JP4917116B2 - Data encryption system, communication device, and data encryption method - Google Patents

Description

  The present invention relates to a data encryption system that performs data encryption, a communication device included in the data encryption system, and a data encryption method.

  2. Description of the Related Art Conventionally, portable electronic media such as notebook PCs (Personal Computers) and mobile phones have been increasingly carried with data such as trade secrets and personal information stored therein. These electronic media are carried around. Since it is easy, the possibility of losing is high. In recent years, social awareness about information security has increased. For this reason, various methods for preventing information leakage from data stored in an electronic medium have been studied (for example, see Patent Document 1).

  As one of the methods for preventing the above information leakage, data in electronic media is encrypted, password authentication at the time of decryption, use of USB (Universal Serial Bus) memory for decryption, and distribution of encryption keys A method of increasing security by restricting the decryption of data encrypted by using, for example, is also used.

JP 2008-139996 A

  However, when security management related to the above-described data decryption is adopted, if there is a means for decryption (password, USB memory, distributed encryption key, etc.), the data can be decrypted regardless of time and place. can do. Therefore, for example, when a malicious third party obtains the above-described means for decryption, it is difficult to maintain security because decryption can be easily performed.

  The present invention has been made in view of the above, and an object of the present invention is to provide a data encryption system, a communication device, and a data encryption method with improved security.

In order to achieve the above object, a data encryption system according to the present invention includes one host device that holds encryption target data to be encrypted, a plurality of member devices that are different from the host device, a data encryption system according to a plurality of communication devices consisting of said host device, said plurality of the number of communication devices is n, when the threshold is k, a n> k, and the When information specifying a plurality of communication devices is notified to each other and the information is held in each of the plurality of communication devices, it is determined that the plurality of communication devices configure the same network. At the time of encryption, an encryption method for creating encrypted data obtained by encrypting the encryption target data by using an encryption method including a procedure for collecting partial data related to the encryption target data. A distribution unit that distributes the encrypted data and generates n different pieces of secret sharing data that are partial data related to the data to be encrypted; and n−1 member devices. Distribution means for distributing n-1 secret sharing data different from each other.

Further, the host device included in the data encryption system according to the present invention includes one host device that holds encryption target data to be encrypted, a plurality of member devices that are different from the host device, a host device included in the data encryption system according to a plurality of communication devices consisting of said number of plurality of communication devices is n, when the threshold is k, a n> k, and the When information specifying a plurality of communication devices is notified to each other and the information is held in each of the plurality of communication devices, it is determined that the plurality of communication devices configure the same network. At the time of encryption, encrypted data obtained by encrypting the encryption target data is created using an encryption method including a procedure of collecting partial data related to the encryption target data. An encryption unit, a distribution unit that distributes the encrypted data and generates n different pieces of secret sharing data that are partial data related to the data to be encrypted; and n−1 member devices. Distribution means for distributing n-1 secret sharing data different from each other.

In addition, the data encryption method according to the present invention provides a plurality of communications including one host device that holds encryption target data that is an encryption target and a plurality of member devices that are different from the host device. A data encryption method by a data encryption system comprising devices, wherein n> k when the number of the plurality of communication devices is n and the threshold value is k by the encryption means of the host device. And the information specifying the plurality of communication devices is notified to each other, and by holding these pieces of information in the plurality of communication devices, it is specified that the plurality of communication devices constitute the same network. case, encryption by encrypting the encryption target data using the encryption method comprising the steps during decoding to collect partial data related to the encryption target data An encryption step for generating data, and a distribution step for distributing the encrypted data by the distribution means of the host device to generate n different secret sharing data that are partial data related to the data to be encrypted And a distribution step of distributing different n-1 secret sharing data to each of the n-1 member devices by the distribution unit of the host device.

  According to the data encryption system, the communication device included in the data encryption system, and the data encryption method, the network is configured between the plurality of communication devices that are physically close to each other. When the secret sharing data of the data to be encrypted is decrypted by the host device included in the network configured by the n communication devices determined by the above, partial data related to the data to be encrypted (that is, the secret sharing data) ) And is distributed to the host device and the member device. Here, when encrypting the data to be encrypted, it is determined that the plurality of communication devices are physically close to each other, and encryption is performed after configuring a network capable of sharing this information. Therefore, the security of the secret sharing data created using this data encryption system can be improved as compared with the case where the data is encrypted by the conventional encryption method.

  Here, as a configuration that effectively exhibits the above-described operation, specifically, an aspect in which the network is an ad hoc network can be given.

  Further, as another configuration that effectively achieves the above-described operation, specifically, the encryption unit is configured so that each of the plurality of communication devices obtains position information of the communication device, and the position information is obtained from the plurality of pieces of position information. A mode in which the encrypted data is created when it is determined that the plurality of communication devices are physically close to each other by sharing in a network configured between the communication devices.

  Further, as another configuration that effectively exhibits the above-described operation, specifically, an aspect in which the encryption method is a threshold secret sharing scheme can be cited.

