WO2024069879A1

WO2024069879A1 - Security of communications relayed by terminal device

Info

Publication number: WO2024069879A1
Application number: PCT/JP2022/036515
Authority: WO
Inventors: 仁中里; 紗季田中; 遥堀内; 啓佑高見
Original assignee: 楽天モバイル株式会社
Priority date: 2022-09-29
Filing date: 2022-09-29
Publication date: 2024-04-04

Abstract

The present invention provides a key management device including a memory and one or more processors connected to the memory. The one or more processors execute processing of obtaining, from a first terminal device, a relay request which requests relay by another terminal device, identifying a terminal device which is positioned in a vicinity of the first terminal device and is a candidate of a relay station, generating a primary key for encryption on the basis of a public key of the terminal device which is the candidate of the relay station, transmitting the primary key to the first terminal device, acquiring, from the first terminal device, a secondary key for decryption corresponding to the primary key, and storing the primary key and the secondary key in association with each other in the memory.

Description

Security of communications relayed by terminal equipment

This disclosure relates to the security of communications relayed by terminal devices.

Generally, in a mobile network, a terminal device owned by a user, such as a mobile phone or smartphone, can communicate data volumes according to the contract with the telecommunications carrier. Each user is assigned a data communication capacity per month, for example, that allows high-speed data communication, and the terminal device owned by the user performs high-speed data communication within the range of this data communication capacity (for example, Patent Document 1).

Because communication usage patterns vary from user to user, the data communication capacity specified in the contract does not necessarily match the amount of data actually used for communication. For example, some users' terminal devices may communicate data volumes that exceed the data communication capacity specified in the contract, while other users' terminal devices may only communicate data volumes that do not meet the data communication capacity specified in the contract.

JP 2020-174235 A

However, the above-mentioned mobile network has a problem in that the data communication capacity under the user's contract is not used efficiently and sufficiently. In other words, since not all terminal devices communicate in accordance with the terms of their contract, available data communication capacity may remain unused. This results in waste of communication facilities and wireless resources that are reserved on the assumption that all data communication capacity will be consumed. In addition, some terminal devices consume all of their available data communication capacity and end up with a data communication capacity shortage, resulting in uneven usage of data communication capacity.

The present disclosure has been made in consideration of the above, and aims to provide security for communications relayed by terminal devices that can efficiently utilize data communication capacity and level out usage conditions.

According to one aspect of the present disclosure, a key management device has a memory and one or more processors connected to the memory. The one or more processors execute a process of acquiring a relay request from a first terminal device, which requests relaying by another terminal device. The one or more processors also execute a process of identifying a terminal device that is a candidate for a relay station and is located in the vicinity of the first terminal device. The one or more processors also execute a process of generating a primary key for encryption based on a public key of the terminal device that is a candidate for a relay station. The one or more processors also execute a process of transmitting the primary key to the first terminal device. The one or more processors also execute a process of acquiring a secondary key for decryption corresponding to the primary key from the first terminal device. The one or more processors also execute a process of storing the primary key and the secondary key in association with each other in the memory.

According to one aspect of the present disclosure, the key management method includes obtaining, from a first terminal device, a relay request requesting relay by another terminal device. The key management method also includes identifying a terminal device that is a candidate relay station and is located in the vicinity of the first terminal device. The key management method also includes generating a primary key for encryption based on a public key of the terminal device that is a candidate relay station. The key management method also includes transmitting the primary key to the first terminal device. The key management method also includes obtaining, from the first terminal device, a secondary key for decryption that corresponds to the primary key. The key management method also includes storing the primary key and the secondary key in a memory in association with each other.

FIG. 1 is a diagram illustrating an example of a configuration of a wireless communication system according to an embodiment. FIG. 2 is a block diagram showing a configuration of a key management device according to an embodiment. FIG. 3 is a block diagram showing a configuration of a terminal device according to an embodiment. FIG. 4 is a sequence diagram showing a communication method according to an embodiment. FIG. 5 is a diagram showing a specific example of primary key generation. FIG. 6 is a block diagram illustrating an example of a hardware configuration of a key management device. FIG. 7 is a block diagram illustrating an example of a hardware configuration of a terminal device.

