JP2009212850A - Encrypted communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encrypted communication system can flexibly perform update of keys in the encrypted communication system including a server which distributes keys and a plurality of client terminals. <P>SOLUTION: A key distribution server sequentially distributes the keys to the client terminals (S24). If there is no response to distribution (S25: No), distribution of the keys is stopped (S29). In addition, after finishing distribution of the keys, the client terminals to which the keys are distributed are sequentially notified of update instructions to update the keys (S26, S27). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an encryption communication system that performs communication using a common key encryption method between apparatuses, and more particularly to a key update technique.

  2. Description of the Related Art Conventionally, in communication between devices, a common key type cryptographic communication system that performs communication using a common key for encryption and decryption is known in order to ensure confidentiality of communication contents.

In such a cryptographic communication system, if the same common key is continuously used, the risk of the common key being decrypted increases. For this reason, a technique for updating the common key is known (Patent Document 1).
JP 2007-267301 A

  The present inventors are considering the introduction of encryption for inter-device communication in an entrance / exit management system that performs entrance / exit management such as door locking / unlocking control. The entrance / exit management system includes, for example, a card authentication terminal device installed on the door side and a monitoring device, and door opening / closing control with good response is required within a limited specification.

In a common common key system, the number of keys increases as the number of devices increases ( _N C ₂ = n (n−1) / 2 is required when communication is performed between N devices). In the introduction, in consideration of the above-mentioned request, the same common key is used between devices, thereby avoiding the key management burden.

  When the same common key is updated, it is necessary to distribute new common keys from the key distribution server to each device in the system. In particular, when the system is scaled up, some devices may not receive a new common key.

  Such a non-reception may also be due to the fact that the key could not be received due to a temporary communication failure or the like. In consideration of this, it is not appropriate to force the key update as it is and to drop the device that has failed to receive the key uniformly from the communication within the system.

  Further, when updating the common key, it is necessary to search for an optimal update timing so as not to hinder communication between the apparatuses.

  The problem described above is not a problem limited to the entrance / exit management system, but is similarly a problem when a key is updated in a system that performs communication using a common key cryptosystem.

  The present invention has been made in view of the above-described problems, and provides a cryptographic communication system that can flexibly update a key in a cryptographic communication system including a server that distributes a key and a plurality of client terminals. Objective.

  In order to solve the problems to be solved by the present invention, an encryption communication system according to the present invention is an encryption communication system including a key distribution server and a plurality of client terminals that perform mutual common key encryption communication. The key distribution server includes a distribution unit that sequentially distributes the same key to the plurality of client terminals, a reception unit that receives a response to the distribution from the plurality of client terminals that distributed the key, and all the distributed client terminals Only when a response is received from each of the plurality of client terminals, the notification means for notifying the update instruction indicating that the use of the distributed key should be started sequentially to the plurality of client terminals. A receiving unit that receives the received key, a transmitting unit that transmits a response to the distribution, and encryption or data encryption using the first key in encrypted communication. And encryption processing means for performing No., when receiving the update instruction, characterized in that it comprises a key setting means for setting the received key as the first key.

  According to the configuration described in the means for solving the problem, the notification means notifies the update instruction only when responses from all distributed clients are received. It is possible to prevent the client from failing to receive and updating the key.

  Even if the communication amount is minimized, the data amount at the time of key distribution is larger than the data amount of the update instruction, so that the time required for key distribution tends to be longer than that of key update. Since the server notifies the update instruction only when responses from all clients are received, the timing of updating the key setting of each of the plurality of clients can be adjusted to some extent.

  The encryption processing means uses a second key when data decryption using the first key fails during encryption communication, and when the key setting means receives the update instruction, The key that has been used as the first key until is set as the second key.

  Since the update instructions are sequentially notified to the client terminals, if the number of client terminals is large, the timing difference between the update instruction and the key update becomes significant. According to this configuration, in order to set the key used as the first key before the update as the second key and use it as a backup, for example, a client terminal that has already updated the key still does not update the key. Data received from a client terminal that has not been performed can be correctly decoded.

  The key distribution server and the plurality of client terminals each store the same initial key, and the key distribution server includes an encryption unit that encrypts the same key to be distributed in advance using the initial key. The distribution means distributes the encrypted key to each client terminal, the encryption processing means decrypts the distributed key using the initial key, and the key setting means determines the decrypted key. It is set as the first key.

