JP2008199181A - System, device and method for communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically set an encryption key without input through a PC for an arbitrary pair of communication devices selected by a user. <P>SOLUTION: A communication system has a pair of communication devices A and B which can constitute a local network, and an encryption key is transmitted and received between the communication devices A and B to share the key. Each of the communication devices A and B stores encryption information related to whether encryption operations are completed. In this state, one of the communication devices receives the encryption information from the other device, and then determines whether encryption operations are completed based on the encryption information on both of the devices. In response to the determination results, an encryption key is transmitted and received between them. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a communication system, a communication apparatus, and a communication method for performing encryption by transmitting / receiving a control frame for encryption setting including an encryption key.

For example, a power line communication system (hereinafter referred to as a PLC system) is a high-frequency signal (as high as several kHz to several tens of MHz or more) on a power line through which a commercial current with a frequency of 50 Hz or 60 Hz flows. To communicate with each other.
Such a PLC system has attracted attention as a system capable of transmitting and receiving large-capacity data using an existing power line (also called a distribution line or a light line) drawn into each house without using a dedicated communication line. ing.

In the above-mentioned PLC system, power line communication devices (such as PLC modems and information home appliances capable of PLC communication) can be freely communicated with each other by using a power line stretched in the house as if it were a LAN. It is physically connected to the house through power lines.
For this reason, in order to construct a local network by the PLC system, it is necessary that the power line communication device constituting the network has authentication information of the network, and this authentication information includes a network ID for specifying the network. There are encryption keys for encrypting signals transmitted and received in the network.

By sharing these pieces of authentication information among the power line communication devices included in the local network, it is possible to perform communication while distinguishing data of other networks from data of the own network. For example, in a conventional PLC system, one encryption key is set in one home in order to avoid communication with adjacent houses, and encrypted communication is performed using this encryption key.
In this case, each communication device included in the same network has the same encryption key, but since this encryption key is different from that of the adjacent house, the power line communication devices belonging to other networks of the adjacent house Communication data from cannot be decoded. In this way, the network can be logically separated even on physically connected power lines (see Patent Document 1).

JP 2006-166273 A

However, an encryption key setting method for a conventional power line communication apparatus is performed by accessing a power line communication apparatus from a personal computer (hereinafter referred to as a PC) and inputting a command by the user, or a dedicated GUI for accessing the power line communication apparatus from the PC. This is a complicated operation for a user who is not familiar with network and PC operations.
In the PLC system, it is considered that there will be an increasing number of cases where it is necessary to construct a network without using a PC, such as a connection between a video playback / recording device capable of power line communication and a TV monitor. In such a case, a user who does not have a PC cannot perform encryption key setting work.

On the other hand, in the encryption key setting method described in Patent Document 1, the head end device centrally manages the encryption key, and the head end device requests the assignment of the encryption key starting with connection to the network. The encryption key is automatically assigned to the terminal.
However, even in such a system in which the head end device centrally manages the encryption key, it is necessary to input a command to the head end device from the PC. In addition, such a unified management method has a drawback that an encryption key setting operation cannot be easily performed between any pair of terminals.

  In view of such a situation, the present invention enables an encryption key to be set automatically for an arbitrary pair of communication devices selected by a user without input by a PC, so that the encryption key can be easily set. The purpose is to provide a system.

The present invention is a communication system that includes a pair of communication devices capable of configuring a local network, and transmits and receives the encryption key in order to share the encryption key between one communication device and the other communication device,
The one and the other communication devices respectively store encryption information regarding whether or not the encryption work has been completed, and the own device receives the encryption information of the other device from the other device, and the encryption of the own device It is determined whether the encryption information or the encryption information of the other device or both of them is not yet received, and transmission / reception of the encryption key is started according to the determination result.

According to the communication system of the present invention, one and the other communication devices that can constitute the local network store in advance encryption information (unencrypted or encrypted) regarding whether or not the encryption work has been completed. Yes.
In this state, when the own device receives the encryption information of the other device from the other device, it is determined whether either or both of the encryption information of the own device and the encryption information of the other device is not yet. It is possible to automatically determine whether or not these communication devices should perform encryption work. For this reason, even if it is an arbitrary pair of communication apparatus which the user selected, an encryption key can be automatically set without input by PC.