Below, an embodiment of the present disclosure will be described with reference to the attached drawings. The embodiment described below is an example, and should not be construed as being limited by this description.

Typically, a terminal device, also known as UE (User Equipment), communicates data within the range of data communication capacity according to its contract with a telecommunications carrier. However, the amount of data communication by a terminal device is not always constant, so there may be cases where the data communication capacity according to the contract is insufficient or where there is surplus data communication capacity according to the contract. Therefore, a terminal device that does not have enough data communication capacity according to the contract may communicate by using the surplus data communication capacity according to the contract of another terminal device. In other words, a terminal device that has insufficient data communication capacity uses, for example, a terminal device with surplus data communication capacity as a relay station, and communicates by using the data communication capacity of the terminal device that is the relay station.

In such cases, data sent from the source terminal device is transmitted via a terminal device that acts as a relay station, and so there is a risk of unauthorized viewing or theft of the data by the terminal device that acts as a relay station. In other words, there is a problem in that the security of communications relayed by other terminal devices cannot be ensured. Therefore, in this disclosure, a communication system and a communication method that can ensure the security of communications relayed by terminal devices are described.

FIG. 1 is a diagram showing an example of the configuration of a wireless communication system according to one embodiment. The wireless communication system shown in FIG. 1 includes a base station device 10, a key management device 100, a terminal device 200, and a communication server 300.

The base station device 10 is a wireless base station located in a RAN (Radio Access Network) and performs wireless communication with terminal devices 200 within the cell formed by the base station device 10. The base station device 10 may have an RU (Radio Unit) having an antenna, and a DU (Distributed Unit) and CU (Centralized Unit) that control the RU. The DU may be a virtual DU (vDU) constructed on a virtualization platform, and the CU may be a virtual CU (vCU) constructed on a virtualization platform.

The key management device 100 can communicate with the terminal devices 200 via the RAN, collects location information for each terminal device 200, and selects a terminal device 200 to serve as a relay station based on the location information when the terminal device 200 performs data communication via another terminal device 200. In addition, when the terminal device 200 performs data communication via another terminal device 200, the key management device 100 registers a key pair of encryption keys used by the terminal device 200 for data communication. The configuration and operation of the key management device 100 will be described in detail later.

The terminal device 200 is a terminal device owned by a user, and performs wireless communication with the base station device 10. By entering into a contract with a communications carrier, the user is allocated a data communication capacity that is the capacity for data communication using the terminal device 200, and the terminal device 200 performs high-speed data communication within the range of this data communication capacity. Each terminal device 200 has its own unique key pair of public key and private key to encrypt and decrypt data during data communication. When the terminal device 200 receives data encrypted with its own public key, it can obtain the decrypted data by decrypting the received data with its own private key.

In addition, when the terminal device 200 has insufficient data communication capacity under the contract, it wirelessly connects to another terminal device 200 that will be a relay station and executes data communication using the data communication capacity of the terminal device 200 that will be a relay station. At this time, the terminal device 200 acquires a primary key based on the public key of the terminal device 200 that is a candidate for the relay station from the key management device 100, generates a key pair by generating a secondary key corresponding to the primary key, and registers the generated key pair in the key management device 100. Then, the terminal device 200 transmits the primary key for data encryption to the communication server 300 that will be the communication partner, and when the other terminal device 200 is used as a relay station, the communication server 300 encrypts the data with the primary key. In other words, when data is relayed by the other terminal device 200, the terminal device 200 encrypts the data using the primary key of the key pair, which is more robust, rather than the public key of the terminal device itself. The configuration and operation of the terminal device 200 will be described in detail later.

The communication server 300 can communicate with the terminal devices 200 via the RAN, and transmits and receives data between the terminal devices 200. When the communication server 300 receives a primary key from a terminal device 200, it encrypts the data to be sent to the terminal device 200 using the primary key before transmitting it.

