JP2020036270A - Communication system - Google Patents

Abstract

To prevent the unauthorized use for updating a secret key in an authentication device while avoiding revocation of a device.SOLUTION: A server 2 includes an update key 52 for updating a secret key 51 and a revocation list describing identification information on user devices to be revoked, and generates update information 54 including the update key 52 and the revocation list 55. An authentication device 4 receives update information 54 via a user device 3, makes a revocation determination on the basis of the revocation list 55, and updates the secret key 51 with the update key 52 if it is not revoked.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a communication system capable of invalidating a device of a user who has subscribed to the communication system and restricting access to distribution information.

  Conventionally, in order to restrict access to information distributed in a communication system, there is known a technique for stopping distribution of an encryption key to a device of a specific subscribing user so that the distribution information cannot be decrypted. I have. However, for example, in the case of distributing information to a plurality of vehicles moving at a high speed as in the case of the Intelligent Transport System (ITS), it is necessary to select a specific vehicle (device) and stop the distribution of the encryption key. Is very difficult.

  In order to solve this problem, a technique is known in which a revocation list is distributed by broadcasting, and a user device that receives the revocation list finds an identifier of the own device in the revocation list and invalidates the own device. I have. For example, Patent Literature 1 discloses a technique for suppressing processing of a reproduction unit of distribution content when its own identification information is described in a revocation list received from a server.

WO2013 / 031124

  However, according to the technique of Patent Document 1, it is possible to analyze the distribution content and receive only the information for updating the encryption key and not receive only the revocation list, or discard only the revocation list. Therefore, there is a problem that the user device cannot be invalidated properly.

  Therefore, an object of the present invention is to provide a communication system in which a user device can reliably receive an invalidation list and invalidate its own device.

  In order to solve the above problems, a communication system according to the present invention includes a user device incorporating an authentication device, and a server that distributes update information for updating the authentication device, wherein the server exchanges a secret key in the authentication device. An update key to be updated, a revocation list including identification information of the user device to be revoked, and means for generating update information including the update key and the revocation list, wherein the authentication device uses the update key to It is characterized by including means for updating a secret key and means for revoking itself based on a revocation list.

  In this case, the authentication device is a tamper-resistant device, the server includes an operation key that operates and manages the communication system, and the update information generation unit includes a unit that signs the update information using the operation key, The authentication device may include an operation key and means for verifying the signature of the update information using the operation key. It is also preferable that the update information generating means includes means for encrypting the update key using the operation key, and the authentication device includes means for decrypting the update key using the operation key.

  In addition, the user device forms a group, the server includes distribution destination information including the identification information of the group, the user device includes the identification information of the group to which the user belongs, and the update information generation unit transmits the distribution destination information. The update information may be generated by including the update information, and the authentication device may discard the update information based on the distribution destination information. In this case, the update information generating means may generate different update information for each group.

  According to the communication system of the present invention, since the update key and the revocation list are comprehensively distributed in the update information, the user device must receive the revocation list when updating the first encryption key. And has an excellent effect that the user device can be appropriately invalidated.

It is a schematic diagram showing one embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration of the communication system in FIG. 1. FIG. 9 is a block diagram illustrating a procedure for generating update information. FIG. 9 is a block diagram illustrating the operation of the authentication device that has received update information. FIG. 11 is a block diagram illustrating another embodiment of the communication system. FIG. 6 is a block diagram illustrating a procedure for generating update information in the communication system of FIG. 5. FIG. 6 is a block diagram illustrating an operation of an authentication device that has received update information in the communication system of FIG. 5.

  An embodiment in which the present invention is embodied in a communication system that updates a secret key by broadcasting will be described with reference to the drawings. As shown in FIGS. 1 and 2, the communication system 1 of this embodiment includes a user device 3 incorporating an authentication device 4, a server 2, and a relay device 5 for relaying distribution information of the server 2. I have. In the following description, all the update information 54 sent from the server 2 is assumed to be distributed to the user device 3 via the relay device 5, and the description of the relay device 5 is omitted.

