JPWO2016147382A1 - Cryptographic communication system terminal device, cryptographic communication system relay device, and cryptographic communication system control method - Google Patents

Abstract

In one-time pad encryption communication using a mobile terminal device, the mobile terminal device grasps a one-time pad encryption key held by another mobile terminal device before the one-time pad encryption communication processing. The terminal apparatuses 101 and 102 periodically transmit the key ID list that the self-confidence possesses to the relay apparatus 201, and the relay apparatus 201 receives and retains the retained key ID list of each terminal apparatus. The terminal device performs communication via the relay device, thereby confirming the possessed key ID list of the partner terminal device with which one-time pad encryption communication is to be performed, and determines whether encryption communication is possible.

Description

  The present invention relates to an encryption communication system using, for example, a one time pad (OTP) encryption and a control method thereof.

By sharing the encryption algorithm key and encrypting the communication contents between the communication terminals among a plurality of communication terminals, it is possible to prevent wiretapping of the communication contents.
At this time, when the block encryption algorithm is used as the encryption algorithm, the plaintext data is divided into units called blocks (usually fixed length), and the encryption process using the encryption key is repeated for each block.
When a stream encryption algorithm is used as the encryption algorithm, a pseudo-random number called a key stream is generated from the encryption key, and plaintext data encryption processing is repeatedly performed in bit units using the key stream.
In any case, the length of the encryption key shared between the communication terminals is 128 bits, 256 bits, or the like. That is, the communication content is encrypted based on an encryption key having a shorter length than the plain text data. In these methods, the range of values that can be taken as encryption keys is a combination of 2 <128> to 2 <256>, and when using the current computer technology, brute force attempts to decrypt with all combinations of encryption keys Attacks are considered impossible.
However, this does not apply to new technologies such as quantum computers that far exceed existing computer technologies.

On the other hand, there is an encryption method called a one-time pad in which a random number having the same length as that of plaintext data is prepared and used for one-time encryption using the random number as a key.
With the one-time pad encryption method, the range of values that can be taken as encryption keys is a huge space equal to plaintext data, so it is possible to prove that decryption is impossible even if the computer technology has evolved dramatically It is. Varnam's Cipher is a kind of one-time pad encryption method, and uses an exclusive OR (XOR) of plaintext data and an encryption key as ciphertext.

  In order to encrypt communication contents using the one-time pad encryption method, it is necessary to share in advance a one-time pad encryption key that is longer than the length of plaintext data between communication terminals. Quantum key distribution (QKD) technology is considered to be a powerful technology for sharing one-time pad encryption keys.

One application using a shared one-time pad encryption key is one-time pad encryption communication using a mobile communication terminal. In order to share the one-time pad encryption key between two points, the quantum key distribution device uses weak light that is neither permitted to be duplicated nor amplified. For this reason, the communication distance is about 150 km, which is the current limit, and a breakthrough such as quantum relay technology is required.
This limitation of communication distance can be overcome as an application by storing and using a one-time pad encryption key in a mobile terminal. This is an advantage of one-time pad encryption communication using a mobile communication terminal.

  However, when a mobile communication terminal is used, connection to the key sharing system linked with the quantum key distribution device is performed irregularly. This may cause a mismatch of one-time pad encryption keys between mobile communication terminals. In addition, sufficient consideration is required for the one-time pad encryption key depletion in mobile communication terminals. Further, since the one-time pad encryption method is a one-to-one method between the sender and the receiver, in order to perform one-time pad encryption communication with a plurality of communication terminals, the one-time pad encryption corresponding to the terminal that wants to communicate is performed. A key is required. Even if there is no problem if it is a call, to send and receive one-time pad encryption data such as large-capacity video to multiple communication terminals, it is necessary for the terminal to send and receive one-time pad encryption key with the same amount of data as large-capacity data, There is a limit to the correspondence with only mobile communication terminals.

  Therefore, conventionally, various techniques for solving the above-described problems have been proposed (see, for example, Patent Documents 1-3).

  In Patent Document 1, when there is a possibility that the one-time pad encryption key does not completely match between the communication terminals, the encrypted communication is performed by adjusting which part of the one-time pad encryption key is used. Realize.

  In Patent Document 2, whether to encrypt communication data with a one-time pad encryption key or a block encryption key is controlled according to the number of remaining bits of the one-time pad encryption key. This makes it possible to continue encryption communication even when the one-time pad encryption key is exhausted.

  On the other hand, in Patent Document 3, a secure environment is ensured in the encrypted communication path, and in addition to arranging the relay device, the relay device has a one-time pad encryption key corresponding to the communication terminal. One-time pad encryption communication is possible between arbitrary communication terminals instead of 1.