  Here, the data encryption system further includes a management server connected to the plurality of communication devices via a wireless communication network, and the host device is different from the encryption target data and the n pieces of data. Data transmission means for transmitting secret sharing data to the management server, wherein the management server receives the encryption target data and the n different secret sharing data from the host device. It can be set as the aspect provided with a data storage means.

  Further, the member device stores a secret sharing data distributed from the host device, and transmits the secret sharing data stored in the storing device to the management server. Secret distribution data verification means for requesting verification of validity and receiving the result of verification of validity transmitted from the management server, wherein the management server distributes the secret distribution from the member devices Receiving data, verifying the validity of the secret sharing data from the member device based on the n different secret sharing data and the encryption target data transmitted from the host device, It can be set as the aspect further provided with the validity verification means transmitted with respect to a member apparatus.

  By adopting the above aspect, it is possible to verify the validity of the member data that is the secret sharing data stored in the member device based on the data to be encrypted stored in the management server and the n secret sharing data. it can. Therefore, it is possible to confirm whether or not the secret sharing data stored in the member device has been tampered with, and it is possible to prevent data from being decrypted using the falsified secret sharing data.

  Here, as a configuration that effectively performs the above-described operation, specifically, the validity verification unit includes the n-number of different secret sharing data transmitted from the host device and the member device from the member device. Decrypted using k−1 secret shared data different from secret shared data and the secret shared data from the member device, and the decrypted data and the encryption target data from the host device And when the data to be encrypted and the decrypted data match, it is determined that the validity of the secret sharing data from the member device has been verified.

  In addition, the decryption device included in the plurality of communication devices that decrypts the encryption target data includes k decryption devices and other communication devices that hold the secret sharing data. Configuring a decryption network for determining that the decryption device and the other communication device are physically close to each other, and sharing the secret from the other communication device via the decryption network Secret shared data acquisition means for acquiring k−1 or more data, and decryption means for performing decryption using the acquired secret shared data and the secret shared data held in the decryption device to generate decrypted data And further comprising.

  As described above, the decryption device, which is a communication device that performs decryption, includes the secret sharing data acquisition unit and the decryption unit, thereby determining whether the decryption device and the other communication device are physically close to each other. The secret sharing data can be obtained from another communication device via the decryption network for decrypting the data. In this way, only in the case where the decryption network is configured, the data can be decrypted, so that the encryption target data can be decrypted by a third party who cannot configure the decryption network. Since decryption can be avoided, data can be handled under higher security management.

  In addition, the decryption device included in the plurality of communication devices that decrypts the encryption target data includes k decryption devices and other communication devices that hold the secret sharing data. When a decoding network for determining that the decoding device and the other communication device are physically close to each other is configured, k is transmitted from the other communication device via the decoding network. -1 or more secret sharing data acquisition means for acquiring the secret sharing data whose validity has been verified, decryption using the acquired secret sharing data and the secret sharing data held in the decrypting device, And a decoding unit that generates the decoded data.

  As described above, when the decryption device acquires k or more pieces of secret shared data whose validity has been verified from the communication devices constituting the decryption network, the decryption device generates decrypted data by performing decryption. Thus, the decryption can be performed using only the secret sharing data whose validity has been verified in advance by the management server, so that the data to be encrypted can be decrypted more reliably.

  Here, as a configuration that effectively exhibits the above-described operation, specifically, an aspect in which the decoding network is an ad hoc network can be cited.

  The decoding device may further include a deletion unit that deletes the decoded data held by the decoding device when the number of communication devices constituting the decoding network is equal to or less than k. Good.

  As described above, when the number of communication devices configuring the decoding network is smaller than the threshold value k, the decoded data is deleted by deleting the decoded data decoded in each communication device. The risk of being referred to by a third party or the like can be reduced, and security is further improved.

  The decoding device further includes position information acquisition means for acquiring position information of the decoding device, and position information transmission means for transmitting the position information to the management server. In the storage means, the decryption device further stores a decryption condition indicating position information that is a condition for performing decryption using the secret sharing data, and the position information from the decryption device is the decryption condition. If it is determined that the decryption condition is satisfied, k−1 pieces of secret shared data different from the secret shared data held by the decryption device are transmitted to the decryption device. And further comprising a decryption condition determination means, wherein the decryption means of the decryption device uses secret shared data transmitted from the management server and secret shared data held in the decryption device It performs decoding may be a mode for generating decoded data.

  When it is set as said aspect, the decoding apparatus itself acquires the positional information on a decoding apparatus, and transmits this with respect to a management server. When the management server determines that the information transmitted from the decryption device satisfies the decryption condition, k−1 pieces of secret sharing data are transmitted to the decryption device. For this reason, the decoding device can perform data decoding not when the above-described decoding network is configured, but when the management server determines that a predetermined decoding condition is satisfied. Therefore, since the data is not decrypted unless the decryption device satisfies the decryption condition, the security can be improved. Further, according to this aspect, even when the decryption device cannot configure the above-described decryption network with another communication device, data decryption is realized with high security. .