  According to this configuration, since the key to be distributed is encrypted using the initial key, the client terminal that is the distribution destination can be surely decrypted using the initial key. That is, it can be expected that the distributed key can be reliably decrypted by the client terminal while the key is secretly distributed using the initial key.

  The key distribution server includes table storage means for storing a client terminal management table including identifiers of a plurality of client terminals under management, and the distribution means includes a plurality of clients registered in the client terminal management table. The key distribution server further comprising: an entry request sending means for delivering to the terminal, and each of the plurality of client terminals further sending an entry request including information about itself under the control of the key distribution server. When receiving the entry request, displays information on the client client terminal of the entry request, and receives user interface means for accepting selection of entry, and if accepting entry, the sender client terminal The identifier was registered in the client terminal management table, and an entry rejection item was accepted. Expediently, characterized in that it comprises a table management means does not perform registration.

  According to this configuration, the user interface means of the key distribution server accepts the selection of whether or not to enter, so for example, by allowing the user who has grasped the number of client terminals and the operation status to select with this user interface, from the impersonation terminal Unauthorized entry can be prevented.

  The key distribution server includes a schedule unit that repeatedly executes the distribution according to a given schedule, a table storage that stores a client terminal management table including identifiers of a plurality of client terminals under management, and a client terminal. The received entry request under the management of the key distribution server is decrypted for authentication using the previously distributed key in the given schedule, and if the decryption fails, the previously distributed key is used. And a permission management unit that permits entry when the decryption is successful, and a table management unit that registers the identifier of the transmission source client terminal in the client terminal management table when entry is permitted. It is characterized by.

  According to this configuration, in order to decrypt the data received by the client terminal at the key distribution server using the previously distributed common key, for example, the key distributed before the previous time without the previously distributed key is used. It is possible to perform encryption communication by relieving a client terminal that has the client terminal, that is, a client terminal that could not be updated last time.

  The key distribution server includes schedule means for repeatedly executing the distribution according to a given schedule, and the schedule means until the responses from all the distributed client terminals are received. The next distribution in the schedule is prohibited from being executed.

  According to this configuration, by prohibiting the next distribution from being executed in the given schedule, it is possible to prevent the client terminal that has not been able to update the key from being left behind. In addition, it is possible to avoid a situation in which the keys used between the client terminals are complicated by forcibly renewing the key.

  In addition, the key distribution server further includes a monitoring unit that monitors a survival status indicating whether each of the plurality of client terminals is alive / non-alive, and an identifier of each of the plurality of client terminals under management. And a table storage means for storing a client terminal management table in which each survival status is associated, and the distribution means is alive among a plurality of client terminals with reference to the client terminal management table Distribution is performed to client terminals, and distribution is not performed to non-living client terminals.

  According to this configuration, for example, wasteful use of communication resources can be suppressed by not distributing keys to non-surviving client terminals.

  Further, the key setting means sets the received key as the first key when a predetermined time has elapsed since the reception of the key by the receiving means.

  According to this configuration, for example, even when the key distribution server is down, each client terminal can be updated to the distributed key. In particular, when the key distribution server goes down while notifying the update instruction, it is useful because the client terminal that has not received the update instruction can also update the key.

  The plurality of client terminals include an authentication terminal that reads information related to door opening and closing, and a management device that performs door opening and closing control based on the information related to door opening and closing, between the authentication terminal and the management device Then, using the key distributed by the distribution means, encrypted communication of information relating to the door opening and closing is performed.

(Embodiment 1)
<Configuration>
FIG. 1 is a diagram showing a configuration of the cryptographic communication system according to the first embodiment.

  As shown in FIG. 1, the cryptographic communication system 1 includes a key distribution server 100, eight card authentication terminals 4a to 4h, and four entry / exit management devices for managing two card authentication terminals 4a to 4h. 2a-2d.

  Here, the card authentication terminals 4a to 4h, the entrance / exit management devices 2a to 2d, and the doors 6a to 6h in FIG. 1 constitute an entrance / exit management system. The entrance / exit management system is a system that secures physical security by restricting the entrance and exit of people to and from the office.

  The doors 6a to 6h are doors of an office. The electric locks of the doors 6a to 6h are normally locked, and when the unlock signal is received, the lock is temporarily released.

  The card authentication terminals (card reading terminals) 4a to 4h are installed on the doors 6a to 6h, respectively, and read a card held over the user 9. Then, the card ID information read from the card is transmitted to the entrance / exit management devices 2a to 2d.

