JP4680730B2 - Road-to-vehicle communication system, in-vehicle terminal, and road-to-vehicle communication method - Google Patents

Description

  The present invention relates to a road-to-vehicle communication system using an authentication technique based on a public key cryptosystem.

  In recent years, it has been studied to distribute various types of information such as traffic jam information and signal information from roadside units (base stations) to vehicles by road-to-vehicle communication. As such broadcast-type road-to-vehicle communication becomes widespread, there is an increasing need to confirm whether the distributed information is actually distributed from a roadside device. In other words, when a Service-to-Self disguises information as information from a roadside machine and distributes information, a mechanism is required that can detect this on the received vehicle side.

  As such a mechanism, an authentication method in which a roadside machine logs in to a vehicle using an ID and a password may be considered, but each roadside machine needs to have a set of ID and password for each vehicle. This method is practically impossible. Therefore, it is necessary to use an authentication method based on a public key cryptosystem.

  A technique for preventing spoofing and tampering using a public key cryptosystem is described in Non-Patent Document 1. The public key cryptosystem uses a secret key that is secretly managed and a public key that is open to the public, and a ciphertext encrypted with one key can be decrypted without using the other key. . That is, in order to prevent impersonation and tampering, the sender encrypts the data to be transmitted using its own secret key and then transmits it. After receiving the data, the receiver decrypts the data using the sender's public key. If it can be correctly decrypted with the sender's public key, it is guaranteed that the sender of the data is the person holding the secret key, and it is possible to prevent impersonation and tampering.

  More specifically, the sender obtains a hash value (message digest) from the data to be transmitted, encrypts this hash value using a secret key, adds it to the original data (plain text), and transmits it. The hash value encrypted in this way is called an electronic signature (hereinafter simply referred to as a signature). The receiver decrypts the hash value using the sender's public key, and obtains the hash value from the plaintext data. If they match, it can be determined that no spoofing or tampering has occurred.

The problem here is how to obtain the sender's public key. That is, how to ensure that the public key that is publicly known as the sender's public key is actually the sender's public key is a problem. In general, the certificate authority guarantees the validity of the public key by distributing and signing the sender's public key. In this case, how to trust the public key of the certificate authority becomes a problem, but a higher-level certificate authority signs and distributes the public key. In this way, the certification authority has a hierarchical structure, and finally, the trust of the root certificate self-signed by the root certification authority ensures the validity of the public key.
By Seiji Kumagai, "Continued-Nobody has taught me how Internet security works", Nikkei Business Publications, pp93-134

  However, when the above public key cryptosystem is simply applied to road-to-vehicle communication, the following problems arise. That is, considering a signal information providing system, for example, a roadside device repeatedly transmits a large number of data, so that the risk of decryption by receiving these data increases.

  To prevent this, it is conceivable to use an electronic certificate with a long key length. However, if the key length is increased, it takes time for the decryption process, and it is received when the vehicle moving at high speed finishes decryption. Data will not make sense.

  In order not to make the key length of each electronic certificate longer, there is a method to update the electronic certificate frequently by providing multiple levels of certificate authorities and issuing lower-level certificate authorities with shorter validity period. . In this case as well, a plurality of electronic certificates must be verified in order to verify the validity of the electronic certificate at the time of authentication, resulting in a problem that it takes time for the authentication process.

  The present invention has been made in view of the above problems, and an object thereof is to provide a high-security and high-speed authentication technique in a road-to-vehicle communication system.

  In order to achieve the above object, in the present invention, authentication is performed in a road-vehicle communication system by the following means or processing.

  The road-to-vehicle communication system according to the present invention is a road-to-vehicle communication system that verifies the validity of distribution information by using a public key cryptosystem in a vehicle-mounted terminal when distributing information from a base station to the vehicle-mounted terminal. That is, the information delivered from the base station to the in-vehicle terminal is guaranteed not to be spoofed or falsified. The road-to-vehicle communication system according to the present invention includes a regional authentication station, a base station, and an in-vehicle terminal.

The regional certificate authority is a certificate authority (CA) and issues an electronic certificate to a base station belonging to the management area of the local certificate authority.

The base station is a communication terminal provided on the road or on the road side, and distributes, for example, information on the state of traffic lights, information on traffic jams, and POI (Point of Interest) information to the in-vehicle terminal. The base station distributes the local certificate, which is the electronic certificate of the local certification authority that issued the electronic certificate to itself, to the in-vehicle terminal. On the other hand, the base station distributes the above-described information, a signature for the information, and the electronic certificate of the local station to the in-vehicle terminal.

  The in-vehicle terminal that receives these electronic certificate (regional certificate) and distribution information verifies the validity of the region certificate. Then, by verifying the validity of the electronic certificate of the base station using this regional certificate, the public key (electronic certificate) distributed as the public key of the base station is actually It turns out that it is a public key. Furthermore, by verifying the signature of the distribution information using the public key of this base station, it is confirmed that the distributed information has been correctly distributed from this base station, and has not been spoofed or altered. Can be verified.

  While the in-vehicle terminal receives the same area certificate as the area certificate trusted immediately before, the in-vehicle terminal regards this area certificate as trustworthy, and uses this area certificate for the information distributed from the base station. Verify correctness.

  In this way, as long as the digital certificate delivered as the regional certificate does not change, the in-vehicle terminal can omit the confirmation process of the validity of the received regional certificate by trusting this regional certificate, High-speed authentication can be performed.

The present invention utilizes a feature unique to an in-vehicle terminal, in that the in-vehicle terminal moves along a road, and thus information is often distributed from base stations belonging to the management area of the same area certification authority. That is, the in-vehicle terminal uses the same local certificate authority digital certificate almost every time when verifying the validity of the digital certificate of the base station.

  Therefore, as long as the regional certificate distributed from the base station is the same as described above, trusting this regional certificate eliminates the process of verifying the validity of the regional certificate, and enables high-speed processing. Is possible. On the in-vehicle terminal side, it is not necessary to store electronic certificates of regional certification authorities nationwide, and only the regional certificate received immediately before needs to be stored, so that the amount of memory used can be reduced.