  Specifically, when it is determined that the encryption information of the own device and the encryption information of the other device are not yet present in the one and the other communication devices, the own device uses a new encryption key. And the encryption key is distributed to the other device, and the other device that has received the distribution stores the encryption key as its own encryption key, so that the encryption key can be automatically set.

In addition, in the one and the other communication devices, when it is determined that the encryption information of the own device is completed and the encryption information of the other device is not yet, the own device has already stored The other key may be distributed to the other device, and the other device receiving the distribution may store the encryption key as its own encryption key.
Similarly, in the one and the other communication devices, when it is determined that the encryption information of the own device is not yet and the encryption information of the other device has been completed, the other device has already stored the reverse. It is only necessary to distribute the own encryption key to the own device and store the encryption key as the own encryption key.

  In the one and other communication devices, when it is determined that the encryption information of the own device has been completed and the encryption information of the other device has been completed, the already set encryption key is changed. Since there is no need, it is sufficient to keep the own encryption key stored in the own device and the other device without changing them.

In the present invention, it is preferable that the communication device includes an operation member (for example, an operation button) serving as a user interface for starting transmission of the encrypted information. In this case, if the determination is performed when the operation timing for the operation member is within a certain time (for example, within 1 minute) between the own device and the other device, the user has not selected It is possible to prevent the encryption key setting operation from being started with the other communication device.
For example, when the operation members of three or more communication devices are operated and the operation timing is within the predetermined time, the determination is performed between the two communication devices operated first. Thus, it is possible to prevent an encryption key setting operation from being started with an unexpected communication device.

As described above, in the present invention, when the encryption information of both the own device and the other device has been completed, the own device and the other device retain their own encryption keys without change. The transmission / reception of the encryption setting control frame is not started. For this reason, if the communication device does not have a function to return the encrypted information to the unset state, the encryption key once set cannot be changed again.
Therefore, in the present invention, it is preferable that the communication device has a reset function that initializes an encrypted encryption key and resets the encryption information of the own device to an unreturned state by an external reset operation.
In this case, if the initial encryption key after being initialized by the reset function has a different value for each communication device, it is constructed in an adjacent house or the like compared to the case where the initial encryption key is the same. In addition, the probability of establishing communication with a communication device in another local network is reduced, which is more preferable in terms of security.

  As described above, in the present invention, it is determined whether or not to perform encryption work in combination with the encryption information of the own device and the other device, and the encryption key once given may be reset. It is preferable that the communication device is provided with a display unit that displays at least the encryption information, the success / failure of the encryption work, and the success / failure of the reset operation so that the user can recognize the operation state of the communication device. .

  As described above, according to the present invention, since an encryption key can be automatically set for any pair of communication devices selected by the user without input by a PC, the encryption key setting operation can be performed more easily. Can do.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Home network configuration]
FIG. 1 shows a home network (LAN) constructed using a power line communication technique in a plurality of houses H1, H2.
In this home network using power line communication, an independent network (LAN) is constructed for each of the buildings H1 and H2 using the home distribution lines 10 and 11 in the houses H1 and H2.

The in-house distribution lines (in-building power lines) 10 and 11 of the houses H1 and H2 are connected to the outdoor power lines 100 in the vicinity of the houses H1 and H2 through the lead-in lines 12 and 13 by being installed on a power pole. Yes.
The lead-in wires 12 and 13 are connected to the distribution boards 14 and 15 of the houses H1 and H2, and a plurality of in-house distribution lines 10 and 11 branched from the distribution boards 14 and 15 are connected to the indoors H1 and H1, respectively. It is laid on H2.

  Each of the in-house distribution lines 10 and 11 is provided with one or a plurality of terminal portions, and a plurality of power outlets (wall outlets) 16 and 17 are connected to each terminal portion. A plurality of power line communication devices (hereinafter simply referred to as “modems”) A to F are connected to the outlets of these outlets 16 and 17, respectively. Each of the modems A to F transmits a PLC signal and receives power supply via the distribution lines 10 and 11.

