JP2016036159A - On-vehicle device and method for obtaining momentum to update common key - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system and a communication method that give at least active momentum to the update of a common key mainly in an on-vehicle device, and promote reliable update.SOLUTION: A communication system or communication method of the present invention maintains security by encrypting data with a common key regarding communication between a roadside device 2 and an on-vehicle device 3 and communication between on-vehicle devices 3 in road traffic. Communication is performed by encrypting the data with the common key, and each on-vehicle device 3 has stored common keys in the past in addition to a common key recognized as the latest by itself. The on-vehicle device 3 receives data from a communication opposite party, and tries to decrypt the received data with the common key recognized as the latest. If the on-vehicle device 3 cannot decrypt it, it determines whether or not it can decrypt the data with the common keys in the past, and at least determines whether the common keys of itself and a communication opposite device are newer or older among them depending on the determination result.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a communication system and a communication method for maintaining security in an intelligent transport system (ITS).

  In recent years, for the purpose of promoting traffic safety and preventing traffic accidents, an advanced road traffic system that receives information from infrastructure devices installed on the road and uses this information to improve vehicle driving safety has been studied. (For example, refer to Patent Document 1).

  Such an intelligent road traffic system is mainly composed of a plurality of roadside devices that are infrastructure-side communication devices and vehicle-mounted devices that are wireless communication devices mounted on each vehicle traveling on the road. In this case, the combination of communication performed between the communication subjects includes road-to-road communication performed by road-side devices, and road-to-vehicle (or vehicle-road) communication between the road-side devices and the vehicle-mounted device. Vehicle-to-vehicle communication performed between vehicle-mounted devices is included.

  Here, in road-to-vehicle communication and vehicle-to-vehicle communication, for example, a malicious person may impersonate an in-vehicle device and enter the system. If this is allowed, an attack that disrupts communication may occur. In order to prevent such a situation, it is necessary to ensure security by data encryption. In general, as an encryption method, for example, a common key encryption method or a public key encryption method is known.

Japanese Patent No. 2806801

  Here, in the common key method, it is considered that it is desirable to update for a certain period or the like in preparation for a person who decrypts the key by some method or a person who obtains the key by an unauthorized method. In that case, the update of the common key in the roadside device is performed under the management of the infrastructure side, so it can be considered that the update is basically surely performed except for an exceptional situation such as a failure. However, the update of the common key in the in-vehicle device is not always reliably updated because the in-vehicle device itself is basically left to the independent management of the vehicle owner. If the update of the common key in the in-vehicle device is not performed with certain certainty, communication between the road and the vehicle and between the vehicles cannot be performed.

  In view of such a problem, an object of the present invention is to provide a communication system and a communication method that provide at least a positive opportunity to update a common key in an in-vehicle device and promote reliable update.

(1) The present invention relates to a communication system that maintains security by encrypting data with a common key for communication between a roadside device and an in-vehicle device in road traffic and between in-vehicle devices. Is
A communication unit that encrypts and transmits data with the common key, receives or demodulates it, a common key that the user recognizes as the latest, a storage unit that also stores past common keys, and receives from a communication partner If the data cannot be demodulated with the common key that is recognized as the latest, it is determined whether it can be demodulated with the past common key, and at least the relative old and new of the other common key are determined according to the determination result. And a determination unit.

  In the above communication system, the road-to-vehicle communication between the roadside device and the vehicle-mounted device and the vehicle-to-vehicle communication between the vehicle-mounted devices are maintained with security by being encrypted with a common key, for example, malicious A situation in which a person enters the communication system and disrupts the communication is prevented. Also, since the in-vehicle device has an opportunity to check whether the common key that it recognizes is the latest based on the data received from the communication partner, it is at least proactive in updating the common key. You can give an opportunity.

(2) Also, in the communication system of (1) above, when the determination unit can demodulate with the past common key, the determination unit determines that the common key used by the communication partner is older than the common key that it recognizes as the latest. And if a past common key cannot be demodulated, a second judgment is made to determine that the common key recognized as the latest is older than the common key used by the communication partner. can do.
In this case, it is possible to quickly and accurately determine which one is older by a simple method of whether or not demodulation using a past common key is possible.

(3) In the communication system of (2) above, the in-vehicle device that has made the first determination may notify the communication partner of the necessity for updating the common key.
In this case, the communication partner can know the necessity of updating. Further, if only the “necessity” is notified, the latest common key is not leaked by the notification.

(4) Also, in the communication system of (2) or (3) above, the in-vehicle device that has made the first determination transmits a common key that it recognizes as the latest to the communication partner. Also good.
In this case, the communication partner can obtain a new common key from the in-vehicle device when his / her common key is old.

(5) Also, in the communication system of (3) or (4) above, the in-vehicle device that has made the first determination can use the common key for the latest common key that it owns. When the effective period, which is a period, is acquired and the effective period has passed, it is preferable to notify the communication partner to that effect.
In this case, the communication partner can obtain a new common key from the in-vehicle device when his / her common key is old, and can also obtain information that it is not the latest.

