JP7684147B2 - Key information update system - Google Patents

Description

The present invention relates to a key information update system, a key information update method, and a key information update program.

Conventionally, technology has been proposed that uses a key to encrypt and decrypt messages sent and received between multiple communication devices. In order to maintain secure communications between communication devices, it is recommended that the keys used to encrypt and decrypt messages be updated periodically. However, there are cases in which the keys are not updated due to failure to deliver messages regarding key updates, etc.

Patent document 1 discloses a key information control device that updates keys used in a network including multiple communication devices through multicast communication. If key updating fails, the key information management device disclosed in patent document 1 performs unicast communication with a retransmission function to update the key.

JP 2015-133589 A

In the key information management device disclosed in Patent Document 1, if key updating fails, it is necessary to switch to unicast communication with a retransmission function, which is a different communication method from normal multicast communication. In other words, the key information management device disclosed in Patent Document 1 needs to be provided with a separate communication method in case key updating fails, and each communication device also needs to be compatible with multiple communication methods.

The present invention was made in consideration of the problems inherent in the conventional technology. The object of the present invention is to provide a key information update system that is capable of performing key updates with a simple configuration.

A key information update system according to an embodiment of the present invention is a key information update system that updates a session key used to encrypt and decrypt messages transmitted between a wireless master and a wireless slave. The wireless master includes an update key information transmission unit that transmits, to the wireless slave, update key information obtained by encrypting a planned update key stored in the master memory unit with a session key stored in the master memory unit of the wireless master, a master information transmission unit that transmits master information about the wireless master encrypted with the planned update key to the wireless slave, a master determination unit that determines whether or not slave information about the wireless slave transmitted from the wireless slave has been received, and a master key update unit that updates the session key to the planned update key. The wireless slave device has an update key information receiving unit that receives update key information transmitted from the wireless master device, decrypts the update key information with a session key stored in a slave device storage unit of the wireless slave device to obtain a planned update key, and stores the updated key in the slave device storage unit; a master device information receiving unit that receives master device information transmitted from the wireless master device and decrypts the updated key; a slave device determination unit that determines whether or not to transmit the slave device information to the wireless master device based on the update key information and the master device information; a slave device information transmitting unit that transmits the slave device information encrypted with the planned update key to the wireless master device when the slave device determination unit determines that the slave device information should be transmitted; and a slave device key updating unit that updates the session key to the planned update key.

A key information update method according to another aspect of the present invention is a key information update method executed by a computer, which updates a session key used for encrypting and decrypting a message transmitted and received between a wireless master and a wireless slave, and transmits update key information obtained by encrypting a planned update key stored in the master memory unit with a session key stored in the master memory unit of the wireless master, to the wireless slave, receives the update key information transmitted from the wireless master, decrypts the update key information with the session key stored in the slave memory unit of the wireless slave to obtain a planned update key, stores the update key in the slave memory unit, and transmits the encrypted update key to the wireless master. The wireless device transmits parent device information related to the wireless slave device to the wireless slave device, receives parent device information transmitted from the wireless master device and decrypts it with the planned update key, determines whether or not to transmit slave device information related to the wireless slave device to the wireless master device based on the update key information and parent device information, and if it is determined that the slave device information is to be transmitted, transmits the slave device information encrypted with the planned update key to the wireless master device, determines whether or not the slave device information transmitted from the wireless slave device has been received, and if it is determined that the slave device information has been received, updates the session key of the wireless master device to the planned update key, and if the slave device information has been transmitted to the wireless master device, updates the session key of the wireless slave device to the planned update key.

A key information update program according to another aspect of the present invention is a key information update program for causing a computer to execute an update of a session key used for encryption and decryption of messages transmitted and received between a wireless master unit and a wireless slave unit, and includes the steps of: transmitting, to the wireless slave unit, update key information obtained by encrypting a planned update key stored in the master unit storage unit with a session key stored in the master unit storage unit of the wireless master unit; receiving the update key information transmitted from the wireless master unit, decrypting the update key information with the session key stored in the slave unit storage unit of the wireless slave unit to obtain a planned update key, and storing the key in the slave unit storage unit; and transmitting master unit information regarding the wireless master unit encrypted with the planned update key to the wireless slave unit. the step of receiving the host information transmitted from the wireless master and decrypting it with the planned update key; the step of determining whether to transmit the host information regarding the wireless slave to the wireless master based on the update key information and the host information; the step of transmitting the host information encrypted with the planned update key to the wireless master when it is determined that the host information is to be transmitted; the step of determining whether the host information transmitted from the wireless slave has been received; the step of updating the session key of the wireless master to the planned update key when it is determined that the host information has been received; and the step of updating the session key of the wireless slave to the planned update key when the host information has been transmitted to the wireless master.

The present invention provides a key information update system that can perform key updates with a simple configuration.