FIG. 2 is a block diagram showing the configuration of a key management device 100 according to one embodiment. The key management device 100 shown in FIG. 2 has a communication interface unit (hereinafter abbreviated as "communication I/F unit") 110, a location information collection unit 120, a location information storage unit 130, a public key acquisition unit 140, a primary key generation unit 150, a key pair registration unit 160, and a key pair storage unit 170.

The communication I/F unit 110 communicates with the terminal device 200 via the RAN. Specifically, the communication I/F unit 110 receives location information and a public key from the terminal device 200, and transmits a primary key generated based on the public key to the terminal device 200.

The location information collection unit 120 periodically collects location information of the terminal devices 200. In other words, the location information collection unit 120 acquires location information that is periodically reported by each of the multiple terminal devices 200 and received by the communication I/F unit 110.

The location information storage unit 130 stores the location information collected by the location information collection unit 120. The location information storage unit 130 stores the location information in association with the identification information of each terminal device 200.

When the public key acquisition unit 140 receives a relay request from a terminal device 200 requesting that communication by another terminal device 200 be relayed, the public key acquisition unit 140 identifies a terminal device 200 located near the terminal device 200 that sent the relay request, based on the location information stored in the location information storage unit 130. The public key acquisition unit 140 then instructs the identified nearby terminal device 200 to send a public key, and acquires the public key received by the communication I/F unit 110 in response to the instruction. In other words, the public key acquisition unit 140 acquires the public key of a terminal device 200 located near the terminal device 200 that sent the relay request. The terminal device 200 from which the public key is acquired becomes a candidate for a relay station that relays communication by the terminal device 200 that sent the relay request.

The primary key generation unit 150 generates a primary key based on the public key acquired by the public key acquisition unit 140. Specifically, when public keys are acquired from multiple terminal devices 200 that are candidates for relay stations, the primary key generation unit 150 may generate a primary key by adding these public keys. The primary key generation unit 150 may also process each public key using location information of the terminal device that holds the public key, and add the processed public keys to generate a primary key. Furthermore, when there is one terminal device 200 that is a candidate for a relay station, the primary key generation unit 150 may generate a primary key by adding the public key of the candidate terminal device 200 and a predetermined dummy public key.

The primary key generation unit 150 transmits the generated primary key from the communication I/F unit 110 to the terminal device 200 that has sent the relay request. At this time, the primary key generation unit 150 transmits identification information of the terminal device 200 that is a candidate for the relay station together with the primary key. This allows the terminal device 200 that has sent the relay request to identify the terminal device 200 that is a candidate for the relay station.

The key pair registration unit 160 obtains the secondary key sent from the terminal device 200, which is the destination of the primary key, and received by the communication I/F unit 110, and creates a key pair by combining the primary key and the secondary key. The key pair registration unit 160 then registers the created key pair in the key pair storage unit 170.

The key pair storage unit 170 stores the key pair created by the key pair registration unit 160. Specifically, the key pair storage unit 170 stores the primary key and secondary key used when the terminal device 200 executes communication via the relay station terminal device 200, in association with the identification information of the terminal device 200 that has sent the relay request. By storing the key pair in the key pair storage unit 170, it becomes possible to provide the terminal device 200 with the primary key or secondary key before the update, for example, when updating the key pair.

FIG. 3 is a block diagram showing the configuration of a terminal device 200 according to one embodiment. FIG. 3 shows the configuration of a terminal device 200 that is relayed by one of

terminal devices

200a and 200b that are candidates for a relay station. The terminal device 200 shown in FIG. 3 has a wireless communication unit 210, a location information reporting unit 220, a relay request unit 230, a secondary key generating unit 240, and a communication control unit 250.

The wireless communication unit 210 performs wireless communication with the base station device 10 or the

terminal devices

200a, 200b that are to serve as relay stations. That is, when there is sufficient data communication capacity remaining under the contract of the terminal device 200, the wireless communication unit 210 performs wireless communication with the base station device 10 using the remaining data communication capacity. On the other hand, when there is insufficient data communication capacity under the contract of the terminal device 200, the wireless communication unit 210 wirelessly connects to one of the

terminal devices

200a, 200b as a relay station, and performs wireless communication using the data communication capacity of the

terminal device

200a, 200b that is to serve as a relay station.