(6) In the communication system of (2) above, the in-vehicle device in the case of performing the second determination may request the communication partner to transmit the latest common key.
In this case, the in-vehicle device can obtain a new common key from the communication partner when its own common key is old.

(7) On the other hand, the present invention relates to communication between roadside devices and in-vehicle devices in road traffic and communication between in-vehicle devices, in order to maintain security by encrypting data with a common key, The communication method is based on the assumption that data is encrypted with the common key and communicated, and in addition to the common key that the user recognizes as the latest, the past common key is also stored.
Receiving data from the communication partner, trying to demodulate the received data with a common key that is recognized as the latest, if unable to demodulate, determine whether it can be demodulated with the past common key, and depending on the determination result At least, the relative old and new of the other common key are judged.

  In the above communication method, the road-to-vehicle communication between the roadside device and the vehicle-mounted device and the vehicle-to-vehicle communication between the vehicle-mounted devices are maintained with security by being encrypted with a common key. A situation in which a person enters the communication system and disrupts the communication is prevented. Also, since the in-vehicle device has an opportunity to check whether the common key that it recognizes is the latest based on the data received from the communication partner, it is at least proactive in updating the common key. You can give an opportunity.

  According to the communication system and the communication method of the present invention, at least a positive opportunity can be given to the update of the common key in the in-vehicle device. Thereby, reliable update of the common key can be promoted.

It is a figure which shows only the principal part in the whole structure of an intelligent transport system including the communication system (and communication method) which concerns on embodiment of this invention. It is a block diagram which shows the internal structure of a roadside machine and vehicle equipment. It is a figure which shows an example of the data format which an onboard equipment transmits. It is a flowchart which shows operation | movement of the vehicle equipment regarding a key update about the case where an update period may be irregular, in other words, the case where an update period is unknown.

<< Overall system configuration >>
FIG. 1 is a diagram schematically showing only main parts in the overall configuration of an intelligent road traffic system (ITS) including a communication system (and communication method) according to an embodiment of the present invention. In FIG. 1, for example, a roadside device 2 that is a roadside communication device is attached to a support 1 installed on the side of a road. The antenna 20 of the roadside machine 2 is attached to the upper part of the column 1. Vehicles A and B are each equipped with an in-vehicle device (not shown in FIG. 1), which is a wireless communication device, and includes an antenna 30.

The roadside device 2 can perform road-to-vehicle communication with the vehicle-mounted device. In addition, vehicle-to-vehicle communication can be performed between the in-vehicle devices of the vehicles A and B within a communicable distance, for example, by a carrier sense method. In addition, with respect to the roadside machine 2, signal transmission / reception is performed, for example, by wire from the central device 4 of the traffic control center.
Each roadside device 2 has a downlink area (range where the transmission signal of the roadside device 2 can reach sufficiently) spreading around it, and receives the downlink signal to the in-vehicle device of the vehicle traveling in its own downlink area. Can be made.

Each roadside device 2 assigns a time slot for wireless transmission by its own device by the TDMA method, and does not perform wireless transmission in a time zone other than this time slot. Therefore, the time zone other than the time slot for the roadside device 2 is open as a transmission time by the CSMA method for the in-vehicle device.
Further, the roadside device 2 has a time synchronization function with other roadside devices 2 in order to control its transmission timing. The time synchronization of the roadside device 2 is performed by, for example, GPS synchronization for adjusting its own clock to the GPS time, air synchronization for adjusting its own clock to a transmission signal from another roadside device 2, or the like.

<< Configuration of circuit block diagram and basic communication operation >>
FIG. 2 is a block diagram showing the internal configuration of the roadside device 2 and the in-vehicle device 3.
The roadside unit 2 mainly includes a wireless communication unit 21 to which an antenna 20 for wireless communication is connected, a wired communication unit 22 that performs bidirectional communication with the central device 4, and a control unit that includes a CPU that performs communication control thereof. 23 and a storage unit 24 composed of a storage device such as a ROM or a RAM connected to the control unit 23.

  In addition to the central device 4, a GPS receiver 25 is connected to the wired communication unit 22 of the roadside device 2. The GPS receiver 25 receives GPS signals from a plurality of GPS satellites (not shown) by a GPS antenna 26. The GPS receiver 25 may be provided in the roadside device 2.

  The control unit 23 may temporarily store traffic information or the like from the central device 4 received by the wired communication unit 22 in the storage unit 24 and broadcast it to its own downlink area via the wireless communication unit 21. it can. However, as will be described later, it is preferable not to transmit security-related information by broadcasting. In addition, the control unit 23 can temporarily store the information from the in-vehicle device 3 received by the wireless communication unit 21 in the storage unit 24 and transfer the information to the central apparatus 4 via the wired communication unit 22.

  In addition, the control unit 23 broadcasts the time slot allocation information stored in the storage unit 24 to its own downlink area via the wireless communication unit 21. This allocation information is for notifying the in-vehicle device 3 of the transmission time of the roadside device 2. The vehicle-mounted device 3 of the vehicle traveling in the downlink area performs radio transmission by the carrier sense method in a time zone when the roadside device 2 does not transmit.