  The decoding device further includes position information acquisition means for acquiring position information of the decoding device, and position information transmission means for transmitting the position information to the management server. In the storage means, the decryption device becomes a condition for performing decryption using the secret sharing data, and further stores an individual decryption condition indicating position information different for each communication device holding the secret sharing data, When the position information from the decoding device determines whether or not the dedicated decoding condition is satisfied, and there are k or more communication devices that are determined to satisfy the dedicated decoding condition, including the decoding device, The apparatus further comprises decryption condition determining means for transmitting to the decryption device k-1 secret share data different from the secret share data held by the decryption device. It means performs decoding using a secret sharing data held in the secret sharing data and the decryption device transmitted from the management server may be a mode for generating decoded data.

  As in the above-described aspect, only when k or more devices satisfy the individual decoding condition predetermined for each device among the communication devices including the decoding device, k− from the management server. One piece of secret sharing data is transmitted to the decryption device, and decryption data is generated in the decryption device. Therefore, even when a plurality of communication devices including a decoding device does not constitute the above-described decoding network, decoding is not performed unless k communication devices satisfy the individual decoding conditions. Security can be improved. Further, even when the decryption device cannot configure the above-described decryption network with another communication device, data decryption can be realized with high security.

  Here, the decoding device may further include a deletion unit that deletes the decoded data held by the decoding device when the decoding device no longer satisfies the decoding condition after decoding. .

  In this way, when the decryption device does not satisfy the decryption conditions after decryption, the risk that the decrypted data is referred to by a third party or the like is eliminated by deleting the decrypted data decrypted by the decryption device. It can be reduced, and security is further improved.

  According to the present invention, a data encryption system, a communication device, and a data encryption method with improved security are provided.

It is a figure explaining the structure of the data encryption system 1 which concerns on 1st Embodiment of this invention. 2 is a diagram illustrating a hardware configuration of a communication terminal 10. FIG. 2 is a diagram illustrating a hardware configuration of a management server 20. FIG. It is a figure explaining the function part contained in the communication terminal 10 which concerns on 1st Embodiment. It is a figure explaining the function part contained in the management server 20 which concerns on 1st Embodiment. It is a figure which shows the example of the data stored in the management server 20 in 1st Embodiment. It is a sequence diagram explaining the data encryption method by the data encryption system 1 which concerns on 1st Embodiment. FIG. 5 is a sequence diagram for explaining a series of processes related to validity verification between a communication terminal 10 _m that is a member terminal that performs validity verification in the first embodiment and a management server 20. It is a flowchart explaining the method of the validity verification in the management server 20 in 1st Embodiment. It is a sequence diagram explaining a series of processes concerning the decryption of secret sharing data in the first embodiment. It is a flowchart explaining the collection | recovery method of the secret sharing data in the middle stage of a decoding in 1st Embodiment. It is a sequence diagram explaining the process which concerns on deletion of decoding data in 1st Embodiment. It is a conceptual diagram explaining the outline | summary of the process demonstrated in 2nd Embodiment. It is a block diagram explaining the function part contained in the communication terminal 10 in 2nd Embodiment. It is a figure which shows the example of the data which concern on the decoding conditions stored in the management server. It is a sequence diagram explaining the data encryption method in 2nd Embodiment. It is a sequence diagram explaining the process at the time of decrypting encryption object data in 2nd Embodiment. It is a conceptual diagram explaining the conditions at the time of deleting decoding data in 2nd Embodiment. It is a flowchart explaining the process which concerns on decoded data in 2nd Embodiment. It is a conceptual diagram explaining the outline | summary of the process demonstrated in 2nd Embodiment. It is a figure which shows the example of the data which concern on the decoding conditions stored in the management server. It is a sequence diagram explaining the data encryption method in 3rd Embodiment. It is a sequence diagram explaining the process at the time of decrypting encryption object data in 3rd Embodiment.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

<First Embodiment>
(Configuration of data encryption system 1)
FIG. 1 is a diagram for explaining the configuration of a data encryption system 1 according to the first embodiment of the present invention. As shown in FIG. 1, the data encryption system 1 includes a plurality of communication terminals (communication devices) 10 (10 ₁ to 10 _n ) and a management server 20. The data encryption system 1 is a system provided in the communication terminal 10 and having a function of encrypting data to be encrypted, which is data that needs security management, and decrypting the encrypted data. In FIG. 1, four communication terminals 10 (10 ₁ , 10 ₂ , 10 ₃ , 10 _n ) are illustrated as examples of the plurality of communication terminals 10 ₁ to 10 _n .

  In the data encryption system 1 described in this embodiment, data encryption using a threshold secret sharing scheme is used as an encryption method. In this “threshold secret sharing scheme”, data to be encrypted, which is data to be encrypted, is encrypted and then distributed to a plurality (eg, n) of different data (secret sharing data). ), When there are k or more arbitrarily designated pieces of distributed data, the data can be decrypted. At this time, the number k of data that can be decoded is referred to as a “threshold value”. In this embodiment, the number of distributions is n, the threshold value is k, and the encryption target data is distributed. When k or more of the distributed data (secret sharing data) are collected, the encryption target data is decrypted. The technique that enables the threshold value is called “threshold secret sharing (k, n) type”. The encryption method is not limited to the “threshold secret sharing scheme” described above. In other words, various methods including a method of collecting at least a part of the distributed partial data (at least a part) at the time of decryption and being distributed to a plurality of different partial data can be used. .