  The entrance / exit management device determines whether or not there is authority to enter and exit the room by comparing the received card ID information with a card ID management table in which entry / exit authority for each ID is described. If authorized, the entrance / exit management devices 2a to 2d send an unlock signal to the electric locks of the doors 6a to 6h corresponding to the card authentication terminals 4a to 4h, and unlock the doors 6a to 6h. If there is no authority, the entrance / exit management devices 2a to 2d send error signals to the card authentication terminals 4a to 4h, and cause the card authentication terminals 4a to 4h to perform error notification by sound.

  In the present embodiment, information communicated between the card authentication terminals 4a to 4h and the entrance / exit management devices 2a to 2d, such as the card ID information, is encrypted on the communication line by using a key. The confidentiality of information flowing through

  Then, as described in the means for solving the problem, the 12 entry / exit management devices 2a to 2d, taking into account the restrictions on the CPU and memory specifications of the card authentication terminals 4a to 4h and the key management burden, The card authentication terminals 4a to 4h perform encrypted communication using the same key.

  Hereinafter, the entry / exit management devices 2a to 2d and the card authentication terminals 4a to 4h that receive key distribution from the key distribution server may be collectively referred to as client terminals.

  FIG. 2 is a functional block diagram of the key distribution server.

  The key distribution server 100 includes a user interface unit 110, a control unit 120, and a storage unit 140.

  The user interface unit 110 includes a display unit 112 and an operation unit 114.

  The display unit 112 is configured by a liquid crystal display, for example, and performs various displays for the management user of the entry / exit management system in accordance with a display control signal from the control unit 120.

  The operation unit 114 includes, for example, a keyboard and a mouse, receives various inputs such as menu item selection and command input from the management user, and sends a control signal indicating the input contents to the control unit 120.

  The control unit 120 includes a control program stored in a ROM and a CPU that executes the control program, and includes an encryption processing unit 122, a key generation unit 128, a key distribution unit 130, a key management unit 132, a scheduler 134, a liveness. A state monitoring unit 136 and a transmission / reception unit 138 are provided.

  The encryption processing unit 122 includes an encryption unit 124 that converts plaintext into ciphertext and a decryption unit 126 that converts ciphertext into plaintext.

  The key generation unit 128 generates a 128-bit key. The encryption, decryption, and key generation are performed according to a known standard (for example, AES (Advanced Encryption Standard)).

  The key distribution unit 130 distributes the key generated by the key generation unit 128 to the client terminal. The distribution destination client terminal is determined based on the client management table 144.

  The key management unit 132 sends a key update notification indicating a key update instruction to the client terminal. Further, the key management table 146 of the storage unit 140 is managed.

  The scheduler 134 executes key updating by sending an execution instruction to the key generation unit 128 and the key distribution 130 based on a given schedule. The given schedule is a schedule customized by user settings (for example, every 60 minutes).

  The survival state monitoring unit 136 acquires the survival state of each client terminal by polling to the client terminal as needed, and updates the client management table 144 based on the acquisition result.

  The transmission / reception unit 138 transmits / receives data.

  The storage unit 140 stores a key storage unit 142, a client management table 144, and a key management table 146.

  The key storage unit 142 stores (1) an initial key incorporated in advance from an initial state, and (2) a key generated each time a key is updated. In the present embodiment, the initial key is stored in advance in each of the key distribution server 100 and the client terminal.

  The client management table 144 is a table including items of IDs, addresses, and survival states of managed client terminals (FIG. 3).

  The key management table 146 is a table in which the key ID stored in the key storage unit 142 and the usage priority of the key ID are described (FIG. 4).

  FIG. 3 is a diagram illustrating a client management table.

  The client management table 144 stored in the storage unit 140 of the key distribution server 100 includes items of “client ID” 144a, “IP address” 144b, and “survival state” 144c as table items.

  The “survival state” 144c is an item indicating the monitoring result of the surviving state by the surviving state monitoring unit 136, and takes a value of survival (value 1) or absence (value 0). In FIG. 3, four units GU-1 to GU-4 are in a living state.

  FIG. 4 is a diagram showing a key management table. (A) shows a state before key generation, (b) shows a state after key generation, and (c) shows a state after key update.