When a network is configured by PLC, the network needs to include a parent modem that controls power line communication.
Of course, this parent modem function may be assigned to the parent modem dedicated machine, but all modems have a function as a parent modem, and the modem that has been powered on for the longest time is the parent modem. The modem that is turned on later may be a child modem, so that the parent modem may be appropriately determined according to the state of the network.

Here, even if an independent network (LAN) is to be constructed for each of the houses H <b> 1 and H <b> 2, the in-house distribution lines 10 and 11 of the houses H <b> 1 and H <b> 2 are connected via the power line 100. Therefore, the signal of one network can reach the other network. Therefore, in order to make each network independent, each modem A to F can set data relating to a network identifier and an encryption key as security information.
The network identifier is uniquely set for each network so as to distinguish the own network from other networks, and the modems A to C belonging to the same network have a common network identifier. The modems A to C belonging to the same network have a common encryption key and cannot read signals from outside the network.

[Modem configuration]
FIG. 2 is a block diagram showing the internal configuration of the modems A and B. As shown in FIG. The configurations of the other modems C, D, E, and F are the same.
As shown in FIG. 2, the modems A and B have a power cord 21 extending from the housing 20 and can be connected to an outlet via a power plug 22 provided at the tip of the cord 21. It has become. The power cord 21 is connected to a power circuit 23 and a PLC transmission / reception unit (communication unit) 24 in the housing 20. The transmission / reception unit 24 performs processing such as signal modulation / demodulation to perform power line communication with other modems. The modems A and B include a control unit 25 that controls the PLC transmission / reception unit 24, processes transmission / reception data, and performs an encryption operation and a reset operation, which will be described later.

The PLC transmitting / receiving unit 24 of the modems A and B is a frequency multiplexing method using a plurality of carriers (multicarrier) in a predetermined frequency band for power line communication, more specifically, orthogonal frequency multiplexing (OFDM). Modulation is performed using a modulation method called Multiplex. For this reason, the PLC transmission / reception unit 24 has a quadrature amplitude modulation (QAM) function, and distributes and allocates data to be transmitted to a plurality of carriers. Based on the allocated data, the carrier amplitude ( Power) and phase.
In this embodiment, 2 MHz to 30 MHz is used as a frequency band in normal power line communication, and the number of carriers in the entire band (2 MHz to 30 MHz) is set to 2048 (N), but the present invention is limited to this. It is not a thing.

The control unit 25 of the modems A and B includes an encryption setting processing unit 26 that performs an operation of setting an encryption key that is one of the security information. The processing unit 26 is connected to the other modems A and B. In order to share the encryption key, it is possible to cause the PLC transmission / reception unit 24 to perform the encryption setting control frame 35 (or 38) including the encryption key.
A non-volatile memory 27 is connected to the control unit 25, and the memory 27 stores the encryption key storage area and encryption information (“unencrypted”) regarding whether or not an encryption operation described later has been completed. Or “encrypted”) storage area.

The casings 20 of the modems A and B are provided with a push button 28 that is an operation member for encryption work and a reset button 29 that is an operation member for reset work.
Both of these buttons 28 and 29 are connected to the control unit 25. When the user presses the push button 28, the encryption setting processing unit 26 starts an encryption operation described later, and when the user presses the reset button 29, the same operation is performed. The encryption setting processing unit 26 starts a reset operation described later.

Thus, in this embodiment, the user operates the push button 28 to start the encryption work, or the user operates the reset button 29 to start the reset work.
For this reason, it is important for the user to know the encryption state (encrypted or unencrypted) of each of the modems A and B and whether the encryption or reset after the button operation is successful. Therefore, the casing 20 of the modems A and B is provided with a display unit 30 made up of LEDs or the like for allowing the user to recognize the change in the state of each work.
The display unit 30 according to the present embodiment is configured to change the state of modems A and B described later (not shown in FIG. 4 and FIG. 5). , Setting reset failure). Such display distinction can be expressed by, for example, a change in the emission color of LEDs, a change in the number of lights or the number of times of lighting of a plurality of LEDs, and the like.