  Also, if the Service-to-Self distributes a fake electronic certificate as a regional certificate, it will receive an electronic certificate that is different from the regional certificate received immediately before, and will be detected immediately on the in-vehicle terminal side It is possible. In addition, even when the electronic certificate is updated, it can be easily detected on the in-vehicle terminal side. In addition, the latest situation can be grasped compared to the method of confirming the revocation list distributed in a predetermined issuance period, and the confirmation process takes less time than the method of inquiring the server for revocation information every time authentication is performed. Also have.

  In the present invention, when the in-vehicle terminal receives a regional certificate that is different from the trusted local certificate, it is preferable to verify the validity of the received regional certificate. The received regional certificate is different from the previously received regional certificate in addition to the case where a fake regional certificate is sent, when the regional certificate is renewed, or in the management area of a different regional certification authority. It is conceivable that the in-vehicle terminal has moved. In such a case, it is possible to authenticate correctly by verifying the validity of the received electronic certificate.

  However, it is not necessary to verify the validity every time a regional certificate different from the trusted regional certificate is received. For example, the in-vehicle terminal according to the present invention may verify the validity of a regional certificate when a regional certificate different from the trusted local certificate is received a predetermined number of times. Note that “receive continuously for a predetermined number of times” includes the case of receiving only once as described above.

  In addition, the in-vehicle terminal according to the present invention verifies the received regional certificate when a predetermined time or more has elapsed in consideration of the time that has elapsed since the last time the validity of the regional certificate was confirmed. May be. In this way, when the in-vehicle terminal obtains a regional certificate that is different from the trusted local certificate, it obtains the reliability of the received regional certificate and verifies the regional certificate based on the calculated reliability. It is also preferable to determine whether or not to do so. Since the verification of the validity of the electronic certificate takes time, the verification process is performed when there is a high probability that the in-vehicle terminal has moved to the management area of a different regional certification authority. This enables efficient processing.

  In addition, the in-vehicle terminal in the present invention stores a regional certificate that has been validated in the past, and if it receives the same regional certificate as the stored certificate, it is considered that this regional certificate can be trusted. It is also preferable to verify the validity of the information distributed from the base station using this regional certificate.

As described above, in addition to the area certificate trusted immediately before, the area certificate that has been validated in the past is stored, so that efficient processing can be performed even near the boundary of the management area of the area certification authority. It becomes possible. That is, there is a possibility that there may be a place in the vicinity of the management area of the regional certification authority where radio waves for transmitting regional certificates of a plurality of regional certification authorities can be received. In addition, there may be a place where radio waves from base stations belonging to the management areas of different regional certification authorities can be received. In such a case, a different regional certificate is received, and distribution information signed using a different regional certificate is received from the base station. Therefore, by storing a plurality of reliable regional certificates in the in-vehicle terminal in advance, it is possible to perform an efficient process that omits the verification process of the regional certificate.

  It is preferable that a predetermined maximum number is provided for the number of area certificates that have been confirmed in the past and stored in the in-vehicle terminal. When a maximum number of regional certificates have already been stored and a new regional certificate whose validity has been confirmed is stored, it is preferable to delete at least one stored regional certificate. In this way, the used memory capacity can be reduced.

  The area certificate to be deleted is preferably determined based on an elapsed time or a travel distance since the last time the area certificate was received or stored. After a long time has passed since the last receipt of the regional certificate or after traveling a long distance, the in-vehicle device is likely to be outside the management area of the regional certification authority. This is because there are fewer opportunities to verify the signature by using. The same applies to the case where it is based on the elapsed time / travel distance since the regional certificate was stored. In this way, by determining the regional certificate to be deleted, it is possible to store a regional certificate that is highly likely to be used for signature verification.

  In addition, the in-vehicle terminal according to the present invention preferably verifies the validity of the received regional certificate when a regional certificate different from the stored regional certificate is received at a frequency equal to or higher than a predetermined frequency. As described above, it is conceivable to obtain two or more area certificates near the boundary of the management area of the area certification authority. In this case, it is not known in what order the area certificate of the area certificate authority is acquired, but the acquisition frequency of the area certificate to be acquired changes as the in-vehicle terminal moves. When moving from the management area of the regional certification authority where the in-vehicle terminal is located to the management area of another regional certification authority, the frequency of acquiring the regional certificate of the regional certification authority after the movement gradually increases.

  Therefore, if the frequency of receiving a regional certificate different from the stored regional certificate is low, the regional certificate may be false, but if the frequency of reception is high, it is the correct regional certificate. The possibility increases. As described above, after the frequency of reception becomes high, that is, after the possibility that the certificate is correct, it is possible to improve the efficiency of processing by verifying the validity of the received certificate. it can.

  Further, the in-vehicle terminal according to the present invention has a location information acquisition unit, and the management area of the regional certification authority that issued the received regional certificate and the location information of the in-vehicle terminal acquired by the location information acquisition unit have a predetermined distance. When the distance is more than the above, it is preferable to ignore the received regional certificate. In this way, for regional certificates that can be determined to be incorrect based on the location of the regional certification authority and the in-vehicle terminal, it is unnecessary to calculate the reception frequency or ignore it without checking its validity. This makes it possible to dispense with unnecessary processing.

  In addition, the road-to-vehicle communication system according to the present invention preferably includes a certificate authority having one or a plurality of hierarchies above the regional certificate authority. In this case, it is preferable that each certificate authority issues an electronic certificate with a validity period shorter than the validity period of the electronic certificate of the local station to the nearest certificate authority belonging to the management area of the local station. Therefore, the lower-level certificate authority is updated frequently, and the base station electronic certificate is updated most frequently.

  Since the risk of the private key being decrypted increases as the number of digital certificates and signatures issued increases, the certificate authority having a long-term electronic certificate can be electronically created by providing a hierarchical structure for the certificate authority in this way. Reduce the frequency of issuing certificates and signatures, and increase the frequency of renewal of electronic certificates at lower-level certificate authorities and base stations that issue many electronic certificates and signatures. It becomes a communication system.

Further, in such a road-to-vehicle communication system having one or more certificate authorities above the regional certificate authority, in order to verify the validity of the electronic certificate, the electronic certificate of the highest certificate authority is originally used. Therefore, it is necessary to verify the validity of the electronic certificates of all the certificate authorities, and this verification process takes time. By applying the present invention to such a system and verifying the reliability of the electronic certificate of the regional certification authority, the electronic certificate can be verified at high speed. That is, in such a system, the merit of applying the present invention is great.