  On the other hand, the in-vehicle device 3 includes a communication unit 31 connected to an antenna 30 for wireless communication, a control unit 32 including a CPU that performs communication control on the communication unit 31, and a ROM connected to the control unit 32. And a storage unit 33 including a storage device such as a RAM. The control unit 32 also includes a function as a determination unit 32a that makes a later-described determination regarding security. In addition, a GPS receiver 34 and a speed sensor 36 are connected to the communication unit 31. The GPS receiver 34 receives GPS signals from a plurality of GPS satellites (not shown) by the GPS antenna 35. The GPS receiver 34 may be provided in the in-vehicle device 3.

The control unit 32 of the in-vehicle device 3 causes the communication unit 31 to perform wireless communication by the carrier sense method for inter-vehicle communication, and has a communication control function using the time division multiplexing method with the roadside device 2. Not done.
Therefore, the communication unit 31 of the in-vehicle device 3 always senses the reception level of the predetermined carrier frequency, and when the value is equal to or higher than a certain threshold, the wireless transmission is not performed, and only when the value is less than the threshold. Wireless transmission is performed.

  The control unit 32 of the in-vehicle device 3 can wirelessly transmit vehicle information including the current position, direction, speed, vehicle type, and the like of the vehicle (the in-vehicle device 3) via the communication unit 31. In addition, the control unit 32 of the in-vehicle device 3 performs a right-right collision or encounter head based on the position, speed, and direction included in the information received directly from other vehicles or the information of other vehicles received from the roadside device 2. Safe driving support control for avoiding a collision or the like can be performed.

《Security communication system》
The above road-to-vehicle communication and vehicle-to-vehicle communication are encrypted with a common key. Encryption and demodulation are performed by the wireless communication unit 21 and the communication unit 31. With encryption, for example, it is possible to prevent a situation in which a malicious person impersonates an in-vehicle device and enters a communication system to disrupt communication. In addition, the common key needs to be updated sequentially for security. Such an update may be performed irregularly or periodically.

  FIG. 3 is a diagram illustrating an example of a data format transmitted by the in-vehicle device 3 (the roadside device 2 is substantially the same). In the figure, the transmission signal of the in-vehicle device 3 includes, in order from the top, an L2 (MAC) header, a communication control header, a security header, an L7 (application control) header, application data, and a security footer. Among these, the security header includes a caller ID, a key ID, an in-vehicle device / roadside device identification ID, position and time information, an authentication random number, and the like. The application data may include position and time information. In this case, this information can be used. The security footer includes signature data.

《Common key renewal: When renewal period may be irregular》
Next, the update of the common key will be described. First, the case where the update period (the effective period during which the key can be used) can be irregular, in other words, the case where the update period is unknown will be described with reference to the flowchart of FIG. The process of this flowchart is performed using the communication unit 31, the control unit 32 (determination unit 32a), and the storage unit 33 in the in-vehicle device 3.

  Each in-vehicle device 3 stores a key for a plurality of generations including a common key that it recognizes as the latest and a past common key before update. Here, the vehicle-mounted device 3 of any one vehicle is assumed. When the update of the common key is irregular, it is necessary to frequently check whether or not the own common key is the latest. Therefore, for example, the process of the flowchart of FIG. 4 is periodically executed.

  First, the vehicle-mounted device 3 waits for a signal to be received by the communication unit 31 (No in step S1). When the signal is received, the in-vehicle device 3 determines whether or not the detected reception level is a sufficient level (amplitude) equal to or higher than a predetermined value (step S2), and if not, returns to step S1 and returns to the next step. Wait for an opportunity. If the reception level is sufficient, the communication unit 31 attempts to demodulate the encryption with the key that it recognizes as the latest (step S3). As a result, if the demodulation is possible, the processing ends as it is (step S4).

  However, if demodulation is not possible in step S4, the key before update, in other words, the key for the previous generation is read from the storage unit 33, and demodulation is attempted again using this key (step S5). As a result, if demodulation is possible (Yes in step S6), it means that the other party used the old key, so it is determined that the other party's key that transmitted the signal is older than his own key ( Step S7). The opponent in the case of this determination result is mainly an in-vehicle device. The fact that the key used by the roadside device 2 on the infrastructure side is older is usually considered to be extremely unlikely. Then, based on the determination result, the in-vehicle device 3 performs a process of notifying the other party that the key is old or transmitting to give the latest key owned by itself. Perform (step S8).

  Sending to give the latest key has the risk of leaking information about the common key that maintains security, so it is safer to give notification that the key is old in that respect. . In either case, it is preferable to send a signal (notification / key) encrypted using an old key that can be demodulated by the other party.

  On the other hand, if the demodulation cannot be performed in step S6, it means that any key owned by the user cannot be demodulated. This means that even the key that I recognized as the latest is no longer an old key, so the in-vehicle device 3 is older than the key of the other party that sent the signal. Is determined (step S9). Further, based on the determination result, the in-vehicle device 3 displays the determination result on a display (not shown) of the car navigation device, or gives a warning to the driver, for example, by voice notification. (Step S10).