[Encryption work]
In the present embodiment, when the user presses the push button 28 of the pair of modems A and B, the control unit 25 enters an encryption operation mode described below and clears the predetermined change condition shown in FIG. In order to share the encryption key between the modems A and B, the PLC communication unit 24 is caused to perform control communication. Details of this control communication (FIGS. 6 and 7) will be described later.
That is, the user can start the control communication by substantially simultaneously pressing the push buttons 28 of the two modems A and B to share the encryption key. In this case, the order of pressing is not relevant. In this manner, the work of simultaneously pressing the push buttons 28 of the pair of modems A and B to share the encryption key is referred to as “encryption work”.

Each of the modems A and B stores either “not encrypted” or “encrypted” in the memory 27 as encryption information. And the control part of each modem A and B determines whether an encryption key is changed by the combination of the state of a pair of modems A and B based on the change conditions shown in FIG.
Here, “unencrypted” means that the encryption operation has not been performed and the initial encryption key is owned. This initial encryption key is assumed to be set by the manufacturer of the PLC device at the time of factory shipment, and this initial encryption key may be the same or different for each PLC device.

Of course, it is desirable in terms of security to have different initial encryption keys for each PLC device. The reason is that after the user obtains the modem, it can be connected to other PLC devices with the initial encryption key (including the modem in the neighboring house) until the encryption work is performed, so unintended information is entered. This is because there is a possibility of coming out or spilling.
On the other hand, “encrypted” means a state where the encryption work is completed. The state change from “unencrypted” to “encrypted” occurs due to the encryption operation. Further, the state change from “encrypted” to “unencrypted” occurs due to a reset operation described later.

[Encryption key change conditions]
As shown in the table of FIG. 3, when it is determined that the encryption information of the modem A and the encryption information of the modem B are both “unencrypted” in the modem A and the modem B that perform encryption work. The modem A that presses the push button 28 earlier generates a new encryption key, and the modem A and the modem B use the encryption key thereafter.
In this case, as will be described later, the encryption key is set to the modem B by distributing a control frame 35 including the encryption key to the modem B, and the modem B receiving the distribution stores the encryption key as its own encryption key. Is done by doing.

If it is determined that the encryption information of the modem A is “unencrypted” and the encryption information of the modem B is “encrypted” in the modem A and the modem B that perform encryption work, A uses the encryption key that the modem B has already stored.
In this case, as will be described later, the encryption key is set to the modem A by the modem B distributing the control frame 38 including the encryption key to the modem A, and the modem A receiving the distribution uses the encryption key as its encryption key. Done by memorizing.

If it is determined that the encryption information of the modem A is “encrypted” and the encryption information of the modem B is “unencrypted” in the modem A and the modem B that perform encryption work, B uses the encryption key that modem A has already stored.
In this case as well, the encryption key is set to the modem B by distributing the control frame 35 including the encryption key to the modem B by the modem A and storing the encryption key as its own encryption key. Is done by doing.

When it is determined that both the modem A and the modem B are “encrypted”, the modems A and B both keep their own encryption keys without being changed. The encryption operation fails.
For this reason, when it is desired to share the encryption key between the "encrypted" modems A and B, the reset described later returns the encryption information to "unencrypted" once for either modem. After performing the work, the encryption work is performed.

As described above, in this embodiment, the encryption operation is performed for each pair of modems selected by the user.
Therefore, for example, if there are five "unencrypted" modems A to E, for example, modem A and modem B, modem B and modem C, modem C and modem D, modem D and modem E, etc. Therefore, it is necessary to perform encryption for each pair of modems selected by the user.

