JP6953680B2 - Key management device, communication system, terminal device, key management method, communication method, processing method, program - Google Patents

Description

The present invention relates to a key management device, a communication system, a terminal device, a key management method, a communication method, a processing method, and a program.

While the spread of mobile terminals has diversified communication methods, illegally obtained communication contents may be misused as a result of eavesdropping of communication contents and interception of communication routes during communication by mobile terminals. , Cases have been confirmed that are leaked or spread to the outside. In addition, in terms of security, there are cases where a third party impersonates a legitimate user from a lost or stolen communication terminal and illegally invades the system, illegally obtains data in the system, and falsifies or destroys the system. Threats are also expanding, diversifying, and becoming malicious in proportion to the spread of mobile terminals. Patent Document 1 discloses a technique for using key information in order to improve security in communication.

International Publication No. 2013/076848

In such a situation, technology has been established that enables eavesdropping and interception on any network of mobile phone lines, wired telephone networks, and Internet networks, and anyone who can obtain equipment can easily eavesdrop on communications via network lines. Unauthorized acquisition of communication data by interception is possible. Research is being conducted to improve cryptographic strength, but there is a possibility that even high-strength ciphers will eventually be cracked, and it is required to enhance communication security. In the case of communication using key information, communication security is maintained while maintaining the correspondence between the key information used for decryption and encryption between the communication source and the communication destination when using the key information. Is required to increase.

Therefore, an object of the present invention is to provide a key management device, a communication system, a terminal device, a key management method, a communication method, a processing method, and a program that solve the above-mentioned problems.

According to the first aspect of the present invention, the key management device uses an available authentication key among a plurality of authentication keys stored and available by the terminal device as identification information of the terminal device based on a notification from the terminal device. It is detected from the authentication keys that are linked and stored as information that can be used in the key information table, and the authentication key is designated as the first authentication key used when the terminal device communicates with its own device, and the first authentication key is specified. The first authentication key information indicating that the terminal device is used is notified to the terminal device, and the terminal device is connected to the terminal device using the authentication session encrypted with the first authentication key, and the identifier of the communication destination device is transmitted from the terminal device. the first call request said encrypted with the first authentication key a first call request decoded by said first authentication key can be used among the plurality of authentication keys available to store the communications apparatus comprises detecting an authentication key from the authentication key stored as information available cord association with the key information table identifier of the communications apparatus on the basis of the notification from the communications apparatus, said communications apparatus the authentication key Designates the second authentication key to be used when communicating with the own device, notifies the communication destination device of the second authentication key information indicating that the second authentication key is used, and encrypts with the second authentication key. When the second call request is transmitted to the communication destination device and a call success signal is received from the communication destination device based on the second call request, the communication between the terminal device and the communication destination device is performed. The common key to be used is specified, the common key is encrypted by the first authentication key and transmitted to the terminal device, the common key is encrypted by the second authentication key and transmitted to the communication destination device, and the terminal is transmitted. When the communication between the device and the communication destination device is completed, the notification of the used authentication key information regarding the used authentication key is acquired from each of the terminal device and the communication destination device, and the notification is recorded in the key information table. An authentication key other than the used authentication key is specified from the key information table as information that can be used .

Further, according to the second aspect of the present invention, the communication system includes a terminal device and a key management device, and the key management device can use an authentication key among a plurality of authentication keys stored and used by the terminal device. Is detected from the authentication keys stored as information that can be used in the key information table by associating with the identification information of the terminal device based on the notification from the terminal device, and the terminal device determines the authentication key with its own device. It is designated as the first authentication key to be used during communication, and the first authentication key information indicating that the first authentication key is used is notified to the terminal device, and the authentication session encrypted with the first authentication key is used. the connection with the terminal device, the terminal encrypted said first call request at the first authentication key a first call request including an identifier of the communication destination device from the device and decrypted by said first authentication key, stored as information available to the key information table in association string an identifier of the communication destination apparatus based on the notification of the authentication key from the communication destination device available among a plurality of authentication keys available to store the communication destination apparatus The second authentication key information indicating that the second authentication key is used is specified by detecting the authentication key from the authentication keys to be used, designating the authentication key as the second authentication key used when the communication destination device communicates with the own device, and using the second authentication key. Along with notifying the communication destination device, a second call request encrypted with the second authentication key is transmitted to the communication destination device, and a call success signal is received from the communication destination device based on the second call request. In this case, a common key used for communication between the terminal device and the communication destination device is specified, the common key is encrypted by the first authentication key and transmitted to the terminal device, and the common key is transmitted to the terminal device. (Ii) When the communication between the terminal device and the communication destination device is completed by encrypting with the authentication key and transmitting to the communication destination device, the used authentication key related to the authentication key used by the terminal device and the communication destination device is used. A notification of the authentication key information is acquired and recorded in the key information table, and an authentication key other than the used authentication key is specified from the key information table as information that can be used .

Further, according to the third aspect of the present invention, the key information in which the terminal device in the communication system including the key management device and the terminal device stores a plurality of authentication keys that can be used between the key management device and the key management device. The storage unit, the identification information notification unit for notifying the identification information of the terminal device to the key management device, and the key management device are used when communicating with the key management device among the authentication keys based on the identification information. information about the specified authentication key specified for a key information identification unit that receives from the key management device, an encrypted call request by using the authentication key by the key management device is specified, the communication destination device A call request unit that transmits a call request including an identifier to the key management device, and the communication destination that the key management device identifies based on the call request and is encrypted by the authentication key specified by the key management device. A communication unit that decrypts and acquires a common key used for communication with the device by the authentication key, and performs encrypted communication using the acquired common key in communication with the communication destination device, and the above. A new usage status management unit that determines that the used authentication key cannot be used based on the use of the authentication key, and a new key supply device based on the number of the authentication keys that are determined to be unusable among the plurality of authentication keys. When the communication between the key information acquisition unit that acquires a key authentication key and stores it in the key information storage unit and the communication destination device is completed, a used flag is attached and the key information storage unit stores the key information. It is provided with a notification unit for notifying the key management device of used authentication key information regarding the completed authentication key.

Further, according to the fourth aspect of the present invention, in the key management method, the usable authentication key among the plurality of authentication keys stored and used by the terminal device is identified as the identification information of the terminal device based on the notification from the terminal device. It is detected from the authentication keys stored as information that can be used in the key information table linked to, and the authentication key is designated as the first authentication key used when the terminal device communicates with its own device, and the first authentication is performed. The first authentication key information indicating that the key is used is notified to the terminal device, and the terminal device is connected to the terminal device using the authentication session encrypted with the first authentication key, and the identifier of the communication destination device is transmitted from the terminal device. and decoded by said encrypted said first call request at the first authentication key a first call request first authentication key including, utilization of the plurality of authentication keys available to store the communication destination apparatus the authentication key can be detected from the authentication key is stored as the information available to the key information table in association string an identifier of the communications apparatus on the basis of the notification from the communication destination apparatus, the communication destination the authentication key The device specifies the second authentication key to be used when communicating with its own device, notifies the communication destination device of the second authentication key information indicating that the second authentication key is used, and encrypts with the second authentication key. when the phased second call request is transmitted to the communication destination device, receives the call success signal from the communications apparatus on the basis of the second call request, the communication between the terminal device and the communication destination device The common key used for is specified, the common key is encrypted with the first authentication key and transmitted to the terminal device, the common key is encrypted with the second authentication key and transmitted to the communication destination device, and the above. When the communication between the terminal device and the communication destination device is completed, the notification of the used authentication key information regarding the used authentication key is acquired from each of the terminal device and the communication destination device and recorded in the key information table. , An authentication key other than the used authentication key is specified from the key information table as information that can be used .