  As for the in-vehicle device that recognizes that its own key is old or has received a notification that “the key is old” from another device by the determination in step S7 or S9, for example, the owner of the vehicle is the dealer The update processing may be performed by bringing the vehicle-mounted device into the network and receiving information on the common key that has been legally distributed from the operator of the communication system (such as the police).

  Moreover, in the said step S10, you may perform the process of sending the signal which requests | requires transmission of the newest key with respect to the other party. In this case, the other party (other in-vehicle device or roadside device) transmits to give the latest key, but there is also a risk that information on the common key that maintains security leaks, so the in-vehicle device that receives the information It is preferable to send an encrypted signal (latest common key) using an old key that can be demodulated.

In addition, in order to provide the latest common key from the roadside device 2 to the in-vehicle device 3, it is preferable to perform one-to-one transmission instead of broadcast in order to prevent information leakage of the common key.
Moreover, the roadside machine 2 should transmit only when there exists a request | requirement of provision from the vehicle equipment 3, and must not provide unnecessarily.
Moreover, it is preferable to suppress transmission power below a certain value and make it difficult for information to reach other in-vehicle devices or unspecified recipients.
Moreover, it is preferable that the roadside device 2 monitors the traffic volume, and when the traffic volume is small, the roadside device 2 aims at the specific vehicle-mounted device 3 and transmits it.
In addition, in order to prevent information from leaking to a receiving device other than the on-vehicle device installed in the vehicle, the information is provided only when it is confirmed that the on-vehicle device requiring the provision of the latest common key is moving. You may make it do.

  In the flowchart of FIG. 4, it has been described that the process of step S5 is performed only once, but this is only an example. That is, demodulating with the key before the update is not necessarily limited to the key one generation before, so the demodulation may be tried in order so as to go back to the plurality of generations stored. For example, a process may be performed in which a predetermined number of types of keys including three or more generations including the latest key are stored and the old key is sequentially tried until it can be demodulated.

In the communication system as described above, the road-to-vehicle communication and the vehicle-to-vehicle communication are encrypted with a common key to maintain security. For example, a malicious person enters the communication system and disrupts communication. Unforeseen circumstances are prevented. Further, since the vehicle-mounted device 3 has an opportunity to check whether the common key it recognizes is the latest based on the data received from the communication partner, it is proactive in updating the common key. You can give an opportunity. Also, based on this, reliable update of the common key can be promoted.
In addition, it is possible to quickly and accurately determine which is older by a simple method of whether or not demodulation using a past common key is possible.

《Common key renewal as a reference example: When the renewal period is regular》
Next, as a reference example, a description will be given of the response of the in-vehicle device 3 when the common key is regularly updated. The processing in this case is completely different from the flowchart of FIG.
(I) First, the in-vehicle device 3 acquires information on a predetermined update period (valid period) tr. The in-vehicle device 3 compares the elapsed time t from the update of the key to the current time with the update period tr, and determines whether or not the own key is the latest.
(Ii) When the ratio (t / tr) of the elapsed time t to the update period tr becomes equal to or greater than a predetermined value (for example, 0.9), the update time approaches the driver using a car navigation device or the like. Keep them alert and alert.
(Iii) In response to this, the driver brings the vehicle equipped with the in-vehicle device to a predetermined place (dealer or the like) where the key can be updated, and updates the key.

<Others>
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

For example, the common key may be updated periodically, but a communication system may be used as necessary.
In this case, for example, when an in-vehicle device that determines that the communication partner's key is old and that it is newer sends its key to the communication partner, in fact, the user has passed the latest update period of the common key. It can happen. In such a case, if the communication partner is also notified of the fact of the error, the communication partner must obtain a new common key from the in-vehicle device when his / her common key is old. You can also get information that it is not up-to-date.

3: Vehicle-mounted device 31: Communication unit 32a: Judgment unit 33: Storage unit

  The present invention relates to an in-vehicle device and the like for maintaining security in an intelligent transport system (ITS).

  In recent years, for the purpose of promoting traffic safety and preventing traffic accidents, an advanced road traffic system that receives information from infrastructure devices installed on the road and uses this information to improve vehicle driving safety has been studied. (For example, refer to Patent Document 1).

  Such an intelligent road traffic system is mainly composed of a plurality of roadside devices that are infrastructure-side communication devices and vehicle-mounted devices that are wireless communication devices mounted on each vehicle traveling on the road. In this case, the combination of communication performed between the communication subjects includes road-to-road communication performed by road-side devices, and road-to-vehicle (or vehicle-road) communication between the road-side devices and the vehicle-mounted device. Vehicle-to-vehicle communication performed between vehicle-mounted devices is included.

  Here, in road-to-vehicle communication and vehicle-to-vehicle communication, for example, a malicious person may impersonate an in-vehicle device and enter the system. If this is allowed, an attack that disrupts communication may occur. In order to prevent such a situation, it is necessary to ensure security by data encryption. In general, as an encryption method, for example, a common key encryption method or a public key encryption method is known.