The location information reporting unit 220 periodically acquires location information of the terminal device 200 and transmits it from the wireless communication unit 210 to the key management device 100. The location information reported by the location information reporting unit 220 is usually transmitted from the wireless communication unit 210 to the base station device 10 and then transferred to the key management device 100 via the RAN.

The relay request unit 230, following instructions from the communication control unit 250, transmits a relay request from the wireless communication unit 210 to the key management device 100, requesting relay by another terminal device 200. Specifically, for example, when the remaining data communication capacity under the contract of the terminal device 200 falls below a predetermined threshold, the relay request unit 230 transmits a relay request to the key management device 100, requesting relay by a nearby terminal device 200.

When the wireless communication unit 210 receives the identification information and primary key of the terminal device 200 (

terminal devices

200a and 200b in this case) that is a candidate for a relay station, the secondary key generation unit 240 generates a secondary key that forms a key pair with the primary key. That is, the secondary key generation unit 240 uses the received primary key and the private key of the terminal device 200 to generate a secondary key that can decrypt data encrypted by the primary key. The secondary key generation unit 240 then transmits the generated secondary key from the wireless communication unit 210 to the key management device 100 via the base station device 10. The secondary key generation unit 240 also notifies the communication control unit 250 of the identification information, primary key, and secondary key of the

terminal devices

200a and 200b that are candidates for a relay station.

The communication control unit 250 controls the communication between the terminal device 200 and the communication server 300. Specifically, when the remaining data communication capacity of the terminal device 200 decreases due to communication with the communication server 300 via the base station device 10, the communication control unit 250 instructs the relay request unit 230 to request relay by another terminal device 200. Then, when the secondary key generation unit 240 notifies the communication control unit 250 of the identification information, primary key, and secondary key of the

terminal devices

200a and 200b that are candidates for the relay station, the communication control unit 250 selects the terminal device that will be the relay station. That is, the communication control unit 250 selects one of the

terminal devices

200a and 200b that are candidates for the relay station as the relay station. Then, the communication control unit 250 transmits the primary key to the communication server 300 via the terminal device that is the relay station and the base station device 10. As a result, when data addressed to the terminal device 200 is relayed by the terminal device that is the relay station, the communication server 300 uses the primary key to encrypt the data.

When data encrypted with the primary key is received from the communication server 300, the communication control unit 250 decrypts the received data using the secondary key. In this way, when communication between the terminal device 200 and the communication server 300 is relayed by a terminal device that serves as a relay station, the data is encrypted with a primary key based on the public key of the terminal device 200 that is a candidate for the relay station. As a result, the data is encrypted with an encryption key that is more robust than the public key of the terminal device 200, ensuring the security of the communication relayed by the terminal device.

Next, a communication method in the wireless communication system configured as described above will be described with reference to the sequence diagram shown in FIG. 4. In the following description, it is assumed that

terminal devices

200a and 200b are located near terminal device 200, and that

terminal devices

200a and 200b are candidates for a relay station.

Terminal devices

200, 200a, 200b each periodically report their own location information to key management device 100 (step S101). The location information is transmitted from each of

terminal devices

200, 200a, 200b to key management device 100 via base station device 10. By collecting the location information by key management device 100, it is possible to easily identify

terminal devices

200a, 200b located near terminal device 200, for example, and select

terminal devices

200a, 200b as candidates for relay stations for communications of terminal device 200.

When the remaining data communication capacity under the contract decreases, the terminal device 200 transmits a relay request to the key management device 100 requesting relay by the other terminal device 200 in order to utilize the data communication capacity of the other terminal device 200 (step S102). When the relay request is received by the key management device 100, the key management device 100 selects a terminal device 200 located near the terminal device 200 as a candidate for the relay station based on the location information (step S103). In other words, the key management device 100 selects a terminal device 200 located within a predetermined range from the location of the terminal device 200 that sent the relay request as a candidate for the relay station. Here, the explanation will continue assuming that the

terminal devices

200a and 200b are selected as candidates for the relay station.