International Publication No. 2012/025987 Pamphlet International Publication No. 2012/025988 Pamphlet JP 2014-78875 A

However, the prior art has the following problems.
In Patent Documents 1-3, before performing one-time pad encryption communication, the IDs of the one-time pad encryption keys held by each other are confirmed, and the commonly held one-time pad encryption key is derived. , Mobile communication terminals perform the process. In addition to this process, there is no process for the mobile communication terminal to confirm the amount of one-time pad encryption key held by the communication partner, and a key supply device that supplies the one-time pad encryption key to the mobile terminal. The amount of pad encryption key held is not grasped.

  Even if key consumption is performed simultaneously with the transmitting and receiving terminals, key supply is not necessarily performed simultaneously. Therefore, in the current model, there is a possibility that an unnecessary confirmation process is performed with a terminal that does not hold a common one-time pad encryption key, and there is room for improvement. In addition, when considering one-time pad encryption for calls other than one-to-one calls (for example, mail and group chat), there may be a problem in convenience that cannot be absorbed by the operation method.

  The present invention has been made in order to solve the above-described problems, and is an encryption that can be used in common between terminal devices in an encryption communication system that performs pre-distribution of encryption keys as well as one-time pad encryption communication. It is an object of the present invention to provide an encryption communication system and a control method therefor, in which a key is grasped in advance and whether or not encryption communication is possible can be determined before the start of communication processing.

  The present invention relates to a terminal device of a cryptographic communication system that performs cryptographic communication between a plurality of terminal devices using a cryptographic key distributed in advance via a relay device, and a cryptographic key bundle distributed from the key distribution device An encryption key storage unit that stores information, an owned key ID list transmission unit that periodically transmits an owned key ID list indicating the currently owned encryption key to the relay device, and is stored in the relay device or the relay device From the held key ID list of each terminal device in the communicable area of the relay device, which is periodically sent from the own key device, refer to the held key ID list of the communication partner terminal device before communication, And a cryptographic communication enable / disable determining unit that determines that cryptographic communication is possible when there is an encryption key that is common to the encryption key stored in the terminal.

  According to the present invention, in an encryption communication system that performs not only one-time pad encryption communication but also pre-distribution of encryption keys, the encryption keys that can be used in common between terminal devices are grasped in advance, and whether or not encryption communication is possible before communication processing is started. Therefore, it is possible to provide a cryptographic communication system and a control method thereof.

It is a figure which shows the structure and operation | movement outline | summary of the encryption communication system which concerns on Embodiment 1 of this invention. It is a figure which shows the structure and operation | movement outline | summary of the encryption communication system which concerns on Embodiment 2 of this invention. It is a figure which shows the structure and operation | movement outline | summary of the encryption communication system which concerns on Embodiment 3 of this invention. It is a figure which shows the structure and operation | movement outline | summary of the encryption communication system which concerns on Embodiment 4 of this invention. It is a figure which shows the structure and operation | movement outline | summary of the encryption communication system which concerns on Embodiment 5 of this invention. It is a figure which shows the structure and operation | movement outline | summary of the encryption communication system which concerns on Embodiment 6 of this invention. It is a figure which shows the outline | summary of operation | movement of an example of the relay apparatus in the encryption communication system of this invention. It is a figure which shows the outline | summary of operation | movement of another example of the relay apparatus in the encryption communication system of this invention. It is a figure which shows the outline | summary of operation | movement of another example of the relay apparatus in the encryption communication system of this invention. It is a figure which shows a structure when the three or more terminal devices in the encryption communication system of this invention are connected. It is a schematic block diagram which shows an example of the hardware constitutions of the terminal device of each embodiment of the encryption communication system which concerns on this invention, and a relay apparatus. It is a functional block diagram of an example of the terminal device which concerns on Embodiment 1, 2 of this invention. It is a functional block diagram of an example of the terminal device which concerns on Embodiment 3-6 of this invention. It is a functional block diagram of an example of the relay apparatus which concerns on Embodiment 1, 2 of this invention. It is a functional block diagram of an example of the relay apparatus concerning Embodiment 3-6 of this invention.

An encryption communication system according to the present invention is an encryption communication system including a relay device and a plurality of mobile terminal devices connected to the relay device, and the mobile terminal device periodically relays an encryption key ID held by itself. Send to device.
In addition, transmission of the encryption key ID held by the mobile terminal device to the relay device is permitted not from the mobile terminal device but from the key distribution device.
The relay device can have an encryption key ID list held by all mobile terminal devices. Therefore, the mobile terminal device can refer to the encryption key ID list of the mobile terminal device that desires encrypted communication via the relay device, and knows in advance the remaining encryption key remaining amount that can be used in common between the mobile terminal devices. In addition, since it is possible to determine whether or not encryption communication is possible before starting communication processing with the counterpart mobile terminal device, it is possible to prevent unnecessary confirmation processing through communication.
In addition, it is assumed that the relay device is a device that performs simple relaying, holds the encryption key of the mobile terminal as described in Patent Document 3, and once decrypts the encryption by the relay device, any mobile terminal device The present invention can be applied to all of these devices that enable encrypted communication or devices that perform direct communication between terminals simply by having a transmission / reception connection such as a SIP server.
Furthermore, the present invention can be applied not only to one-time pad encryption communication but also to an encryption communication system that performs pre-distribution of encryption keys.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a cryptographic communication system and a control method thereof according to the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same or corresponding reference numerals and redundant description is given. Is omitted.