  In the road-vehicle communication system according to the present invention, the base station preferably distributes the regional certificate at a frequency lower than the distribution frequency of the distribution information. Further, when one or more certificate authorities are further provided above the regional certificate authority, it is preferable that the electronic certificate of the superior certificate authority is distributed with lower frequency.

  Since the electronic certificate of the higher certificate authority has a longer validity period and the area in which the electronic certificate can be used is wider, notification to the in-vehicle terminal is sufficiently performed even if the frequency of distribution is low. Thus, by reducing the distribution frequency for the electronic certificate of the higher-order certificate authority, it is possible to reduce the amount of communication.

  In addition, the base station in the present invention preferably distributes the distribution information including the current time. If the current time is not included in the information delivered from the base station, it becomes possible to retransmit the packet received by the Service-to-Self later (replay attack). In other words, the in-vehicle terminal that receives the distribution information knows that the information is distributed from the base station, but does not know when the information is, so it is vulnerable to Service-to-Self attacks. It will be. By including the current time in the distribution information as described above, it is possible to prevent such an attack.

  In addition, this invention can be grasped | ascertained as a vehicle-mounted terminal and base station which have at least one part of the said means.

  For example, an in-vehicle terminal as one aspect of the present invention is an in-vehicle terminal that verifies the validity of information distributed from a base station using a public key cryptosystem, and issues an electronic certificate to the base station. The regional certificate acquisition unit that acquires the regional certificate that is the certificate authority's electronic certificate, the regional certificate verification unit that verifies the validity of the acquired regional certificate, and the regional certificate verification unit immediately verify the validity. It has an area certificate storage means for storing the confirmed area certificate, and the area certificate acquisition means receives while receiving the same area certificate as the area certificate stored in the area certificate storage means. The regional certificate is regarded as reliable without being verified by the regional certificate verification means, and the validity of the information distributed from the base station is verified using the regional certificate.

  When the regional certificate acquisition unit continuously acquires a regional certificate different from the regional certificate stored in the regional certificate storage unit a predetermined number of times, the validity of the acquired regional certificate is determined by the regional certificate verification unit. It is preferable to verify by Note that “obtained for a predetermined number of times” includes a case where the information is acquired only once.

  The regional certificate storage means further stores a regional certificate whose validity has been confirmed in the past, and the regional certificate acquisition means acquires the same regional certificate as the regional certificate stored in the regional certificate storage means. In this case, it is also preferable to verify the validity of the information delivered from the base station using this regional certificate, assuming that this regional certificate is reliable without being verified by the regional certificate verification means. It is.

  The regional certificate storage means is provided with a predetermined maximum number of regional certificates to be stored, and the regional certificate whose validity has been confirmed when the maximum number of regional certificates are already recorded. When storing a new one, it is preferable to delete at least one stored regional certificate.

  In addition, the regional certificate storage means determines the regional certificate to be deleted based on the elapsed time or the distance traveled since the last time the regional certificate whose validity was confirmed in the past was received or stored. Is preferred.

  In addition, when a regional certificate different from the regional certificate stored in the regional certificate storage unit is received at a frequency higher than a predetermined frequency, the validity of the received regional certificate can be verified by the regional certificate verification unit. Is preferred.

  Further, the in-vehicle terminal in the present invention has position information acquisition means, the management area of the regional certification authority stored in the area certificate acquired by the area certificate acquisition means, and the position of the own vehicle acquired by the position information acquisition means If the information is more than a predetermined distance away, it is preferable to ignore this regional certificate.

  A base station as one aspect of the present invention is a base station that distributes information to an in-vehicle terminal using an electronic certificate issued from a regional certification authority, and a regional station that distributes an electronic certificate of the regional certification authority It has certificate distribution means and information distribution means for signing the distribution information when distributing information to the in-vehicle terminal and distributing the electronic certificate of the local station issued from the regional certification authority.

  And it is preferable that the delivery frequency of a regional certificate delivery means is lower than the delivery frequency of an information delivery means. The information distributed by the information distribution means preferably includes the current time.

  Furthermore, the road-to-vehicle communication method as one aspect of the present invention provides a method for distributing information from a base station to an in-vehicle terminal in a road-to-vehicle communication system including an area authentication station, a base station, and an in-vehicle terminal. This is a road-to-vehicle communication method for verifying the validity of distribution information using a public key cryptosystem in an in-vehicle terminal. In the road-to-vehicle communication method as one aspect of the present invention, the regional certification authority issues an electronic certificate to a base station belonging to the management area of the local station, and the base station issues an electronic certificate to the local station. The regional certificate, which is an electronic certificate of the regional certification authority, is distributed to the in-vehicle device at a predetermined frequency. While the in-vehicle device is receiving the same regional certificate as the region certificate trusted immediately before, this regional certificate The base station distributes the distribution information, the signature for this information, and its own electronic certificate to the in-vehicle terminal. When the in-vehicle terminal receives the information from the base station, the It is characterized by verifying the legitimacy of distribution information using a regional certificate deemed to be possible.

  According to the present invention, high-speed and high-speed authentication is possible in a road-vehicle communication system.

  Exemplary embodiments of the present invention will be described in detail below with reference to the drawings.

(First embodiment)
<System configuration>
FIG. 1 is a diagram showing an outline of a road-to-vehicle communication system according to a first embodiment of the present invention. As shown in FIG. 1, in the present embodiment, the central certificate authority 1, the regional certificate authority 2, and the roadside device (base station) 3 have a hierarchical structure. The central certificate authority 1 issues an electronic certificate to the regional certificate authority 2, and the regional certificate authority 2 issues an electronic certificate to the roadside device 3. When the roadside device 3 distributes information to the vehicle 4 (onboard terminal mounted on the vehicle 4), the vehicle 4 authenticates using these electronic certificates, and no spoofing or tampering has occurred. I can confirm that. Hereinafter, the electronic certificates of the central certificate authority, the regional certificate authority, and the roadside device are referred to as a central certificate, an area certificate, and a roadside device certificate, respectively. The electronic certificate is ITU (International Telecommunication Union) X
. Use one that conforms to the 509 recommendation.

  The central certificate authority 1 is a root certificate authority and issues a self-signed central certificate (root certificate). The regional certificate issued by the central certificate authority 1 to the regional certificate authority 2 has a validity period shorter than the validity period of the central certificate.