  Hereinafter, the communication terminal 10 and the management server 20 included in the data encryption system 1 will be described.

  The communication terminal 10 is a communication device that is used by its owner and has a function of encrypting data to be encrypted and decrypting the encrypted data. Further, the communication terminal 10 has a function of configuring the ad hoc network N1 and a function of connecting to the wireless communication network N2. Specifically, a mobile communication terminal such as a mobile phone or a PDA (Personal Digital Assistant) is preferably used as the communication terminal 10. In addition, the communication apparatus used suitably as the communication terminal 10 which concerns on this embodiment is not limited to a mobile communication terminal, It can apply to the various communication apparatus which has a communication function, for example, household appliances which have a communication function It can also be applied to a safe or the like. In the following embodiments, description will be made assuming a mobile phone having a function of connecting to the ad hoc network N1 and the wireless communication network N2 as a communication device.

  The ad hoc network N1 in the present embodiment is a method of configuring a network without going through a base station or a fixed network when communication devices are physically close to each other. Data is directly exchanged between communication terminals. Therefore, by configuring the ad hoc network among the plurality of communication terminals, it is possible to mutually confirm that the plurality of communication terminals constituting the ad hoc network are physically close to each other. Since this ad hoc network does not need to communicate via a specific device or the like, it is easy to configure a new network and dissolve the network, and a communication terminal connected to the network. It has a feature that it can easily cope with fluctuations in the number. In addition, in an ad hoc network, when the communication terminal of the data transmission destination is in an area where the terminal itself cannot be directly connected, the other communication terminals that also make up the ad hoc network are requested to relay data. Data can be transmitted and received via the communication terminal. The wireless communication network N2 in the present embodiment is a cellular network, for example, but a wireless LAN (Local Area Network) or the like is also preferably used.

  FIG. 2 is a diagram illustrating a hardware configuration of the communication terminal 10. As shown in FIG. 2, the communication terminal 10 includes a CPU (Central Processing Unit) 101, a RAM (Random Access Memory) 102, a ROM (Read Only Memory) 103, an operation unit 104, a wireless communication unit 105, a display 106, and an antenna. It is configured by hardware such as 107. When these components operate, each function of the communication terminal 10 described later is exhibited.

  Next, the management server 20 will be described. The management server 20 is a device that is connected to the plurality of communication terminals 10 via the wireless communication network N2 and assists the processing related to encryption of the data to be encrypted by the plurality of communication terminals 10. Specifically, the management server 20 stores the secret sharing data held in the communication terminal 10 after encryption and the data to be encrypted before encryption, and the communication terminal 10 based on a request from the communication terminal 10. Has the function of verifying the validity of the secret sharing data held by. In addition, the management server 20 has a function of performing processing such as providing alternative data when data is damaged in the communication terminal 10.

  FIG. 3 is a diagram illustrating the hardware configuration of the management server 20. As shown in FIG. 3, the management server 20 includes hardware such as a CPU 201, a RAM 202 and a ROM 203 as main storage devices, a communication module 204 as a data transmission / reception device such as a network card, and an auxiliary storage device 205 such as a hard disk. Configured as a computer. By operating these components, each function of the management server 20 described later is exhibited.

  Next, functions of the communication terminal 10 and the management server 20 constituting the data encryption system 1 will be described with reference to FIGS. 1 and 4 to 6. 4 is a diagram illustrating functional units included in the communication terminal 10, FIG. 5 is a diagram illustrating functional units included in the management server 20, and FIG. 6 illustrates data stored in the management server 20. It is a figure which shows the example of.

As shown in FIG. 1, the data encryption system 1 includes a plurality of communication terminals 10, and these communication terminals 10 have a function of configuring the same ad hoc network N1. When these communication terminals 10 form the ad hoc network N1, in order to specify which communication terminal 10 currently forms the ad hoc network N1, information for specifying each communication terminal 10 (for example, the communication terminal 10 performs mobile communication). In the case of a terminal, the MSISDN (Mobile Subscriber ISDN number) of the terminal is notified to each other, and each communication terminal 10 holds the information. In the present embodiment, a plurality of communication terminals 10 (10 ₁ to 10 _n ) configuring the same ad hoc network N1 are referred to as “network members”. Specifically, among the plurality of communication terminals 10 (10 ₁ to 10 _n ), only the communication terminal 10 configuring the ad hoc network N1 is referred to as a “network member”. Further, in the present embodiment, in FIG. 1, among the communication terminals 10 included in “network members” configuring the ad hoc network N1, the communication terminal 10 (10 ₁₎ that holds the encryption target data D0 to be encrypted. ) as the "host terminal (host apparatus)", the communication terminal 10 constituting the ad-hoc network N1 other than the communication terminal 10 _{1 (10} 2 to 10 _n) to "member terminal (member devices)." The distinction between the “host terminal” and the “member terminal” is made according to whether or not the encryption target data D0 is held when the processing according to the present embodiment is started. Thus, if in the present embodiment, a case is described where the host terminal is a communication terminal 10 _1, the encryption target data is held in the other communication terminals 10 (one of the communication terminal 10 ₂ to 10 _n), The host terminal is changed to the communication terminals 10 ₂ to 10 _n .