Further, according to a fifth aspect of the present invention, the communication method is a communication method including a terminal device and a key management device, in which the key management device is among a plurality of authentication keys that can be stored and used by the terminal device. Based on the notification from the terminal device, the usable authentication key is linked to the identification information of the terminal device and detected from the authentication keys stored as information that can be used in the key information table, and the terminal device detects the authentication key. Designated as the first authentication key to be used when communicating with the own device, the terminal device is notified of the first authentication key information indicating that the first authentication key is used, and the authentication encrypted with the first authentication key is performed. using the session connection with the terminal device, the first authentication key to the first call request is encrypted with the first authentication key a first call request including an identifier of the communication destination device from the terminal device and decoded by, using the authentication key available among the plurality of authentication keys available to store the communication destination device by correlating string to the key information table identifier of the communications apparatus on the basis of the notification from the communication destination device A second indicating that the second authentication key is used by detecting the authentication key from the authentication keys stored as information that can be generated, designating the authentication key as the second authentication key used when the communication destination device communicates with the own device, and using the second authentication key. The authentication key information is notified to the communication destination device, the second call request encrypted with the second authentication key is transmitted to the communication destination device, and the call is successful from the communication destination device based on the second call request. When a signal is received, a common key used for communication between the terminal device and the communication destination device is specified, the common key is encrypted by the first authentication key and transmitted to the terminal device, and the common key is transmitted. When the key is encrypted by the second authentication key and transmitted to the communication destination device, and the communication between the terminal device and the communication destination device is completed, the authentication used by the terminal device and the communication destination device is completed. A notification of used authentication key information regarding a key is acquired and recorded in the key information table, and an authentication key other than the used authentication key is specified from the key information table as usable information .

Further, according to the sixth aspect of the present invention, in the processing method, the terminal device in the communication system including the key management device and the terminal device can be used between the key management device and the key information storage unit. storing a plurality of authentication keys, the notified identification information of the terminal device to the key management device, since the key management device is used when communicating with the key management device of the authentication key based on said identification information information about the specified authentication key specified in, received from the key management device, an encrypted call request by using the authentication key by the key management device is specified, the call request including an identifier of the communication destination apparatus A common key that is transmitted to the key management device, specified by the key management device based on the call request, and used for communication with the communication destination device encrypted by the authentication key specified by the key management device. and acquired by decoding by the authentication key, the communication between the communication destination device to communicate encrypted using a common key the acquired, the authentication key and the usage based on the utilization of the authentication key It is determined that the key cannot be used, and a new authentication key is acquired from the key supply device based on the number of the authentication keys determined to be unusable among the plurality of authentication keys , stored in the key information storage unit, and the communication is performed. When the communication with the destination device is completed, the used authentication key information regarding the used authentication key stored in the key information storage unit with a used flag is notified to the key management device.

Further, according to the seventh aspect of the present invention, the program stores the available authentication key among the plurality of authentication keys stored and used by the terminal device in the computer of the key management device based on the notification from the terminal device. It is detected from the authentication keys stored as information that can be used in the key information table linked to the identification information of the terminal device, and the authentication key is designated as the first authentication key used when the terminal device communicates with its own device. , Notify the terminal device of the first authentication key information indicating that the first authentication key is used, and connect to the terminal device using the authentication session encrypted with the first authentication key, and from the terminal device. the encrypted with the first authentication key a first call request including an identifier of the communications apparatus said first call request decoded by the first authentication key, the communication destination apparatus stores a plurality of available detecting an authentication key that can be used among the authentication key from the authentication key is stored as the information available to the key information table in association string an identifier of the communications apparatus on the basis of the notification from the communication destination device, the authentication The key is designated as the second authentication key used by the communication destination device when communicating with the own device, and the second authentication key information indicating that the second authentication key is used is notified to the communication destination device, and the second authentication key is notified. (Ii) When a second call request encrypted with the authentication key is transmitted to the communication destination device and a call success signal is received from the communication destination device based on the second call request, the terminal device and the communication destination device are used. The common key used for communication with is specified, the common key is encrypted by the first authentication key and transmitted to the terminal device, and the common key is encrypted by the second authentication key and the communication destination device is used. When the communication between the terminal device and the communication destination device is completed, the notification of the used authentication key information regarding the used authentication key is acquired from each of the terminal device and the communication destination device, and the key is transmitted to the key. A function of recording in an information table and specifying from the key information table as information that can use an authentication key other than the used authentication key is executed.

Further, according to an eighth aspect of the present invention, the program uses a computer of the terminal device in a communication system including the key management device and the terminal device with a plurality of authentication keys that can be used between the key management device and the computer. Key information storage means for storing the above, identification information notification means for notifying the identification information of the terminal device to the key management device, communication of the key management device with the key management device among the authentication keys based on the identification information. sometimes the information on specifying the authentication key specified to use, the key information specific means for accepting from the key management device, an encrypted call request by using the authentication key by the key management device is specified, the communication destination A call request means for transmitting a call request including an identifier of the device to the key management device, the communication specified by the key management device based on the call request and encrypted by the authentication key designated by the key management device. A communication means that decrypts and acquires a common key used for communication with a destination device with the authentication key , and performs encrypted communication using the acquired common key in communication with the communication destination device. A usage status management means that determines that the used authentication key cannot be used based on the use of the authentication key, and a new key supply device based on the number of the authentication keys that are determined to be unusable among the plurality of authentication keys. A used key information acquisition means that acquires an authentication key and stores it in the key information storage means, and is stored in the key information storage means with a used flag when communication with the communication destination device is completed. It functions as a notification means for notifying the key management device of used authentication key information related to the authentication key.

According to the present invention, while maintaining the correspondence between the communication source and the communication destination of the key information used for encrypting the communication, the possibility of decrypting the encrypted communication is reduced and the security of the communication is improved. Can be enhanced.

It is a figure which shows the structure of the communication system by one Embodiment of this invention. It is a functional block diagram of the AP server by one Embodiment of this invention. It is a functional block diagram of the terminal by one Embodiment of this invention. The key management function of the communication system according to one embodiment of the present invention is shown. It is the first figure which shows the processing flow of the communication system by one Embodiment of this invention. It is a second figure which shows the processing flow of the communication system by one Embodiment of this invention. It is a figure which shows the management example of the key information by one Embodiment of this invention.