  The regional certification authority 2 issues a roadside machine certificate to the roadside machine 3 in the management area of the local station. In this way, since the regional certification authority 2 issues a roadside machine certificate to the roadside machine 3 belonging to a predetermined area, the vehicle 4 moving along the road basically receives an electronic certificate from the same regional certification authority 2. The distribution of information is received from the roadside machine 3 that has received the certificate. The validity period of the roadside machine certificate is shorter than the validity period of the regional certificate.

  In the present embodiment, the roadside device 3 distributes information related to the state of the traffic signal. In addition to this, the information distributed by the roadside device 3 may be any information such as traffic jam information, road surface information, and POI information. The roadside device 3 attaches its own signature when distributing information to ensure that no spoofing or tampering has occurred. The roadside machine 3 also obtains a central certificate from the central certification authority 1 and a regional certificate from the regional certification authority 2 that issued the roadside machine certificate to itself, and sends these electronic certificates to the vehicle 4. And deliver.

  In FIG. 1, the communication areas of the roadside machine 3 overlap each other and the vehicle 4 can always receive information from the roadside machine 3, but there may be an area where the vehicle 4 cannot communicate with the roadside machine 3. Absent.

  The vehicle 4 receives information from the roadside machine 3 as it moves. When the information is received, the signature of the roadside machine 3 is authenticated to confirm that no spoofing or tampering has been performed. At this time, authentication is performed using a regional certificate distributed from the roadside device 3. Details of the authentication process will be described later.

  As described above, the validity period of an electronic certificate is longer for a higher-order certificate authority. For example, the validity period of the central certificate is several years to 10 years, the regional certificate is January, and the roadside machine certificate is one day. That is, the central certification authority 1 issues a new regional certificate to the regional certification authority 2 every month, and the regional certification authority 2 issues a roadside machine certificate to the roadside machine 3 every day. Since the roadside device 3 advertises a very large amount of data, there is a high risk that the certificate will be decrypted. In this way, since the roadside device certificate is updated in a short period of time, high security can be realized.

[Roadside machine]
The structure of the roadside machine 3 is demonstrated using FIG. FIG. 2 is a block diagram showing a functional configuration of the roadside machine 3. The roadside machine 3 includes a communication unit 31, a certificate storage unit 32, a certificate distribution unit 33, and an information distribution unit 34.

The roadside device 3 performs wireless communication with the vehicle 4 via the communication unit 31. As a wireless communication method, for example, a wireless LAN such as IEEE 802.11x, DSRC (Dedicated Short Range Communication), or the like can be used. In addition, the roadside device 3 communicates with the central certificate authority 1 and the regional certificate authority 2 via the communication unit 31, but this communication may be wireless communication or wired communication.

  The certificate storage unit 32 is composed of a readable / writable memory, and the central certificate of the central certificate authority 1, the regional certificate of the regional certificate authority 2, and the electronic certificate of the local station issued by the regional certificate authority 2 (roadside Machine certificate).

  The certificate distribution unit 33 distributes the central certificate, the regional certificate, and the roadside device certificate stored in the certificate storage unit 32 via the communication unit 31. At this time, the certificate distribution unit 33 may distribute the regional certificate together with the central certificate. Since the central certificate is used for verifying the validity of the regional certificate, by distributing these centrally, the vehicle 4 does not need to receive twice and the processing becomes efficient. Similarly, the certificate distribution unit 33 may distribute the roadside device certificate when distributing the regional certificate.

  The information distribution unit 34 distributes information on traffic lights. The structure of the packet distributed by the information distribution unit 34 is shown in FIG. The packet includes information on the traffic light and the time of distribution. Then, the roadside machine 3 signs the information. The signature is obtained by obtaining a hash value from the traffic signal information and the time information and encrypting the hash value with the secret key of the roadside device 3. Further, the information distribution unit 34 distributes the information with the signature and the roadside machine certificate of the local station as a single packet. The vehicle 4 that has received this packet can verify the validity of the signature for the distribution information using this roadside device certificate. In addition, since time information is stored in the distribution information, this can be detected even when previous information is distributed late, such as when a Service-to-Self resends a packet.

  The signal information distributed by the information distribution unit 34 and the distribution frequency of the regional certificate and the central certificate distributed by the certificate distribution unit 33 are distributed in the order of the regional certificate and the central certificate. Deliver at a lower frequency. For example, the traffic signal information may be 900 times per second, the regional certificate 30 times per second, and the central certificate once per second. Since the management area of the upper certificate authority is wide, even if the frequency of distribution is lowered, the vehicle 4 can be sufficiently spread. Therefore, it is possible to reduce the amount of communication by reducing the distribution frequency for the electronic certificate of the higher-order certificate authority.

  The functions of the certificate distribution unit 33 and the information distribution unit 34 are realized by the CPU executing a program stored in the memory.

[In-vehicle terminal]
The configuration of the in-vehicle terminal 41 mounted on the vehicle 4 will be described with reference to FIG. FIG. 4 is a block diagram showing a functional configuration of the in-vehicle terminal 41. The in-vehicle terminal 41 includes a reception unit 42, a regional certificate acquisition unit 43, a regional certificate verification unit 46, a regional certificate storage unit 44, and an authentication unit 45.

  The receiving unit 42 receives a packet distributed from the roadside device 3, and is a wireless receiver. The wireless communication method is the same as that of the roadside device 3.

  The regional certificate acquisition unit 43 acquires a regional certificate of the regional certification authority 2 that manages the roadside device 3 distributed from the roadside device 3.

  The regional certificate verification unit 46 verifies the validity of the regional certificate acquired by the regional certificate acquisition unit 43 and stores it in the regional certificate storage unit 44 when the validity is confirmed.

When the authentication unit 45 receives distribution information from the roadside device 3, the authentication unit 45 verifies the validity of the information. At this time, if the area certificate acquired by the area certificate acquisition unit 43 and the area certificate stored in the area certificate storage unit 44 are the same, the area certificate is used as the area certificate verification unit 46. Trust without verifying with. That is, the public key included in the regional certificate is trusted as the public key of the regional certification authority 2. And the authentication part 45 verifies the validity of the roadside machine certificate distributed from the roadside machine 3 using the area certificate of the area certification authority 2. If the authentication is successful, it can be seen that the public key included in the roadside device certificate is the public key of the roadside device 3. Further, the validity of the signature of the distribution information is verified using the roadside machine certificate of the roadside machine 3.
If this authentication is successful, it can be seen that the information distributed from the roadside machine 3 is actually delivered from the roadside machine 3, and no spoofing or tampering has occurred.