  The key management table 146 stored in the storage unit 40 of the key distribution server 100 includes items of “order” 146a, “key ID” 146b, and “key icon” 146c as table items. Note that the item “key icon” 146c is added for the convenience of visualizing the explanation, and is not necessarily required.

  The item of “rank” 146a is a key usage priority, and ranks key IDs used for encryption and decryption. The ranking “-” indicates that no ranking is given.

The item of “key ID” 146b is an item indicating a key ID for uniquely specifying a key. 4 (a), the key K ₁ of the third ranking is the initial key as described above. The key K _n in the first rank is a key distributed last time (it can be said to be a “current key” because it is a key normally used in the first rank). The second-ranked key K _n-1 is a key distributed two times before (it can be said to be an “old key” because it is a key normally used until the previous key update).

  FIG. 5 is a functional block diagram of the entrance / exit management device.

  Since the entrance / exit management devices 2a to 2d have the same configuration, the entrance / exit management device 2a will be described as a representative. In FIG. 5, the same functional blocks as the functional blocks of the key distribution server 100 shown in FIG.

  The entrance / exit management device 2 a includes a control unit 20 and a storage unit 40.

  The control unit 20 includes an encryption processing unit 22 including an encryption unit 24 and a decryption unit 26, a key management unit 32, an entrance / exit management unit 50, and a transmission / reception unit 38.

  The storage unit 40 stores an initial key, a key distributed last time, and a key storage unit 42 that stores a key distributed last time, a key management table 46, and a card ID management table 48.

  The entrance / exit management unit 50 compares the card ID information received from the card authentication terminals 4a and 4b under management with the card ID management table 48, and determines whether or not there is authority to enter / exit. If authorized, an unlock signal is sent to the electric locks of the corresponding doors 6a to 6b to release the lock.

  FIG. 6 is a diagram illustrating a key management table. (A) shows a state before receiving a new key, (b) shows a state after receiving the key, and (c) shows a state after key update setting.

  The management table 46 stored in the storage unit 40 of the entrance / exit management device 2a, which is a client terminal, includes items of “rank” 46a, “key ID” 46b, and “key icon” 46c as table items.

  FIG. 7 is a functional block diagram of the card authentication terminal.

  Of the card authentication terminals 4a to 4d having the same configuration, only the card authentication terminal 4a will be described as a representative. Also, the same reference numerals are given to the functional blocks similar to the entrance / exit management device 2a shown in FIG.

  The card authentication terminal 4a includes a control unit 20, a storage unit 40, a card reading unit 52, and a speaker 54.

  The control unit 20 includes an encryption processing unit 22 including an encryption unit 24 and a decryption unit 26, a key management unit 32, and a transmission / reception unit 38.

  The storage unit 40 is composed of, for example, a flash ROM, and stores a key storage unit 42 for storing an initial key, a key management table 46, and a card ID management table 48. As described above, since the card authentication terminal 4a is particularly limited in terms of specifications, it tends to require a longer time to store various data in the flash ROM than other devices. In consideration of capacity restrictions and safety, it is preferable that the number of keys stored in the key storage unit 42 is small.

  The card reading unit 52 reads the card ID held by the user. The read card ID information is transmitted by the transmission / reception unit 38 to the entrance / exit management device 2a that manages the card authentication terminal 4a.

The speaker 54 emits a predetermined number of beeps in response to the audio control signal from the control unit 20. For example, one beep sound is generated when normal, and two beeps sound when an error occurs.
<Survival status monitoring>
Next, with reference to FIG. 8 and FIG. 9, the client terminal survival state monitoring (survival confirmation) performed by the key distribution server 100 will be described.

  As shown in FIG. 8, when the polling period comes (S11: Yes), the survival state monitoring unit 136 performs polling to the client terminal (S12). If the response of the survival notification can be received within the timeout period from the polling execution (S13: Yes), the item of the survival state of the corresponding client terminal is updated in the client management table 144 and the polling cycle timer is reset (S14). ). If the response of the survival notification is not received within the timeout time (S13: No), the survival status item is updated to non-survival (absent) (S15).

  FIG. 9 shows data exchange when the key distribution server 100 monitors the survival state of two client terminals (ID: GU-1, GU-2). In this way, the survival state monitoring unit 136 executes the survival state monitoring in parallel for each client terminal.