The key management device 100 instructs the

terminal devices

200a and 200b, which are candidates for relay stations, to transmit their public keys, and receives the public keys of the

terminal devices

200a and 200b (step S104). The key management device 100 then generates a primary key based on the received public keys (step S105).

Specifically, the primary key generation unit 150 of the key management device 100 may generate a public key (A+B) by adding the public key (A) of the terminal device 200a and the public key (B) of the terminal device 200b, as shown in FIG. 5(a), for example, and use this public key (A+B) as the primary key. Also, the primary key generation unit 150 processes the public key (A) of the terminal device 200a and the public key (B) of the terminal device 200b using the location information (A) of the terminal device 200a and the location information (B) of the terminal device 200b, respectively, as shown in FIG. 5(b), for example. The primary key generation unit 150 may then generate a public key (A'+B') by adding the processed public keys (A') and (B'), and use this public key (A'+B') as the primary key.

The key management device 100 transmits the generated primary key to the terminal device 200 (step S106). At this time, the key management device 100 transmits the primary key together with the identification information of the

terminal devices

200a and 200b that are candidates for the relay station. When the primary key is received by the terminal device 200, the terminal device 200 generates a secondary key that forms a key pair with the primary key using its own device's private key and the primary key (step S107). The secondary key generated here is used when decrypting data encrypted with the primary key. The primary key and secondary key that form the key pair are generated using the public key of the

terminal devices

200a and 200b that are candidates for the relay station and the private key of the terminal device 200. Therefore, the primary key and secondary key used to encrypt and decrypt data are changed according to the situation, and encryption and decryption with higher robustness is possible compared to the case where the public key and private key of the terminal device 200 that are always fixed are used.

The terminal device 200 transmits the generated secondary key to the key management device 100 via the base station device 10 (step S108). The key management device 100 receives the secondary key and creates a key pair from the primary key transmitted to the terminal device 200 and the received secondary key, and registers the key pair in the key pair storage unit 170 (step S109). That is, the key management device 100 registers the key pair of the primary key and secondary key to be used when the terminal device 200 communicates via a terminal device that serves as a relay station, in association with the identification information of the terminal device 200.

Then, the terminal device 200 selects one of the

terminal devices

200a and 200b, which are candidates for the relay station, as the relay station, and starts communication with the communication server 300, the communication partner, via the terminal device that will be the relay station. For example, if the terminal device 200a is selected as the relay station, the terminal device 200 transmits the primary key to the communication server 300 via the terminal device 200a (step S110). The primary key is transmitted to the communication server 300 by using the data communication capacity of the terminal device 200a, which is the relay station.

When the communication server 300 receives the primary key, it encrypts the data addressed to the terminal device 200 using the primary key. The communication server 300 then transmits the encrypted data to the terminal device 200 via the terminal device 200a (step S111). This data is transmitted to the terminal device 200 using the data communication capacity of the terminal device 200a, which is the relay station.

As described above, according to this embodiment, when a terminal device requests relaying by another terminal device, the key management device acquires a public key from the terminal device that is a candidate for relay station, generates a primary key based on the public key, and transmits it to the terminal device. The terminal device also generates a secondary key that forms a key pair with the received primary key and transmits it to the key management device. Then, when the terminal device communicates with the communication server via the terminal device of the relay station, it encrypts data using the primary key and decrypts the data using the secondary key. Therefore, when the terminal device and the communication server communicate via the terminal device of the relay station, data is encrypted using a highly robust encryption key, and the security of the communication relayed by the terminal device can be ensured.

In the above embodiment, the key management device 100 acquires public keys from the

terminal devices

200a and 200b that are candidates for the relay station and generates a primary key, but the present disclosure is not limited to this. For example, the key management device 100 may collect public keys of all the terminal devices 200 in advance, select the

terminal devices

200a and 200b that are candidates for the relay station based on the location information, and then transmit the public keys of the

terminal devices

200a and 200b from the collected public keys to the terminal device 200.