Hereinafter, a key management device, a communication system, a terminal device, a key management method, a communication method, a processing method, and a program according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a communication system according to an embodiment of the present invention.
The communication system shown in this figure includes a terminal 1, a terminal 2, an application server 3, an authentication device 4, a first key supply device 5, a second key supply device 6, and a third key supply device 7. The application server 3 will be referred to as AP server 3 below. The terminal 1 and the terminal 2 communicate with the AP server 3 via the wireless communication line 10. The AP server 3, the authentication device 4, and the first key supply device 5 are connected via a LAN (Local Area Network) 20. The terminal 1 and the terminal 2 can communicate with the authentication device 4 and the first key supply device 5 via the AP server 3. The terminal 1 can be detachably connected to the second key supply device 6. The terminal 2 can be detachably connected to the third key supply device 7.

The terminal 1 and the terminal 2 are, for example, mobile phones. Although these two terminals are shown in FIG. 1, a large number of terminals can actually be connected to the communication system of the present embodiment. The terminal 1 and the terminal 2 function as a communication source or a communication destination with each other. Further, for the terminal 1 and the terminal 2, the AP server 3 and the authentication device 4 may serve as communication destinations. The terminal 1 and the terminal 2 first access the AP server 3 when communicating with another terminal. Then, the terminal 1 and the terminal 2 are authenticated by the function of the authentication device 4. The terminal 1 acquires key information from the first key supply device 5 and the second key supply device 6. The terminal 2 acquires key information from the first key supply device 5 and the third key supply device 7. The terminal 1 and the terminal 2 use the acquired key information for communication with the communication destination. For example, the terminal 1 and the terminal 2 use the acquired key information to encrypt or decrypt the communication with the communication destination. Alternatively, the terminal 1 and the terminal 2 use the acquired key information to encrypt or decrypt the information transmitted to the communication destination.

In the communication system according to the present embodiment, in particular, the AP server 3 (key management device) detects key information suitable for use among a plurality of key information stored and available by the terminal 1 and the terminal 2. The AP server 3 designates the appropriate key information among the plurality of key information as the key information used by the terminal 1 or the terminal 2 when communicating with the communication destination.
The AP server 3 may determine the key information used by the terminal 1 or the terminal 2 as inappropriate key information.
The AP server 3 may also notify the communication destination of the terminal 1 or the terminal 2 that the corresponding key information of the communication destination corresponding to the key information determined to be inappropriate by the terminal 1 or the terminal 2 cannot be used.
When the AP server 3 detects the suspension of use of the terminal 1 or the terminal 2, it may determine that all the key information stored in the terminal 1 or the terminal 2 is inappropriate key information.
The AP server 3 may also specify new key information supplied to the terminal 1 or the terminal 2 based on the number of plurality of key information available to the terminal 1 or the terminal 2.

The first key supply device 5, the second key supply device 6, and the third key supply device 7 are based on the number of available key information among the key information stored in the connected terminal 1 or the terminal 2. New key information may be supplied to the terminal device.

The terminal 1 and the terminal 2 store a plurality of key information. The plurality of key information may be key information acquired from the connected one of the first key supply device 5, the second key supply device 6, and the third key supply device 7. The terminal 1 and the terminal 2 specify the key information to be used at the time of communication with the communication destination among the stored key information. The key information may be specified by the AP server 3 or the own terminal. The terminal 1 and the terminal 2 determine that the used key information cannot be used based on the use of the key information. Further, the terminal 1 and the terminal 2 are among the first key supply device 5, the second key supply device 6, and the third key supply device 7 based on the number of key information determined to be unusable among the plurality of key information. New key information may be obtained from the connected device. The terminal 1 or the terminal 2 may output information indicating the number of available key information to a display screen or the like based on the plurality of key information and the key information determined to be unusable.

In this embodiment, the AP server 3, the first key supply device 5, the second key supply device 6, and the third key supply device 7 may each be one aspect of the key management device. The AP server 3 may be provided with the functions of the first key supply device 5 and the authentication device 4.

FIG. 2 is a functional block diagram of the AP server.
The AP server 3 internally retains the functions of the communication unit 31, the call control unit 32, and the key management unit 33 by executing the application program. The communication unit 31 is a processing unit that communicates with another device. The call control unit 32 is a processing unit that controls for establishing communication between terminals. The key management unit 33 is a processing unit that manages the key information stored in the terminal 1 and the terminal 2.

FIG. 3 is a functional block diagram of the terminal.
By executing the in-terminal program, the terminal 1 and the terminal 2 internally perform the functions of the communication control unit 121, the key information identification unit 122, the usage status management unit 123, the key information acquisition unit 124, and the key information output unit 125. Hold.
The communication control unit 121 is a processing unit that controls communication with the communication destination.
The key information specifying unit 122 is a processing unit that specifies the key information to be used at the time of communication with the communication destination among the key information stored in the own terminal.
The usage status management unit 123 is a processing unit that determines that the used key information cannot be used based on the use of the key information. The usage status management unit 123 determines that the key information once used cannot be used. The key information determined to be unusable may be deleted from the own terminal. Alternatively, the key information determined to be unusable may be managed as unusable key information inside the own terminal.
The key information acquisition unit 124 is new from the first key supply device 5, the second key supply device 6, the third key supply device 7, and the like based on the number of key information determined to be unavailable among the plurality of key information. It is a processing unit that acquires key information.
The key information output unit 125 is a processing unit that outputs information indicating the number of available key information to a display screen or the like based on a plurality of key information and key information determined to be unusable.

The terminal 1, the terminal 2, the AP server 3, the authentication device 4, the first key supply device 5, the second key supply device 6, and the third key supply device 7 are computers. In other words, each of these devices has a hardware configuration such as a CPU (Central Processing Unit), IF (Interface), communication module, ROM (Read Only Memory), RAM (Random Access Memory), and HDD (Hard Disk Drive). I have. The IF is a functional unit for inputting a signal from, for example, a keyboard or a mouse.