In addition, as shown in FIG. 9, also in normal communication (for example, transmission of card ID information) from GU-1 to the key distribution server, the survival state monitoring unit 136 determines that the survival of GU-1 has been confirmed. And reset the timer.
<Key distribution / key update>
Next, key distribution and update will be described with reference to FIGS. FIG. 10 is a flowchart showing key distribution / key update processing on the key distribution server side.

  On the key distribution server side, as shown in FIG. 10, when the key distribution period arrives (S21: Yes), the scheduler 134 makes the determinations in steps S22 and S23.

  If the new key has been distributed to all client terminals (S22: Yes), and all client terminals have been instructed to update to the new key (S23: Yes), the key management unit 132 sends a new key to the key generation unit 128. Is generated (S24). The new key is encrypted by the encryption unit 124 before distribution with the key ranked first in the key management table 146. In addition, the new key in step S24 is the next generation key from the new key in step S23.

  If the new key has not been distributed (S22: No), the process proceeds to the distribution processing in steps S25 to S28. If the new key has been distributed and the update instruction has not been completed (S22: Yes, S23: No), the process proceeds to the update process of steps S29 to S31.

  When a new key is generated in step S24, the scheduler 134 refers to the client management table 144 and sets undistributed terminals among the surviving client terminals as distribution targets (S23). In the example of the client management table 144 shown in FIG. 3, four GU-1 to GU-4 that are alive and undistributed are set as distribution targets. Although not shown, the client management table 144 includes information indicating the distribution / non-distribution of a new key and information indicating the key update / non-update for each client terminal.

  The key distribution unit 130 sequentially distributes the keys to the set distribution target client terminals (S26). The distribution order is, for example, the descending order of the client ID.

  If distribution to the distribution target client terminal (whether successful or unsuccessful) has been completed (S27: Yes) and all distributions have been successful (S28: Yes), the process proceeds to the update processing in steps S29 to S31. . If there is any client terminal that does not respond to distribution in the distributed client terminal, it is determined that the distribution has failed (S28: No), and the process ends. For a client terminal that has failed to be distributed, it is determined that a new key has not been distributed in the next distribution cycle (S21) (S22: No). For this reason, a new key is again distributed to these terminals (S25, S26).

  In this way, unless a new key is distributed to all distribution target client terminals, the key update is not performed. Therefore, a client terminal that fails to receive a new key due to a communication failure or the like is rekeyed. The situation can be prevented.

  In the update processing in steps S29 to S31, the key management unit 132 refers to the client management table 144 and sets terminals that have not been instructed to update among the surviving client terminals as update instruction targets (S29). ). Then, the key management unit 132 sequentially notifies the update instruction to the update instruction target client terminal (S30). When the notification to the update instruction target client terminal is completed (S31), the process ends.

  After step S31, the key management unit 132 (1) retreats the first rank key to the second rank in the server 100's own key management table 146, and (2) updates the distributed new key to the first rank. To do.

  FIG. 11 is a flowchart showing key distribution / update processing on the client terminal side.

  On the client terminal side, as shown in FIG. 9, the data received by the transmission / reception unit 38 from the key distribution server is decrypted by the decryption unit 26 using the key ranked first in the key management table 46. When the key management unit 32 determines that the decrypted data is a new key (S41: Yes), the key management unit 32 stores the received new key in the key storage unit 42 (S42). When the storage is completed, the key management unit 32 transmits a response to the key reception to the key distribution server 100 (S43).

  When an update instruction notification is received as an event (S44: “update instruction”), the key management unit 32 deletes (1) the second-ranked key from the key storage unit 42 in the key management table 46, and (2) rank-one. The key of the place is moved back to the second place, and (3) the received new key is updated and set to the first place (S45).

  In addition, since the case where the key distribution server 100 cannot perform the update instruction notification and goes down (when the notification in step S31 in FIG. 10 cannot be performed) is also considered, in step S44, a predetermined time has elapsed since the reception of the new key. (Timeout) may be shifted to step S45.

  In the present embodiment, the key distribution is performed prior to the key update in order to prevent the client terminal from being left as described above. However, another purpose is to keep the key update between the client terminals. It is for aligning. This will be described with reference to FIG.

  FIG. 12 is a diagram showing data transmission / reception and processing between the key distribution server and the three client terminals in time series.

  As shown in FIG. 12, key distribution tends to require a lot of time compared to key update (key distribution period A> key distribution period B). The causes of the time difference are as follows: (1) Key distribution requires a larger amount of communication data than key update. (2) In key distribution, the time it takes to store the key distributed on the client terminal side in a flash ROM. , Etc.