1 is a diagram showing a configuration of a key information updating system according to an embodiment of the present invention. 1 is a diagram showing a configuration of a wireless device used in a key information updating system according to an embodiment of the present invention. 2 is a diagram showing a functional configuration of a wireless master device of the key information updating system according to the present embodiment. FIG. 2 is a diagram illustrating a functional configuration of a wireless slave device of the key information updating system according to the present embodiment. FIG. FIG. 2 is a sequence diagram for explaining an example of a process of the key information update system according to the present embodiment. 4 is a diagram showing an example of a message transmitted and received in the key information update system according to the embodiment; FIG. 4 is a sequence diagram showing an example of communication performed between a wireless master device and a wireless slave device in the key information update system according to the present embodiment. FIG. 4 is a sequence diagram showing an example of communication performed between a wireless master device and a wireless slave device in the key information update system according to the present embodiment. FIG. 4 is a sequence diagram showing an example of communication performed between a wireless master device and a wireless slave device in the key information update system according to the present embodiment. FIG.

The key information update system according to this embodiment will be described in detail below with reference to the drawings. Note that the dimensional ratios in the drawings have been exaggerated for the sake of explanation and may differ from the actual ratios. In addition, in the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

Figure 1 is a diagram showing the configuration of a wireless communication system 1 to which the key information update system according to this embodiment is applied. As shown in Figure 1, the wireless communication system 1 includes a meter reading network 10, a management device 30, and a network 40.

In this embodiment, the meter reading network 10 includes a plurality of meters 20, and the meters 20 are equipped with radio equipment to enable mutual communication between the meters 20. In this embodiment, the meters 20 are, for example, meters installed in homes that measure water, gas, electricity, etc. The communication standard used in the meter reading network 10 is, for example, "U-Bus Air," which is used in wireless telemetering systems. This "U-Bus Air" is a communication method that enables communication between radio equipment equipped in the meters 20, and is a short-range wireless communication method that uses the 920 MHz band and achieves ultra-low power consumption.

The multiple meters 20 included in the meter reading network 10 include a master meter 20a and multiple slave meters 20b connected to the master meter 20a. Hereinafter, when there is no need to distinguish between the master meter 20a and the slave meters 20b, they will simply be referred to as "meters 20."

The slave meter 20b is equipped with an MT radio 200 (meter radio) as a slave radio. The MT radio 200 corresponds to a wireless slave.

The master meter 20a also includes a gateway 100 that performs wireless communication with each of the multiple MT radios 200 and further communicates with the management device 30 via the network 40. The gateway 100 corresponds to a wireless master.

The management device 30 is a communication center (centralized monitoring center) that manages the information of each meter 20 included in the meter reading network 10. For example, the management device 30 sends a meter reading data request message to each meter 20 via the GW radio 100, and the GW radio 100 and MT radio 200 that receive the meter reading data request message return the meter reading data of the meter 20 to the management device 30. Some of the information managed by this management device 30 is provided to gas suppliers, water suppliers, etc.

In this embodiment, the network 40 is a wide area communication network in which the management device 30 and the GW radio 100 can communicate with each other, and is configured, for example, by a carrier network such as a mobile phone network, or the Internet. In other words, the GW radio 100 has a function as a gateway that relays the different wireless standards of the network 40 and the meter reading network 10. Note that the communication standard of the network 40 and the communication standard of the meter reading network 10 may be the same communication standard.

(Configuration of key information update system)
Next, the configurations of the GW radio 100 and the MT radio 200 provided in the key information update system will be described. Fig. 2 is a block diagram showing the configurations of the GW radio 100 and the MT radio 200. Note that since the configuration of the MT radio 200 is similar to the configuration of the GW radio 100, the configuration of the GW radio 100 will be described below.

The GW radio 100 includes a control unit 110, a memory unit 120, an input/output IF 130, and a communication IF 140.

The control unit 110 may be configured as, for example, a general-purpose microcomputer. In this case, a computer program for causing the microcomputer to function as the GW radio 100 may be installed in the microcomputer. By executing the computer program, the microcomputer functions as multiple information processing circuits provided in the GW radio 100. The control unit 110 may also realize the multiple information processing circuits provided in the GW radio 100 by software, or it is also possible to prepare dedicated hardware and configure the information processing circuits. The multiple information processing circuits may also be configured by individual hardware.

The memory unit 120 stores master key information 121 and/or session key information 122, which will be described later, as data. Note that there may be one or more memory units 120 for storing these pieces of data. For example, a single memory unit 120 may be configured to store the data in separate areas. Alternatively, the data may be distributed and stored in multiple storage devices installed in physically separate locations. Note that the memory unit 120 of the GW radio 100 corresponds to a parent device memory unit, and the memory unit 220 of the MT radio 200 corresponds to a child device memory unit.

The input/output IF 130 is, for example, a component (interface) that allows the user to exchange data with the GW radio 100. The user can configure the meter 20 or the GW radio 100 via the input/output IF 130. The input/output IF 130 can also display information about the meter 20 or the GW radio 100 via a display unit (not shown) provided in the meter 20 or the GW radio 100 or connected to the meter 20 or the GW radio 100. The user can obtain information about the meter 20 or the GW radio 100 displayed on the display unit via the input/output IF 130.

The communication IF 140 of the GW radio 100 is an interface that enables communication between the GW radio 100 and the MT radio 200 via the communication IF 240 of the MT radio 200. The communication IF 140 of the GW radio 100 also has a function that enables communication with the management device 30 via the network 40.