[Reset work]
When it is desired to return the encryption information of the modems A and B from “encrypted” to “unencrypted”, a reset operation using the reset button 29 is performed. That is, when the reset button 29 is pressed, the control unit 25 of the modems A and B changes the encryption information stored in the memory 27 from “encrypted” to “unencrypted”. Unlike the encryption operation, this reset operation can be performed independently for one modem A or B.
This reset operation is performed when the modem that has already been encrypted and entered into some network is to be disconnected, or when the encryption setting of the modem is reset when it is desired to enter another network.

When the reset button 29 is pressed, the control unit 25 sets the encryption state to “unencrypted” and at the same time initializes the value of the encryption key recorded in the memory 27. There are two methods for initializing the encryption key.
One method is to restore the default encryption key when the modems A and B store the factory default encryption key as a default. The other method is to randomly change the encryption key by a random number or the like. It is a method of resetting to something.
In the former method, the encryption key is the same every time resetting is performed, but the modem needs to store the encryption key at the time of factory shipment. In the latter method, since the encryption key changes every reset operation, the management becomes complicated, but the initial encryption key can be made different for each of the modems A and B.

[Change in state when push button 28 is pressed]
FIG. 4 shows the state change of the encryption work in the modems A and B.
Among these, FIG. 4A shows a change in state when the push button 28 of the modems A and B “unencrypted” is pressed.
As shown in the figure, when the push buttons 28 of the modems A and B that are “unencrypted” are pressed, the state of “encryption work in progress” is entered. Then, if the encryption operation is successful, the state becomes “encrypted”, and if it fails, the state becomes “encryption failure”. Note that, as indicated by the dashed arrow in FIG. 4A, the push button 28 can be pressed from the “encryption failure” state to reenter the “encryption work” state.

FIG. 4B shows a change in state when the push buttons 28 of the encrypted modems A and B are pressed.
As shown in the figure, when the push buttons 28 of the modems A and B which are “encrypted” are pressed, the state of “encryption work in progress” is entered. When the encryption operation described later succeeds successfully, the state returns to the “encrypted” state, and when it fails, the state becomes “encryption failure”. Note that, as indicated by a broken line arrow in FIG. 4B, the push button 28 can be pressed from the “encryption failure” state to reenter the “encryption work” state.

[Change in state when the reset button 29 is pressed]
FIG. 5 shows a change in state of the reset operation in the modems A and B.
Among these, FIG. 5A shows a change in state when the reset button 29 of the “encrypted” modems A and B is pressed.
As shown in the figure, when the reset button 29 of the modems A and B which are “encrypted” is pressed, the state of “setting resetting” is entered. If the reset operation is successful, the state becomes “unencrypted”, and if it fails, the state becomes “setting reset failure”. Note that, as indicated by the dashed arrow in FIG. 5A, the “setting reset failure” state can be pressed again to re-enter the “setting resetting” state.

FIG. 5B shows a change in state when the reset button 29 of the unencrypted modems A and B is pressed.
As shown in the figure, when the reset button 29 of the modems A and B that are “unencrypted” is pressed, a “setting resetting” state is entered. If the reset operation is successful, the state returns to the “encryption not performed” state. If the reset operation is unsuccessful, the state is “setting reset failed”. Note that, as indicated by a broken line arrow in FIG. 5B, the “setting reset failure” state can be pressed again to return to the “setting resetting” state again.

[Contents of control communication (2 units)]
FIG. 6 shows control communication for encryption work performed between the modem A and the modem B. In the example of FIG. 6, it is assumed that the push button 28 for the modem A is pushed for a while within a certain time (for example, within one minute) after the push button 28 is pushed for the modem A. is doing.
In this case, the modem A whose push button 28 is first pressed first broadcasts the first notification frame 31 including its own encryption information from the PLC transmission / reception unit 24, and thereby the partner to which encryption work should be performed. Search for modems.

Thereafter, when the push button 28 of the modem B is pressed, the modem B enters the encryption work mode. When the modem B receives the first notification frame 31, the modem B returns a second notification frame 32 including its own encryption information to the modem A, thereby establishing a handshake between them. Further, when the modem B receives the first notification frame 31, the modem B determines whether or not the encryption key change condition in FIG.
On the other hand, when the modem A receives the second notification frame 32, the modem A determines whether or not the encryption key change condition in FIG.