  As shown in FIG. 4, the communication terminal 10 includes a short-range wireless communication unit 12 (distribution unit, secret sharing data acquisition unit) and a long-range wireless communication unit 13 (secret sharing data verification unit) which are communication units 11, The control unit 14 includes an encryption processing unit 15 (encryption unit, distribution unit), a decryption processing unit 16 (decryption unit), and a storage unit 17 (storage unit).

  The communication unit 11 has a function of configuring the ad hoc network N1 to communicate with other communication terminals 10 and a function of communicating with the management server 20 via the wireless communication network N2. Among the communication units 11, the short-range wireless communication unit 12 has a function of configuring the ad hoc network N <b> 1 and performing communication with other communication terminals 10. Specifically, when the communication terminal 10 is a host terminal, the short-range wireless communication unit 12 stores n different pieces of secret shared data created by encryption and distribution in an encryption processing unit 15 described later. Among them, different n−1 pieces of secret sharing data are distributed to the other communication terminals 10 which are n−1 member terminals. Further, when decryption is performed in the communication terminal 10, secret sharing data transmitted from another communication terminal 10 constituting the ad hoc network N1 is received. On the other hand, the long-distance wireless communication unit 13 has a function of performing communication with the management server 20 via the wireless communication network N2. In the present embodiment, the name of the long-range wireless communication unit 13 is used for the purpose of distinguishing from the short-range wireless communication unit 12 that performs communication via the ad hoc network N1. Specifically, the long-distance wireless communication unit 13 is created in association with secret sharing data encrypted and distributed by the encryption processing unit 15 of the communication terminal 10, data to be encrypted before encryption, and encryption described later. The related data to be transmitted is transmitted to the management server 20 via the wireless communication network N2. In addition, when the communication terminal 10 verifies the validity of secret sharing data, which will be described later, the long distance wireless communication unit 13 transmits the secret sharing data to the management server 20 and verifies the validity of the secret sharing data. And a verification result of validity transmitted from the management server 20 is received. As described above, the data transmitted and received in the short-range wireless communication unit 12 and the long-range wireless communication unit 13 is sent to the control unit 14.

  The control unit 14 has a function of controlling processing performed in each functional unit of the communication terminal 10. Specifically, when the communication terminal 10 encrypts the data to be encrypted, the encryption processing unit 15 is instructed to that effect, and when the secret sharing data is decrypted, the decryption processing unit 16 is instructed to perform the process. In addition, after the encryption processing unit 15 or the decryption processing unit 16 performs processing related to encryption or decryption, the result is received and stored in the storage unit 17 when holding in the own terminal is necessary. When transmission is required for the other communication terminal 10 or the management server 20, the communication unit 11 is instructed to transmit.

  The encryption processing unit 15 has a function of encrypting data to be encrypted when the terminal itself is a host terminal. In the present embodiment, as described above, the encryption target data is encrypted and distributed using the threshold secret sharing scheme. Therefore, when the ad hoc network is configured by a plurality of communication terminals, the encryption processing unit 15 determines the distribution number n and the threshold value k, and uses the threshold secret sharing (k, n) type to set the threshold value Encrypted data is created by encrypting the data to be encrypted D0 using the secret sharing scheme. Further, the encryption processing unit 15 distributes the encrypted data to generate n different secret sharing data. The distribution number n used when the encryption processing unit 15 encrypts the data to be encrypted is the total number of communication terminals 10 (that is, network members at the time of encryption) constituting the ad hoc network N1. The threshold value k is arbitrarily determined in the communication terminal 10 (host terminal) that performs encryption. When the communication terminal 10 is not a host terminal but a member terminal, no particular processing is performed in the encryption processing unit 15.

  Here, when the secret sharing data is generated in the encryption processing unit 15, the related data is also created. The related data created in the encryption processing unit 15 includes “encryption target data ID” for specifying “encryption target data”, and the encryption target data among the communication terminals 10 constituting the ad hoc network N1. “Host ID” (for example, MSISDN of the host terminal) that is information for identifying the host terminal that is the communication terminal 10 that holds and encrypts the information, and “Member ID” (for information that identifies the member terminal) ( For example, the member terminal MSISDN). These pieces of information are used in a process related to the validity verification and decryption of secret shared data described later.

  Of the n pieces of secret sharing data distributed by the encryption processing unit 15, n-1 pieces of secret sharing data include the communication unit 11 together with related data generated in the encryption processing unit 15 as described above. From the short-range wireless communication unit 12 to the other communication terminals 10 constituting the ad hoc network N1. The remaining one piece of secret sharing data is stored in the own terminal. In the present embodiment, storing the secret sharing data created by encryption and distribution by the own terminal in the storage unit 17 of the own terminal is also referred to as “distribution”. As a result, the n secret sharing data distributed by the host terminal is distributed to the n communication terminals 10 (network members) constituting the ad hoc network N1, and held individually in each terminal.