Japanese Patent No. 2806801

  Here, in the common key method, it is considered that it is desirable to update for a certain period or the like in preparation for a person who decrypts the key by some method or a person who obtains the key by an unauthorized method. In that case, the update of the common key in the roadside device is performed under the management of the infrastructure side, so it can be considered that the update is basically surely performed except for an exceptional situation such as a failure. However, the update of the common key in the in-vehicle device is not always reliably updated because the in-vehicle device itself is basically left to the independent management of the vehicle owner. If the update of the common key in the in-vehicle device is not performed with certain certainty, communication between the road and the vehicle and between the vehicles cannot be performed.

  In view of such a problem, an object of the present invention is to provide at least a positive opportunity to update a common key mainly in an in-vehicle device and promote reliable update.

  (1) An in-vehicle device that communicates encrypted data between a roadside device and other in-vehicle devices in road traffic.

  The in-vehicle device stores a plurality of generations of common keys including three or more generations including a common key that it recognizes as the latest, and data received from the communication partner using the common key stored in the storage unit. And a communication unit for demodulating, for updating the common key that the self recognizes as the latest, based on the data received from the communication partner, using a plurality of generations of common keys stored in the storage unit, It is configured to check whether or not the common key that it recognizes is the latest.

  The in-vehicle device has an opportunity to check whether the common key it recognizes is the latest based on the data received from the communication partner, so at least a positive opportunity to update the common key. Can be given.

(2) The communication partner preferably includes a roadside machine.

  The in-vehicle device is configured to determine whether or not the common key recognized by the communication partner is older than the common key used by the communication partner in order to update the common key recognized by the communication device. It is preferable.

  (3) Another aspect is a method in which an in-vehicle device that communicates encrypted data between a roadside device and another in-vehicle device in road traffic obtains an opportunity to update the common key.

  The in-vehicle device demodulates the data received from the communication partner using the common key stored in the storage unit and the storage unit that stores a plurality of generations of common keys including three or more generations including the common key that it recognizes as the latest A communication unit.

  In order to update the common key that the in-vehicle device recognizes as the latest, the in-vehicle device uses a plurality of generations of common keys stored in the storage unit based on the data received from the communication partner. It includes checking whether the common key recognized as the latest is the latest.

  The in-vehicle device has an opportunity to check whether the common key it recognizes is the latest based on the data received from the communication partner, so at least a positive opportunity to update the common key. Can be given.

  According to the present invention, at least a positive opportunity can be given to the update of the common key in the in-vehicle device. Thereby, reliable update of the common key can be promoted.

It is a figure which shows only the principal part in the whole structure of an intelligent transport system including the communication system (and communication method) which concerns on embodiment of this invention. It is a block diagram which shows the internal structure of a roadside machine and vehicle equipment. It is a figure which shows an example of the data format which an onboard equipment transmits. It is a flowchart which shows operation | movement of the vehicle equipment regarding a key update about the case where an update period may be irregular, in other words, the case where an update period is unknown.

<< Overall system configuration >>
FIG. 1 is a diagram schematically showing only main parts in the overall configuration of an intelligent road traffic system (ITS) including a communication system (and communication method) according to an embodiment of the present invention. In FIG. 1, for example, a roadside device 2 that is a roadside communication device is attached to a support 1 installed on the side of a road. The antenna 20 of the roadside machine 2 is attached to the upper part of the column 1. Vehicles A and B are each equipped with an in-vehicle device (not shown in FIG. 1), which is a wireless communication device, and includes an antenna 30.

The roadside device 2 can perform road-to-vehicle communication with the vehicle-mounted device. In addition, vehicle-to-vehicle communication can be performed between the in-vehicle devices of the vehicles A and B within a communicable distance, for example, by a carrier sense method. In addition, with respect to the roadside machine 2, signal transmission / reception is performed, for example, by wire from the central device 4 of the traffic control center.
Each roadside device 2 has a downlink area (range where the transmission signal of the roadside device 2 can reach sufficiently) spreading around it, and receives the downlink signal to the in-vehicle device of the vehicle traveling in its own downlink area. Can be made.

Each roadside device 2 assigns a time slot for wireless transmission by its own device by the TDMA method, and does not perform wireless transmission in a time zone other than this time slot. Therefore, the time zone other than the time slot for the roadside device 2 is open as a transmission time by the CSMA method for the in-vehicle device.
Further, the roadside device 2 has a time synchronization function with other roadside devices 2 in order to control its transmission timing. The time synchronization of the roadside device 2 is performed by, for example, GPS synchronization for adjusting its own clock to the GPS time, air synchronization for adjusting its own clock to a transmission signal from another roadside device 2, or the like.

<< Configuration of circuit block diagram and basic communication operation >>
FIG. 2 is a block diagram showing the internal configuration of the roadside device 2 and the in-vehicle device 3.
The roadside unit 2 mainly includes a wireless communication unit 21 to which an antenna 20 for wireless communication is connected, a wired communication unit 22 that performs bidirectional communication with the central device 4, and a control unit that includes a CPU that performs communication control thereof. 23 and a storage unit 24 composed of a storage device such as a ROM or a RAM connected to the control unit 23.