  As a specific example of the time difference, for example, in an environment with 100 client terminals, the key update period may be several hundred milliseconds at most, while the key distribution period may take several tens of seconds. However, the time difference varies depending on the specifications of the client terminal and the communication line used.

As described above, since there is a large difference in required time between key distribution and key update, it is possible to minimize the difference in timing of key update between client terminals by distributing the key in advance and postponing the update. That is, it is possible to suppress the occurrence of a time zone in which communication is not possible between client terminals whose key update timings are shifted.
<Data reception>
Now, even if it can be said that the timing difference in key update between client terminals can be minimized as described above, especially when the number of client terminals is large, between terminals that have already been updated and terminals that have not been updated. In some cases, communication may occur. Since both the terminals have different keys in the first rank, there is a possibility that normal communication cannot be performed.

  Therefore, in this embodiment, the client terminal uses the second-ranked key (the key distributed twice before) as a backup.

  FIG. 13 is a flowchart showing data reception processing on the client terminal side.

  That is, when data is received (S51: Yes), the key management unit 32 attempts to decrypt with the key of the first rank in the key management table 46 (S52), and when it cannot be correctly decrypted and fails (S53). : No), the decryption is attempted with the key of the second rank (S54). It should be noted that whether or not decoding has been correctly performed is determined using a known verification method.

  Furthermore, when the decryption with the key of the second rank has failed (S55: No), the key management unit 32 sends a key distribution request to the key distribution server (S56).

According to this configuration, even if the client terminals having the highest rank in the key update timing gap are different, the terminal that has already completed the key update is the data from the terminal that has not yet completed the key update. Reception can be correctly decoded.
(Embodiment 2)
In the second embodiment, processing when a client terminal enters a cryptographic communication system will be described. The description of the same configuration as that of Embodiment 1 is omitted.

  FIG. 14 is a flowchart showing the activation process in the client terminal.

  In the activation process of the client terminal, first, the key management unit 32 refers to the key management table 32, causes the encryption unit 24 to encrypt the activation notification with the key ranked first, and transmits it to the key distribution server 100 (S61). . This activation notification includes information about its own client ID and MAC address.

  If the client terminal performs key update normally, the key ranked first at the time of transmission is a new key distributed by the key distribution server last time.

  In addition, if the client terminal has successfully updated the key until the previous time and has not been able to update the key only the previous time, the key ranked first is the key distributed by the key distribution server 100 the previous time.

  Further, if the client terminal newly enters the entry / exit management system, the key with the first rank becomes the initial key.

  When a startup processing instruction is received as an event from the key distribution server 100 (S62: “Startup processing instruction reception”), the startup processing instruction is executed. When the client terminal is the entrance / exit management device 2a, the startup process is, for example, (1) start of door locking / unlocking monitoring process and (2) time synchronization of the built-in clock.

  When a new key is received as an event (S62: “Reception of new key”), the key management unit 32 updates the key as in step S45 (S64).

  FIG. 15 is a flowchart showing entry permission / prohibition determination processing in the key distribution server.

  When data is received from the client terminal (S71: Yes), the key management unit 132 tries to decrypt with the key of the first rank in the key management table 146 (S72). If the key management unit 32 determines that the decryption has been correctly performed (S73: Yes), it returns a startup processing instruction to the client terminal (S80).

  If the key management unit 32 fails to decrypt with the key with the first rank (S73: No), the key management unit 32 tries to decrypt with the key with the second rank (S74) or the initial key with the third rank (S76). If any key can be correctly decrypted (S75: Yes or S77: Yes), the previously delivered key is encrypted using the key that has been correctly decrypted in step S75 or step S77, and distributed to the source client terminal.

  If decryption cannot be performed correctly with both keys (S75: No and S77: No), the process proceeds to menu processing (S79).

  FIG. 16 is a diagram showing a flowchart of menu processing in the key distribution server.

  First, the control unit 120 displays the entry availability menu 116 on the display unit 112 (S91). The entry availability menu 116 accepts a message “Do you want to enter the next device?”, (1) GU number (2) IP address (3) MAC address as information indicating the transmission source client, and acceptance permission An “OK” button 118 and a “NO” button 119 are included.

  In addition, since the information displayed on the entry permission / prohibition menu 116 is displayed as a reference for selecting permission / prohibition to the user, the information is not limited to the above (1) to (3) and may be any information that can identify a device.