(Functions of the key information update system)
Next, the functions of the key information updating system will be described. Fig. 3A is a functional block diagram showing the functions of the GW radio device 100. Fig. 3B is a functional block diagram showing the functions of the MT radio device 200. Below, the functions of the key information updating system shown in Fig. 3A and Fig. 3B will be described using the sequence diagram shown in Fig. 4.

As shown in FIG. 3A, the control unit 110 of the GW radio 100 has as its functions an update key information transmission unit 111, a parent device information transmission unit 112, a determination unit 113, and a session key update unit 115. The memory unit 120 of the GW radio 100 stores master key information 121 and session key information 122. The determination unit 113 of the GW radio 100 corresponds to a parent device determination unit. The session key update unit 115 of the GW radio 100 corresponds to a parent device key update unit.

In this embodiment, the master key is key information used when generating, duplicating, or processing a key, and is used, for example, when generating a session key. Also, in this embodiment, the session key is key information used to encrypt and decrypt messages transmitted and received in communication between the GW radio device 100 and the MT radio device 200.

As shown in FIG. 3B, the control unit 210 of the MT radio device 200 has the following functions: an update key information receiving unit 211, a parent device information receiving unit 212, a determination unit 213, a child device information transmitting unit 214, and a session key updating unit 215. The determination unit 213 of the MT radio device 200 corresponds to a child device determination unit. The session key updating unit 215 of the MT radio device 200 corresponds to a child device key updating unit.

The storage unit 220 of the MT radio device 200 also stores the session key information 222. Note that in the example shown in FIG. 3B, the storage unit 220 does not have an area for master key information, but this configuration does not limit the configuration of this embodiment, and the storage unit 220 of the MT radio device 200 may be configured to have an area for master key information.

The session key information 122 and the session key information 222 shown in FIG. 4 have two areas, an area C (Current area) and an area N (Next area), and a session key is stored in the area C and/or the area N. The session key used for messages exchanged between the current GW radio 100 and the MT radio 200 is stored in the area C. The update-scheduled key to be updated in the next session key update is stored in the area N. In this embodiment, the session key, which is the update-scheduled key stored in the area N, is also used for some of the messages exchanged between the current GW radio 100 and the MT radio 200. Details of the application of the session key stored in the area N will be described later.

At the start of the process shown in FIG. 4, an example is shown in which the session key S1 is stored in the C area of the session key information 122 as the session key currently being used. Also, in the example shown in FIG. 4, an example is shown in which the session key S2 is stored in the N area of the session key information 122 as the key to be updated in the next key update process.

Similarly, FIG. 4 shows an example in which, at the start of the process, the C area of the session key information 222 stores the session key S1 as the currently used session key. On the other hand, FIG. 4 shows an example in which, at the start of the process, the N area of the session key information 222 does not store the update key to be updated in the next update process.

An example of a message transmitted between the GW radio 100 shown in FIG. 4 and the MT radio 200 is shown in FIG. 5. In this embodiment, messages related to key setting or key update include "update key information" transmission, "parent device information" transmission, and "child device information" transmission. Messages related to data transmission and reception between the GW radio 100 and the MT radio 200 include, for example, messages of "meter reading data request" and "meter reading data response". Note that the "session key (C area)" and "update key (N area)" described in the "encryption/decryption key information" column in FIG. 5 are information on the key used to encrypt the message and the key used to decrypt the message, respectively. In this embodiment, information on the key corresponding to this message is stored in the header of each message, and the radio receiving the message decrypts the message based on the information on the key stored in the header.

The update key information transmission unit 111 of the GW radio 100 transmits the "update key information" to be updated to the MT radio 200. Specifically, the update key information transmission unit 111 transmits to the MT radio 200 update key information obtained by encrypting the key to be updated stored in the N area of the session key information 122 with the session key stored in the C area of the session key information 122 in the memory unit 120 of the GW radio 100. The process of transmitting the "update key information" by the update key information transmission unit 111 corresponds to step S401 in the example of FIG. 4.

Specifically, in step S401, the GW radio 100, which is the parent device, transmits a message of "update key information" to the MT radio 200, which is the child device. Here, the "update key information" is assumed to include information about the session key S2. Furthermore, the "update key information" is information encrypted by the session key S1, and is a message that can be decrypted by the session key S1.

In FIG. 4, the messages transmitted and received between the GW radio 100 and the MT radio 200 have the encryption and decryption keys shown in parentheses. That is, in the example shown in FIG. 4, each message is encrypted by the session key S1 or session key S2 corresponding to the key shown in parentheses (S1 or S2), and is a decodable message.

The update key information receiving unit 211 of the MT radio 200 receives the "update key information" transmitted from the GW radio 100. Specifically, the update key information receiving unit 211 receives the "update key information" transmitted from the GW radio 100, and decrypts the "update key information" with the session key stored in the C area of the session key information 222 to obtain the planned update key. Furthermore, the update key information receiving unit 211 stores the decrypted planned update key in the N area of the session key information 222 of the storage unit 220. The process in which the update key information receiving unit 211 receives the "update key information" corresponds to step S402 in the example shown in FIG. 4.