FIG. 4 shows the key management function of the communication system according to the present embodiment.
The terminal 1 acquires a plurality of key information used for encryption or decryption from the second key supply device 6 via the first key supply device 5 or the AP server 3 when communicating with the communication destination. The terminal 2 acquires a plurality of key information used for encryption or decryption from the second key supply device 6 via the first key supply device 5 or the AP server 3 when communicating with the communication destination. The communication destination of the terminal 1 and the terminal 2 is another terminal, the AP server 3, and the like. The AP server 3 acquires a plurality of key information used for encryption or decryption from the first key supply device 5 when communicating with the communication destination. The number of the plurality of key information acquired by the terminals 1 and 2 and the AP server 3 may be a large number of key information such as 100 or 1000. The communication destination for the AP server 3 is the terminal 1 or the terminal 2. The key information acquired by the terminal 1, the terminal 2, or the AP server 3 is the key information corresponding to the key information used by the communication destination. What is the corresponding key information? The key information corresponding to the public key may be the private key, the key information corresponding to the private key may be the public key, and in the case of the common key, the corresponding key information may be the same common key. Any algorithm or method may be used for holding the key information corresponding to the key information used by the communication destinations of the terminal 1, the terminal 2, and the AP server 3. For example, the first key supply device 5 generates key information so that the key generation device not shown in FIG. 4 holds the key information corresponding to the key information used by the communication destinations of the terminal 1, the terminal 2, and the AP server 3. , The second key supply device 6 and the third key supply device 7 may be used for recording. Alternatively, the first key supply device 5, the second key supply device 6, and the third key supply device 7 hold the key information corresponding to the key information used by the communication destinations of the terminal 1, the terminal 2, and the AP server 3. , The key information may be generated by the own device.

The terminal 1 and the terminal 2 may directly perform encrypted communication with each other based on the call control by the AP server 3. The terminal 1 and the terminal 2 receive the key information designation from the AP server 3 and use the designated key information when communicating with the communication destination. When the AP server 3 specifies the key information, it detects the key information appropriate for use and specifies the use of the key information. The AP server 3 detects, for example, the key information once used as inappropriate key information. The AP server 3 stores a plurality of key information stored in the terminals 1 and 2. Any algorithm or function for the AP server 3 to grasp the key information held by the terminal 1 or the terminal 2 may be used. As an example, the above-mentioned key generation device, first key supply device 5, second key supply device 6, and third key supply device 7 notify the AP server 3 of the key information stored in the terminal 1 and the terminal 2. May be good. The AP server 3 may calculate the key information stored in the terminal 1 or the terminal 2 by some algorithm.

FIG. 5 is a first diagram showing a processing flow of the communication system.
FIG. 6 is a second diagram showing a processing flow of the communication system.
Next, the processing flow of the communication system in this embodiment will be described step by step.
The subsequent processing is a processing flow when the terminal 1 communicates with the terminal 2. Although the processing of each functional unit of the terminal 1 and the terminal 2 has been described with reference to FIG. 3, it is described with one figure because of the same configuration. Therefore, for convenience of explanation, each functional unit of the terminal 1 will be described in the following description. In this case, a is added to the reference numeral of each functional unit in FIG. Further, in the following description, when each functional unit of the terminal 2 is described, b is added to the reference numeral of each functional unit in FIG.

The terminal 1 acquires an authentication key from the second key supply device 6 in advance (S501). Similarly, the terminal 2 has acquired the authentication key from the third key supply device 7 in advance. In such a situation, the communication control unit 121a of the terminal 1 transmits the ID of the terminal 1 to the AP server 3 when the communication program for communicating with the terminal 2 is activated (S502). The call control unit 32 of the AP server 3 transmits the ID of the terminal 1 to the authentication device 4 (S503). The authentication device 4 establishes an authentication session with the terminal 1 based on the ID of the terminal 1 and performs an authentication process (S504). At this time, the authentication device 4 requests the key management unit 33 of the AP server 3 to specify the key information. The key management unit 33 stores in the storage unit 35 a key information table that holds usable key information and unusable key information among a plurality of key information stored in the terminal 1 in association with the ID of the terminal 1. The key management unit 33 detects the authentication key A that can be used by the terminal 1 from the key information table, and designates it as the key information used when the terminal 1 communicates with the AP server 3. The key management unit 33 notifies the call control unit 32 of the designated authentication key A. The call control unit 32 encrypts the authentication session with the authentication key A. At this time, the call control unit 32 may notify the terminal 1 that the authentication key A will be used. The key information specifying unit 122a of the terminal 1 specifies that the authentication key A is used. Then, the communication control unit 121a of the terminal 1 also communicates with the AP server 3 by the authentication session (A) using the authentication key A. In the authentication session, the authentication device 4 notifies the AP server 3 of the authentication result indicating the success or failure of the authentication. If the authentication is successful, the call control unit 32 of the AP server 3 transmits the authentication success to the terminal 1.

Next, the communication control unit 121a of the terminal 1 transmits the address book information request to the AP server 3 (S505). The call control unit 32 of the AP server 3 acquires the address book information stored in the storage unit 35 and transmits it to the terminal 1 (S506). The address book information includes a list of IDs of terminals with which the terminal 1 can communicate. For example, the address book information includes the ID of the terminal 2. The terminal 1 outputs the address book information to the display screen. The user of the terminal 1 can specify the terminal to be the communication destination based on the address book information. The user specifies terminal 2 as the communication destination. Then, the communication control unit 121a of the terminal 1 encrypts the call request (INVITE) including the ID of the terminal 2 with the authentication key A and transmits it to the AP server 3 (S507). The call control unit 32 of the AP server 3 decrypts the call request with the authentication key A. The call control unit 32 transmits a calling signal to the terminal 1 based on the call request (S508). The communication control unit 121a of the terminal 1 outputs a ringing tone from the speaker of the terminal 1 based on the ringing signal (S509).

On the other hand, the call control unit 32 requests the key management unit 33 to specify the key information when communicating with the ID of the terminal 2 included in the call request. The key management unit 33 reads the key information table of the terminal 2 from the storage unit 35, detects the authentication key B that can be used by the terminal 2, and designates the key information to be used when the terminal 2 communicates with the AP server 3. The key management unit 33 notifies the call control unit 32 of the designated authentication key B. The call control unit 32 transmits an encrypted call request (INVITE) using the authentication key B to the terminal 2 (S510). At this time, the call control unit 32 notifies the terminal 2 that the authentication key B is used. The key information specifying unit 122b of the terminal 2 specifies that the authentication key B is used. Then, the communication control unit 121b of the terminal 2 decodes the INVITE request with the authentication key B. The communication control unit 121b outputs a ringing tone from the speaker of the terminal 2 based on the call request (S511). Further, the communication control unit 121b transmits a calling signal to the AP server 3 (S512).

When the user of the terminal 2 performs an off-hook operation (S513), the communication control unit 121b transmits a call success signal (B) encrypted with the authentication key B to the AP server 3 (S514). The call control unit 32 of the AP server 3 decodes the call success signal (B) and transmits the call success signal (A) encrypted with the authentication key A to the terminal 1 (S515). The communication control unit 121a of the terminal 1 transmits the confirmation response (A) encrypted with the authentication key A to the AP server 3 (S516). Further, the communication control unit 121a stops the output of the ringing tone (S517).