  When the control unit 120 accepts the pressing of the “OK” button from the operation unit 114 (S92: permission), the control unit 120 registers the client terminal in the client management table and distributes the key ranked first (S93).

  When the control unit 120 accepts pressing of the “NO” button from the operation unit 114 (S92: Reject), the control unit 120 ends the process without registering the client terminal in the client management table (S94).

  As described above, according to the present embodiment, the key distribution server 100 distributes a key to a client terminal that does not have a previously distributed key but has a key distributed before the last time. The terminal can participate in encrypted communication. That is, the client terminal that has temporarily left the cryptographic communication system can be smoothly restored.

  Moreover, since the key distribution server 100 distributes the key to the client terminal having the initial key, it is possible to appropriately make a new entry into the encrypted communication.

In addition, when the data received from the client terminal cannot be correctly decrypted on the key distribution server 100 side, the entry permission / prohibition menu 116 can be displayed to allow the administrator user of the key distribution server 100 to make a determination.
(Embodiment 3)
In the first embodiment, the key distribution server 100 has been described as pre-encrypting the key to be distributed with the first-ranked key in advance. However, in the third embodiment, only the key to be distributed is encrypted with the initial key. Distribute. As described above, since all client terminals have an initial key, the distributed key can be reliably decrypted using the initial key on the client terminal side, thereby avoiding problems during key distribution. be able to.

  FIG. 17 is a flowchart showing key distribution / key update processing in the key distribution server. The flowchart in FIG. 17 is substantially the same as that in FIG. 10, and the same processing is denoted by the same step number to simplify the description.

  First, when the distribution period comes (S21: Yes), the scheduler 134 causes the key generation unit 128 to generate a new key. The key management unit 32 encrypts the generated new key with the initial key (S102).

  In this way, the new key to be distributed is encrypted with the initial key exceptionally in a form ignoring the key management table 146, so that the client terminal that receives the new key can be surely decrypted using the initial key. This effect will be described with reference to FIG.

  FIG. 18 is a diagram illustrating a key management table in the client terminal according to the third embodiment. (A) shows a state before receiving a new key, (b) shows a state after receiving the key, and (c) shows a state after key update setting.

  The key management table 47 stored in the storage unit 40 of the client terminal includes items of “order” 47a, “key ID” 47b, and “key icon” 47c as table items. Unlike the key management table 46 (see FIG. 6) described in the first embodiment, the key management table 47 has an initial key set at the second rank. For this reason, even if it cannot be decrypted with the key with the first rank, the new key received from the key distribution server can be securely decrypted by using the initial key with the second rank.

Even if the initial key is not set to the second rank on the client terminal side as shown in FIG. 18, for example, information specifying the key to be decrypted as the initial key is added to the new key distributed from the key distribution server. Thus, the initial key can be used on the client terminal side, and the same effect can be obtained.
<Supplement>
While the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments. For example, it can also be carried out as follows.
(1) In the first embodiment, as shown in FIG. 12, it has been described that a response from the client terminal is not received regarding the notification of the update instruction from the key distribution server 100 to the client terminal. Alternatively, it is possible to wait for a response to the notification of the update instruction. In particular, if there is no response to the notification of the update instruction, the key update may be stopped in order to prevent a non-responding client terminal from missing the key update.

1 is a diagram showing a configuration of a cryptographic communication system according to a first embodiment. It is a functional block diagram of a key distribution server. It is a figure which shows a client management table. It is a figure which shows a key management table. It is a functional block diagram of an entrance / exit management apparatus. It is a figure which shows a key management table. It is a functional block diagram of a card authentication terminal. It is a flowchart which shows the survival state monitoring process in a key distribution server. It is a figure which shows the exchange of data between a key distribution server and two client terminals. It is a flowchart which shows the key distribution and key update process in a key distribution server. It is a flowchart which shows the key reception / key update process in a client terminal. It is a figure which shows the transmission and reception of data and a process in a key distribution server and three client terminals along a time series. It is a flowchart which shows the data reception process in a client terminal. It is a flowchart which shows the starting process in a client terminal. It is a flowchart which shows the entry permission determination processing in a key distribution server. It is a figure which shows the flowchart of the menu process in a key distribution server. It is a flowchart which shows the key distribution / key update process in a key distribution server. FIG. 10 is a diagram showing a key management table in a client terminal according to Embodiment 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Encryption communication system 2a-2d Entrance / exit management apparatus 4a-4h Card authentication terminal 20 Control part 40 Storage part 22 Encryption processing part 24 Encryption part 26 Decryption part 32 Key management part 40 Storage part 42 Key storage part 46 Key management table 50 Entrance / exit management unit 52 Card reading unit 100 Key distribution server 110 User interface unit 112 Display unit 114 Operation unit 116 Accessability menu 120 Control unit 122 Encryption processing unit 124 Encryption unit 126 Decryption unit 128 Key generation unit 130 Key distribution unit 132 Key Management unit 134 Scheduler 144 Client management table 146 Key management table