Specifically, in step S402, the update key information receiving unit 211 of the MT radio 200 receives the "update key information" transmitted from the GW radio 100 and stores it in the session key information 222 of the memory unit 220. In the example shown in FIG. 4, the MT radio 200 decrypts the "update key information" including information related to the session key S2 with the session key S1 based on the information set in the header of the message of the "update key information", and stores it in the N area of the session key information 222. In the example shown in FIG. 4, the N area of the session key information 222 stores the session key S2, which is the key to be updated.

Then, the parent unit information transmission unit 112 transmits a message of "parent unit information" from the GW radio 100 to the MT radio 200. Specifically, the parent unit information transmission unit 112 transmits to the MT radio 200 the "parent unit information" regarding the GW radio 100 encrypted with the "scheduled update key" stored in the N area of the session key information 122. This process of the parent unit information transmission unit 112 transmitting the "parent unit information" corresponds to step S403.

Specifically, in step S403, the parent information transmission unit 112 of the GW radio 100 transmits "parent information" to the MT radio 200. In the example shown in FIG. 4, the "parent information" transmitted in step S403 is encrypted with the session key S2, which is the key to be updated. Furthermore, the "parent information" transmitted in step S403 is information related to the GW radio 100, which is the parent, and is, for example, information for identifying the GW radio 100.

In addition, in step S403, the parent information receiving unit 212 of the MT radio 200 receives the "parent information" transmitted from the GW radio 100. Specifically, the parent information receiving unit 212 receives the "parent information" transmitted from the GW radio 100 and decrypts it with the "scheduled update key" stored in the N region of the session key information 222. As shown in FIG. 5, the key for decrypting the "parent information" is the session key S2 of the planned update key stored in the N region. In the example shown in FIG. 4, at the timing when the parent information receiving unit 212 receives the "parent information" transmitted from the GW radio 100 in step S403, the session key S2 is stored in the N region of the session key information 222. Therefore, in step S403, the parent information receiving unit 212 of the MT radio 200 decrypts the "parent information" using the session key S2 in the N region, and acquires the "parent information" which is information related to the GW radio 100.

The determination unit 113 of the GW radio 100 determines whether or not it has received "child unit information" transmitted from the MT radio 200 in step S404 described below. Furthermore, the determination unit 213 of the MT radio 200 determines whether or not to transmit "child unit information" to the GW radio 100 based on the transmission status of the "update key information" and "parent unit information" transmitted from the GW radio 100 in steps S401 and S403. In this embodiment, the determination unit 213 of the MT radio 200 determines to transmit "child unit information" to the GW radio 100 when it has received "update key information" and "parent unit information" or when it has received "update key information" at least twice. Details of the processing of the determination unit 113 and the determination unit 213 will be described in processing examples 1 to 3 of the key information update system described below.

The handset information transmission unit 214 of the MT radio 200 transmits the "handset information" to the GW radio 100 based on the result of the determination by the determination unit 213. Specifically, when the determination unit 213 determines that the "handset information" is to be transmitted, the handset information transmission unit 214 transmits the "handset information" encrypted with the "scheduled update key" stored in the N area of the session key information 222 to the GW radio 100. The process in which the handset information transmission unit 214 transmits the "handset information" to the GW radio 100 corresponds to step S404 in the sequence diagram of FIG. 4.

Specifically, in step S404, the child unit information transmission unit 214 of the MT radio 200 encrypts and transmits the "child unit information" to the GW radio 100. In the example shown in FIG. 4, the "child unit information" transmitted in step S404 is encrypted with the session key S2, which is the key to be updated. Furthermore, the "child unit information" transmitted in step S404 is information related to the MT radio 200, which is a child unit, and is, for example, information for identifying the MT radio 200.

In addition, in step S404, the handset information receiving unit 114 of the GW radio 100 receives the "handset information" transmitted from the MT radio 200. The handset information receiving unit 114 of the GW radio 100 decrypts the "handset information" encrypted with the scheduled update key using session key S2, which is the scheduled update key for the N region of the session key information 122, and obtains the "handset information" that is information related to the MT radio 200.

The session key update unit 115 of the GW radio device 100 updates the session key in the C region of the session key information 122 to the session key in the N region. Specifically, when the determination unit 113 determines that "child device information" has been received, the session key update unit 115 updates the session key in the C region of the session key information 122 to the "scheduled update key" stored in the N region. This process of updating the key in the session key update unit 115 corresponds to step S405.

Specifically, in step S405, the session key update unit 115 of the GW radio 100 updates the session key. In the example shown in FIG. 4, the session key stored in the C area of the session key information 122 is updated from session key S1 to session key S2.

The session key update unit 215 of the MT radio 200 also updates the session key information 222. Specifically, when the child device information transmission unit 214 transmits "child device information" to the GW radio 100, the session key update unit 215 updates the session key in the C region of the session key information 222 to the key to be updated in the N region. This process of updating the key in the session key update unit 215 corresponds to step S406.

Specifically, in step S406, the session key update unit 215 of the MT radio device 200 updates the session key. In the example shown in FIG. 4, the session key stored in the C area of the session key information 222 is updated from session key S1 to session key S2. This process of updating the session key of the MT radio device 200 in step S406 is performed based on the process of transmitting the "child device information" in step S404.