  In addition to the central device 4, a GPS receiver 25 is connected to the wired communication unit 22 of the roadside device 2. The GPS receiver 25 receives GPS signals from a plurality of GPS satellites (not shown) by a GPS antenna 26. The GPS receiver 25 may be provided in the roadside device 2.

  The control unit 23 may temporarily store traffic information or the like from the central device 4 received by the wired communication unit 22 in the storage unit 24 and broadcast it to its own downlink area via the wireless communication unit 21. it can. However, as will be described later, it is preferable not to transmit security-related information by broadcasting. In addition, the control unit 23 can temporarily store the information from the in-vehicle device 3 received by the wireless communication unit 21 in the storage unit 24 and transfer the information to the central apparatus 4 via the wired communication unit 22.

  In addition, the control unit 23 broadcasts the time slot allocation information stored in the storage unit 24 to its own downlink area via the wireless communication unit 21. This allocation information is for notifying the in-vehicle device 3 of the transmission time of the roadside device 2. The vehicle-mounted device 3 of the vehicle traveling in the downlink area performs radio transmission by the carrier sense method in a time zone when the roadside device 2 does not transmit.

  On the other hand, the in-vehicle device 3 includes a communication unit 31 connected to an antenna 30 for wireless communication, a control unit 32 including a CPU that performs communication control on the communication unit 31, and a ROM connected to the control unit 32. And a storage unit 33 including a storage device such as a RAM. The control unit 32 also includes a function as a determination unit 32a that makes a later-described determination regarding security. In addition, a GPS receiver 34 and a speed sensor 36 are connected to the communication unit 31. The GPS receiver 34 receives GPS signals from a plurality of GPS satellites (not shown) by the GPS antenna 35. The GPS receiver 34 may be provided in the in-vehicle device 3.

The control unit 32 of the in-vehicle device 3 causes the communication unit 31 to perform wireless communication by the carrier sense method for inter-vehicle communication, and has a communication control function using the time division multiplexing method with the roadside device 2. Not done.
Therefore, the communication unit 31 of the in-vehicle device 3 always senses the reception level of the predetermined carrier frequency, and when the value is equal to or higher than a certain threshold, the wireless transmission is not performed, and only when the value is less than the threshold. Wireless transmission is performed.

  The control unit 32 of the in-vehicle device 3 can wirelessly transmit vehicle information including the current position, direction, speed, vehicle type, and the like of the vehicle (the in-vehicle device 3) via the communication unit 31. In addition, the control unit 32 of the in-vehicle device 3 performs a right-right collision or encounter head based on the position, speed, and direction included in the information received directly from other vehicles or the information of other vehicles received from the roadside device 2. Safe driving support control for avoiding a collision or the like can be performed.

《Security communication system》
The above road-to-vehicle communication and vehicle-to-vehicle communication are encrypted with a common key. Encryption and demodulation are performed by the wireless communication unit 21 and the communication unit 31. With encryption, for example, it is possible to prevent a situation in which a malicious person impersonates an in-vehicle device and enters a communication system to disrupt communication. In addition, the common key needs to be updated sequentially for security. Such an update may be performed irregularly or periodically.

  FIG. 3 is a diagram illustrating an example of a data format transmitted by the in-vehicle device 3 (the roadside device 2 is substantially the same). In the figure, the transmission signal of the in-vehicle device 3 includes, in order from the top, an L2 (MAC) header, a communication control header, a security header, an L7 (application control) header, application data, and a security footer. Among these, the security header includes a caller ID, a key ID, an in-vehicle device / roadside device identification ID, position and time information, an authentication random number, and the like. The application data may include position and time information. In this case, this information can be used. The security footer includes signature data.

《Common key renewal: When renewal period may be irregular》
Next, the update of the common key will be described. First, the case where the update period (the effective period during which the key can be used) can be irregular, in other words, the case where the update period is unknown will be described with reference to the flowchart of FIG. The process of this flowchart is performed using the communication unit 31, the control unit 32 (determination unit 32a), and the storage unit 33 in the in-vehicle device 3.

  Each in-vehicle device 3 stores a key for a plurality of generations including a common key recognized by itself as well as a past common key before update. Here, the vehicle-mounted device 3 of any one vehicle is assumed. When the update of the common key is irregular, it is necessary to frequently check whether or not the own common key is the latest. Therefore, for example, the process of the flowchart of FIG. 4 is periodically executed.

  First, the vehicle-mounted device 3 waits for a signal to be received by the communication unit 31 (No in step S1). When the signal is received, the in-vehicle device 3 determines whether or not the detected reception level is a sufficient level (amplitude) equal to or higher than a predetermined value (step S2), and if not, returns to step S1 and returns to the next step. Wait for an opportunity. If the reception level is sufficient, the communication unit 31 attempts to demodulate the encryption with the key that it recognizes as the latest (step S3). As a result, if the demodulation is possible, the processing ends as it is (step S4).