  When the area certificate acquired by the area certificate acquisition unit 43 is different from the area certificate stored in the area certificate storage unit 44, the area certificate verification unit 46 determines that the acquired area certificate is valid. Verify sex. At this time, the regional certificate verification unit 46 performs verification using, for example, a central certificate distributed from the roadside device 3.

  The functions of the regional certificate acquisition unit 43, the regional certificate verification unit 46, and the authentication unit 45 are realized by a program stored in the memory being executed by the CPU.

<Processing flow>
The details of the authentication process performed by the in-vehicle terminal 41 will be described with reference to FIGS. FIG. 5 is a flowchart showing the flow of processing when the in-vehicle terminal 41 receives a regional certificate from the roadside device 3.

  The in-vehicle terminal 41 acquires a regional certificate distributed from the roadside device 3 in step S101. In step S <b> 102, the authentication unit 45 determines whether the received regional certificate and the regional certificate whose validity was confirmed immediately before being stored in the regional certificate storage unit 44 are the same. If these regional certificates are the same, the process proceeds to step S103, and the obtained regional certificate is considered to be reliable without verifying its validity. If these regional certificates are different, the process proceeds to step S104, and the obtained regional certificate is not trusted.

  FIG. 6 is a flowchart showing a flow of authentication processing performed when distribution information is received from the roadside device 3 when the acquired regional certificate is considered to be reliable. As described above, the roadside machine 3 delivers delivery information, a signature for the delivery information, and a roadside machine certificate as a single packet.

  In step S201, the authentication unit 45 verifies the validity of the roadside device certificate using the area certificate deemed to be reliable. In this verification, the signature of the regional certification authority 2 applied to the roadside device certificate is decrypted with the regional certificate (public key of the regional certification authority 2), and this is the hash value (message digest) obtained from the plaintext of the roadside device certificate. ) By verifying that it is the same. If it is determined in step S202 that the roadside device certificate is valid, the process proceeds to step S203.

  In step S203, the signature of the roadside device 3 on the distribution information is verified using the roadside device certificate whose validity has been confirmed. If it is determined in step S204 that the signature of the distribution information is valid, the process proceeds to step S205, and the authentication unit 45 trusts the information distributed from the roadside device 3. That is, it can be seen that the information distributed from the roadside device 3 has been improperly distributed from the roadside device 3 without impersonation and has not been altered.

  When it is determined in step S202 or step S204 that the roadside device certificate or the distribution information signature is invalid, the process proceeds to step S206, and the authentication unit 45 does not trust the information distributed from the roadside device 3. That is, since there is a possibility of being spoofed or altered, the distributed information is not used.

Next, a process when the acquired area certificate is different from the stored area certificate (step S104) will be described. In this case, the regional certificate verification unit 46 may verify the validity of the regional certificate acquired using the central certificate distributed from the roadside device 3. When the validity of the regional certificate is confirmed, the regional certificate is trusted and the regional certificate storage unit 44 is trusted.
To record.

  Further, as shown in the flowchart of FIG. 7, when the same regional certificate is continuously acquired, the validity of the regional certificate may be verified. That is, in step S301, the acquired area certificate is temporarily stored as an unauthenticated area certificate. In step S302, the next regional certificate is acquired. In step S303, it is determined whether the acquired regional certificate is the same as the temporarily stored regional certificate. If they are the same, the process proceeds to step S304, and the validity of the regional certificate is verified using the central certificate. If they are not the same, the process proceeds to step S101, and it is determined whether or not they are the same as those stored in the regional certificate storage unit 44 as a trusted regional certificate. In this way, when a regional certificate different from that stored in the regional certificate storage unit 44 is received twice in succession, the verification using the central certificate is performed for the first time, so that different regional certification authorities 2 When the probability that the in-vehicle terminal 41 has moved to the management area is high, the verification process can be performed. That is, processing efficiency is improved. However, when a regional certificate different from the stored regional certificate is received three or more times in succession, verification using the central certificate may be performed.

<Effect of embodiment>
The following effects can be obtained by authenticating information from the roadside machine using the road-to-vehicle communication system configured as described above. First, by providing the certificate authority with a hierarchical structure (the central certificate authority 1 and the regional certificate authority 2), it is possible to increase the renewal frequency of the electronic certificate without increasing the risk of being decrypted. In other words, the risk of being decrypted every time an electronic certificate is issued increases, but the frequency of issuing an electronic certificate according to the validity period of the electronic certificate of its own station (the certificate authority having an electronic certificate with a long validity period) The frequency of issuing electronic certificates can be reduced).

In addition, while the in-vehicle terminal 41 receives the same area certificate as the area certificate once confirmed, the authentication process can be accelerated by trusting the area certificate. In order to authenticate the distribution information from the roadside device 3, as shown by a dotted line in FIG. 10A, the regional certificate is verified using the central certificate, and the roadside device certificate is verified using the regional certificate. It is necessary to verify the signature of the roadside device attached to the distribution information using this roadside device certificate. However, since the reliability of the regional certificate can be ensured by adopting the above configuration, the process of verifying the regional certificate using the central certificate is omitted as shown by the solid line in FIG. It becomes possible.

  Further, since the higher-order certificate authority is distributed over a wider range, the roadside device 3 can sufficiently notify the in-vehicle terminal 41 even if the distribution frequency of the regional certificate and the central certificate is lowered. Accordingly, the roadside device 3 can reduce the distribution frequency of the regional certificate and the central certificate. That is, information (for example, signal information) originally desired to be distributed to the in-vehicle terminal 41 can be distributed with high frequency and high speed.

Furthermore, since the area certificate and the central certificate are regularly distributed from the roadside device 3, the in-vehicle terminal 41 immediately updates the new area certificate when the area certificate is updated and a new area certificate is issued. You can see that the old regional certificate is invalid. This has an advantage that a new certificate can be dealt with immediately compared to a method of checking a revocation list such as a CRL (Certificate Revocation List) list issued at a predetermined frequency. In addition, there is an advantage that processing takes less time compared to a method of inquiring the server whether the certificate has expired each time using OCSP (Online Certificate Status Protocol) or the like.

