JP5724389B2 - Communications system - Google Patents

Description

  The present invention relates to a communication system 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 performed wirelessly, 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

With the encryption as described above, it becomes difficult for a third-party communication device that is not a legitimate user to impersonate an in-vehicle device that is a legitimate user. However, since anyone can intercept wireless communication signals in the first place, it may be accidentally decoded, and it is preferable to further improve safety.
In view of such a problem, an object of the present invention is to more reliably suppress impersonation of a third party who is not a regular user in a communication system in road traffic.

(1) The present invention is a communication system relating to communication between roadside devices and in-vehicle devices in road traffic and communication between in-vehicle devices, each of the roadside devices and in-vehicle devices is
A storage unit that stores a key table that is shared with the communication partner and an area classification on road traffic, and an area and a period in which the current area is located A control / communication unit that obtains a key corresponding to 1 from the key table and transmits / receives data using the obtained key.

In the communication system configured as described above, data is transmitted and received using a key corresponding to an area and a period. Accordingly, for example, a key usage mode is possible in which the key is different if the area is different, and the key is different if the period is different even in the same area. Therefore, even if information on a specific key leaks to a non-authorized user, the area and period in which the key can be used are limited. For this reason, it is extremely difficult to communicate with a key whose information has been leaked, and even if it is used maliciously overcoming the difficulty, the damage is limited and it is prevented from becoming a major damage.
In principle, different keys are assigned if the “area and period” are different, but the same key may be assigned even in different areas and periods. For example, about 10 types of keys may be assigned according to the area and period.

(2) Further, in the communication system of (1) above, when data transmitted using a key different from a key to be used in a certain area and time is received, this is treated as invalid data. Information on the key may be notified from the roadside device to the certificate authority.
In this case, it is possible to find out that there is a possibility that information on the key (different key) is leaked by collecting information in the certificate authority.

(3) In the communication system of (1), a plurality of keys corresponding to areas and periods are prepared in the key table, and the control / communication unit randomly selects one of the plurality of keys. You may make it do.
In this case, even if information on a specific key is leaked, the area and period in which the key can be used are changed at random, making it more difficult to communicate with the leaked key.

(4) Moreover, in the communication system of said (1)-(3), you may make it use a mutually different key table by communication with a roadside machine and vehicle equipment, and communication between vehicle equipment.
In this case, even if information on a specific key in the key table in communication between vehicle-mounted devices, which can be said to have a greater risk of leakage in terms of the number of terminals, leaks directly to other key tables. Damage does not reach.

(5) Moreover, in the communication system of said (1)-(4), it is preferable to obtain | require a key with a derivation function.
In this case, the randomness of the key itself can be ensured.

  According to the communication system of the present invention, impersonation of a third party who is not an authorized user can be more reliably suppressed.

It is a figure which shows simply only the principal part in the whole structure of an intelligent road traffic system (ITS) including the communication system which concerns on one 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 (a road side machine is also the same) transmits. It is a figure which shows the area as an example. It is a figure which shows the relationship between an area, a period, and key ID.

<< Overall system configuration >>
FIG. 1 is a diagram schematically showing only a main part of an overall configuration of an intelligent road traffic system (ITS) including a communication system 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. Road-to-vehicle communication and vehicle-to-vehicle communication use the same frequency channel (700 MHz band). In addition, with respect to the roadside machine 2, signal transmission / reception is performed by the cable from the central device 4 of the traffic control center. The central device 4 is also connected to, for example, a wired connection with a certificate authority 5 that manages and manages security. 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. 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. 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.

  As will be described later, in the configuration of FIG. 2, the control unit 32, the communication unit 31, and the GPS receiver 34 in the in-vehicle device 3 grasp the area where the device is located and the period to which the current time belongs, and grasp the area. In the period, the control / communication unit 37 is configured to transmit and receive data using a key different from that in another area or another period. In addition, the control unit 23 and the wireless communication unit 21 in the roadside machine 2 constitute a similar control / communication unit 27.