In addition, when the key management device 100 selects the

terminal devices

200a, 200b that are candidates for relay stations based on the location information, it may instruct these

terminal devices

200a, 200b to transmit public keys to the terminal device 200 that is the sender of the relay request. Then, when the public key transmitted in response to the instruction is received by the terminal device 200, the terminal device 200 may generate a primary key and a secondary key using the public keys of the

terminal devices

200a, 200b.

The key management device 100 according to the embodiment can be configured using a processor and a memory. FIG. 6 is a block diagram showing an example of a hardware configuration of the key management device 100 according to the embodiment. As shown in FIG. 6, the key management device 100 has a processor 101, a memory 102, an input/output unit 103, and a communication unit 104.

The processor 101 has, for example, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array) or a DSP (Digital Signal Processor), and controls the entire key management device 100 and performs various types of information processing.

Memory 102 includes, for example, a RAM (Random Access Memory) or a ROM (Read Only Memory), and stores information used in the information processing performed by processor 101.

The input/output unit 103 is an interface through which the user inputs information and through which information is output to the user. The input/output unit 103 may include, for example, a keyboard, a display, a touch panel, a microphone, or a speaker.

The communication unit 104 communicates with the base station device 10. The communication unit 104 may also communicate with other devices located in the core network or an external network.

The key management device 100 may also have other components not shown, such as storage and operation switches.

The terminal device 200 according to the embodiment can be configured using a processor and a memory. FIG. 7 is a block diagram showing an example of the hardware configuration of the terminal device 200 according to the embodiment. As shown in FIG. 7, the terminal device 200 has a processor 201, a memory 202, an input/output unit 203, and a wireless communication unit 204. Both the

terminal devices

200a and 200b may have the same hardware configuration as the terminal device 200 shown in FIG. 7.

The processor 201 has, for example, a CPU, FPGA, or DSP, and controls the entire terminal device 200 and executes various types of information processing.

The memory 202 includes, for example, a RAM or a ROM, and stores information used in the information processing performed by the processor 201.

The input/output unit 203 is an interface through which the user inputs information and through which information is output to the user. The input/output unit 203 may include, for example, a keyboard, a display, a touch panel, a microphone, or a speaker.

The wireless communication unit 204 wirelessly communicates with other terminal devices 200 or base station device 10 via an antenna.

The terminal device 200 may also have other components not shown, such as storage and operation switches.

The processes performed by the key management device 100 and the terminal device 200 described in the above embodiment can also be written as programs executable by a computer. In this case, the programs can be stored on a computer-readable, non-transitory recording medium and installed on the computer. Examples of such recording media include portable recording media such as CD-ROMs, DVD disks, and USB memory, as well as semiconductor memories such as flash memories.

Note that this disclosure is not limited to the above embodiment, but also includes various modifications in which components are added, deleted, or converted from the above configuration.

The present disclosure described above includes the following [1] to [8].

[1] A memory;
one or more processors coupled to the memory;
The one or more processors:
acquiring, from a first terminal device, a relay request for requesting relay by another terminal device;
Identifying terminal devices that are candidate relay stations located in the vicinity of the first terminal device;
generating a primary key for encryption based on a public key of the terminal device of the relay station candidate;
Transmitting the primary key to the first terminal device;
obtaining a secondary key for decryption corresponding to the primary key from the first terminal device;
a key management device that executes a process of storing the primary key and the secondary key in association with each other in the memory;

[2] The process of generating the primary key includes:
The key management device according to claim 1, wherein the primary key is generated by adding together public keys of a plurality of terminal devices that are candidate relay stations.

[3] The process of generating the primary key includes:
The key management device according to claim 1, wherein the primary key is generated by adding a public key of the terminal device that is a relay station candidate and a predetermined dummy public key.

[4] The process of generating the primary key includes:
The key management device according to claim 1, further comprising: a relay station candidate terminal device that generates the primary key by processing a public key of the terminal device using location information of the terminal device.

[5] The one or more processors:
further performing a process of periodically collecting location information of the first terminal device and other terminal devices;
The process of specifying
The key management device according to any one of [1] to [4], further comprising: a terminal device that is a candidate for a relay station, the terminal device being selected based on collected location information.