Furthermore, the in-vehicle terminal 41 does not need to store a large number of regional certificates, and only needs to store the trusted local certificate received immediately before, so that the memory capacity used can be reduced.

(Second Embodiment)
The second embodiment of the present invention is an embodiment in which more appropriate processing can be performed near the boundary of the management area of the regional certification authority. In the vicinity of the boundary of the management area, there is a possibility that there may be a place where radio waves for transmitting area certificates of a plurality of area certification authorities can be received. In addition, there may be a place where radio waves from base stations belonging to the management areas of different regional certification authorities can be received. In the present embodiment, appropriate processing can be performed even in such a case. Since this embodiment is basically the same as the first embodiment, only different parts will be described.

  In the present embodiment, the regional certificate storage unit 44 stores two regional certificates whose validity has been confirmed in the past, in addition to the regional certificate trusted immediately before. Although the maximum number of regional certificates to be stored is two here, this maximum number may be any number.

  The regional certificate storage unit 44 stores two types of regional certificates, “regional certificate trusted immediately before” and “regional certificate whose validity has been confirmed in the past”. Since it is not necessary, the following description will be made assuming that the regional certificate storage unit 44 stores a total of three regional certificates.

  FIG. 8 is a diagram showing the data structure of the regional certificate storage unit 44. The regional certificate storage unit 44 stores the regional certificate together with the date and time when the regional certificate was last acquired. As described above, the regional certificate storage unit 44 stores the regional certificate and the last acquisition date and time, thereby newly storing the regional certificate in a state where the maximum number of stored regional certificates is stored. In this case, it becomes easy to determine the regional certificate to be deleted. That is, when deleting a stored regional certificate, such as when storing a new regional certificate, the regional certificate storage unit 44 deletes the certificate with the oldest last acquisition date. The more recently acquired regional certificates are more likely to be used when verifying signatures. Therefore, by deleting the oldest regional certificate, it is possible to leave a regional certificate that is highly likely to be used.

  Here, the area certificate storage unit 44 stores the date and time when the area certificate was last acquired, but the date and time stored in the area certificate storage unit 44 may be stored. The same effect can be obtained also by this.

  In addition, the area certificate storage unit 44 may store the accumulated travel distance when the area certificate is last acquired or stored. The cumulative travel distance is the distance that the vehicle 4 has traveled so far, and can be acquired from a travel meter or the like. By storing the accumulated mileage in this way, the accumulated mileage at the time when the area certificate was stored is compared with the accumulated mileage at the current time, and the mileage after obtaining or storing the area certificate Can be calculated. Then, when deleting the area certificate, the area certificate having the longest travel distance after acquiring or storing the area certificate is deleted. It is considered that the possibility of using the regional certificate becomes lower as the distance travels longer after obtaining the regional certificate. Therefore, by doing the above, it becomes possible to leave a regional certificate that is highly likely to be used.

  The authentication process performed by the in-vehicle terminal 41 in the present embodiment is the same as that in the first embodiment, as shown in the flowcharts of FIGS. In the present embodiment, the received regional certificate is compared with a plurality of regional certificates stored in the regional certificate storage unit 44 in step S102 of the flowchart of FIG. If the received regional certificate matches the regional certificate stored in the regional certificate storage unit 44, the process proceeds to step S103, and the trust is performed without verifying the validity of the regional certificate.

  In the present embodiment, the processing in the case where the acquired regional certificate is different from the stored regional certificate (step S104) is also different from the first embodiment. In the present embodiment, the contents of this processing will be described using the flowchart of FIG.

  In step S401, the regional certificate storage unit 44 temporarily stores this regional certificate as an unauthenticated regional certificate. At this time, the acquired date and time are also stored. Next, in step S402, it is determined whether or not the acquired regional certificate has been acquired with a frequency equal to or higher than a predetermined frequency. If it is acquired at a predetermined frequency or more, the process proceeds to step S403, and the validity of the acquired regional certificate is verified using the central certificate. If the frequency is lower than the predetermined frequency, the process is terminated.

  In this way, when a regional certificate is obtained at a predetermined frequency or more, different regional certificates, such as near the boundary of the regional management area of the regional certification authority, are randomly distributed by verifying the validity. It is possible to efficiently cope with such a situation. This is because acquiring the area certificate at a predetermined frequency or more indicates that the in-vehicle terminal 41 has approached the management area of the area certificate authority. In addition, when the frequency of obtaining the regional certificate is low, there is a possibility that it is a fake regional certificate transmitted from a Service-to-Self. Therefore, by adopting the above-described method, the validity verification process is performed when the probability that the regional certificate is correct is high, and the process becomes efficient.

  In this embodiment, by storing a plurality of area certificates whose validity has been confirmed in the past as described above, a plurality of legitimate area certificates such as the vicinity of the boundary of the management area of the area certification authority are received. It is possible to perform processing efficiently even at a place. When storing a regional certificate, it is possible to perform efficient processing because it is determined which regional certificate is stored based on the possibility of verifying the signature using the regional certificate in the future. .

  In addition, by verifying the validity of the newly received regional certificate after acquiring the regional certificate at a predetermined frequency or more, it is also effective in locations where new regional certificates cannot be received continuously. It is possible to obtain the timing for verifying the characteristics.

  Note that the regional certificate temporarily stored in the regional certificate storage unit 44 as described above is preferably deleted when it has not been received for a predetermined period. This makes it possible to reduce the memory used.

<Modification>
-Hierarchy of certificate authorities In the above embodiment, only the central certificate authority 1 and the regional certificate authority 2 exist as the certificate authority. However, as shown in FIG. It is also preferable to have an intermediate certificate authority such as the certificate authority 5 and the mid-range certificate authority 6. In this case, the wide-area certificate authority 5 and the mid-area certificate authority 6 issue electronic certificates to the mid-range certificate authority 6 and the regional certificate authority 2 in their own management area, respectively. However, the number of intermediate certificate authorities between the central certificate authority 1 and the regional certificate authority 2 is not limited.

  By deepening the hierarchy of certificate authorities in this way, the number of certificate authorities managed by each certificate authority can be reduced, and the processing in the certificate authorities is distributed. Even if the frequency of updating the roadside machine certificate is increased, the number of times the electronic certificate is issued by the certificate authority is not excessively higher than the validity period of the electronic certificate, so that the security is improved.