  The decryption processing unit 16 has a function of decrypting the encryption target data from the secret sharing data. Since the secret sharing data is distributed by the threshold secret sharing (k, n) type as described above, the communication terminal 10 decrypts the data only when it holds k pieces or more of secret sharing data. Can be made. When recovering secret sharing data from another communication terminal 10 for decryption, it is necessary to determine that other communication devices are physically close to each other with the other communication terminal 10. It is necessary to configure an ad hoc network N1 that is a decoding network. Details thereof will be described later. Note that the decryption of the secret sharing data by the decryption processing unit 16 has a function of decrypting the communication terminal 10 of either the host terminal or the member terminal.

  In this embodiment, the decryption processing unit 16 obtains k−1 or more pieces of secret sharing data whose validity has been verified from the other communication terminals 10 configuring the ad hoc network N1 via the ad hoc network N1. The aspect which needs to be described is demonstrated. Here, “secret shared data whose validity has been verified” means that the secret shared data is the same as the data created when the host terminal encrypted and distributed the data to be encrypted ( This means that the data is verified. A specific method for verifying the validity will be described later.

  When the communication terminal 10 is a host terminal, the storage unit 17 has a function of storing data to be encrypted and storing secret shared data and related data created from the data to be encrypted. However, after transmitting the secret sharing data and the related data to each member terminal and further transmitting the data to be encrypted, the n secret sharing data and the related data to the management server 20, the own terminal holds it. Other data is deleted from the storage unit 17 while leaving one secret sharing data. This is intended to ensure security. When the communication terminal 10 is a member terminal, the storage unit 17 has a function of storing secret sharing data and related data transmitted from the host terminal.

  Next, the management server 20 will be described. As shown in FIG. 5, the management server 20 includes a communication unit 21, a data storage unit 22, and a validity verification unit 23.

  The communication unit 21 has a function of communicating with the communication terminal 10 via the wireless communication network N2. Specifically, the data to be encrypted, the secret sharing data and the related data transmitted from the host terminal included in the communication terminal 10 are received and stored in the data storage unit 22, and the secret sharing data from the communication terminal 10 is stored. When a request for validity verification is received, verification is performed by a later-described validity verification unit 23, and the result is transmitted from the communication unit 21 to the communication terminal 10. In addition, it has a function of transmitting secret sharing data stored in the data storage unit 22 of the management server 20 to the communication terminal 10 in response to a request from the communication terminal 10.

  The data storage unit 22 has a function of storing data transmitted from the communication terminal 10. As described above, the data transmitted from the communication terminal 10 includes data to be encrypted, secret sharing data, and related data. FIG. 6 is a diagram illustrating an example of information stored in the data storage unit 22. FIG. 6A is a table showing an outline of the encryption target data and secret sharing data stored in the data storage unit 22, and an “encryption target data ID” for specifying the encryption target data, and encryption Information specifying the encryption target data specified by the target data ID (for example, file name), “host ID” which is information specifying the communication terminal as the host terminal, threshold k, and network member The number (dispersion number) n is associated.

  On the other hand, FIG. 6B is a table showing details of the secret sharing data created in association with each data to be encrypted, and the host terminal and member to which the secret sharing data of the data to be encrypted is distributed. A “network member ID” that identifies the terminal (network member), information that identifies secret shared data held by the network member identified by the network member ID (for example, a file name), and the validity of the secret shared data Information related to the verification is associated. As the “network member ID” and “host ID”, individual terminal IDs for specifying each communication terminal 10 are used. For example, MSISDN can be used as the terminal ID. Among these pieces of information, information other than the information related to the validity verification is created and transmitted by the communication terminal 10 as the host terminal, and is stored in the data storage unit 22. The validity verification will be described later.

  The validity verification unit 23 receives the secret sharing data from the member terminal, and based on n different secret sharing data and encryption target data transmitted from the host terminal, the validity of the secret sharing data from the member terminal And the result is transmitted to the member terminal that requested the verification of validity. The verification of legitimacy here refers to confirming whether the data content has been changed due to tampering / damage after the secret sharing data is distributed at the host terminal. The validity verification unit 23 uses the secret sharing data transmitted from the communication terminal 10 for the purpose of checking the validity and the secret sharing data transmitted in advance from the host terminal and stored in the data storage unit 22. The validity of the secret sharing data is determined by determining whether the result (decrypted data) is the same as the data to be encrypted that is transmitted from the host terminal and stored in the data storage unit 22 in advance. The details of the process will be described later. The secret sharing data verified by the validity verification unit 23 is returned from the management server 20 to the communication terminal 10 with an electronic signature indicating that the validity is verified. . If the validity verification unit 23 determines that there is a problem with validity (incorrect data), the management server 20 notifies the communication terminal 10 of the result.

  The above is the configuration of the communication terminal 10 and the management server 20 included in the data encryption system 1.

(About processing by the data encryption system 1)
(1-1. Encryption of data to be encrypted)
Subsequently, processing (data encryption method, justification verification method, decryption method, etc.) related to data encryption by the data encryption system 1 according to the present embodiment will be described with reference to FIGS. First, the data encryption method will be described with reference to the sequence diagram shown in FIG.

