that is shared and concealed among the plurality of nodes 100. For example, the authentication key storage device 140 includes a non-volatile storage medium such as a flash memory, and stores a plurality of authentication keys in the storage medium.

  In one example, the authentication key storage device 140 further stores a plurality of authentication key identifiers, each associated with one authentication key. For example, the authentication key storage device 140 stores an authentication key and an authentication key identifier in the form of a table. In this case, all the authentication key storage devices 140 of the plurality of nodes 100 store the same table.

  The authentication logic switching control unit 150 performs control to switch the authentication logic used by the MAC value generation unit 125 among a plurality of authentication logics. Here, the authentication logic refers to a combination of calculation logic and an authentication key used as a parameter of the calculation logic. The MAC value generation unit 125 calculates a message authentication code value for transmission data and reception data using a calculation logic and an authentication key included in the authentication logic after the authentication logic switching control unit 150 switches.

  The authentication logic switching control unit 150 functions as a calculation logic switching unit 151 and an authentication key switching unit 152. The calculation logic switching unit 151 switches the calculation logic used by the MAC value generation unit 125. The authentication key switching unit 152 switches an authentication key used as a parameter of calculation logic used by the MAC value generation unit 125.

  Switching control by the authentication logic switching control unit 150 is performed so that the authentication logic used by the MAC value generation unit 125 is the same among the plurality of nodes 100. For example, the calculation logic switching unit 151 of the slave node 100B switches to the same calculation logic in synchronization with the calculation logic switching by the calculation logic switching unit 151 of the master node 100A. Further, for example, in synchronization with switching of the authentication key by the authentication key switching unit 152 of the slave node 100B, the authentication key switching unit 152 of the slave node 100B switches to the same authentication key.

  In one example, the calculation logic switching unit 151 included in the slave node 100B instructs switching of calculation logic from the calculation logic switching unit 151 included in the master node 100A via the network 200 or a dedicated communication path (not shown). Receive information. The information for instructing the switching of the calculation logic includes, for example, the calculation logic (the calculation logic identifier) of the switching destination and information indicating the switching timing. Next, the calculation logic switching unit 151 included in the slave node 100B acquires the calculation logic associated with the received calculation logic identifier from the calculation logic storage device 130, and at the timing indicated in the information indicating the switching timing. Switch to the obtained calculation logic.

  In one example, the authentication key switching unit 152 included in the slave node 100B is information that instructs to switch the authentication key from the authentication key switching unit 152 included in the master node 100A via the network 200 or a dedicated communication path (not shown). Receive. The information for instructing switching of the authentication key includes, for example, a switching destination authentication key (an authentication key identifier thereof) and information indicating switching timing. Next, the authentication key switching unit 152 included in the slave node 100B acquires the authentication key associated with the received authentication key identifier from the authentication key storage unit 140, and acquires the authentication key at the timing indicated in the information indicating the switching timing. Switch to the authentication key.

  The authentication logic switching control unit 150 included in the slave node 100B collectively receives information that instructs calculation logic switching and information that instructs authentication key switching from the master node 100A as information that instructs authentication logic switching. May be.

  Next, components unique to the master node 100A that the slave node 100B does not have will be described.

  The master node 100A further includes an authentication logic determination control unit 160. The CPU of the master node 100A, for example, reads a program corresponding to the processing content from the ROM and expands it in the RAM, and performs centralized control of the operation of the authentication logic determination control unit 160 in cooperation with the expanded program. The authentication logic determination control unit 160 functions as a travel route determination unit 161, a vehicle state detection unit 162, a security risk detection unit 163, a risk level determination unit 164, and an authentication key update instruction unit 165.

  The travel route determination unit 161 determines the travel route of the vehicle. In one example, when the vehicle can acquire vehicle position information from a GPS (not shown) or the like and can acquire map information from a car navigation system (not shown) or the like, The travel route determination unit 161 determines the travel route of the vehicle based on the acquired position information and map information of the vehicle. In another example, the travel route determination unit 161 acquires and diverts a travel route determined by an automatic driving system (not shown). In this case, the travel route determination unit 161 may be a part of the automatic driving system.

  The vehicle state detection unit 162 detects the vehicle state. Here, the vehicle state refers to a state relating to a vehicle that can be determined based on information acquired by the vehicle state detection unit 162. In one example, the vehicle state detection unit 162 detects the vehicle state based on vehicle control information that can be acquired from the vehicle. In this case, the vehicle state is, for example, a vehicle speed, a steering wheel horn, a gear state, or a brake state.