When the call control unit 32 of the AP server 3 receives the confirmation response (A), it transmits the ID of the terminal 2 to the authentication device 4 (S518). The authentication device 4 establishes an authentication session with the terminal 2 based on the ID of the terminal 2 and performs an authentication process (S519). The call control unit 32 encrypts the authentication session with the authentication key B. In the authentication session, the authentication device 4 notifies the AP server 3 of the authentication result indicating the success or failure of the authentication (S520). If the authentication is successful, the call control unit 32 of the AP server 3 transmits the authentication success to the terminal 2. When the authentication of the terminal 2 is successful, the call control unit 32 requests the first key supply device 5 to supply a common key for the terminal 1 and the terminal 2 to directly communicate with each other (S521). The first key supply device 5 stores the key information that can be used among the plurality of key information held by the terminal 1 and the terminal 2, respectively. The first key supply device 5 identifies the same common key C that can be used by both the terminal 1 and the terminal 2. For example, the first key supply device 5 specifies a common key C other than the already used common key. The first key supply device 5 transmits the common key C to the AP server 3 (S522). The call control unit 32 of the AP server 3 encrypts the common key C with the authentication key A and transmits it to the terminal 1 (S523). Further, the call control unit 32 encrypts the common key C with the authentication key B and transmits it to the terminal 2 (S524).

The communication control unit 121a of the terminal 1 decrypts the common key C with the authentication key A. The communication control unit 121b of the terminal 2 decrypts the common key C with the authentication key B. Then, the communication control unit 121a of the terminal 1 and the communication control unit 121b of the terminal 2 directly perform RTP communication via the communication line 10 (S525). Then, when the communication connection is made with each other, the communication control unit 121a of the terminal 1 and the communication control unit 121b of the terminal 2 make an encrypted connection using the common key C and perform encrypted communication (encrypted call) with each other (S526). When the operation of ending the call is performed on at least one of the terminal 1 or the terminal 2, the communication control unit 121a of the terminal 1 and the communication control unit 121b of the terminal 2 notify the AP server 3 of the disposal of the authentication key and the common key, respectively. (S527, S528). After receiving the authentication key and common key discard notification from the terminal 1 and the terminal 2, the key management unit 33 of the AP server 3 discards the authentication key and the common key used by the authentication device 4 and the first key supply device 5. Is notified (S529). Further, the key management unit 33 of the AP server 3 discards the used authentication key A and the authentication key B from the authentication keys held in the storage unit 35 (S530). Further, if the common key C is held in the storage unit 35, the key management unit 33 of the AP server 3 may discard the common key C. Similarly, the authentication device 4 may discard the authentication key A, the authentication key B, and the common key C (S531). Similarly, the first key supply device 5 may discard the authentication key A, the authentication key B, and the common key C (S532). Alternatively, the AP server 3, the authentication device 4, and the first key supply device 5 are managed by attaching a used flag or the like so that the used authentication key A, the authentication key B, and the common key C are not used later. It may be. Further, the usage status management unit 123a of the terminal 1 discards the authentication key A and the common key C from the storage unit 146a, or manages them with a used flag. Similarly, the usage status management unit 123b of the terminal 2 discards the authentication key A and the common key C from the storage unit 146b, or manages them with a used flag.

Although the embodiment of the present invention has been described above, according to the above processing, the AP server 3 has a plurality of authentication keys and common keys that can be stored and used by the terminal 1 and the terminal 2, which are suitable for use. The common key is detected, and the authentication key or the common key is designated as the key information used by the terminal 1 or the terminal 2 when communicating with the communication destination. In the above example, the terminal 1 and the terminal 2 determine that the authentication key and the common key other than the used key information are suitable for use, and do not use the used key information for encrypted communication. This makes it possible to reduce the possibility of decrypting the encrypted communication.

According to each process in the above-mentioned communication system, the key information held in the terminal 1 and the terminal 2 in advance is only the authentication key used for communication with the AP server 3 and the authentication device 4, and is used for encrypted communication between the terminals. The common key to be used is separately distributed from the first key supply device 5 after authentication with the authentication device 4. As a result, the key information held in the terminals 1 and 2 can be suppressed to only a plurality of authentication keys.
Further, in the above processing, the AP server 3, the authentication device 4, and the first key supply device 5 may store the authentication key and the common key holding / use status used by the terminal 1 and the terminal 2. Then, the AP server 3, the authentication device 4, and the first key supply device discard the authentication key and the common key used by the terminal 1 and the terminal 2 after their use, and determine that they will not be used thereafter. As a result, the terminal 1 and the terminal 2 do not perform encrypted communication using the used authentication key or common key, and change each time. Therefore, it is possible to reduce the risk of decryption of encrypted communication.
Further, the terminal 1 and the terminal 2 acquire the address book information necessary for communication with the communication destination terminal from the AP server 3 every time. As a result, the address book information is not left in the terminal, and even if the terminal is lost or stolen, the leakage of the address book information can be avoided.
Further, by providing a mechanism for delivering the authentication key to the terminal 1 and the terminal 2 in advance, the authentication time between the terminal 1 and the terminal 2 and the authentication device 4 can be shortened, and the key is exchanged by the public key. If this is not the case, secure communication can be realized by not applying an encryption method that has an uncertain factor in maintaining the encryption strength in the future. The present invention may use a public key or a private key.
Further, a mechanism is provided for delivering the terminal 1 and the terminal 2 by encrypting the common key for performing encrypted communication between the terminals from the first key supply device 5 with the authentication key after the authentication. As a result, the time for cryptographic connection between terminal 1 and terminal 2 can be shortened, and secure communication is realized by not applying cryptographic methods such as key exchange using a public key, which are uncertain about maintaining the cryptographic strength in the future. can do.
In addition, since terminals 1 and 2 are expected to be operated by a wide range of users regardless of age, gender, and whether or not they have specialized knowledge, encrypted communication can be performed easily and with familiar operations even without specialized knowledge. It is possible to realize an operation means that can carry out.

In the above example, the second key supply device 6 and the third key supply device 7 may be provided inside, for example, a cradle device to which the terminal 1 and the terminal 2 receive power supply. For example, when the terminal 1 is connected to the cradle, power is supplied to the battery of the terminal 1. On the other hand, the second key supply device 6 provided inside the cradle communicates with the terminal 1 to acquire the number of unused key information. The second key supply device 6 determines that the key information is supplied when the number of acquired key information is equal to or less than a predetermined value or when the decrease in the number from the previously acquired key information is equal to or more than a predetermined value. .. When the second key supply device 6 determines that the key information is supplied, the second key supply device 6 writes the key information in the storage unit 146a of the terminal 1. The key information may be an authentication key or a common key. The second key supply device 6 and the third key supply device 7 may be provided with an interface capable of communicating and connecting to the terminals 1 and 2. For example, the interface between the second key supply device 6 or the third key supply device 7 and the terminals 1 and 2 is a wired interface such as USB (Universal Serial Bus), FeLiCa Ad-hoc Link Protocol (hereinafter, “FALP””. ) Etc., a non-contact serial interface, a recording medium such as a microSD card, or the like.