First, in the present embodiment, the communication terminal 10 ₁ is to be held the encryption target data (S101). The communication terminal 10 ₁ as a host terminal if thereby performing encryption of the data to be encrypted. Furthermore, when performing encryption of data to be encrypted, the threshold k in performing encrypted by the communication terminal 10 ₁ as a host terminal is determined (S102). The threshold value k is the owner of the communication terminal 10 ₁ can also be determined as appropriate, when creating the encrypted target data, it may be determined in advance by the risks during importance and leakage of the data. When the encryption target data for which the threshold value k is determined is prepared in the host terminal, the subsequent encryption processing is started.

First, the communication terminal 10 ₁ as a host terminal searches the surroundings of the terminal, to the communication terminal ₁₀ 2 to 10 _n, querying whether connectable against ad hoc network N1 (S103a, S103b). The query to the communication terminal 10 ₁ may be performed separately to each communication terminal 10, as shown in FIG. 7, may also be queried in message format. In this case, the communication terminal 10 ₂ which can be connected to the ad hoc network N1 performs a response to the effect which is connectable to the communication terminal 10 ₁ (S104). The communication terminal 10 ₁ that has received this reply, makes a connection request to the ad hoc network N1 to the communication terminal 10 ₂ (S105), the communication terminal 10 ₂ responds thereto (S106) by the communication terminal 10 ₂ Are connected to the ad hoc network N1. Also different communication terminal 10 (for example, the communication terminal 10 _n) from the communication terminal 10 _2, when it is possible to connect to the ad hoc network N1 is a response to that effect to the communication terminal 10 ₁ (S107) Therefore, the process according to the connection of the ad hoc network N1 is performed (S108, S109), the communication terminal 10 _n is connected to an ad hoc network N1. By repeating this process, the ad hoc network N1 is configured by the n communication terminals 10 including the host terminal.

Here the communication terminal 10 ₁ as a host terminal, the terminal number n to the ad-hoc network N1 to check whether the threshold value k than the predetermined (S110). Here, when the number n of terminals is smaller than the threshold value k, the number n of terminals is small, and the process related to encryption of the data to be encrypted is stopped (S111). On the other hand, if the terminal number n is greater than or equal to the threshold value k is a communication terminal 10 ₁ of the encryption processing unit 15 is a host terminal, encrypting the encryption target data is performed, the encrypted data is generated (S112). Further, secret sharing data in which encrypted data is distributed to n based on the number of terminals n is created (S113). Then, in relation to the secret sharing data, information for specifying the encryption target data (encryption target data ID), n secret sharing data generated from the encryption target data, and the secret sharing data Information (network member ID) for identifying the network member that is the communication terminal 10 of the distribution destination (including the host terminal and member terminal), information (host ID) for identifying the host terminal, and a threshold value k The related data to be included is created in the encryption processing unit 15 (S114).

Secret sharing data and related data generated in this way, transmitted from the wireless communication unit 12 of the communication terminal 10 ₁ of the communication unit 11 is a host terminal to the communication terminal 10 ₂ to 10 _n is a member terminal (S115, S116). In this case secret sharing data transmitted to each communication terminal ₁₀ 2 to 10 _n (secret sharing data (2) - secret sharing data (n)) are those associated with each of the communication terminals ₁₀ 2 to 10 _n . The secret sharing data distributed from the communication terminal 10 ₁ are respectively stored in the storage unit 17 of the communication terminal 10.

Further, the management server 20 from the communication terminal 10 ₁ as a host terminal, the series of data created or used in the encryption process described above is transmitted. That is, data to be encrypted, n pieces of secret shared data, and related data are transmitted to the management server 20 from the communication terminal 10 ₁ of the long-range wireless communication unit 13 (S117). These data are received by the communication unit 21 of the management server 20 and then stored in the data storage unit 22. The management server 20 in the communication terminal 10 ₁ that has transmitted the data for, in order to ensure security, except secret sharing data held in its own terminal (secret sharing data (1)), remove other data ( S118). As a result, each of the communication terminals 10 ₁ to 10 _n (network members) constituting the ad hoc network N1 is in a state where one piece of different secret sharing data is held. With the above processing, the processing related to encryption of the data to be encrypted ends.

When encryption of the encryption target data is performed by performing the above processing, the encryption target data can be encrypted only when the ad hoc network N1 is configured by the communication terminals 10 ₁ to 10 _n , and The secret sharing data is distributed and held by the communication terminals 10 ₁ to 10 _n . Accordingly, since encryption and storage can be performed only by the communication terminal 10 constituting the ad hoc network N1, it is possible to prevent a malicious third party from participating in the processing related to encryption, and to improve security. Can be achieved.

(1-2. Validity verification of secret sharing data)
Next, processing related to the validity verification of secret sharing data by the member terminals will be described with reference to FIGS. FIG. 8 is a sequence diagram illustrating a series of processes related to validity verification between the communication terminal 10 _m (1 <m ≦ n), which is a member terminal that performs validity verification, and the management server 20. FIG. 9 is a flowchart for explaining a method of validity verification in the management server 20.