  Hereinafter, in all the embodiments, communication between mobile terminals (hereinafter also referred to as terminal devices) is always performed via a relay device. The terminal device is not necessarily limited to a device that performs wireless communication such as a mobile terminal, and may be a terminal device that performs wired communication.

  Hereinafter, in all the embodiments, the one-time pad encryption key used in the terminal device and its key ID list are distributed from the key distribution device by a wired connection such as USB (universal serial bus) or a short-range wireless connection. Shall be.

  Hereinafter, in all the embodiments, a means for grasping the one-time pad encryption key held by the communication partner terminal device before the one-time pad encryption communication will be described.

  Hereinafter, in the introduction diagrams of all the embodiments, for convenience of explanation, a case where the transmitting side terminal device grasps the one-time pad encryption key of one receiving side terminal device will be described. It is possible to grasp the one-time pad encryption key of the terminal device, and there is no limit on the number of terminals due to the invention itself. Further, the encryption key is not limited to the one-time pad encryption key, and any encryption communication system using an encryption key that is pre-distributed is applicable.

Embodiment 1 FIG.
FIG. 1 is a diagram showing an outline of the configuration and operation of the cryptographic communication system according to Embodiment 1 of the present invention.
The encryption communication system performs encryption communication via the relay device 201, for example, the terminal device A101 and the terminal device B102, which are mobile terminal devices, and the terminal device A101, the terminal device B102, the relay device 201 and the like. It consists of a key distribution device 301 communicatively connected so as to distribute.
In FIG. 1, the terminal device A 101 and the terminal device B 102 receive, for example, a bundle of OTP keys, which are encryption keys capable of mutual encryption communication, from the key distribution device 301 in advance. However, the OTP key ring OTPKS-A (including 1, 2, 3) owned by the terminal apparatus A 101 and the OTP key ring OTPKS-B (including 2, 3, 4) owned by the terminal apparatus B 102 are completely It does not correspond to. Also, the terminal device A101 stores the owned key ID list KIDL-A of the currently owned OTP key ring OTPKS-A, and the terminal device B102 stores the owned key ID list KIDL-B of the currently owned OTP key ring OTPKS-B. In possession. The one-time pad encryption communication is performed via the relay device 201.

  In the first embodiment, the terminal device A 101 and the terminal device B 102 periodically transmit the possessed key ID lists KIDL-A and KIDL-B of the OTP key ring possessed by the confidence to the relay device 201. The relay apparatus 201 receives and holds the possessed key ID list KIDL-A from the terminal apparatus A101 and the retained key ID list KIDL-B from the terminal apparatus B102.

  The terminal device A101 communicates with the relay device 201 before the one-time pad encryption communication with the terminal device B102, and refers to the possessed key ID list KIDL-B of the terminal device B102 to determine whether the one-time pad encryption communication is possible. Determine. In the example of FIG. 1, since there is a common OTP key, one-time pad encryption communication is possible. If there is no OTP key held in common, the terminal device A 101 can determine that there is no OTP key held in common when the terminal device A 101 communicates with the relay device 201, and performs unnecessary communication with the terminal device B 102. No need.

  FIG. 11 shows an example of the hardware configuration of each terminal device (101, 102, 103) and each relay device (201, 201a, 201b, 201c) of the cryptographic communication system according to the present invention including each embodiment described later. The schematic block diagram which shows is shown. In FIG. 11, a wireless / wired communication device 123a capable of wireless and wired communication, a processor 123b, a processing program executed by the processor 123b, and a memory 123c storing various data relating to the processing, such as a display with a touch panel, etc. A human interface device (HID) 123d through which information is displayed and a user inputs data and information is connected to the bus line BL by a bus.

FIG. 12 shows a functional block diagram of an example of the terminal device 10n (101, 102, 103) according to the first and second embodiments of the present invention. The terminal device 10n includes an encryption key storage unit 10n-1, a possessed key ID list transmission unit 10n-2, an encryption communication availability determination unit 10n-3, and a communication unit 10n-4.
FIG. 14 shows a functional block diagram of an example of the relay device 201 (201, 201a, 201b, 201c) according to the first and second embodiments of the present invention. The relay device 201 includes an owned key ID list storage unit 201-1, an owned key ID list inquiry receiving unit 201-2, an owned key ID list providing unit 201-3, and a communication unit 201-4.
Each of these functions is executed by the processor 123b in accordance with a program stored in advance in the memory 123c.