Thereafter, the modem A transmits a determination frame 33 in which the determination result indicating whether or not the change condition is satisfied is transmitted to the modem B, and the modem B determines whether or not the determination result matches its own determination result. If they match, the response frame 34 is returned to the modem A.
Here, when the modem A is “unencrypted” and the modem B is also “unencrypted”, the modem A newly generates an encryption key, and generates a control frame 35 including the generated encryption key. Transmit to modem B. The modem B that has received the control frame 35 changes its encryption key to the encryption key described in the control frame 35.

Thereafter, the encryption operation is completed through the exchange of the change completion frame 36 for notifying the modem A of the completion of the encryption key change and the end frame 37 for notifying the end of the encryption operation.
When the modem A is “encrypted” and the modem B is “unencrypted”, the modem A transmits a control frame 35 including its encryption key to the modem B, and the change completion frame is transmitted. After the exchange of 36 and the end frame 27, the encryption work is completed.

On the other hand, when the modem A is “unencrypted” and the modem B is “encrypted”, the modem B transmits the control frame 38 including its encryption key to the modem as shown by a broken line in FIG. The modem A that has transmitted to A and received the control frame 38 changes its encryption key to the encryption key described in the control frame 38. In this case, the modem A whose encryption key has been changed transmits the change completion frame 36a (dashed line in FIG. 6) to the modem B, and the modem B receiving this transmits the end frame 37a (dashed line in FIG. 6) to the modem. A is returned to A, and the encryption operation is completed.
Further, when the modem A is “encrypted” and the modem B is also “encrypted”, the control frames 35 and 38 are not transmitted from any of the modems A and B. The described end frame 37 is transmitted to the modem B, and the encryption operation is completed.

  As described above, according to the present embodiment, the pair of modems A and B capable of configuring the local network stores the encryption information (not encrypted or encrypted) in advance, and the encryption information of the own device is stored. When the notification frames 31 and 32 are received from the other device, it is determined whether or not the encryption key change condition shown in FIG. 3 is satisfied. Therefore, the modems A and B should perform the encryption operation. It is possible to automatically determine whether or not they are things. For this reason, even with any pair of modems A and B selected by the user, the encryption key can be automatically set without input by the PC.

[Contents of control communication (3 units)]
FIG. 7 shows control communication when the push button 28 is pressed for the three modems A to C configuring the same network.
FIG. 7A shows a case where the encryption operation has already started between the modem A and the modem B, and then the push button 28 of the modem C is pressed.
In this case, the modem C broadcasts a notification frame 39 for searching for a modem to perform encryption work with itself, but the modem A and the modem B that have already started the encryption work are in the notification frame 39. On the other hand, the NG frame 40 indicating that the encryption operation is not performed is transmitted to the modem C, whereby the encryption operation of the modem C is ended with failure.

FIG. 7B shows a case where both the modem B and the modem C return the second notification frames 32 and 32 in response to the first notification frame 31 of the modem A.
In this case, the modem A transmits the determination frame 33 to the modem B that has transmitted the second notification frame 32 first, and establishes an encryption operation with the modem B. On the other hand, for the modem C that has issued the second notification frame 32 later, an NG frame 40 indicating that the encryption operation is not performed is transmitted to the modem C, whereby the encryption operation of the modem C fails. In this way, in this embodiment, “encryption work” is established between the two modems A and B whose push buttons 28 are first pressed, and the third unit fails. Yes. The same applies when there are four or more modems.

The present invention is not limited to the above embodiment.
For example, in the above embodiment, the push button 28 and the reset button 29 are configured as separate buttons, but these can be shared by one button. In this case, the encryption operation and the reset operation can be distinguished by changing the operation method for the one button (long press, short press, etc.).
Moreover, although the case where this invention was applied to the power line communication system was illustrated in the said embodiment, this invention can also be employ | adopted as the communication system using other communication apparatuses, such as a wireless LAN apparatus.