In step S407, the GW radio 100 transmits a "meter reading data request" message to the MT radio 200. This "meter reading data request" message is encrypted with the session key S2. In step S407, the MT radio 200 receives the "meter reading data request" message. The header of this "meter reading data request" message contains information indicating that the message is to be decrypted with the key stored in the C area. Based on the header information, in step S406, the MT radio 200 decrypts the "meter reading data request" with the session key S2 stored in the C area. As described above, in step S406, the session key update unit 215 can decrypt the message regarding the "meter reading data request" without any problems because the key in the C area of the session key information 222 has been updated from the session key S1 to the session key S2. In the example shown in FIG. 4, the normal transmission and reception of messages between the GW radio 100 and the MT radio 200 after the "meter reading data request" will not be described.

Next, using Figures 6 to 8, the process when a failure occurs in any of the messages transmitted and received between the GW radio 100 and the MT radio 200. Note that in the examples of Figures 6 to 8 below, the same processes as those shown in the sequence diagram of Figure 4 will be explained with a simplified explanation or omitted. In this embodiment, a failure to deliver a message refers to a situation in which a message sent from the transmitting side of the radio cannot be received by the receiving side for some reason. Furthermore, the cause of failure to deliver can be due to various factors, such as a fixed failure in the radio or communication path, a temporary intermittent failure, or a single failure.

(Processing example 1 of the key information update system)
FIG. 6 shows an example of processing to be performed when a message of “update key information” transmitted from the GW radio 100 to the MT radio 200 fails to arrive.

Step S601 shows a case where the "update key information" message sent from the GW radio 100 to the MT radio 200 does not arrive, and the "update key information" cannot be received by the update key information receiving unit 211 of the MT radio 200. In this case, the information of the session key S2 is not stored in the N area of the session key information 222 in the MT radio 200.

In step S602, the GW radio 100 transmits "parent unit information" to the MT radio 200. Here, the parent unit information receiving unit 212 of the MT radio 200 cannot decrypt the "parent unit information" because session key S2 is not stored in the N area of the session key information 222. Therefore, the determination unit 213 of the MT radio 200 determines not to transmit "child unit information" to the GW radio 100 based on the transmission status of the "update key information" and "parent unit information" transmitted from the GW radio 100.

In step S603, the determination unit 113 of the GW radio 100 determines whether or not the "child unit information" transmitted from the MT radio 200 has been received. In the example shown in FIG. 6, as described above, the "update key information" has not arrived, and the determination unit 213 of the MT radio 200 determines that the "child unit information" should not be transmitted. Therefore, at the timing of step S603 in FIG. 6, the "child unit information" from the MT radio 200 is not transmitted, and the GW radio 100 does not receive the "child unit information". If the GW radio 100 does not receive the "child unit information" for a predetermined period in step S603, the update key information transmission unit 111 of the GW radio 100 retransmits the "update key information" to the MT radio 200 (step S604). In addition, the parent unit information transmission unit 112 retransmits the "parent unit information" (step S606).

Here, in the example shown in FIG. 6, if the "update key information" from the GW radio 100 to the MT radio 200 remains undelivered, loop L6 is executed in which the processes from step S603 to step S606 are repeated. This loop L6 is executed a predetermined number of times, for example, 10 times. Note that the number of times this loop is executed does not limit the configuration of this embodiment, and the number of times the loop may be less than 10 times or more than 10 times.

For example, if some kind of fixed failure occurs in the MT radio 200 and the "update key information" message remains undelivered, the processing of the sequence shown in FIG. 6 ends after a predetermined number of loops of loop L6 are executed. Then, the GW radio 100 performs the processing from step S601 on other MT radios 200 included in the meter reading network 10 that are to be subject to key updating.

On the other hand, if an "update key information" message is sent to the MT radio 200 in fewer than the specified 10 loops due to a single (intermittent) communication failure or the like, the processes from step S605 to step S609 are performed, and the session key is updated. Note that the processes from step S607 to step S610 are similar to the processes from step S404 to step S407 shown in FIG. 4, and therefore a description thereof will be omitted. Also, in the example shown in FIG. 6, a description of normal transmission and reception of messages between the GW radio 100 and the MT radio 200 after the "meter reading data request" will be omitted.

In this way, in the key information update system, even if the "update key information" message does not arrive, if the failure is a one-off (intermittent) occurrence, the "update key information" message will be sent again, and the key information will be updated without any problems.

(Processing Example 2 of Key Information Update System)
FIG. 7 shows an example of processing to be performed when a message of “master unit information” transmitted from the GW radio 100 to the MT radio 200 fails to arrive.

In step S701 shown in FIG. 7, unlike step S601 shown in FIG. 6, a message of "update key information" is transmitted from the GW radio 100 to the MT radio 200. Therefore, the update key information receiving unit 211 of the MT radio 200 receives the "update key information" from the GW radio 100 and stores the planned update key in the N area of the session key information 222.

The example shown in FIG. 7 shows a case where the "parent unit information" message in step S703 does not arrive. Because the "parent unit information" message in step S703 does not arrive, the determination unit 213 of the MT radio 200 determines not to send the "child unit information" based on the situation in which the "parent unit information" message does not arrive. Therefore, in response to the failure to arrive at step S703, the MT radio 200 does not send the "child unit information" message.