  The server 2 distributes the update information 54, the update information generation unit 24 that generates the update information 54, the storage unit 23 that stores the operation key 53 that operates and manages the communication system, the CPU 21 that controls the server 2, and the server 2. And an interface 22 for performing the operation. The storage unit 23 stores, in addition to the operation key 53, an invalidation list 55 including a device identifier 57 as identification information of the user device 3 to be invalidated. The update information generation unit 24 includes an encryption unit 26 that encrypts the update key 52 using the operation key 53, and a signature unit 25 that signs the update information 54 using the operation key 53. I have. The update information 54 includes an update key 52 and a revocation list 55. The update key 52 is encrypted by the operation key 53, and the update information 54 is signed by the operation key 53.

  The user device 3 includes a storage unit 33 that stores a device identifier 57 as identification information for identifying the user device 3, a CPU 31 that controls the user device 3, and an interface 32 that receives update information 54 from the server 2. Have been. An authentication device 4 is incorporated in the user device 3.

  The authentication device 4 includes a signature verification unit 44 that verifies the signature attached to the update information 54, an invalidation determination unit 45 that invalidates the authentication device 4 based on the revocation list 55, and an encryption unit 26 of the server 2. A decryption unit 46 for decrypting the update key 52 encrypted by the encryption key, a secret key update unit 47 for updating the secret key 51 using the decrypted update key 52, a secret key 51 for decrypting predetermined distribution service information, and a server. And a storage unit 43 for storing the same operation key 53 as the second operation key 53. Further, the authentication device 4 has tamper resistance, and is configured so that information in the authentication device 4 cannot be extracted from the user device 3 or the user device 3 cannot control the authentication device 4.

  Next, the operation of the communication system 1 having the above configuration will be described with reference to FIGS. As shown in FIG. 3A, the update information generation unit 24 of the server 2 generates an update key 52, reads the revocation list 55 from the storage unit 23, and generates update information. When the update information is generated, the encryption unit 26 encrypts the update key 52 using the operation key 53 read from the storage unit 23, as shown in FIG. When the encryption is completed, as shown in FIG. 3C, the signature unit 25 gives a signature to the update information 54 using the operation key 53 read from the storage unit 23.

  As shown in FIG. 4, the update information 54 distributed from the server 2 is input to the authentication device 4 via the user device 3. The signature verification unit 44 verifies the signature of the input update information 54 using the operation key 53 read from the storage unit 43. If the verification fails, that is, if the update information 54 has been tampered with, the signature verification unit 44 discards the update information 54.

  On the other hand, if the verification is successful, the invalidation determination unit 45 reads the device identifier 57 from the storage unit 33 of the user device 3 and compares the device identifier 57 with the invalidation list 55. Then, when the device identifier 57 is described in the revocation list 55, the revocation determination unit 45 revoked the authentication device 4. Examples of the invalidation of the authentication device 4 include a method of deleting the update key 52, a method of invalidating the update key 52, and a method of invalidating the secret key update unit 47 of the authentication device 4 and not updating the secret key 51. You can choose.

  When the device identifier 57 is not described in the revocation list 55 and revocation is not performed, the decryption unit 46 decrypts the update key 52 using the operation key 53 read from the storage unit 43. Thereafter, the secret key updating unit 47 updates the secret key 51 stored in the storage unit 43 using the combined update key 52.

  According to the communication system 1 configured as described above, since the revocation list 55 and the update key 52 are combined into one to generate the update information 54, the act of illegally receiving the update key 52 while avoiding the revocation list 55. There is an excellent effect that can be prevented. In particular, when the update information 54 is signed using the operation key 53 and the operation key 53 is stored in the tamper-resistant authentication device 4, there is an effect that the falsification of the update information 54 can be prevented. . Also, when the update key 52 is encrypted using the operation key 53, the update key 52 can be distributed safely.