The encryption key storage unit 10n-1 of the terminal device A101 in FIG. 12 receives the encryption key bundle OTPKS-A distributed from the key distribution device 301 by the wireless / wired communication device 123a and stores it in the memory 123c. Similarly, the encryption key storage unit 10n-1 of the terminal device B102 also receives the encryption key bundle OTPKS-B distributed from the key distribution device 301 by the wireless / wired communication device 123a and stores it in the memory 123c.
The possessed key ID list transmitting unit 10n-2 of the terminal device A101 periodically transmits the retained key ID list KIDL-A indicating the currently owned encryption key OTPK to the relay device 201 by the wireless / wired communication device 123a. In FIG. 1, the possessed key ID list KIDL-A transmitted from the terminal device A101 indicates the OTP keys 1, 2, and 3.
Similarly, the possessed key ID list transmission unit 10n-2 of the terminal device B102 also periodically transmits the retained key ID list KIDL-B indicating the encryption key OTPK currently retained to the relay device 201 by the wireless / wired communication device 123a. In FIG. 1, the possessed key ID list KIDL-B transmitted from the terminal device B102 indicates the OTP keys 2, 3, and 4.
For example, when performing cryptographic communication from the terminal device A101 to the terminal device B102, the encryption communication availability determination unit 10n-3 of the terminal device A101 communicates with the relay device 201 by the wireless / wired communication device 123a, and the relay device 201 From the possessed key ID lists KIDL-A and KIDL-B of the terminal apparatuses 101 and 102 in the communicable area of the relay apparatus 201 stored in the memory 123c, the retained key ID list KIDL-B of the terminal apparatus B102 of the communication counterpart Is determined before communication, and it is determined that encryption communication is possible when there is an encryption key OTPK that is common to the encryption key OTPK in the encryption key bundle OTPKS-A stored in the memory 123c of the terminal device A101.
If it is determined by the encryption communication availability determination unit 10n-3 that encryption communication is possible, the communication unit 10n-4 of the terminal device A101 uses the wireless / wired communication device 123a to store the memory of the terminal device A101 via the relay device 201, for example. Encrypted communication with the terminal apparatus B102 is performed using the common encryption key OTPK stored in 123c.

  On the other hand, in the relay device 201, the possessed key ID list storage unit 201-1 in FIG. 14 is periodically transmitted from each terminal device 101, 102 by the wireless / wired communication device 123a. , KIDL-B is received and stored in the memory 123c. Then, for example, when there is a reference request for the possessed key ID list KIDL-B of the terminal device B102 which is a desired communication partner from the terminal device A101, the retained key ID list reference accepting unit 201-2 receives the request for the retained key ID list according to the request. Enable browsing. When performing cryptographic communication between the terminal device A101 and the terminal device B102, the communication unit 201-4 of the relay device 201 uses the wireless / wired communication device 123a of the relay device 201 to connect the terminal device A101 and the terminal device B102. Mediates cryptographic communication between them.

  It should be noted that the encryption key bundle OTPKS distributed from the key distribution device 301 to the terminal devices 101 and 102 may be common to the terminal devices 101 and 102 (OTPKS) or may be partially different (OTPKS (A)). , OTPKS (B)). The possessed key ID list KIDL or the retained key ID lists KIDL (A) and KIDL (B) indicating the encryption key bundle OTPKS may be distributed from the key distribution apparatus 301 to the terminal apparatuses 101 and 102 together with the encryption key bundle OTPKS. Alternatively, the encryption key bundle OTPKS distributed in the encryption key storage unit 10n-1 of each terminal device 101, 102 may be generated and stored. When the encryption key OTP is a one-time disposable encryption key such as a one-time pad encryption key, the encryption key storage unit 10n-1 deletes the used encryption key OTPK from the memory 123c, and in accordance with this deletes the memory 123c. The key ID of the encryption key OTPK deleted from the possessed key ID list KIDL stored in is deleted and updated.

Embodiment 2. FIG.
FIG. 2 is a diagram showing an outline of the configuration and operation of the cryptographic communication system according to Embodiment 2 of the present invention. The difference between the second embodiment and the first embodiment is that the relay device 201 sends each terminal device 101, 102 to the key ID list of each terminal device (for example, all terminal devices) in the communicable area of the relay device 201. The terminal possessed key ID list KIDL-ALL is periodically transmitted, and the terminal devices 101 and 102 thereby determine whether or not encryption communication such as one-time pad encryption communication to the partner terminal device is possible. That is the point.