In step S704, the determination unit 113 of the GW radio 100 determines whether or not a "child unit information" message has been sent from the MT radio 200. In the example shown in FIG. 7, the "child unit information" is not sent from the MT radio 200 at the timing of step S704. Therefore, the update key information transmission unit 111 and the parent unit information transmission unit 112 of the GW radio 100 send the "update key information" and the "parent unit information" to the MT radio 200 (steps S705 and S706).

Here, in the example shown in FIG. 7, it is assumed that the "parent unit information" message in step S706 is not delivered again. The determination unit 213 of the MT radio 200 determines that the "child unit information" is to be transmitted to the GW radio 100, triggered by the reception of the second "update key information" after the first "update key information" has been received. That is, the determination unit 213 of the MT radio 200 determines that the "child unit information" is to be transmitted to the GW radio 100 when the "update key information" has been received at least twice. In step S702, since the session key S2 is stored in the N region of the session key information 222, there is no problem in communication with the GW radio 100 even if the key information in the C region is updated to the session key S2. That is, in the example shown in FIG. 7, even if the "parent unit information" from the GW radio 100 remains undelivered, the session key update process is performed without any problem.

The processing from step S708 to step S711 is similar to step S404 to step S407 in the sequence shown in FIG. 4, so a description thereof will be omitted. Also, in the example shown in FIG. 7, a description of normal transmission and reception of messages between the GW radio 100 and the MT radio 200 after the "meter reading data request" will be omitted.

In the example shown in FIG. 7, the "Parent Information" message of step S706 remains undelivered. Here, for example, even if the "Update Key Information" message of step S705 does not arrive and the "Parent Information" message of step S706 is sent, the session key is updated without any problems. That is, in the example shown in FIG. 7, the MT radio device 200 is in a state where the "Update Key Information" message of step S701 has been sent. Therefore, in the MT radio device 200, if the "Update Key Information" message of step S705 does not arrive and the "Parent Information" message of step S706 is sent, the reception of the "Parent Information" of step S706 causes the same processing as in the normal protocol to be performed.

In this way, in the key information update system of this embodiment, even if the "parent device information" message fails to be delivered, it is possible to update the session key information regardless of whether the failure to deliver the "parent device information" message is permanent or one-off (intermittent).

(Processing Example 3 of Key Information Update System)
FIG. 8 shows an example of processing to be performed when a message of “child unit information” transmitted from the MT radio device 200 to the GW radio device 100 fails to arrive.

The processing from step S801 to step S803 is similar to the processing from step S401 to step S403 shown in FIG. 4, so a description thereof will be omitted here.

The example shown in FIG. 8 shows a case where the "child unit information" message from the MT radio 200 does not arrive in step S804.

In step S805, the determination unit 113 of the GW radio 100 determines whether or not "child unit information" transmitted from the MT radio 200 has been received. At the timing of step S805 in FIG. 8, "child unit information" is not transmitted from the MT radio 200. If the GW radio 100 does not receive "child unit information" for a predetermined period in step S805, the update key information transmission unit 111 of the GW radio 100 resends "update key information" to the MT radio 200 (step S806). In addition, the parent unit information transmission unit 112 resends "parent unit information" (step S807).

Here, in the example shown in FIG. 8, if the "child unit information" from the MT radio 200 to the GW radio 100 remains undelivered, loop L8 is performed in which the processes from step S804 to step S807 are repeated. This loop L8 is performed a predetermined number of times, for example, 10 times. Note that the number of times this loop is performed does not limit the configuration of this embodiment, and the number of times the loop may be less than 10 times or more than 10 times.

For example, if some kind of fixed failure occurs in the MT radio 200 and the "child unit information" message remains undelivered, the processing of the sequence shown in FIG. 8 ends after a predetermined number of loops of loop L8 are executed. Then, the GW radio 100 performs the processing from step S801 on other MT radios 200 included in the meter reading network 10 that are to be subject to key updating.

On the other hand, if a "child unit information" message is sent to the GW radio 100 in fewer than the specified 10 loops due to a single (intermittent) communication failure or the like, the processes from step S808 to step S810 are carried out and the session key is updated. Note that the processes from step S808 to step S811 are similar to the processes from step S404 to step S407 shown in FIG. 4, and therefore a description thereof will be omitted. Also, in the example shown in FIG. 8, a description of normal transmission and reception of messages between the GW radio 100 and the MT radio 200 after the "meter reading data request" will be omitted.

In this way, in the key information update system of this embodiment, even if the "child unit information" message does not arrive, if the failure is a one-off (intermittent) occurrence, the "child unit information" message will be sent again, and the key information will be updated without any problems.

As described above, the key information update system in this embodiment is a key information update system that updates a session key used to encrypt and decrypt messages transmitted and received between a wireless master and a wireless slave. The wireless master of the key information update system includes an update key information transmission unit 111 and a master information transmission unit 112. The wireless slave includes an update key information reception unit 211, a master information reception unit 212, and a slave determination unit. The update key information transmission unit 111 transmits update key information obtained by encrypting a planned update key stored in the master storage unit with a session key stored in the master storage unit of the wireless master to the wireless slave. The master information transmission unit 112 transmits master information related to the wireless master encrypted with the planned update key to the wireless slave. The slave determination unit determines whether to transmit slave information related to the wireless slave to the wireless master based on the update key information and master information transmitted from the wireless master.