《Security communication system》
The above road-to-vehicle communication and vehicle-to-vehicle communication are encrypted with a common key. Encryption and demodulation (decryption) 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. As the common key (hereinafter also simply referred to as a key), a large number of keys can be used from the key table stored in the storage unit 24 of the roadside device 2. The same key table is also stored in the storage unit 33 of the in-vehicle device 3, and the ID information of the key to be used is recognized, and the signal is encrypted on the transmission side and decrypted on the reception side. Can do. The key is created using a derivation function (hash, scramble, etc.). By using the derivation function, the randomness of the key itself can be ensured.

  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 the identification ID of the in-vehicle device / roadside device, position and time information, authentication random number, and the like in addition to the caller ID. The application data may include position and time information. In this case, this information can be used. The security footer includes signature data.

In this embodiment, in the common key system, as a rule, different keys are used for each area on road traffic, and different keys are used for each period to which the current time belongs even in the same area.
FIG. 4 is a diagram illustrating areas A1 to A9 as an example. The diagonal line in the figure represents a road, and the circle at the intersection represents the roadside machine 2.

  Various area divisions are possible. For example, it can be divided at equal intervals by latitude and longitude as shown in the figure, like a map code mesh in a car navigation system. In addition to such simple divisions, the mesh may be made small in roadside machines with many accidents, areas with dense intersections (for example, in the city center), places with heavy traffic, and the like. Further, the mesh size may be determined according to the road density and the road size (main line / main / narrow street) entering one area.

  (A) of FIG. 5 has shown the relationship of the area, the period, and key ID about area A5. (B) has shown the relationship of the area, the period, and key ID about area A6. Thus, one unit of the key table indicates the relationship of how the key ID corresponds to the area and the period, and this is a compilation of all the area divisions in Japan, for example, It is a table. As described above, a function is used to derive the key. The roadside device 2 and each vehicle-mounted device 3 as a regular user store the same (common) key table in the respective storage units 24 and 33. In addition, the certificate authority 5 is the issuer of the key table and manages this.

  In FIG. 5A, in the area A5, for example, the keys change every hour. In this case, 24 keys are used in one day. Similarly, in (b), in area A6, the keys change every hour, and 24 keys are used in one day. In this example, as a simple example of saving the total number of keys, the area A5 and the area A6 are set so that the key IDs are shifted every hour. The key IDs are different from each other. However, this is only an example, and the key IDs may be prepared so that they are completely different (there is no same thing) between the area A5 and the area A6.

  In the case of FIG. 5A, if the key 1 is leaked, the malicious terminal is located in the area A5, and if the condition of time 0:00 to 0:59 is not satisfied, the key 1 Data transmission cannot be performed using. If the key 1 is leaked in the case of (b), the malicious terminal uses the key 1 if it is located in the area A6 and does not satisfy the condition of time 1:00 to 1:59. Data cannot be transmitted. However, the malicious terminal does not know these conditions. Therefore, in reality, even if the key 1 is leaked, it is extremely difficult for a malicious terminal to perform data transmission that disrupts communication.

  Even if data transmission is made maliciously overcoming the difficulty, if the malicious terminal leaves the area A5, the key 1 can be used unless it is conveniently in the area A6 from 1:00 to 1:59. Disappear. Even if the user stays in the area A5, the key 1 cannot be used after the above period. Therefore, it is possible to avoid being attacked by the Service-to-Self in the form of “sequential terrorism”. In this way, even if a malicious terminal can perform data transmission that disrupts communication, the damage caused by the transmission is limited and it can be prevented from becoming a major damage.