  In the possessed key ID list providing unit 201-3 of the relay device 201 shown in FIG. 14, the terminal possessed key that is the retained key ID list of each of the terminal devices 101 and 102 in the communicable area stored in the memory 123c of the relay device 201. The ID list KIDL-ALL is periodically sent to each of the terminal devices 101 and 102 by the wireless / wired communication device 123a. Thereby, for example, the encryption communication permission determination unit 10n-3 of the terminal device 10n of FIG. 12 can obtain the possessed key ID list KIDL-B of the communication partner terminal device 102 without performing communication with the relay device 201.

  The cryptographic communication system according to the following embodiments is particularly effective for a cryptographic communication system that uses a one-time-use cryptographic key.

Embodiment 3 FIG.
FIG. 3 is a diagram showing an outline of the configuration and operation of the cryptographic communication system according to Embodiment 3 of the present invention. The third embodiment differs from the first embodiment in the following three points.
First, the relay apparatus 201 obtains from the key distribution apparatus 301 an all-key ID list KIDL-ALL that is a key ID list of each terminal apparatus 101 and 102.
Secondly, each terminal device 101, 102 sends a used key ID list (U-KIDL-A, U-KIDL-B) to the relay device 201 instead of the owned key ID list (KIDL-A, KIDL-B). To send.
Thirdly, the relay device 201 transmits the key ID list KIDL-ALL of each terminal device transmitted from the key distribution device 301 and the used key ID list (U-KIDL-) transmitted from each terminal device (101, 102). A, U-KIDL-B) and the latest key ID lists (L-KIDL-A, L-KIDL-B) that are the latest key ID lists currently held by the terminal devices (101, 102) ).

In the case of this Embodiment 3,
The terminal apparatuses 101 and 102 periodically transmit only the used key ID list U-KIDL indicating the used key IDs, not the key ID list KIDL indicating the key IDs of all the encryption keys OTPKS owned by the terminal devices 101 and 102. There is,
The used key ID list U-KIDL once transmitted to the relay device 201 does not need to be transmitted twice;
From the above two points, there is an advantage that even if the transmission line from the terminal apparatus 101, 102 to the relay apparatus 201 is very weak, it can be operated without any trouble.

FIG. 13 shows a functional block diagram of a terminal device 10n (101, 102, 103) according to Embodiment 3-6 of the present invention. The terminal device 10n includes an encryption key storage unit 10n-1, a used key ID list transmission unit 10n-5, an encryption communication availability determination unit 10n-3, and a communication unit 10n-4.
FIG. 15 is a functional block diagram showing an example of a relay device 201 (201, 201a, 201b, 201c) according to Embodiment 3-6 of the present invention. The relay device 201 includes a key ID list storage unit 201-5, a key ID list changing unit 201-6, a latest key ID list providing unit 201-7, and a communication unit 201-4.
Each of these functions is executed by the processor 123b in accordance with a program stored in advance in the memory 123c.

The encryption key storage unit 10n-1 of the terminal device A101 in FIG. 13 receives the encryption key bundle OTPKS-A distributed from the key distribution device 301 by the wireless / wired communication device 123a and stores it in the memory 123c. Similarly, the encryption key storage unit 10n-1 of the terminal device B102 also receives the encryption key bundle OTPKS-B distributed from the key distribution device 301 by the wireless / wired communication device 123a and stores it in the memory 123c.
The used key ID list transmission unit 10n-5 of the terminal device A101 transmits the used key ID list U-KIDL-A indicating the used encryption key OTPK to the relay device 201 by the wireless / wired communication device 123a. For example, in FIG. 3, the used key ID list U-KIDL-A transmitted from the terminal device A 101 indicates the OTP key 1.
Similarly, the used key ID list transmission unit 10n-5 of the terminal device B102 also sends the used key ID list U-KIDL-B indicating the used encryption key OTPK to the relay device 201 by the wireless / wired communication device 123a. For example, in FIG. 3, the used key ID list U-KIDL-B transmitted from the terminal apparatus B102 indicates the OTP keys 1 and 2.
For example, when performing cryptographic communication from the terminal device A101 to the terminal device B102, the encryption communication availability determination unit 10n-3 of the terminal device A101 communicates with the relay device 201 by the wireless / wired communication device 123a, and the relay device 201 From the key ID list KIDL-ALL of each terminal device 101, 102 distributed from the key distribution device 301 to the relay device 201, stored in the memory 123c, the used key ID list U-KIDL from each terminal device 101, 102 The latest key ID list L-KIDL of the terminal device B102 of the communication partner is selected from the latest key ID list L-KIDL-ALL of the terminal devices 101 and 102 from which the encryption key IDs of A and U-KIDL-B are respectively deleted. -B is referred to before communication, and it is stored in the encryption key ring OTPKS-A stored in the memory 123c of the own terminal device A101. Determining possible cryptographic communication when there is an encryption key OTPK in common with No. key OTPK.