It is a block diagram of the home network constructed | assembled in the some house. It is a block diagram which shows the internal structure of a PLC modem. It is a table | surface which shows the change conditions of an encryption key. It is a figure which shows the state change of the encryption operation | work in a PLC modem. It is a figure which shows the state change of the reset operation | work in a PLC modem. It is a figure which shows the control communication for encryption work performed between the modem A and the modem B. FIG. It is a figure which shows control communication when a pushbutton is pressed down with respect to three modems A-C which comprise the same network.

Explanation of symbols

H1: house, H2: house, 10: in-house distribution line, 11: in-house distribution line, 12: lead-in line,
13: Lead-in wire, 14: Distribution board, 15: Distribution board, 16: Power outlet,
17: power outlet, 20: housing, 21: power cord, 22: power plug,
23: Power supply circuit, 24: PLC transmission / reception unit (communication unit), 25: Control unit,
26: Encryption setting processing unit, 27: Memory, 28: Push button (operation member),
29: Reset button (operation member), 30: Display unit, 31: First communication frame,
32: second communication frame, 33: determination frame, 34: response frame,
35: Control frame (A → B), 36, 36a: Change completion frame,
37, 37a: End frame, 38: Control frame (B → A), 39: Notification frame, 40: NG frame, 100: Outdoor power line

Claims (10)

A communication system comprising a pair of communication devices capable of forming a local network, and transmitting and receiving the encryption key in order to share the encryption key between one communication device and the other communication device,
The one and the other communication devices respectively store encryption information regarding whether or not the encryption work has been completed, and the own device receives the encryption information of the other device from the other device, and the encryption of the own device The communication system is characterized in that it determines whether or not both the encrypted information and the encrypted information of the other device have been received, and starts transmission / reception of the encryption key in accordance with the determination result.   In the one and the other communication devices, when it is determined that both the encryption information of the own device and the encryption information of the other device are not yet, the own device generates a new encryption key and The communication system according to claim 1, wherein a key is distributed to the other device, and the other device that has received the distribution stores the encryption key as its own encryption key.   In the one and the other communication devices, when it is determined that the encryption information of the own device has been completed and the encryption information of the other device is not yet, the own encryption key that the own device has already stored The communication system according to claim 1, wherein the other device that has received the distribution stores the encryption key as its own encryption key.   In the one and the other communication devices, when it is determined that the encryption information of the own device is not yet and the encryption information of the other device is already completed, the other device already stores its own encryption key The communication system according to claim 1, wherein the communication device distributes the device to the own device, and the own device that has received the distribution stores the encryption key as its own encryption key.   In the one and the other communication devices, when it is determined that the encryption information of the own device has been completed and the encryption information of the other device has been completed, the own device and the other device have already stored. The communication system according to claim 1, wherein the encryption key is held as it is without being changed. The communication device includes an operation member serving as a user interface for starting transmission of the encrypted information,
The communication system according to any one of claims 1 to 5, wherein the determination is performed when an operation timing with respect to the operation member is within a predetermined time between the own device and another device.   The communication system according to claim 6, wherein the determination is performed between the two communication devices operated first when operation timings of the three or more communication devices with respect to the operation member are within the predetermined time.   8. The communication device according to claim 1, wherein the communication device has a reset function of initializing an encrypted encryption key and resetting the encrypted information of the own device to an unreturned state by an external reset operation. Communications system. A communication device that transmits and receives the encryption key to share the encryption key with other communication devices,
A storage unit for storing encryption information regarding whether the encryption work has been completed or not;
A communication unit capable of receiving encryption information of another device from the other device; and
A control unit for determining whether the encryption information of the own device or the encryption information of the other device or both of them is not yet, and causing the communication unit to transmit and receive the encryption key according to the determination result; A communication device comprising: A communication method for transmitting and receiving the encryption key in order to share the encryption key between one communication device and the other communication device,
Encryption information regarding whether or not encryption work has been completed is stored in the own machine, and the encryption information of the other machine is received from the other machine to the own machine, and the encrypted information of the own machine or the other machine is stored. A communication method characterized in that the encryption key is transmitted / received when it is determined that the encryption information or both of them is not yet available.

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