  In one example, the vehicle state detection unit 162 detects the vehicle state based on information acquired from an in-vehicle sensor (not shown). The in-vehicle sensor is, for example, an in-vehicle camera, an out-of-vehicle camera, or a sonar. In this case, the vehicle state is, for example, the presence / absence of an obstacle in the traveling direction of the vehicle and the presence / absence of a curve.

  The security risk detection unit 163 detects a security risk in the communication system 1000. Here, the security risk is a risk that may harm the security of the node 100. The security risk is, for example, a security breach such as hijacking or spoofing of the node 100, or a decrease in the ratio of the number of messages whose validity is authenticated to the total number of messages. Any known method can be applied for detecting a security breach.

  The risk level determination unit 164 determines a risk level indicating the degree of danger in the situation where the vehicle is placed. In one example, the risk level determination unit 164 determines the risk level according to the vehicle state acquired from the vehicle state detection unit 162.

  In general, the higher the vehicle speed, the higher the influence of the cyber attack on the vehicle. Therefore, in one example, the risk level determination unit 164 determines a higher risk level as the vehicle speed included in the vehicle state increases. In this way, the level of message authentication can be strengthened according to the vehicle speed.

  In one example, the risk level determination unit 164 determines a risk level for the security risk detected by the security risk detection unit 163. For example, when the security risk detection unit 163 detects a security breach, the risk level determination unit 164 determines a risk level that is higher than the risk level determined when a security breach is not detected. Further, for example, the risk level determination unit 164 determines a higher risk level as the ratio of the number of messages whose validity is authenticated to the total number of messages is lower.

  In one example, the risk level determination unit 164 determines whether or not the vehicle can maintain the travel route determined by the travel route determination unit 161 according to the vehicle state detected by the vehicle state detection unit 162. Next, when it is determined that it cannot be maintained, the risk level determination unit 164 determines a risk level higher than the risk level determined when it is determined that it can be maintained.

  In one example, the vehicle state detected by the vehicle state detection unit 162 includes straight traveling or meandering of the vehicle. For example, when the travel route determined by the travel route determination unit 161 is a straight route, the risk level determined according to meandering is higher than the risk level determined according to straight travel. Further, for example, when the travel route determined by the travel route determination unit 161 is a curved route, the risk level determined according to straight travel is higher than the risk level determined according to meandering. In these cases, there is a high possibility that the vehicle deviates from the original travel route. In general, there are various reasons why the vehicle deviates from the original travel route. For example, as a result of taking over the node 100 related to the control of the vehicle, the vehicle deviates from the original travel route. It is also conceivable that it is under control. Even in such a case, the risk level determination unit 164 can determine a higher risk level, so that it is possible to indirectly cope with a clever takeover that the security risk detection unit 163 has failed to detect.

  In one example, when the vehicle state detection unit 162 can detect the presence or absence of an obstacle in the traveling direction of the vehicle, the risk level determination unit 164 responds to the obstacle on the travel route determined by the travel route determination unit 161. To determine the risk level. For example, the risk level determined when there is an obstacle is higher than the risk level determined when there is no obstacle.

  The risk level determination unit 164 instructs the authentication logic switching control unit 150 to switch to an authentication logic according to the determined risk level from a plurality of authentication logics having different complexity levels and safety levels. The authentication logic switching control unit 150 switches the authentication logic used by the MAC value generation unit 125 in response to an instruction from the risk level determination unit 164.

  The authentication key update instruction unit 165 instructs the authentication key switching unit 152 to update the authentication key at a timing when the authentication key should be updated. In one example, the authentication key update instructing unit 165 periodically instructs the authentication key switching unit 152 to update the authentication key.

  In one example, the risk level determination unit 164 instructs the authentication key update instruction unit 165 to update the authentication key according to the determined risk level. The authentication key update instruction unit 165 instructs the authentication key switching unit 152 to update the authentication key according to the instructed update frequency.

  When all the nodes 100 are the master nodes 100A, the calculation logic can be switched by including the same authentication logic determination control unit 160 having the same input for each of the components of all the master nodes 100A. And authentication key switching can be synchronized.

  FIG. 4 is a flowchart illustrating an operation flow of the master node 100A with respect to the security risk according to the present disclosure. This process is realized, for example, when the CPU of the master node 100A reads a program stored in the ROM and periodically executes it when the vehicle engine is started.