The second key supply device 6 and the third key supply device 7 are instructed by the first key supply device 5 and the AP server 3 to output the key information to the connected terminals such as the terminal 1 and the terminal 2. You may. In this case, the key management unit 33 and the first key supply device 5 of the AP server 3 acquire the number of key information of the terminal 1 and the terminal 2 by some method. The key management unit 33 or the first key supply device 5 of the AP server 3 may be notified of the number of unused key information from, for example, the terminal 1 or the terminal 2. In the key management unit 33 and the first key supply device 5 of the AP server 3, when the number of acquired key information of the terminal is less than or equal to a predetermined value, or the decrease in the number from the previously acquired key information for the terminal is a predetermined value. In the above cases, it is determined that the key information is supplied. When the key management unit 33 or the first key supply device 5 of the AP server 3 determines that the key information is supplied, the key information is sent to the second key supply device 6 or the third key supply device 7 corresponding to the target terminal. Instruct to send. The key management unit 33 and the first key supply device 5 of the AP server 3 may notify the second key supply device 6 and the third key supply device 7 of the type and number of key information to be transmitted. As a result, the second key supply device 6 or the third key supply device 7 may generate one or more key information for the terminal 1 or the terminal 2 by itself and send out the key information. Alternatively, the second key supply device 6 or the third key supply device 7 may acquire the key information to be transmitted to the terminal 1 or the terminal 2 from the key generation device and transmit the key information.

FIG. 7 is a diagram showing an example of managing key information.
FIG. 7 shows the amount of key information held by the terminal 1, the terminal 2, and the terminal 3. It is assumed that the vertical axis shows the key correspondence relationship and the storage range of the key information, and each terminal holds the amount of key information represented by the width of the vertical axis. Further, it is shown that the terminals holding the key information whose positions on the vertical axis match each other hold the corresponding key information. From FIG. 7, the terminal 1 holds the key information in the range of t2 to t6. The terminal 2 holds the key information in the range of t4 to t7. The terminal 3 shows the key information in the range of t1 to t3 and t5 to t7. The range of key information may be, for example, a range represented by a numerical value. When the terminal 1 becomes unusable due to theft, loss, or the like, the AP server 3 or the first key supply device 5 acquires information that the terminal 1 has become unusable. For example, the administrator may input information that the terminal 1 is unavailable. Alternatively, information indicating that it has become unavailable may be received as a signal from a base station or the like. Then, the key management unit 33 of the AP server 3 and the first key supply device 5 detect the key information stored in the terminal 1 based on the key information of the terminal 1 stored by itself. For example, the key management unit 33 of the AP server 3 and the first key supply device 5 detect the range t2 to t6 of the key information stored in the terminal 1. The key management unit 33 stores the ID of the terminal 1 that has become unavailable and the range of key information. Then, when the terminal 1 becomes available again, the range of key information newly held by the terminal 1 may be stored. When the terminal 1 communicates with the communication destination, the key management unit 33 of the AP server 3 and the first key supply device 5 identify the key information outside the range of t2 to t6 stored as unusable, and the terminal 1 is notified of the key information. Instruct to use the key information. The key management unit 33 and the first key supply device 5 of the AP server 3 notify the communication destination (terminal 2, terminal 3, etc.) of the ID of the terminal 1 and the information in the range t2 to t6 of the key information that the terminal 1 cannot use. You may try to do it. When the key information in the range of t2 to t6 held by the terminal 1 becomes unavailable, the key information in the range of t4 to t6 held by the terminal 2 and the t2 held by the terminal 3 among the corresponding key information It may be determined that the key information in the range of ~ t3, t5 to t6 cannot be used during communication with the terminal 1.

Many of the related security technologies for terminal-to-terminal communication are relatively considered to be applied to communication devices in fixed communication networks, and all of the following issues are to be solved when applying them to data communication systems in wireless terminals such as mobile phones. There are few skills to meet. Specifically, (1) elimination of future anxiety factors in cryptography, (2) shortening of processing time corresponding to immediate communication, (3) restrictions and integrity on the hardware of mobile terminals, (4) ) There has been a demand for security technology that adapts to the issues inherent in encryption methods and mobile terminals, such as easy operations adapted to unspecified users.

[Future uncertainties in cryptography]
For the method that is often used for encrypted communication and uses a preset common key for a fixed period (daily, weekly, etc.), if the communication is intercepted multiple times within the fixed usage period of the common key, Since the key information is the same, there is a risk that the cryptographic algorithm and the original communication content can be easily analyzed and decrypted from the intercepted data. If quantum computers, which are currently being researched among research machines and companies around the world, become widespread in the future, a key exchange method using public or private keys (“Defe-Hellman (hereinafter,“ DH ”) method”) , "RSA method", etc.), it is said that the cryptographic algorithm is easily analyzed. Therefore, there is an anxiety factor in terms of cryptographic strength in long-term operation. Therefore, the authentication key and common key used for encrypted communication are not used for a long period of time and are discarded, and the encryption method and authentication key and common key that are not easily analyzed even if intercepted are connected. It was necessary to study and apply the method and device configuration.

[Reduced processing time for immediate communication]
As an example, key exchange using the Diffie-Hellman (hereinafter, "DH") method between a terminal and a server using public key cryptography, which is one of the security-related technologies (Internet Key Exchange (hereinafter, "IKE")). Describe the protocol. In this technology, when performing an encrypted connection, first the key is generated by exchanging the data required for key generation between terminals or between the terminal and the server, and then the key information is used to shift to the encrypted connection. It becomes an operation. Since the key generation procedure from this key exchange is included in the encrypted connection procedure, in a terminal that requires an immediate call, the connection time from the user performing the outgoing call operation to the time when the user can communicate increases, resulting in stress on the user. It becomes a factor to give. Therefore, instead of the cryptographic connection method (key exchange method by using a public key, etc.) that affects the connection time, the connection method and device configuration that allow the terminal and server to transmit the key information required for cryptographic connection at high speed and safely. It was necessary to consider and apply it.

[Terminal hardware restrictions and maintainability]
Although the hardware and software performance of the terminal has improved, it is a fixed system that can build in functions and performance related to cryptographic processing (hereinafter, "cryptographic related functions") such as arithmetic functions and key management / holding functions. Compared to the communication device of, the mobile terminal has a restriction that the encryption-related function must be realized only by software. Therefore, the mobile terminal puts as much load on the hardware and software (operating system, including "OS") of the mobile terminal as possible for the execution application (hereinafter, "app") for the mobile terminal including the encryption-related function. It is necessary to consider and apply a processing method and configuration that will reduce the amount. In addition, while mobile terminals are small and lightweight and convenient to carry, they are vulnerable to loss or theft. Therefore, connection methods, information security methods, and devices that enable them are vulnerable. It was also necessary to consider and apply the configuration.