As a result, even if the message regarding the key update is not delivered, there is no need to provide a separate communication method for key update, and a key information update system that can perform key updates with a simple configuration can be realized. The wireless master device corresponds to the GW wireless device 100. The wireless slave device corresponds to the MT wireless device 200. The slave device determination unit corresponds to the determination unit 213.

The child unit determination unit of the key information update system may determine to transmit the child unit information to the wireless parent unit when it has received update key information and parent unit information, or when it has received update key information at least twice. This makes it possible for the key information update system to update the session key information even if the message for "parent unit information" fails to arrive, regardless of whether the failure to deliver the message for "parent unit information" is permanent or one-off (intermittent).

The update key information transmission unit 111 of the key information update system may transmit the update key information to the wireless slave again if the master determination unit determines that the slave information has not been received. As a result, in the key information update system, even if the "slave information" message is not delivered, if the failure is a one-off (intermittent) occurrence, the "slave information" message is sent again, and the key information can be updated without any problems.

Other Embodiments
Although the embodiments have been described in detail with reference to the drawings, the present embodiments are not limited to the contents described in the above embodiments. The components described above include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described above can be appropriately combined. Various omissions, substitutions, or modifications of the configurations can be made without departing from the spirit of the embodiments.

As an example of the configuration of the key information update system according to this embodiment, an example in which messages are transmitted and received between one GW radio 100 and multiple MT radios 200 is shown in FIG. 1, but this configuration does not limit the embodiment. For example, a slave meter 20b may be connected to another slave meter 20b via an MT radio 200. That is, the key information update system may be configured as a multi-hop system in which the MT radio 200 can relay messages (messages) transmitted and received between the GW radio 100 of the master meter 20a and the MT radio 200 of another slave meter 20b. By realizing the key information update system in a multi-hop configuration, it is possible to efficiently expand the communication area of the meter reading network 10 and eliminate blind areas caused by obstructions, etc.

The scope of this embodiment also includes a computer program (key information update program) that causes a computer to execute the processing (key information update method) in the key information update system described above, and a computer-readable recording medium on which the program is recorded that is readable by the computer. Any type of computer-readable recording medium may be used. The computer program is not limited to being recorded on the recording medium, and may be transmitted via a telecommunications line, a wireless or wired communication line, a network such as the Internet, or the like.

The following describes the key information update system, the key information update method, and the features of the key information update program.

The key information update system according to the first aspect is a key information update system that updates a session key used to encrypt and decrypt messages transmitted between a wireless master and a wireless slave. The wireless master includes an update key information transmission unit 111 that transmits update key information obtained by encrypting a planned update key stored in the master storage unit with a session key stored in the master storage unit of the wireless master to the wireless slave. The wireless master also includes a master information transmission unit 112 that transmits master information regarding the wireless master encrypted with the planned update key to the wireless slave. The wireless master also includes a master determination unit that determines whether or not slave information regarding the wireless slave transmitted from the wireless slave has been received. The wireless master also includes a master key update unit that updates the session key to the planned update key when it is determined in the master determination unit that the slave information has been received. The wireless slave includes an update key information reception unit 211 that receives update key information transmitted from the wireless master, decrypts the update key information with the session key stored in the slave storage unit of the wireless slave to obtain the planned update key, and stores the key in the slave storage unit. The wireless slave device also includes a master device information receiving unit 212 that receives master device information transmitted from the wireless master device and decrypts it with the planned update key. The wireless slave device also includes a slave device determination unit that determines whether or not to transmit slave device information to the wireless master device based on the update key information and the master device information. The wireless slave device also includes a slave device information transmitting unit 214 that transmits slave device information encrypted with the planned update key to the wireless master device when the slave device determination unit determines that the slave device information is to be transmitted. The wireless slave device also includes a slave device key updating unit that updates the session key to the planned update key when the slave device information transmitting unit 214 transmits the slave device information to the wireless master device.

With the above configuration, the key information update system does not need to provide a separate communication method for key updates even if the message regarding key updates is not delivered, and can perform key updates with a simple configuration.

The child device determination unit of the key information update system according to the second aspect may determine to transmit the child device information to the wireless parent device when it receives update key information and parent device information, or when it receives update key information at least twice.

With the above configuration, the key information update system can update the session key information even if the "parent device information" message is not delivered, regardless of whether the failure to deliver the "parent device information" message is permanent or one-off (intermittent).

The update key information transmission unit 111 of the key information update system according to the third aspect may transmit the update key information to the wireless slave device again if the master device determination unit determines that the slave device information has not been received.

According to the above configuration, even if the "child device information" message does not arrive, if the failure is a one-off (intermittent) occurrence, the key information update system will resend the "child device information" message, and the key information will be updated without any problems.

The wireless slave device of the key information update system according to the fourth aspect may be capable of relaying messages transmitted and received between the wireless master device and other wireless slave devices.

With the above configuration, the key information update system can efficiently expand the communication area of the meter reading network 10 and eliminate blind areas caused by obstructions, etc.