  5 to 7 show another embodiment of the communication system 1. In this example, the user devices 3 are grouped, and different update information 54 is received for each group. Other configurations are the same as those of the above-described embodiment, and the same reference numerals are given to the drawings to omit redundant description, and only the differences will be described below.

  In the communication system 1 illustrated in FIG. 5, the user devices 3 configure a plurality of groups, and the storage unit 23 of the server 2 stores a group identifier 58 as identification information of all groups as distribution destination information 56. . The update information 54 includes an update key 52, a revocation list 55, and a group identifier 58. A signature is attached to the update information 54 using the operation key 53.

  The storage unit 33 of the user device 3 stores a group identifier 58 of a group to which the user device 3 belongs. In addition, the authentication device 4 includes a distribution verification unit 48 that discards the update information 54 based on the distribution destination information 56.

  As shown in FIG. 6A, the update information generation unit 24 of the server 2 generates the update key 52, reads the distribution destination information 56 and the revocation list 55 from the storage unit 23, and generates the update information. After performing the encryption using the operation key 53 (FIG. 6B), the signature unit 25 uses the operation key 53 to add a signature to the update information 54 including the group identifier 58 (FIG. 6C). ).

  As shown in FIG. 7, the update information 54 distributed from the server 2 is verified by the signature verification unit 44. If the verification is successful, the distribution verification unit 48 reads the group identifier 58 from the storage unit 33 of the user device 3 and checks the group identifier 58 against the distribution destination information 56. If the verification fails, that is, if the update information is not addressed to itself, the distribution verification unit 48 discards the update information 54. If the collation is successful, the process is continued by the decryption unit 46 and the invalidation determination unit 45 because the update information is addressed to itself.

  According to the communication system 1 configured as described above, the user device 3 forms a group, and the same distribution destination information 56 is attached to each group. There is an excellent effect that the complexity of setting the destination information can be avoided, and the user device 3 can omit the subsequent processing of the distribution verification unit 48 for the update information 54 not related to itself.

  In addition, the present invention is not limited to the above-described embodiment, and can be implemented by arbitrarily changing the configuration of each unit without departing from the spirit of the invention.

DESCRIPTION OF SYMBOLS 1 Communication system 2 Server 3 User device 4 Authentication device 5 Relay device 21,31,41 CPU
22, 32, 42 interfaces 23, 33, 43 storage unit 24 update information generation unit 25 signature unit 26 encryption unit 44 signature verification unit 45 invalidation determination unit 46 decryption unit 47 secret key update unit 48 distribution verification unit 51 private key 52 Update key 53 Operation key 54 Update information 55 Revocation list 56 Distribution destination information 57 Device identifier 58 Group identifier

Claims (5)

A user device incorporating an authentication device, and a server that delivers update information for updating the authentication device,
Means for generating an update key for updating a secret key in the authentication device, an invalidation list including identification information of a user device to be invalidated, and update information including the update key and the invalidation list; , Including
A communication system, wherein the authentication device includes: means for updating the secret key using the update key; and means for invalidating itself based on the revocation list. The authentication device is a tamper-resistant device,
The server includes an operation key for operating and managing the communication system,
The update information generation unit includes a unit that signs the update information using the operation key,
The communication system according to claim 1, wherein the authentication device includes: the operation key; and means for verifying a signature of the update information using the operation key. The update information generating means includes means for encrypting the update key using the operation key,
The communication system according to claim 2, wherein the authentication device includes means for decrypting the update key using the operation key. The user devices form a group,
The server includes distribution destination information including identification information of the group,
The user device includes identification information of a group to which the user device belongs,
The update information generating means generates the update information by including the distribution destination information,
The communication system according to claim 1, wherein the authentication device discards the update information based on the distribution destination information.   The communication system according to claim 4, wherein the update information generating unit generates different update information for each of the groups.

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