On the other hand, in the relay device 201, the key ID list storage unit 201-5 in FIG. 14 receives the key ID list KIDL-ALL of each terminal device 101, 102 distributed from the key distribution device 301 by the wireless / wired communication device 123a. And stored in the memory 123c.
Then, the key ID list changing unit 201-6 uses the wireless / wired communication device 123 a to obtain the used key ID lists U-KIDL-A and U-KIDL-B indicating the used encryption keys from the terminal devices 101 and 102. The corresponding key ID list KIDL in the key ID list KIDL-ALL received by the key ID list storage unit 201-5 is used as the used key ID list U-KIDL-A or the used key ID list U. -The key ID of KIDL-B is deleted and changed to the latest key ID list L-KIDL.

Embodiment 4 FIG.
FIG. 4 is a diagram showing an outline of the configuration and operation of the cryptographic communication system according to Embodiment 4 of the present invention. The difference between the fourth embodiment and the third embodiment is that the relay device 201 sends the used keys of each terminal device (for example, all terminal devices) in the communicable area of the relay device 201 to each terminal device 101, 102. The latest key ID list L-KIDL-ALL from which the ID list U-KIDL has been removed is transmitted, and the terminal devices 101 and 102 use the latest key ID list L-KIDL-ALL to perform one-time pad encryption communication to the partner terminal device, etc. In other words, it is determined whether or not encryption communication is possible.

  The latest key ID list providing unit 201-7 of the relay device 201 illustrated in FIG. 15 is the latest key ID list that is currently held by each of the terminal devices 101 and 102 in the communicable area stored in the memory 123c of the relay device 201. The key ID list L-KIDL-ALL is periodically sent to each of the terminal devices 101 and 102 by the wireless / wired communication device 123a. Accordingly, for example, the encryption communication availability determination unit 10n-3 of the terminal device 10n in FIG. 13 does not communicate with the relay device 201 and becomes the latest key ID list KIDL-B that becomes the possessed key ID list KIDL-B of the communication partner terminal device 102. L-KIDL-B can be obtained.

Embodiment 5. FIG.
FIG. 5 is a diagram showing an outline of the configuration and operation of the cryptographic communication system according to Embodiment 5 of the present invention. The difference from the third embodiment is that the terminal devices 101 and 102 periodically perform a key ID list matching process using an OTP key and a key ID list held in the terminal device 101 and 102 to extract a used key ID. The used key ID list is a used key ID list indicating a used key ID after the key ID list is compared. As a result, it becomes possible to add an OTP key that has been lost for some reason other than OTP communication that cannot be reflected in the third embodiment to the used key ID list, thereby further improving the completeness of the cryptographic communication system. Can do.

The used key ID list transmission unit 10n-5 of the terminal device A101 shown in FIG. 13 uses the encryption key currently held from the key ID of the held key ID list KIDL-A of the encryption key bundle OTPKS-A stored in the memory 123c. A used key ID list LU-KIDL-A including the used key obtained by subtracting the key ID of OTPK and the lost encryption key is generated and sent to the relay apparatus 201 by the wireless / wired communication device 123a. For example, in FIG. 5, the used key ID list LU-KIDL-A transmitted from the terminal device A 101 indicates that the used key 1 and the lost encryption key 4 are included.
Similarly, the used key ID list transmission unit 10n-5 of the terminal device B102 also stores the encryption key OTPK currently held from the key ID of the held key ID list KIDL-B of the encryption key bundle OTPKS-B stored in the memory 123c. A used key ID list LU-KIDL-B including the used key obtained by subtracting the key ID and the lost encryption key is generated and sent to the relay apparatus 201 by the wireless / wired communication device 123a. For example, in FIG. 5, the used key ID list LU-KIDL-B transmitted from the terminal device B 102 shows that the used keys 1 and 2 and the lost encryption key 3 are included.
Note that the used key ID list (LU-KIDL) may be transmitted separately into a used key ID list and a lost encryption key ID list as indicated by broken lines in FIG.

Embodiment 6 FIG.
FIG. 6 is a diagram showing an outline of the configuration and operation of the cryptographic communication system according to Embodiment 6 of the present invention. The difference between the sixth embodiment and the fifth embodiment is that the relay device 201 sends the used keys of the terminal devices (for example, all the terminal devices) in the communicable area of the relay device 201 to the terminal devices 101 and 102. The latest key ID list L-KIDL-ALL from which the ID list LU-KIDL has been removed is transmitted, and the terminal devices 101 and 102 use the latest key ID list L-KIDL-ALL to perform one-time pad encryption communication to the partner terminal device, etc. In other words, it is determined whether or not encryption communication is possible.