The key information update method according to the fifth aspect is a key information update method executed by a computer, which updates a session key used for encryption and decryption of a message transmitted and received between a wireless master and a wireless slave. The key information update method transmits update key information obtained by encrypting a planned update key stored in a master storage unit with a session key stored in a master storage unit of the wireless master to the wireless slave. The key information update method also receives update key information transmitted from the wireless master, decrypts the update key information with a session key stored in a slave storage unit of the wireless slave to obtain a planned update key, and stores the key in the slave storage unit. The key information update method also transmits master information related to the wireless master encrypted with the planned update key to the wireless slave. The key information update method also receives master information transmitted from the wireless master and decrypts it with the planned update key. The key information update method also determines whether to transmit slave information related to the wireless slave to the wireless master based on the update key information and master information. If it is determined that the slave information is to be transmitted, the key information update method also transmits the slave information encrypted with the planned update key to the wireless master. The key information update method also determines whether or not child device information transmitted from the wireless child device has been received. If the key information update method determines that the child device information has been received, it updates the session key of the wireless master device to the key to be updated. If the key information update method transmits child device information to the wireless master device, it updates the session key of the wireless child device to the key to be updated.

According to the above configuration, the key information update method makes it possible to perform key updates with a simple configuration without the need to provide a separate communication method for key updates even if the message regarding key updates is not delivered.

The key information update program according to the sixth aspect is a key information update program for causing a computer to execute an update of a session key used for encryption and decryption of a message transmitted and received between a wireless master and a wireless slave. The key information update program includes a step of transmitting update key information obtained by encrypting a planned update key stored in a master storage unit with a session key stored in a master storage unit of the wireless master to the wireless slave. The key information update program also includes a step of receiving update key information transmitted from the wireless master, decrypting the update key information with a session key stored in a slave storage unit of the wireless slave to obtain a planned update key, and storing the key in the slave storage unit. The key information update program also includes a step of transmitting master information related to the wireless master encrypted with the planned update key to the wireless slave. The key information update program also includes a step of receiving master information transmitted from the wireless master and decrypting the information with the planned update key. The key information update program also includes a step of determining whether or not to transmit slave information related to the wireless slave to the wireless master based on the update key information and master information. The key information update program also includes a step of transmitting, to the wireless master unit, the slave unit information encrypted with the update-to-be-updated key when it is determined that the slave unit information is to be transmitted. The key information update program also includes a step of determining whether or not the slave unit information transmitted from the wireless slave unit has been received. The key information update program also includes a step of updating the session key of the wireless master unit to the update-to-be-updated key when it is determined that the slave unit information has been received. The key information update program also includes a step of updating the session key of the wireless slave unit to the update-to-be-updated key when the slave unit information has been transmitted to the wireless master unit.

With the above configuration, the key information update program makes it possible to perform key updates with a simple configuration without the need to set up a separate communication method for key updates even if the message regarding key updates is not delivered.

REFERENCE SIGNS LIST 1 wireless communication system 10 meter reading network 20 meter 30 management device 40 network 100 GW wireless device 110, 210 control unit 200 MT wireless device 111 updated key information transmission unit 112 master information transmission unit 113, 213 determination unit 114 slave information reception unit 115, 215 session key update unit 120, 220 storage unit 211 updated key information reception unit 212 master information reception unit 214 slave information transmission unit

Claims (4)

A key information update system that updates a session key used for encryption and decryption of a message transmitted and received between a wireless master device and a wireless slave device, comprising:
The wireless base station includes:
an update key information transmission unit that transmits, to the wireless slave device, update key information obtained by encrypting an update-scheduled key stored in the master device storage unit with the session key stored in the master device storage unit of the wireless master device;
a master information transmitting unit configured to transmit master information regarding the wireless master unit encrypted with the update key to the wireless slave unit;
a master determination unit that determines whether or not slave device information regarding the wireless slave device transmitted from the wireless slave device has been received;
a master key update unit that updates the session key to the update-scheduled key when it is determined that the master determination unit has received the slave information,
The wireless slave device includes:
an update key information receiving unit that receives the update key information transmitted from the wireless master device, decrypts the update key information with the session key stored in a slave device storage unit of the wireless slave device to obtain the update-planned key, and stores the update key in the slave device storage unit;
a master information receiving unit that receives the master information transmitted from the wireless master device and decrypts the master information with the update key;
a child device determination unit that determines whether or not to transmit the child device information to the wireless parent device based on the update key information and the parent device information;
a child device information transmitting unit configured to transmit, when the child device determination unit determines that the child device information is to be transmitted, the child device information encrypted with the update key to the wireless master device;
a child device key updating unit that updates the session key to the update-scheduled key when the child device information transmitting unit transmits the child device information to the wireless master device,
Key information update system. the child device determination unit determines that the child device information is to be transmitted to the wireless parent device when the child device determination unit has received the update key information and the parent device information, or when the child device determination unit has received the update key information at least twice.
The key information updating system according to claim 1 . the update key information transmission unit transmits the update key information to the wireless slave device again when the master device determination unit determines that the slave device information has not been received.
3. The key information updating system according to claim 1 or 2. The key information update system according to any one of claims 1 to 3, wherein the wireless slave device is capable of relaying messages transmitted and received between the wireless master device and other wireless slave devices.

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