[6] The process of obtaining the secondary key includes:
The key management device according to any one of [1] to [5], further comprising: a secondary key generated based on the primary key and a private key of the first terminal device.

[7] A wireless communication unit that wirelessly communicates with a base station device or another terminal device;
one or more processors coupled to the wireless communication unit;
The one or more processors:
When requesting relay by another terminal device, acquiring identification information of the terminal device of the relay station candidate and a primary key generated based on a public key of the terminal device of the relay station candidate and used for encrypting the data to be relayed;
generating a secondary key based on the primary key for use in decrypting data to be relayed;
A terminal device that executes a process of transmitting the primary key to a communication partner device via any one of the terminal devices that are relay station candidates.

[8] Obtaining a relay request from a first terminal device, the relay request requesting relay by another terminal device;
Identifying terminal devices that are candidate relay stations located in the vicinity of the first terminal device;
generating a primary key for encryption based on a public key of the terminal device of the relay station candidate;
transmitting the primary key to the first terminal device;
obtaining a secondary key for decryption corresponding to the primary key from the first terminal device;
and storing the primary key and the secondary key in a memory in association with each other.

REFERENCE SIGNS LIST 100

Key management device

101, 201

Processor

102, 202

Memory

103, 203 Input/output unit 104 Communication unit 110 Communication I/F unit 120 Location information collection unit 130 Location information storage unit 140 Public key acquisition unit 150 Primary key generation unit 160 Key pair registration unit 170 Key

pair storage unit

200, 200a,

200b Terminal device

204, 210 Wireless communication unit 220 Location information report unit 230 Relay request unit 240 Secondary key generation unit 250 Communication control unit

Claims

Memory,
one or more processors coupled to the memory;
The one or more processors:
acquiring, from a first terminal device, a relay request for requesting relay by another terminal device;
Identifying terminal devices that are candidate relay stations located in the vicinity of the first terminal device;
generating a primary key for encryption based on a public key of the terminal device of the relay station candidate;
Transmitting the primary key to the first terminal device;
obtaining a secondary key for decryption corresponding to the primary key from the first terminal device;
a key management device that executes a process of storing the primary key and the secondary key in association with each other in the memory;
The process of generating the primary key includes:
The key management device according to claim 1 , wherein the primary key is generated by adding public keys of a plurality of terminal devices which are the relay station candidates.
The process of generating the primary key includes:
The key management device according to claim 1 , wherein the primary key is generated by adding a public key of the terminal device that is the relay station candidate and a predetermined dummy public key.
The process of generating the primary key includes:
The key management device according to claim 1 , wherein the primary key is generated by processing a public key of the terminal device of the relay station candidate using location information of the terminal device.
The one or more processors:
further performing a process of periodically collecting location information of the first terminal device and other terminal devices;
The process of specifying
The key management device according to claim 1 , further comprising: a terminal device that is a candidate for the relay station, the terminal device being selected based on collected location information.
The process of obtaining the secondary key includes:
The key management device according to claim 1 , further comprising: a secondary key generated based on the primary key and a private key of the first terminal device.
A wireless communication unit that wirelessly communicates with a base station device or another terminal device;
one or more processors coupled to the wireless communication unit;
The one or more processors:
When requesting relay by another terminal device, acquiring identification information of the terminal device of the relay station candidate and a primary key generated based on a public key of the terminal device of the relay station candidate and used for encrypting the data to be relayed;
generating a secondary key based on the primary key for use in decrypting data to be relayed;
A terminal device that executes a process of transmitting the primary key to a communication partner device via any one of the terminal devices that are relay station candidates.
Obtaining a relay request from a first terminal device, the relay request being requested to be relayed by another terminal device;
Identifying terminal devices that are candidate relay stations located in the vicinity of the first terminal device;
generating a primary key for encryption based on a public key of the terminal device of the relay station candidate;
transmitting the primary key to the first terminal device;
obtaining a secondary key for decryption corresponding to the primary key from the first terminal device;
and storing the primary key and the secondary key in a memory in association with each other.