  In addition, when the data transmitted in the state which does not satisfy any one of an area and a period are received, the roadside machine 2 and the vehicle equipment 3 in a communicable range handle the data as invalid data. If the roadside device 2 invalidates the data transmission, the roadside device 2 transmits invalid data to the certificate authority 5. If the in-vehicle device 3 invalidates the data transmission, the invalid data is held for a certain period, and the invalid data is transmitted to the roadside device 2 after waiting for an uplink opportunity. In response to this, the roadside device 2 transmits invalid data to the certificate authority 5. The certificate authority 5 that has collected invalid data in this way can read information from the invalid data and estimate the leaked key ID. The certificate authority 5 notifies the roadside device 2 of this as a CRL (Certificate Revocation List).

That is, the certification authority 5 searches for an area and a period (so-called area and time in which the same offender may appear) where the key ID estimated to be leaked may be used again, and the area or the surrounding area. For example, for the roadside machine 2 of
(A) Notify the possibility (risk) of key ID leakage;
(B) ignore data transmission using a key ID that may have been leaked, or
(C) notify the alternative key ID to prevent damage.
It is possible to take measures such as.

<Others>
In addition, since road-to-vehicle communication is often performed near an important intersection on road traffic, it is more important than vehicle-to-vehicle communication. For this reason, if a malicious terminal impersonates the roadside machine 2, more damage is expected. Therefore, it is conceivable that the key table is provided separately for vehicle-to-vehicle communication and road-to-vehicle communication.
In the first place, the number of in-vehicle devices is much larger than the number of roadside devices, and the frequency of transmission is also high. Therefore, it is considered that the possibility of impersonation of the vehicle-mounted device is extremely higher than the possibility of impersonation of the roadside device. Therefore, by providing a key table for road-to-vehicle communication separately from the vehicle-to-vehicle communication having a higher risk, the risk of leakage of the key for road-to-vehicle communication can be reduced.

In the above embodiment, the same key table is used for both communicating with each other, and the key corresponding to the area and the period is used. Further, the key corresponding to the area and the period (a key permitted to be used) is used. A plurality of keys may be prepared in the key table, and the control / communication units 27 and 37 may randomly select one of the plurality of keys.
However, in this case, it is necessary to notify the communication partner of the key ID to be used as data, and for example, the key ID information is included in the security header. In this case, even if a specific key is leaked, the area and period in which the key can be used are changed randomly, so it is considered difficult to communicate with the leaked key.

  In the above embodiment, there is one key for each area, but this is not necessarily one. If there are multiple roadside units in one area, multiple keys are selected and authentication processing is performed. You may make it transmit twice and transmit. In this case, although verification time is required, it is impossible to impersonate a terminal unless a plurality of leaked keys are known.

  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.

2: Roadside device 3: In-vehicle device 5: Certification authority 27: Control / communication unit 37: Control / communication unit

Claims (4)

It is a communication system related to communication between roadside devices and in-vehicle devices in road traffic and communication between in-vehicle devices, each of the roadside devices and in-vehicle devices are
A storage unit for storing a key table common to a communication partner and an area classification on road traffic; and
Understand the area where the current location is and the period to which the current time belongs, and in that area and period, acquire the key corresponding to the area and period from the key table, and send and receive data using the acquired key Equipped with a control and communication unit ,
When data transmitted using a key that is different from the key that should be used in a certain area and time is received, this is treated as invalid data, and information on the key is notified from the roadside device to the certificate authority. A communication system characterized by the above. It is a communication system related to communication between roadside devices and in-vehicle devices in road traffic and communication between in-vehicle devices, each of the roadside devices and in-vehicle devices are
A storage unit for storing a key table common to a communication partner and an area classification on road traffic; and
Understand the area where the current location is and the period to which the current time belongs, and in that area and period, acquire the key corresponding to the area and period from the key table, and send and receive data using the acquired key Equipped with a control and communication unit ,
A communication system , wherein different key tables are used for communication between a roadside device and a vehicle-mounted device, and communication between vehicle-mounted devices . Wherein the key table, key corresponding to the area and duration are more available, the control and communication unit, a communication system according to claim 1 or 2 selects one of the plurality of keys at random. Communication system according to any one of claims 1 to 3, obtaining a key derivation function.

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