  In step S11, master node 100A determines whether or not a security risk has been detected (processing as security risk detection unit 163). In one example, the security risk detection unit 163 determines that a security risk has been detected when the hijacking or spoofing of the node 100 is detected. Further, in one example, when the ratio of the received messages whose validity is authenticated to all the received messages is lower than the predetermined first ratio, the security risk detection unit 163 determines that a security risk has been detected. When it determines with having detected the security risk (step S11: Yes), it progresses to step S12. On the other hand, when it is determined that no security risk has been detected (step S11: No), the process returns to step S11.

  In step S12, master node 100A determines the risk level for the detected security risk (processing as risk level determination unit 164).

  In one example, when the ratio of the number of received messages whose validity is authenticated to the total number of received messages is greater than a predetermined second ratio, the risk level determination unit 164 determines a first risk level. On the other hand, when it is smaller than the predetermined second ratio, the risk level determination unit 164 determines a second risk level that is higher than the first risk level. Here, the predetermined second ratio is a ratio larger than the predetermined first ratio.

  In one example, when the risk level determination unit 164 detects hijacking or impersonation of the node 100, the risk level determination unit 164 determines a second risk level.

  In step S13, the master node 100A determines whether or not the determined risk level is high (processing as the risk level determination unit 164). In one example, when the determined risk level is the first risk level, the risk level determination unit 164 determines that the risk level is not high, and when the determined risk level is the second risk level, the risk level is Judge as high.

  When it is determined that the risk level is high (S13: Yes), the process proceeds to step S14. In step S <b> 14, the master node 100 </ b> A instructs switching from a plurality of calculation logics having different complexity levels and safety levels to a calculation logic having a high complexity level but a high safety level (processing as the risk level determination unit 164). ). Thereby, when a security risk having a high risk level to be determined is detected, the security level of message authentication is further secured. If a calculation logic having a high complexity is already used, the calculation logic may not be switched, or may be switched to another calculation logic having a high complexity.

  In response to the calculation logic switching instruction, the master node 100A switches the calculation logic (processing as the calculation logic switching unit 151).

  On the other hand, when it is determined that the risk level is not high (S13: No), step S14 is skipped and the process proceeds to step S15. Thereby, when a security risk with a high risk level to be determined has already been detected and a calculation logic with a high complexity is used, a calculation logic with a high complexity is used as it is. Further, in a normal case where a security risk having a high risk level to be determined has not yet been detected, the calculation processing load of the node 100 can be reduced by using a calculation logic with low complexity.

  In step S15, the master node 100A instructs the authentication key switching unit 152 to switch the authentication key (processing as the risk level determination unit 164). In response to the instruction, master node 100A switches authentication keys (processing as authentication key switching unit 152).

  Next, in step S16, the master node 100A instructs the slave node 100B to switch authentication logic (processing as the calculation logic switching unit 151 and the authentication key switching unit 152). Thereby, in all the nodes 100, it switches to the same authentication key and calculation logic. In the case of a multi-master configuration in which all nodes 100 are master nodes 100A, step S16 can be skipped.

  FIG. 5 is an explanatory diagram of the relationship between the risk level of the security risk and the authentication logic. The relationship shown in FIG. 5 is used in the flowchart shown in FIG.

  As shown in FIG. 5, when it is determined that the determined risk level is low, the authentication logic 1 with a low complexity of the calculation logic is switched. When it is determined that the determined risk level is high, the authentication logic 2 having a high complexity of calculation logic is switched to.

  In this way, since multiple authentication logics can be used properly according to the level of the risk level determined for the detected security risk, the complexity is low in the normal case where the determined risk level is low Calculation logic can be used.

  FIG. 6 is a flowchart showing an operation flow of the master node 100A in response to a change in the vehicle state according to the present disclosure. This process is realized, for example, when the CPU of the master node 100A reads a program stored in the ROM and periodically executes it when the vehicle engine is started.

  In step S <b> 21, master node 100 </ b> A determines whether or not a change in the vehicle state has been detected (processing as vehicle state detection unit 162). In one example, the vehicle state detection unit 162 determines that a change in the vehicle state has been detected when a change in the vehicle speed is detected. When it determines with having detected the change of the vehicle state (step S21: Yes), it progresses to step S22. On the other hand, when it determines with not detecting the change of a vehicle state (step S21: No), it returns to step S21.