  However, if demodulation is not possible in step S4, the key before update, in other words, the key for the previous generation is read from the storage unit 33, and demodulation is attempted again using this key (step S5). As a result, if demodulation is possible (Yes in step S6), it means that the other party used the old key, so it is determined that the other party's key that transmitted the signal is older than his own key ( Step S7). The opponent in the case of this determination result is mainly an in-vehicle device. The fact that the key used by the roadside device 2 on the infrastructure side is older is usually considered to be extremely unlikely. Then, based on the determination result, the in-vehicle device 3 performs a process of notifying the other party that the key is old or transmitting to give the latest key owned by itself. Perform (step S8).

  Sending to give the latest key has the risk of leaking information about the common key that maintains security, so it is safer to give notification that the key is old in that respect. . In either case, it is preferable to send a signal (notification / key) encrypted using an old key that can be demodulated by the other party.

  On the other hand, if the demodulation cannot be performed in step S6, it means that any key owned by the user cannot be demodulated. This means that even the key that I recognized as the latest is no longer an old key, so the in-vehicle device 3 is older than the key of the other party that sent the signal. Is determined (step S9). Further, based on the determination result, the in-vehicle device 3 displays the determination result on a display (not shown) of the car navigation device, or gives a warning to the driver, for example, by voice notification. (Step S10).

  As for the in-vehicle device that recognizes that its own key is old or has received a notification that “the key is old” from another device by the determination in step S7 or S9, for example, the owner of the vehicle is the dealer The update processing may be performed by bringing the vehicle-mounted device into the network and receiving information on the common key that has been legally distributed from the operator of the communication system (such as the police).

  Moreover, in the said step S10, you may perform the process of sending the signal which requests | requires transmission of the newest key with respect to the other party. In this case, the other party (other in-vehicle device or roadside device) transmits to give the latest key, but there is also a risk that information on the common key that maintains security leaks, so the in-vehicle device that receives the information It is preferable to send an encrypted signal (latest common key) using an old key that can be demodulated.

In addition, in order to provide the latest common key from the roadside device 2 to the in-vehicle device 3, it is preferable to perform one-to-one transmission instead of broadcast in order to prevent information leakage of the common key.
Moreover, the roadside machine 2 should transmit only when there exists a request | requirement of provision from the vehicle equipment 3, and must not provide unnecessarily.
Moreover, it is preferable to suppress transmission power below a certain value and make it difficult for information to reach other in-vehicle devices or unspecified recipients.
Moreover, it is preferable that the roadside device 2 monitors the traffic volume, and when the traffic volume is small, the roadside device 2 aims at the specific vehicle-mounted device 3 and transmits it.
In addition, in order to prevent information from leaking to a receiving device other than the on-vehicle device installed in the vehicle, the information is provided only when it is confirmed that the on-vehicle device requiring the provision of the latest common key is moving. You may make it do.

  In the flowchart of FIG. 4, it has been described that the process of step S5 is performed only once, but this is only an example. That is, demodulating with the key before the update is not necessarily limited to the key one generation before, so the demodulation may be tried in order so as to go back to the plurality of generations stored. For example, a process may be performed in which a predetermined number of types of keys including three or more generations including the latest key are stored and the old key is sequentially tried until it can be demodulated.

In the communication system as described above, the road-to-vehicle communication and the vehicle-to-vehicle communication are encrypted with a common key to maintain security. For example, a malicious person enters the communication system and disrupts communication. Unforeseen circumstances are prevented. Further, since the vehicle-mounted device 3 has an opportunity to check whether the common key it recognizes is the latest based on the data received from the communication partner, it is proactive in updating the common key. You can give an opportunity. Also, based on this, reliable update of the common key can be promoted.
In addition, it is possible to quickly and accurately determine which is older by a simple method of whether or not demodulation using a past common key is possible.

《Common key renewal as a reference example: When the renewal period is regular》
Next, as a reference example, a description will be given of the response of the in-vehicle device 3 when the common key is regularly updated. The processing in this case is completely different from the flowchart of FIG.
(I) First, the in-vehicle device 3 acquires information on a predetermined update period (valid period) tr. The in-vehicle device 3 compares the elapsed time t from the update of the key to the current time with the update period tr, and determines whether or not the own key is the latest.
(Ii) When the ratio (t / tr) of the elapsed time t to the update period tr becomes equal to or greater than a predetermined value (for example, 0.9), the update time approaches the driver using a car navigation device or the like. Keep them alert and alert.
(Iii) In response to this, the driver brings the vehicle equipped with the in-vehicle device to a predetermined place (dealer or the like) where the key can be updated, and updates the key.

<Others>
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

For example, the common key may be updated periodically, but a communication system may be used as necessary.
In this case, for example, when an in-vehicle device that determines that the communication partner's key is old and that it is newer sends its key to the communication partner, in fact, the user has passed the latest update period of the common key. It can happen. In such a case, if the communication partner is also notified of the fact of the error, the communication partner must obtain a new common key from the in-vehicle device when his / her common key is old. You can also get information that it is not up-to-date.