Further, when the certificate authority hierarchy is deepened, it has conventionally been necessary to verify the electronic certificate in each hierarchy, but in this embodiment, the same area certificate as the area certificate whose validity was confirmed immediately before. Since the local certificate is considered to be reliable while the password is received, the authentication process can be performed at high speed. That is, as shown by a dotted line in FIG. 10B, conventionally, a wide area certificate, a middle area certificate, an area certificate, a roadside machine certificate, a roadside machine signature and verification of 5 times are required. When the area certificate is trusted in this embodiment, it is only necessary to verify the roadside machine certificate and the roadside machine signature.

-Combined use of GPS (Global Positioning System) The validity verification process of the regional certificate can be made more efficient by using GPS. The regional certificate stores the identifier of the regional certificate authority. Therefore, the in-vehicle terminal can grasp the position where the regional certification authority exists based on the location information database of the regional certification authority created in advance. The in-vehicle terminal can acquire the current position using GPS.

  Thus, it is preferable to change the processing method of the acquired area certificate based on the location information of the in-vehicle terminal and the area certificate authority. For example, when the location of the regional certification authority is more than a predetermined distance from the current location of the in-vehicle terminal, it is preferable to ignore the acquired regional certificate. In this case, it is preferable to omit the determination as to whether the area certificate matches the area certificate stored in the area certificate storage unit 44. In the first embodiment, when a regional certificate different from the last trusted regional certificate is obtained a predetermined number of times, the validity of the regional certificate is confirmed. It is preferable to consider that the certificate has not been obtained. It is possible to prevent other processes from being adversely affected by obtaining a clearly incorrect regional certificate. Also, in the second embodiment, the same effect can be obtained by regarding that it is not received in the same manner.

  It is also preferable to determine the validity (validity) of the regional certificate using GPS. If you receive two or more types of regional certificates (one of which is legitimate and the other is false) that are considered to be regional certificates of the same regional certification authority, receive the regional certificate by GPS Based on the obtained location information, it may be determined that the regional certificate distributed over the widest range is valid. This exploits the feature that it is difficult for a Service-to-Self to distribute fake electronic certificates over a wide area. Moreover, it is also preferable to determine the regional certificate distributed over the widest range using the date and time when the regional certificate is acquired and the travel distance after the acquisition, in addition to the GPS location information.

-Verification timing of area certificate In the above embodiment, the in-vehicle terminal 41 continues the area certificate different from the area certificate that has been validated in the past stored in the area certificate storage unit 44 a predetermined number of times. The validity of the acquired regional certificate was verified when it was acquired at a predetermined frequency or more.

  However, the timing for verifying the validity of the acquired regional certificate is not limited to this. The regional certificate verification unit 46 of the in-vehicle terminal 41 calculates the reliability of the regional certificate stored in the regional certificate storage unit 44, and determines the validity of the acquired regional certificate based on the calculated reliability. Whether or not to verify may be determined. Depending on the calculated reliability, even if the same area certificate as the area certificate stored in the area certificate storage unit 44 is acquired, the validity of the acquired area certificate is verified. Anyway.

  “Determining whether or not to verify validity based on reliability” means that, for example, when reliability is greater than a predetermined value Rh and smaller than a predetermined value Rl (Rl <Rh) It is conceivable to perform verification when the reliability is not less than Rl and not more than Rh. When the reliability is larger than the predetermined value Rh, it can be regarded as valid without verification, and when the reliability is smaller than the predetermined value Rl, it can be regarded as invalid without verification. It is.

  There are the following methods for calculating the reliability.

  Based on the elapsed time from when the validity of the regional certificate was confirmed immediately before, the longer the elapsed time, the lower the reliability. In addition, this elapsed time may not be the elapsed time from when the effectiveness is actually confirmed, but may be the elapsed time from the last time that it was deemed reliable as described above. In any case, renewal of the regional certificate or different regional certifications will occur as a longer time elapses after receiving a valid regional certificate or a valid regional certificate. Since there is a high possibility that the in-vehicle terminal 41 has moved to the management area of the station, the reliability of the regional certificate stored in the regional certificate storage unit 44 is low.

The in-vehicle terminal 41 includes GPS (Global Positioning System) and map information indicating the management area of each regional certification authority 3, and the in-vehicle terminal 41 is in a different management area from the place where the validity of the area certificate was confirmed immediately before. When moved, the reliability of the regional certificate stored in the regional certificate storage unit 44 is calculated to be low. This is because the regional certificate is different when moving to a different management area.

  Further, when the in-vehicle terminal 41 acquires a regional certificate different from the regional certificate stored in the regional certificate storage unit 44, the in-vehicle terminal 41 initially stores the regional certificate stored in the regional certificate storage unit 44. The reliability is calculated as high. However, as the in-vehicle terminal 41 continues to receive the same area certificate, the reliability of the area certificate stored in the area certificate storage unit 44 is calculated to be low. The continuous reception of the same regional certificate is because there is a high probability that the regional certificate is updated or the in-vehicle terminal 41 has moved to a management region of a different regional certification authority.

  The method for calculating the reliability of the regional certificate may combine the above-described methods as much as possible.

  As described above, the reliability of the area certificate stored in the area certificate storage unit 44 is calculated, and the validity of the area certificate acquired by the area certificate acquisition unit 43 is verified based on the calculated reliability. By determining whether or not, the verification process is performed when there is a high probability that the area certificate stored in the area certificate storage unit 44 has become invalid, and efficient processing becomes possible.