  In step S <b> 22, master node 100 </ b> A determines a risk level for the changed vehicle state (processing as risk level determination unit 164). In one example, when the vehicle speed is low (for example, less than 60 km / h), the risk level determination unit 164 determines the third risk level. In addition, when the vehicle speed is medium (for example, 60 km / h or more and less than 100 km / h), the risk level determination unit 164 determines a fourth risk level that is higher than the third risk level. When the vehicle speed is high (for example, 100 km / h or more), the risk level determination unit 164 determines a fifth risk level that is higher than the fourth risk level.

  In step S23, the master node 100A determines the height of the determined risk level (processing as the risk level determination unit 164).

  When it is determined that the risk level is low (for example, when the determined risk level is the third risk level), the process proceeds to step S24-1. When it is determined that the risk level is medium (for example, when the determined risk level is the fourth risk level), the process proceeds to step S24-2. When it is determined that the risk level is high (for example, when the determined risk level is the fifth risk level), the process proceeds to step S24-3.

  When the process proceeds to step S24-1, the master node 100A instructs switching from a plurality of calculation logics having different complexity and safety levels to a calculation logic having a low safety level but a low complexity level (risk level determination). Processing as the unit 164). If a calculation logic with low complexity is already used, the calculation logic may not be switched, or may be switched to another calculation logic with low complexity.

  When the process proceeds to step S24-2, the master node 100A instructs switching from a plurality of calculation logics having different complexity levels and safety levels to a calculation logic having a medium complexity level and a medium safety level. (Processing as the risk level determination unit 164). If a calculation logic with a medium complexity is already used, the calculation logic may not be switched, or may be switched to another calculation logic with a medium complexity.

  In the case of proceeding to Step S24-3, the master node 100A instructs to switch to a calculation logic having a high complexity but a high safety from a plurality of calculation logics having different complexity and safety (risk level determination). Processing as the unit 164). If a calculation logic having a high complexity is already used, the calculation logic may not be switched, or may be switched to another calculation logic having a high complexity.

  In response to the calculation logic switching instruction, the master node 100A switches the calculation logic (processing as the calculation logic switching unit 151).

  In step S25, the master node 100A instructs the authentication key switching unit 152 to switch the authentication key (processing as the risk level determination unit 164). In response to the instruction, master node 100A switches authentication keys (processing as authentication key switching unit 152).

  Next, in step S26, the master node 100A instructs the slave node 100B to switch authentication logic (processing as the calculation logic switching unit 151 and the authentication key switching unit 152). Thereby, in all the nodes 100, it switches to the same authentication key and calculation logic. Note that in the case of a multi-master configuration in which all nodes 100 are master nodes 100A, step S26 can be skipped.

  FIG. 7 is an explanatory diagram of the relationship between the risk level of the vehicle state and the authentication logic. The relationship shown in FIG. 7 is used in the flowchart shown in FIG.

  As shown in FIG. 7, when it is determined that the risk level determined for the vehicle state is low, the authentication logic 1 with a low complexity of the calculation logic is switched. If the risk level determined for the vehicle state is determined to be medium, the authentication logic 2 is switched to the medium complexity of the calculation logic. When it is determined that the risk level determined for the vehicle state is high, the authentication logic 3 is switched to a high complexity of the calculation logic.

  In this manner, a plurality of authentication logics can be used properly according to the level of the risk level determined for the detected vehicle state. In the case of a normal vehicle state with a determined low risk level, a low-complexity calculation logic can be used.

  As described above, the communication system 1000 according to the first embodiment is a vehicle communication system 1000 including a plurality of nodes 100 connected to the network 200, and each node 100-i of the plurality of nodes 100 includes: The authentication logic is set between the plurality of authentication logics so that the authentication logic used to authenticate the validity of the message received from the other node 100-j of the plurality of nodes 100 is the same among the plurality of nodes 100. The configuration includes an authentication logic switching control unit 150 that switches, and a message authentication unit 123 that authenticates the validity of a message using the authentication logic.

  According to the present disclosure, it is possible to provide a communication system in which unauthorized access and analysis of authentication logic are difficult by switching authentication logic between a plurality of authentication logics. Moreover, since it can be applied as it is to the existing communication standard of the in-vehicle LAN, it is possible to provide a communication system with excellent extensibility. Moreover, since it can switch to the authentication logic provided with moderate complexity according to the determined risk level, moderate obfuscation can be performed according to the change of a condition.