  《Appendix》

(Appendix 1) Another invention is a communication system that maintains security by encrypting data with a common key for communication between roadside devices and in-vehicle devices in road traffic and communication between in-vehicle devices. In-vehicle devices
A communication unit that encrypts and transmits data with the common key, receives or demodulates it, a common key that the user recognizes as the latest, a storage unit that also stores past common keys, and receives from a communication partner If the data cannot be demodulated with the common key that is recognized as the latest, it is determined whether it can be demodulated with the past common key, and at least the relative old and new of the other common key are determined according to the determination result. And a determination unit.

  In the above communication system, the road-to-vehicle communication between the roadside device and the vehicle-mounted device and the vehicle-to-vehicle communication between the vehicle-mounted devices are maintained with security by being encrypted with a common key, for example, malicious A situation in which a person enters the communication system and disrupts the communication is prevented. Also, since the in-vehicle device has an opportunity to check whether the common key that it recognizes is the latest based on the data received from the communication partner, it is at least proactive in updating the common key. You can give an opportunity.

(Appendix 2) In the communication system of (Appendix 1), if the determination unit can demodulate with the past common key, the common key used by the communication partner is older than the common key that it recognizes as the latest. In the case where it is impossible to demodulate even with a past common key, a second determination is made to determine that the common key recognized as the latest is older than the common key used by the communication partner. Can be.
In this case, it is possible to quickly and accurately determine which one is older by a simple method of whether or not demodulation using a past common key is possible.

(Appendix 3) In the communication system of (Appendix 2), when the first determination is made, the vehicle-mounted device notifies the communication partner of the necessity of updating the common key. Good.
In this case, the communication partner can know the necessity of updating. Further, if only the “necessity” is notified, the latest common key is not leaked by the notification.

(Appendix 4) In the communication system of (Appendix 2) or (Appendix 3), when the first determination is made, the in-vehicle device gives the communication partner a common key that it recognizes as the latest. You may send it.
In this case, the communication partner can obtain a new common key from the in-vehicle device when his / her common key is old.

(Appendix 5) In the communication system of (Appendix 3) or (Appendix 4), when the first determination is made, the in-vehicle device uses the common key for the latest common key held by itself. It is preferable to notify the communication partner of the fact that the effective period, which is a period in which the communication is possible, has been acquired and the effective period has been exceeded.
In this case, the communication partner can obtain a new common key from the in-vehicle device when his / her common key is old, and can also obtain information that it is not the latest.

(Appendix 6) In the communication system of (Appendix 2), when the second determination is made, the in-vehicle device may request the communication partner to transmit the latest common key. .
In this case, the in-vehicle device can obtain a new common key from the communication partner when its own common key is old.

(Additional remark 7) On the other hand, in another invention, in order to maintain security by encrypting data with a common key regarding communication between a roadside device and a vehicle-mounted device in road traffic and communication between vehicle-mounted devices, The machine is a communication method based on the premise that the data is encrypted with the common key and communicated, and in addition to the common key that the user recognizes as the latest, the past common key is also stored,
Receiving data from the communication partner, trying to demodulate the received data with a common key that is recognized as the latest, if unable to demodulate, determine whether it can be demodulated with the past common key, and depending on the determination result At least, the relative old and new of the other common key are judged.

  In the above communication method, the road-to-vehicle communication between the roadside device and the vehicle-mounted device and the vehicle-to-vehicle communication between the vehicle-mounted devices are maintained with security by being encrypted with a common key. A situation in which a person enters the communication system and disrupts the communication is prevented. Also, since the in-vehicle device has an opportunity to check whether the common key that it recognizes is the latest based on the data received from the communication partner, it is at least proactive in updating the common key. You can give an opportunity.

3: Vehicle-mounted device 31: Communication unit 32a: Judgment unit 33: Storage unit

Claims (6)

Regarding communication between roadside devices and in-vehicle devices in road traffic and communication between in-vehicle devices, it is a communication system that maintains security by encrypting data with a common key.
A communication unit that encrypts data with the common key and transmits or demodulates and receives the data;
In addition to the common key that you recognize as the latest, a storage unit that also stores past common keys,
If the data received from the communication partner cannot be demodulated with the common key recognized as the latest, determine whether it can be demodulated with the past common key, and at least the relative key of the other common key according to the judgment result A communication system, comprising: a determination unit configured to determine whether new or old. The determination unit
If the past common key can be demodulated, a first determination is made to determine that the common key used by the communication partner is older than the common key that the communication partner recognizes as newest,
If the past common key cannot be demodulated, a second determination is made to determine that the common key recognized as the latest is older than the common key used by the communication partner.
The communication system according to claim 1.   The communication system according to claim 2, wherein the in-vehicle device in the case where the first determination is made notifies the communication partner of the necessity of updating the common key.   The communication system according to claim 2 or 3, wherein the in-vehicle device in the case of performing the first determination transmits a common key recognized as the latest to the communication partner.   When the first determination is made, the in-vehicle device has acquired a valid period during which the common key can be used with respect to the latest common key held by the in-vehicle device, and has passed the valid period. The communication system according to claim 3 or 4, wherein if it is, the fact is notified to the communication partner.   The communication system according to claim 2, wherein the in-vehicle device when making the second determination requests the communication partner to transmit the latest common key.