It is a figure which shows the outline | summary of the road-vehicle communication system in 1st Embodiment. It is a figure which shows the functional block of the base station in 1st Embodiment. It is a figure which shows the structure of the data which the base station in 1st Embodiment distributes. It is a figure which shows the functional block of the vehicle-mounted terminal in 1st Embodiment. It is a flowchart which shows the flow of the authentication process which the vehicle-mounted terminal in 1st Embodiment performs. It is a flowchart which shows the flow of the authentication process which the vehicle-mounted terminal in 1st Embodiment performs. It is a flowchart which shows the flow of the authentication process which the vehicle-mounted terminal in 1st Embodiment performs. It is a figure which shows the data structure of the area certificate memory | storage part in 2nd Embodiment. It is a flowchart which shows the flow of the authentication process which the vehicle-mounted terminal in 2nd Embodiment performs. It is the schematic explaining the authentication process in this embodiment. It is a figure which shows the modification of the road-vehicle communication system in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Central certification authority 2 Regional certification authority 3 Roadside machine 4 Vehicle 5 Wide area certification authority 6 Middle area certification authority 31 Communication part 32 Certificate memory | storage part 33 Certificate delivery part 34 Information delivery part 41 In-vehicle terminal 42 Receiving part 43 Area certificate acquisition Section 44 Regional certificate storage section 45 Authentication section 46 Regional certificate verification section

Claims (16)

A road-to-vehicle communication system that verifies the validity of the information using a public key cryptosystem in the in-vehicle terminal when distributing information from the base station to the in-vehicle terminal,
It consists of a regional certification authority, a base station, and an in-vehicle terminal.
The regional certificate authority
Issuing an electronic certificate to the base station belonging to its own management area,
The base station
While delivering the regional certificate that is the electronic certificate of the regional certification authority that issued the electronic certificate to the local station to the in-vehicle terminal at a predetermined frequency,
Delivering the information, a signature for the information, and an electronic certificate of the local station to the in-vehicle terminal;
The in-vehicle terminal is
While receiving the same area certificate as the area certificate trusted immediately before, the area certificate is considered to be reliable, and the validity of the information distributed from the base station using the area certificate is considered. A road-to-vehicle communication system characterized by verifying The said in-vehicle terminal verifies the validity of the received regional certificate when receiving a regional certificate different from the previously trusted regional certificate a predetermined number of times. The road-to-vehicle communication system described. The in-vehicle terminal stores an area certificate whose validity has been confirmed in the past, and when receiving the same area certificate as the stored area certificate, the in-vehicle terminal regards the area certificate as trustworthy, The road-to-vehicle communication system according to claim 1, wherein validity of information distributed from the base station is verified using a regional certificate. The vehicle-mounted terminal is provided with a predetermined maximum number of regional certificates whose validity has been confirmed in the past, and the validity is confirmed when the maximum number of regional certificates has already been stored. 4. The road-to-vehicle communication system according to claim 3, wherein when the stored regional certificate is newly stored, at least one of the stored regional certificates is deleted. The in-vehicle terminal determines the area certificate to be deleted based on an elapsed time or a travel distance from when the area certificate whose validity was confirmed in the past was last received or stored. The road-to-vehicle communication system according to claim 4. When the in-vehicle terminal receives a regional certificate different from the regional certificate whose validity has been confirmed in the past, the vehicle-mounted terminal confirms the validity of the received regional certificate. The road-to-vehicle communication system according to any one of claims 3 to 5, wherein The in-vehicle terminal has position information acquisition means,
If the management area of the regional certification authority that issued the received regional certificate and the location information of the in-vehicle terminal acquired by the location information acquisition unit are more than a predetermined distance apart, the regional certificate is ignored. The road-to-vehicle communication system according to any one of claims 1 to 6. The road-vehicle communication system according to any one of claims 1 to 7, wherein the base station distributes the regional certificate at a frequency lower than a distribution frequency of the information. An in-vehicle terminal that verifies the validity of information distributed from a base station using a public key cryptosystem,
A regional certificate acquisition means for acquiring a regional certificate that is an electronic certificate of a regional certification authority that issues an electronic certificate to the base station;
A regional certificate verification means for verifying the validity of the acquired regional certificate;
A regional certificate storage means for storing a regional certificate whose validity was confirmed immediately before by the regional certificate verification means;
While the regional certificate acquisition unit receives the same regional certificate as the regional certificate stored in the regional certificate storage unit, the regional certificate is not verified by the regional certificate verification unit. An in-vehicle terminal characterized in that it is considered reliable and verifies the validity of information distributed from the base station using the regional certificate. When the regional certificate acquisition unit continuously acquires a regional certificate different from the regional certificate stored in the regional certificate storage unit a predetermined number of times, the validity of the acquired regional certificate is determined by the regional certificate. The vehicle-mounted terminal according to claim 9, wherein verification is performed by a verification unit. The regional certificate storage means further stores a regional certificate whose validity has been confirmed in the past,
When the regional certificate acquisition unit acquires the same regional certificate as the regional certificate stored in the regional certificate storage unit, the regional certificate is trusted without being verified by the regional certificate verification unit. The in-vehicle terminal according to claim 9, wherein the in-vehicle terminal is considered to be capable of verifying the validity of the information distributed from the base station using the regional certificate. The regional certificate storage means is provided with a predetermined maximum number of regional certificates to be stored, and the regional certificate whose validity has been confirmed when the maximum number of regional certificates are already recorded. The vehicle-mounted terminal according to claim 11, wherein when storing a new one, at least one of the stored regional certificates is deleted. The area certificate storage means determines the area certificate to be deleted based on an elapsed time or a mileage from when the area certificate whose validity was confirmed in the past was last received or stored. The in-vehicle terminal according to claim 12. When a regional certificate different from the regional certificate stored in the regional certificate storage unit is received at a frequency of a predetermined frequency or higher, the validity of the received regional certificate is verified by the regional certificate verification unit. The in-vehicle terminal according to any one of claims 11 to 13. Having position information acquisition means,
When the management area of the regional certification authority stored in the area certificate acquired by the area certificate acquisition means and the position information of the own vehicle acquired by the position information acquisition means are more than a predetermined distance, The in-vehicle terminal according to any one of claims 9 to 14, wherein the regional certificate is ignored. When distributing information from the base station to the in-vehicle terminal in a road-to-vehicle communication system composed of a regional certification authority, a base station, and the in-vehicle terminal, the in-vehicle terminal uses a public key cryptosystem to transmit the information. A road-to-vehicle communication method for verifying validity,
The regional certification authority issues an electronic certificate to the base station belonging to its management area,
The base station delivers an area certificate that is an electronic certificate of an area certification authority that issued an electronic certificate to the local station to the in-vehicle terminal at a predetermined frequency,
While the in-vehicle terminal is receiving the same area certificate as the area certificate trusted immediately before, it is considered that the area certificate can be trusted,
The base station distributes the information, a signature for the information, and an electronic certificate of the local station to the in-vehicle terminal,
A road-to-vehicle communication method characterized by verifying the validity of the information by using the regional certificate deemed to be reliable when the vehicle-mounted terminal is distributed with the information from the base station.

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