  According to the present disclosure, dynamic authentication is performed according to the vehicle state (whether the vehicle is in a driving state with a high safety risk), the cyber attack status, the number of unauthorized accesses, the magnitude of the influence of unauthorized commands, etc. Since the logic can be switched and an appropriate security level can be switched, the security risk can be flexibly dealt with.

  Further, according to the present disclosure, since each node does not need to have a counter for each node 100 connected to the communication system 1000, management is easy and scalability is high.

  Thus, the present disclosure provides one method for verifying the probability of communication data. According to the present disclosure, message authentication data can be incorporated into a communication message so as to maintain a certain level of confidentiality. Further, according to the present disclosure, it is possible to provide a security measure that has the flexibility to change the authentication process in stages according to the security risk, the vehicle state, and the like.

  FIG. 8 is a diagram illustrating an example of a hardware configuration of a computer. The function of each part in each embodiment and each modification described above is realized by a program executed by the computer 2100.

  As shown in FIG. 8, a computer 2100 includes an input device 2101 such as an input button and a touch pad, an output device 2102 such as a display and a speaker, a CPU (Central Processing Unit) 2103, a ROM (Read Only Memory) 2104, and a RAM (Random Access Memory) 2105 is provided. The computer 2100 also reads information from a recording medium such as a hard disk device, a storage device 2106 such as an SSD (Solid State Drive), a DVD-ROM (Digital Versatile Disk Read Only Memory), or a USB (Universal Serial Bus) memory. 2107, a transmission / reception device 2108 that performs communication via a network is provided. Each unit described above is connected by a bus 2109.

  Then, the reading device 2107 reads the program from a recording medium on which a program for realizing the functions of the above-described units is recorded, and stores the program in the storage device 2106. Alternatively, the transmission / reception device 2108 communicates with the server device connected to the network, and causes the storage device 2106 to store a program for realizing the function of each unit downloaded from the server device.

  Then, the CPU 2103 copies the program stored in the storage device 2106 to the RAM 2105, and sequentially reads out and executes the instructions included in the program from the RAM 2105, thereby realizing the functions of the above-described units. Further, when executing the program, the RAM 2105 or the storage device 2106 stores information obtained by various processes described in each embodiment, and is used as appropriate.

(Other embodiments)
In the first embodiment, travel route determination unit 161, vehicle state detection unit 162, and security risk detection unit 163 are all included in master node 100A. Instead of this, an embodiment in which at least one of the travel route determination unit 161, the vehicle state detection unit 162, and the security risk detection unit 163 is provided separately from the node 100 is also conceivable. Further, the travel route determined by the travel route determination unit 161, the vehicle state detected by the vehicle state detection unit 162, and the security risk detected by the security risk detection unit 163 in the form of information indicating them, and the node 100 is externally Embodiments obtained from the components are also conceivable. For example, when the vehicle is an automatic driving vehicle, the node 100 may acquire a travel route from an automatic driving system that controls automatic driving.

  In the above embodiment, the risk level determination unit 164 determines the risk level based on the travel route of the vehicle, the vehicle state, and the security risk. An embodiment is also conceivable in which the range to be monitored is dynamically switched with respect to the vehicle travel route, vehicle state, and security risk. For example, when the vehicle speed is lower than a predetermined speed, the travel route of the vehicle may be excluded from the monitoring target, or the distance to the obstacle to be detected may be shortened. This can further reduce the calculation processing load of the master node 100A.

  In the above-described embodiment, the case where the risk level of two or three levels is determined has been described. In addition to this, an embodiment in which four or more levels of risk are determined is also conceivable. Further, the complexity of the calculation logic may be four or more.

  In the above embodiment, when switching the authentication logic, the authentication key is always switched. Instead of this, when switching the authentication logic, an embodiment in which only the calculation logic included in the authentication logic is switched and the authentication key is not switched is also conceivable.

  The communication system according to the present disclosure is suitable for being applied to an in-vehicle LAN.