[Easy operation adapted to unspecified users]
When connecting mobile terminals and performing encrypted connections between mobile terminals and servers, increasing password operations and key sharing operations will improve security, but at the same time reduce operability, which is an element that puts stress on users. It also becomes. Since mobile terminals are used by various users regardless of age, gender, and whether or not they have specialized knowledge, they need to be able to be easily operated without having specialized knowledge. For example, considering the case of realizing encrypted voice communication, the user does not have to be aware of the special procedure or operation for performing encrypted communication, and the operation (dial operation or dial operation) that the user usually performs on his / her own mobile terminal It is necessary to thoroughly consider the connection method that enables reliable transition to authentication and encrypted connection and the device configuration that enables it by making a call by selecting a phone book, etc. and performing a minimum authentication (password input, etc.). rice field.

The present invention has been made in view of the above problems. According to the communication system according to the present embodiment, the authentication and encryption communication methods that can sufficiently secure the security of communication between the terminals 1 and 2 and the AP server 3 and the authentication device 4 and between the terminals 1 and 2 are adopted, and the user himself / herself However, encrypted communication can be easily realized without being aware of the communication system.

Each of the above devices has a computer system inside. The process of each process described above is stored in a computer-readable recording medium in the form of a program, and the process is performed by the computer reading and executing this program. Here, the computer-readable recording medium refers to a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Further, this computer program may be distributed to a computer via a communication line, and the computer receiving the distribution may execute the program.

The above program may be for realizing a part of the above-mentioned functions. Further, a so-called difference file (difference program) may be used, which can realize the above-mentioned functions in combination with a program already recorded in the computer system.

1, 2, ... Terminal 3 ... AP server 4 ... Authentication device 5 ... First key supply device 6 ... Second key supply device 7 ... Third key supply device

Claims (13)