  The latest key ID list providing unit 201-7 of the relay device 201 illustrated in FIG. 15 is the latest key ID list that is currently held by each of the terminal devices 101 and 102 in the communicable area stored in the memory 123c of the relay device 201. The key ID list L-KIDL-ALL is periodically sent to each of the terminal devices 101 and 102 by the wireless / wired communication device 123a. Accordingly, for example, the encryption communication availability determination unit 10n-3 of the terminal device 10n in FIG. 13 does not communicate with the relay device 201 and becomes the latest key ID list KIDL-B that becomes the possessed key ID list KIDL-B of the communication partner terminal device 102. L-KIDL-B can be obtained.

In addition, the following can be applied as a relay apparatus of each embodiment of this invention.
The relay device 201a in FIG. 7 performs only data transmission of encrypted communication between the terminal devices 101 and 102 using the encrypted data ED.
The relay apparatus 201b in FIG. 8 decrypts encryption during the encryption communication between the terminal apparatuses 101 and 102. That is, after the encrypted data ED1 with the encryption key OTPKA from the terminal device A101 on the transmission side is converted into plain text PT, the plain text PT is converted into the encrypted data ED2 with the encryption key OTPKB of the terminal device 102 on the reception side and sent. As a result, encrypted communication with any sender / receiver becomes possible.
The relay apparatus 201c in FIG. 9 performs communication related only to the above-described communication availability determination at the start of connection between the terminal apparatuses 101 and 102. Communication after it is determined that connection is possible is performed directly between the terminal apparatuses 101 and 102.

  Furthermore, the cryptographic communication system according to each embodiment of the present invention may be configured to perform cryptographic communication among three or more terminal devices A101, B102, and C103 as shown in FIG.

Industrial applicability

  The terminal device of the encryption communication system, the relay device of the encryption communication system, and the control method of the encryption communication system according to the present invention can be applied to encryption communication in various fields.

The present invention relates to a terminal device of a cryptographic communication system that performs cryptographic communication between a plurality of terminal devices using a cryptographic key distributed in advance via a relay device, and a cryptographic key bundle distributed from the key distribution device An encryption key storage unit for storing, a retention key ID list transmission unit for periodically transmitting a retention key ID list indicating the encryption key currently retained to the relay device, and a periodic transmission from the relay device , From the possessed key ID list of each terminal device within the communicable area of the relay device, refer to the retained key ID list of the communication partner terminal device before communication, and is common with the encryption key stored in the own terminal device A terminal device or the like of an encryption communication system including an encryption communication availability determination unit that determines that encryption communication is possible when there is an encryption key.

Claims (17)