100, 100-1, 100-2,..., 100-n Node 100A Master node 100B Slave node 110, 110-1, 110-2,..., 110-n Transceiver 111 Receiver 112 Transmitter 120 Message control unit 121 Transmission data input unit 122 Message generation unit 123 Message verification unit 124 Reception data output unit 125 MAC value generation unit 130 Calculation logic storage device 140 Authentication key storage device 150 Authentication logic switching control unit 151 Calculation logic switching unit 152 Authentication key switching unit 160 Authentication Logic determination control unit 161 Travel route determination unit 162 Vehicle state detection unit 163 Security risk detection unit 164 Risk level determination unit 165 Authentication key update instruction unit 200 Network

Claims (17)

A communication system comprising a plurality of nodes connected to a network, each node of the plurality of nodes,
Authentication for switching the authentication logic between the plurality of authentication logics such that the authentication logic used to authenticate the validity of the messages received from other nodes of the plurality of nodes is the same among the plurality of nodes. A logic switching control unit;
A message authentication unit that authenticates the validity of the message using the authentication logic;
A communication system comprising: At least one of the plurality of nodes includes a risk level determining unit that determines a risk level indicating a degree of danger of a situation where a vehicle is placed;
The communication system according to claim 1, wherein the authentication logic switching control unit of the plurality of nodes switches the authentication logic according to the risk level.   The communication system according to claim 2, wherein the authentication logic switching control unit of the plurality of nodes switches to the authentication logic having a higher complexity for the higher risk level. At least one node of the plurality of nodes includes a security risk detection unit that detects a security risk in the communication system,
The communication system according to claim 2 or 3, wherein the risk level determination unit determines the risk level with respect to the detected security risk.   The communication system according to claim 4, wherein the security risk is hijacking or impersonation. A vehicle state detection unit for detecting a vehicle state that is a state relating to the vehicle;
The communication system according to claim 2, wherein the risk level determination unit determines the risk level according to the vehicle state. The vehicle state includes a vehicle speed,
The communication system according to claim 6, wherein the risk level determination unit determines the higher risk level as the vehicle speed increases. A travel route determination unit for determining a travel route of the vehicle;
The communication according to claim 6 or 7, wherein the risk level determination unit determines the risk level by determining whether or not the vehicle can maintain the travel route according to the vehicle state. system. The vehicle state includes straight traveling or meandering of the vehicle,
The communication system according to claim 8, wherein when the travel route is a straight route, the risk level determined according to the meander is higher than the risk level determined according to the straight traveling. The vehicle state includes straight traveling or meandering of the vehicle,
The communication system according to claim 8, wherein when the travel route is a curved route, the risk level determined according to the straight traveling is higher than the risk level determined according to the meandering. The vehicle state detection unit includes a sensor that detects an obstacle in the traveling direction of the vehicle,
The communication system according to claim 8, wherein the risk level determination unit determines the risk level according to the obstacle on the travel route. The authentication logic includes an authentication key and a calculation logic used to calculate a message authentication code value for the message using the authentication key,
The message authentication unit matches at least a part of the message authentication code value calculated for the message using the authentication key and the calculation logic with at least a part of the message authentication code value included in the message. The communication system according to claim 1, wherein the validity of the message is authenticated by determining whether or not the message is valid. At least one of the plurality of nodes includes an authentication key update instruction unit that instructs to update an authentication key;
The communication system according to claim 12, wherein the authentication logic switching control unit of the at least one node switches the authentication key according to the instruction.   The communication system according to claim 1, wherein the authentication logic switching control unit switches the authentication logic in response to reception from the other node of information instructing switching of the authentication logic. A communication method in a communication system comprising a plurality of nodes connected to a network,
Switching the authentication logic between the plurality of authentication logics such that the authentication logic used to authenticate the validity of messages received from other nodes of the plurality of nodes is the same between the plurality of nodes. When,
Authenticating the validity of the message using the authentication logic;
A communication method comprising: In a communication system including a plurality of nodes connected to a network, the computers provided in each of the plurality of nodes,
Switching the authentication logic between the plurality of authentication logics such that the authentication logic used to authenticate the validity of messages received from other nodes of the plurality of nodes is the same between the plurality of nodes. When,
Authenticating the validity of the message using the authentication logic;
A program that executes A non-transitory recording medium storing a computer-readable program,
In a communication system including a plurality of nodes connected to a network, the computers provided in each of the plurality of nodes,
Switching the authentication logic between the plurality of authentication logics such that the authentication logic used to authenticate the validity of messages received from other nodes of the plurality of nodes is the same between the plurality of nodes. When,
Authenticating the validity of the message using the authentication logic;
A non-transitory recording medium on which a program is recorded.

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