Claims (9)

An encryption communication system including a key distribution server and a plurality of client terminals that perform encryption communication of a common key method with each other,
The key distribution server
Distribution means for sequentially distributing the same key to the plurality of client terminals;
Receiving means for receiving responses to distribution from a plurality of client terminals that have distributed the key;
A notification means for notifying update instructions indicating that the use of the distributed key should be started sequentially to a plurality of client terminals only when responses from all distributed client terminals are received;
Each of the multiple client terminals
A receiving means for receiving the distributed key;
A transmission means for sending a response to the distribution;
Encryption processing means for performing encryption or decryption of data using the first key in encrypted communication;
A cryptographic communication system comprising key setting means for setting the received key as the first key when receiving the update instruction. The encryption processing means uses the second key when the decryption of the data using the first key fails during the encryption communication,
2. The cryptographic communication system according to claim 1, wherein when receiving the update instruction, the key setting unit sets a key that has been used as the first key until then as the second key. Each of the key distribution server and the plurality of client terminals stores the same initial key,
The key distribution server
An encryption means for encrypting the same key to be distributed in advance using the initial key;
The distribution means distributes the encrypted key to each client terminal,
The encryption processing means decrypts the distributed key using the initial key,
2. The encryption communication system according to claim 1, wherein the key setting unit sets a decrypted key as the first key. The key distribution server
Table storage means for storing a client terminal management table including identifiers of each of a plurality of client terminals under management,
The distribution means distributes to a plurality of client terminals registered in the client terminal management table,
Each of the plurality of client terminals is
And an entry request sending means for sending an entry request under the management of the key distribution server, including information about the self,
The key distribution server
When receiving the entry request, user interface means to display information about the client terminal of the entry request and accept selection of whether to enter,
When accepting entry is accepted, the identifier of the sending client terminal is registered in the client terminal management table, and when accepting an entry rejection item, table management means is provided that does not perform registration. The cryptographic communication system according to claim 1. The key distribution server
Scheduling means for repeatedly executing the distribution according to a given schedule;
A table storage for storing a client terminal management table including an identifier of each of a plurality of client terminals under management;
A request to enter the management of the key distribution server received from the client terminal is decrypted for authentication using the key distributed last time in the given schedule, and if the decryption fails, the request is distributed further before Decryption using the key, and permission means to permit entry if correctly decrypted,
2. The cryptographic communication system according to claim 1, further comprising table management means for registering an identifier of the transmission source client terminal in the client terminal management table when entry is permitted. The key distribution server
Scheduling means for repeatedly executing the distribution according to a given schedule,
2. The cryptographic communication system according to claim 1, wherein the schedule unit prohibits execution of the next distribution in the given schedule until responses from all of the distributed client terminals are received. . The key distribution server
The key distribution server further includes monitoring means for monitoring a survival status indicating whether each of the plurality of client terminals is alive or not alive.
A table storage means for storing a client terminal management table in which identifiers of each of a plurality of client terminals under management and respective survival states are associated with each other,
The distribution means refers to a client terminal management table and distributes to a surviving client terminal among a plurality of client terminals, and does not distribute to a non-surviving client terminal. Item 4. The cryptographic communication system according to Item 1. The key setting means, when a predetermined time has elapsed since the reception of the key by the receiving means,
2. The cryptographic communication system according to claim 1, wherein the received key is set as the first key. The plurality of client terminals include an authentication terminal that reads information related to door opening and closing, and a management device that performs door opening and closing control based on the information related to door opening and closing,
2. The cryptographic communication system according to claim 1, wherein cryptographic communication of information related to opening and closing of the door is performed between the authentication terminal and the management device using a key distributed by the distribution unit.

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