Of the plurality of authentication keys that can be stored and used by the terminal device, the available authentication key is associated with the identification information of the terminal device based on the notification from the terminal device and stored as information that can be used in the key information table. It detects from the inside, designates the authentication key as the first authentication key used when the terminal device communicates with its own device, and notifies the terminal device of the first authentication key information indicating that the first authentication key is used. At the same time, connect to the terminal device using the authentication session encrypted with the first authentication key.
The first call request including the identifier of the communication destination device from the terminal device and encrypted with the first authentication key is decrypted with the first authentication key.
Of the plurality of authentication keys that can be stored and used by the communication destination device, the available authentication key is associated with the identifier of the communication destination device based on the notification from the communication destination device and stored as information that can be used in the key information table. The authentication key is detected from the authentication keys to be used, the authentication key is designated as the second authentication key used when the communication destination device communicates with the own device, and the second authentication key information indicating that the second authentication key is used is input. Notifying the communication destination device and transmitting the second call request encrypted with the second authentication key to the communication destination device.
When a call success signal is received from the communication destination device based on the second call request, a common key used for communication between the terminal device and the communication destination device is specified, and the common key is used as the first. Encrypted with the authentication key and transmitted to the terminal device, the common key is encrypted with the second authentication key and transmitted to the communication destination device,
When the communication between the terminal device and the communication destination device is completed, the notification of the used authentication key information regarding the used authentication key is acquired from each of the terminal device and the communication destination device and recorded in the key information table. A key management device that specifies from the key information table as information that can use an authentication key other than the used authentication key. When the communication between the terminal device and the communication destination device is completed, a discard notification regarding the first authentication key and the common key is obtained from the terminal device, and the second authentication key from the communication destination device is obtained. The key management device according to claim 1, wherein a destruction notice relating to the common key is acquired, and the first authentication key, the second authentication key, and the common key notified by the destruction notification are destroyed. Claim 1 or claim 2 that, when the suspension of use of the terminal device is detected, it is determined that all the authentication keys recorded as the information stored in the terminal device in the key information table cannot be used. The key management device described in. Claims 1 to 3 obtain information on the number of authentication keys that can be used by the terminal device from the terminal device and specify a new authentication key to be supplied to the terminal device based on the number of authentication keys. The key management device according to any one of 3. Equipped with a terminal device and a key management device
The key management device
An authentication key that associates an available authentication key among a plurality of authentication keys that can be stored and used by the terminal device with the identification information of the terminal device based on a notification from the terminal device and stores it as information that can be used in the key information table. The authentication key is detected from the inside, the authentication key is designated as the first authentication key used when communicating with the own device, and the first authentication key information indicating that the first authentication key is used is sent to the terminal device. Notify and connect to the terminal device using the authentication session encrypted with the first authentication key.
The first call request including the identifier of the communication destination device from the terminal device and encrypted with the first authentication key is decrypted with the first authentication key.
Of the plurality of authentication keys that can be stored and used by the communication destination device, the available authentication key is associated with the identifier of the communication destination device based on the notification from the communication destination device and stored as information that can be used in the key information table. The authentication key is detected from the authentication keys to be used, the authentication key is designated as the second authentication key used when the communication destination device communicates with the own device, and the second authentication key information indicating that the second authentication key is used is input. Notifying the communication destination device and transmitting the second call request encrypted with the second authentication key to the communication destination device.
When a call success signal is received from the communication destination device based on the second call request, a common key used for communication between the terminal device and the communication destination device is specified, and the common key is used as the first. Encrypted with the authentication key and transmitted to the terminal device, the common key is encrypted with the second authentication key and transmitted to the communication destination device,
When the communication between the terminal device and the communication destination device is completed, the notification of the used authentication key information regarding the used authentication key is acquired from each of the terminal device and the communication destination device and recorded in the key information table. A communication system that specifies from the key information table as information that can use an authentication key other than the used authentication key. A key supply device that acquires information on the number of a plurality of authentication keys that can be used by the terminal device from the terminal device and supplies a new authentication key to the terminal device based on the number of the authentication keys.
The communication system according to claim 5. The terminal device in a communication system including a key management device and a terminal device.
A key information storage unit that stores a plurality of authentication keys that can be used with the key management device,
An identification information notification unit that notifies the key management device of the identification information of the terminal device,
Information about the specified authentication key specified to the key management device is used when communicating with the key management device of the authentication key based on the identification information, and key information identifying unit that receives from the key management device,
A call request unit that is a call request encrypted using the authentication key specified by the key management device and transmits a call request including an identifier of the communication destination device to the key management device.
The common key specified by the key management device based on the call request and used for communication with the communication destination device encrypted by the authentication key specified by the key management device is decrypted by the authentication key. Gets Te, the communication between the communications apparatus including a communication unit that communicates encrypted using a common key the acquired,
The usage status management unit that determines that the used authentication key cannot be used based on the use of the authentication key,
A key information acquisition unit that acquires a new authentication key from the key supply device and stores it in the key information storage unit based on the number of the authentication keys determined to be unusable among the plurality of authentication keys.
A notification unit that notifies the key management device of used authentication key information regarding the used authentication key that is stored in the key information storage unit with a used flag when communication with the communication destination device is completed. When,
A terminal device comprising. The terminal device according to claim 7, further comprising a key information output unit that outputs information indicating the number of available authentication keys based on the plurality of authentication keys and the authentication keys determined to be unavailable. Of the plurality of authentication keys that can be stored and used by the terminal device, the available authentication key is associated with the identification information of the terminal device based on the notification from the terminal device and stored as information that can be used in the key information table. It detects from the inside, designates the authentication key as the first authentication key used when the terminal device communicates with its own device, and notifies the terminal device of the first authentication key information indicating that the first authentication key is used. At the same time, connect to the terminal device using the authentication session encrypted with the first authentication key.
The first call request including the identifier of the communication destination device from the terminal device and encrypted with the first authentication key is decrypted with the first authentication key.
Of the plurality of authentication keys that can be stored and used by the communication destination device, the available authentication key is associated with the identifier of the communication destination device based on the notification from the communication destination device and stored as information that can be used in the key information table. The authentication key is detected from the authentication keys to be used, the authentication key is designated as the second authentication key used when the communication destination device communicates with the own device, and the second authentication key information indicating that the second authentication key is used is input. Notifying the communication destination device and transmitting the second call request encrypted with the second authentication key to the communication destination device.
When a call success signal is received from the communication destination device based on the second call request, a common key used for communication between the terminal device and the communication destination device is specified, and the common key is used as the first. Encrypted with the authentication key and transmitted to the terminal device, the common key is encrypted with the second authentication key and transmitted to the communication destination device,
When the communication between the terminal device and the communication destination device is completed, the notification of the used authentication key information regarding the used authentication key is acquired from each of the terminal device and the communication destination device and recorded in the key information table. A key management method for specifying an authentication key other than the used authentication key as information that can be used from the key information table. In a communication system equipped with a terminal device and a key management device,
The key management device
An authentication key that associates an available authentication key among a plurality of authentication keys that can be stored and used by the terminal device with the identification information of the terminal device based on a notification from the terminal device and stores it as information that can be used in the key information table. The authentication key is detected from the inside, the authentication key is designated as the first authentication key used when communicating with the own device, and the first authentication key information indicating that the first authentication key is used is sent to the terminal device. Notify and connect to the terminal device using the authentication session encrypted with the first authentication key.
The first call request including the identifier of the communication destination device from the terminal device and encrypted with the first authentication key is decrypted with the first authentication key.
Of the plurality of authentication keys that can be stored and used by the communication destination device, the available authentication key is associated with the identifier of the communication destination device based on the notification from the communication destination device and stored as information that can be used in the key information table. The authentication key is detected from the authentication keys to be used, the authentication key is designated as the second authentication key used when the communication destination device communicates with the own device, and the second authentication key information indicating that the second authentication key is used is input. Notifying the communication destination device and transmitting the second call request encrypted with the second authentication key to the communication destination device.
When a call success signal is received from the communication destination device based on the second call request, a common key used for communication between the terminal device and the communication destination device is specified, and the common key is used as the first. Encrypted with the authentication key and transmitted to the terminal device, the common key is encrypted with the second authentication key and transmitted to the communication destination device,
When the communication between the terminal device and the communication destination device is completed, the notification of the used authentication key information regarding the used authentication key is acquired from each of the terminal device and the communication destination device and recorded in the key information table. A communication method for specifying an authentication key other than the used authentication key as information that can be used from the key information table. The terminal device in a communication system including a key management device and a terminal device is
A plurality of authentication keys that can be used with the key management device are stored in the key information storage unit.
Notifying the key management device of the identification information of the terminal device,
Based on the identification information, the key management device receives information from the key management device regarding the designation of the authentication key designated for use in communication with the key management device among the authentication keys.
A call request encrypted using the authentication key specified by the key management device and including an identifier of the communication destination device is transmitted to the key management device.
The common key specified by the key management device based on the call request and used for communication with the communication destination device encrypted by the authentication key specified by the key management device is decrypted by the authentication key. Gets Te, the communication between the communication destination device to communicate encrypted using a common key the acquired,
Based on the use of the authentication key, it is determined that the used authentication key cannot be used.
A new authentication key is acquired from the key supply device based on the number of the authentication keys determined to be unusable among the plurality of authentication keys, and stored in the key information storage unit.
A processing method for notifying the key management device of used authentication key information regarding the used authentication key stored in the key information storage unit with a used flag when communication with the communication destination device is completed. .. On the computer of the key management device,
Of the plurality of authentication keys that can be stored and used by the terminal device, the available authentication key is associated with the identification information of the terminal device based on the notification from the terminal device and stored as information that can be used in the key information table. It detects from the inside, designates the authentication key as the first authentication key used when the terminal device communicates with its own device, and notifies the terminal device of the first authentication key information indicating that the first authentication key is used. At the same time, connect to the terminal device using the authentication session encrypted with the first authentication key.
The first call request including the identifier of the communication destination device from the terminal device and encrypted with the first authentication key is decrypted with the first authentication key.
Of the plurality of authentication keys that can be stored and used by the communication destination device, the available authentication key is associated with the identifier of the communication destination device based on the notification from the communication destination device and stored as information that can be used in the key information table. The authentication key is detected from the authentication keys to be used, the authentication key is designated as the second authentication key used when the communication destination device communicates with the own device, and the second authentication key information indicating that the second authentication key is used is input. Notifying the communication destination device and transmitting the second call request encrypted with the second authentication key to the communication destination device.
When a call success signal is received from the communication destination device based on the second call request, a common key used for communication between the terminal device and the communication destination device is specified, and the common key is used as the first. Encrypted with the authentication key and transmitted to the terminal device, the common key is encrypted with the second authentication key and transmitted to the communication destination device,
When the communication between the terminal device and the communication destination device is completed, the notification of the used authentication key information regarding the used authentication key is acquired from each of the terminal device and the communication destination device and recorded in the key information table. A program that executes a function that identifies an authentication key other than the used authentication key from the key information table as information that can be used. A computer of the terminal device in a communication system including a key management device and a terminal device,
A key information storage means for storing a plurality of authentication keys that can be used with the key management device.
Identification information notification means for notifying the key management device of the identification information of the terminal device,
Key information specifying means for accepting information about the specified authentication key specified for use when communicating with the key management device, from the key management device of the authentication key the key management device based on the identification information,
A call request means that is a call request encrypted using the authentication key specified by the key management device and that transmits a call request including an identifier of the communication destination device to the key management device.
The common key specified by the key management device based on the call request and used for communication with the communication destination device encrypted by the authentication key specified by the key management device is decrypted by the authentication key. Gets Te, the communication between the communication destination device, communication means for communicating encrypted using a common key the acquired,
A usage status management means that determines that the used authentication key cannot be used based on the use of the authentication key.
A key information acquisition means that acquires a new authentication key from a key supply device and stores it in the key information storage means based on the number of the authentication keys determined to be unusable among the plurality of authentication keys.
A notification means for notifying the key management device of used authentication key information regarding the used authentication key to be stored in the key information storage means with a used flag when communication with the communication destination device is completed. ,
A program that functions as.

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