A terminal device of a cryptographic communication system that performs cryptographic communication via a relay device between a plurality of terminal devices using an encryption key distributed in advance,
An encryption key storage unit for storing an encryption key ring distributed from the key distribution device;
A holding key ID list transmission unit that periodically sends a holding key ID list indicating the encryption key currently held to the relay device;
From the possessed key ID list of each terminal device in the communicable area of the relay device, stored in the relay device or periodically sent from the relay device, the retained key of the communication partner terminal device An encryption communication availability determination unit that refers to the ID list before communication and determines that encryption communication is possible when there is an encryption key that is common to the encryption key stored in the terminal device;
A terminal device of a cryptographic communication system comprising: A terminal device of a cryptographic communication system that performs cryptographic communication between a plurality of terminal devices via a relay device using a one-time disposable cryptographic key distributed in advance,
An encryption key storage unit for storing an encryption key ring distributed from the key distribution device;
A used key ID list transmission unit for sending a used key ID list indicating the used encryption key to the relay device;
Each terminal device from the key ID list of the encryption key bundle of each terminal device stored in the relay device or periodically sent from the relay device and distributed from the key distribution device to the relay device From the latest key ID list from which the encryption key ID of the used key ID list is deleted, the latest key ID list of the communication partner terminal device is referred to before communication, and the encryption key stored in the own terminal device An encryption communication availability determination unit that determines that encryption communication is possible when there is a common encryption key;
A terminal device of a cryptographic communication system comprising:   The used key ID list including a used key and a lost encryption key obtained by subtracting the key ID of the encryption key currently held from the key ID of the key ID list of the encryption key bundle by the used key ID list transmission unit The terminal device of the cryptographic communication system according to claim 2, wherein:   The terminal device of the encryption communication system according to any one of claims 1 to 3, wherein encryption communication is performed using a one-time pad encryption key as the encryption key. A relay device of a cryptographic communication system that performs cryptographic communication between a plurality of terminal devices via a relay device using an encryption key distributed in advance,
A possessed key ID list storage unit for storing a retained key ID list indicating a currently retained encryption key of encryption key bundles distributed to each from the key distribution device, which is periodically sent from each terminal device;
A holding key ID list reference receiving unit that enables reference to the holding key ID list according to a reference request of the holding key ID list of a terminal device of a desired communication partner from each terminal device;
With
Each terminal device determines whether communication is possible according to the possessed key ID list of the communication partner terminal device,
A relay device for a cryptographic communication system.   6. The cryptographic communication system according to claim 5, further comprising a possessed key ID list providing unit that periodically transmits the retained key ID list of each terminal device within the communicable area of the relay device to each of the terminal devices. Relay device. A relay device of a cryptographic communication system that performs cryptographic communication between a plurality of terminal devices via a relay device using a one-time-use cryptographic key distributed in advance,
A key ID list storage unit for storing a key ID list of an encryption key bundle of each terminal device distributed from a key distribution device;
Upon receipt of a used key ID list indicating the used encryption key from each terminal device, the corresponding key ID list in the key ID list storage unit is deleted, and the key ID in the used key ID list is deleted. A key ID list changing unit for changing to the latest key ID list;
With
The plurality of terminal devices determine whether communication is possible according to the latest key ID list of a communication partner terminal device,
A relay device for a cryptographic communication system.   8. The cryptographic communication system according to claim 7, further comprising a latest key ID list providing unit that periodically sends the latest key ID list of each terminal device in the communicable area of the relay device to each of the terminal devices. Relay device.   The used key ID list from each terminal device includes a used key and a lost encryption key obtained by subtracting the key ID of the encryption key currently held from the key ID of the key ID list of the encryption key bundle. The relay apparatus of the cryptographic communication system according to claim 7 or 8, wherein   The relay apparatus for a cryptographic communication system according to any one of claims 5 to 9, wherein cryptographic communication is performed using a one-time pad cryptographic key as the cryptographic key. The relay device is
Performing only data transmission of encryption communication between the terminal devices,
After converting encrypted data with an encryption key from the terminal device on the transmission side into plain text, and then converting the plain text into encrypted data with an encryption key of the terminal device on the reception side and sending it,
Those that perform communication related only to whether communication is possible,
The relay apparatus for a cryptographic communication system according to any one of claims 5 to 10, which is any one of the following. A control method of an encryption communication system that performs encryption communication between a plurality of terminal devices via a relay device using an encryption key distributed in advance,
Distributing each encryption key ring from the key distribution device to each terminal device and storing it;
A step of periodically sending a stored key ID list indicating the encryption key currently held from each terminal device to the relay device for storage;
In each terminal device, refer to the possessed key ID list of the communication partner terminal device before communication from the retained key ID list of each terminal device in the communicable area of the relay device stored in the relay device. And determining that encryption communication is possible when there is an encryption key common to the encryption key stored in the terminal device;
A method for controlling a cryptographic communication system comprising: The relay device further comprises a step of periodically sending the retained key ID list of each terminal device in the communicable area of the relay device stored therein to each of the terminal devices,
Each terminal device determines whether or not encryption communication is possible from the possessed key ID list sent from the relay device,
The method for controlling a cryptographic communication system according to claim 12. A method for controlling a cryptographic communication system that performs cryptographic communication between a plurality of terminal devices via a relay device using a one-time disposable cryptographic key distributed in advance,
Distributing each encryption key ring to each terminal device from a key distribution device and storing it;
Sending the key ID list of the encryption key ring sent to each terminal device from the key distribution device to the relay device for storage;
Sending a used key ID list indicating the used encryption key from each terminal device to the relay device;
In the relay device, deleting the encryption key ID of the used key ID list from the terminal device from the stored key ID list of the terminal device, respectively, and storing as a latest key ID list;
In each of the terminal devices, the latest key ID list stored in the relay device is referred to the latest key ID list of the communication partner terminal device before communication, and the encryption key stored in the own terminal device is shared. Determining that encryption communication is possible when there is an encryption key to be processed;
A method for controlling a cryptographic communication system comprising: The relay device further comprises a step of periodically sending the latest key ID list of each terminal device in the communicable area of the relay device stored therein to each of the terminal devices,
Each terminal device determines whether or not encryption communication is possible from the latest key ID list sent from the relay device;
The method for controlling a cryptographic communication system according to claim 14.   Each terminal device provides the relay device with the used key ID list including the used key and the lost encryption key obtained by subtracting the key ID of the currently held encryption key from the key ID of the key ID list of the encryption key bundle. The method of controlling a cryptographic communication system according to claim 14 or 15, wherein the method is controlled.   The method for controlling an encryption communication system according to any one of claims 12 to 16, wherein encryption communication is performed using a one-time pad encryption key as the encryption key.

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