First, long-range wireless communication unit 13 of the communication terminal 10 _m is a member terminal, the secret sharing data held in the storage unit 17 of the own terminal (m), to the management server 20 via the wireless communication network N2 To send. Accordingly, the communication terminal 10 _m requests the management server 20 to verify the validity of the secret sharing data (m) (S201). At this time, information (network member ID) specifying the own terminal attached to the secret sharing data (m) is also transmitted to the management server 20. Timing the communication terminal 10 _m is a member terminal performs validity verification of the secret sharing data, from the time when the communication terminal 10 _m receives the secret shared data from the communication terminal 10 ₁ as a host terminal, by using the secret sharing data can be carried out at any time up to perform the decoding, for example, it is carried out from the communication terminal 10 ₁ upon receiving the secret sharing data.

When the communication unit 21 of the management server 20 receives the request for validity verification from the communication terminal 10 _m , it sends the secret sharing data (m) and the network member ID of the communication terminal 10 _m to the validity verification unit 23. Then, the validity verification unit 23 verifies the validity using the secret sharing data (S202).

Here, verification of validity performed in the validity verification unit 23 will be described with reference to FIG. First, the validity verification unit 23, among the n secret sharing data stored in the data storage unit 22, is k−1 secret sharings different from the secret sharing data (m) transmitted from the communication terminal 10 _m. Data is selected (S221). Then, decryption of the data to be encrypted is performed using k pieces of secret shared data including the secret shared data from the communication terminal 10 _m and k−1 pieces of secret shared data selected from the data storage unit 22. This is performed (S222). Then, the decrypted encryption target data (decrypted data) is compared with the encryption target data before encryption transmitted from the communication terminal 10 ₁ (host terminal) stored in the data storage unit 22. (S223), it is confirmed whether the decrypted data decrypted by the validity verification unit 23 is correctly decrypted (S224). Specifically, the validity verification unit 23 determines that the validity of the secret sharing data from the communication terminal 10 _m has been verified when the decrypted data and the encryption target data match, and the decrypted data If the encryption target data does not match the encryption target data, it is determined that the encryption target data is not correctly decrypted.

Here, when the data to be encrypted is not correctly decrypted, the validity verification unit 23 determines that the secret sharing data (m) transmitted from the communication terminal 10 _m is invalid data, and notifies that fact. It is determined to notify the communication terminal 10 _m as a verification result (S225). At the same time, the validity verification unit 23 changes the item relating to the validity of the secret sharing data stored in the data storage unit 22. Specifically, in the table shown in FIG. 6B, the validity of the term associated with the corresponding member ID is “NG”. On the other hand, when the data to be encrypted is correctly decrypted, it is determined that the secret sharing data (m) transmitted from the communication terminal 10 _m is correct data. An electronic signature that proves the validity is given (S226). Further, the item relating to the validity of the secret sharing data stored in the data storage unit 22 is changed by the validity verification unit 23. Specifically, the validity of the term associated with the corresponding member ID in the table shown in FIG. 6B is set to “OK” (S227). Thereafter, it is determined to transmit, as a verification result, the secret sharing data to which the electronic signature is given from the communication unit 21 of the management server 20 to the communication terminal 10 _m (S228).

As a result of the verification of the validity by the above processing, the process returns to FIG. 8, and either one of the notification indicating that the data is invalid and the secret shared data with the electronic signature that proves the validity is managed as the verification result. It is transmitted from the server 20 to the communication terminal 10 _m (S203). Here, the communication terminal 10 _{m that} has received the verification result confirms whether the verification result is a notification indicating illegal data (S204). At this time, if the verification result received by the communication terminal 10 _m is not a notification indicating unauthorized data but secret sharing data with an electronic signature, the process ends because the validity of the secret sharing data has been confirmed ( S205).

On the other hand, if the verification result is a notification indicating illegal data, the secret shared data cannot be used for decryption, so the communication terminal 10 _m needs to obtain new secret shared data. The process will be described below. Communication terminal 10 _m requests retransmission of secret sharing data to the communication terminal 10 ₁ is a host terminal (S206). Then, based on the secret sharing data retransmission request from the communication terminal 10 _m, to the management server 20 from the communication terminal 10 _1, the retransmission request of the secret sharing data distributed to the communication terminal 10 _m is transmitted (S207). At this time, information (terminal ID) for specifying the communication terminal 10 _m is attached to the retransmission request for the secret sharing data and transmitted to the management server 20.

The communication unit 21 of the management server 20, based on the retransmission request from the communication terminal 10 _1, secret sharing data stored in the data storage unit 22 in association with the network subscriber ID identifying the communication terminal 10 _m (m) is Extracted (S209). Then, the secret shared data (m) is transmitted via a wireless communication network N2 from the communication unit 21 of the management server 20 to the communication terminal 10 ₁ (S209), from the communication terminal 10 ₁ to the communication terminal 10 _m The secret sharing data (m) is transmitted (S210). Note that for the above process (S206～S210), since the communication terminal 10 ₁ and the communication terminal 10 _m is sometimes not the ad-hoc network N1, other wireless communication networks (e.g., wireless communication The secret sharing data (m) can be transmitted and received by communication via the network N2). When the communication terminal 10 _m newly acquires the secret sharing data (m) transmitted from the management server 20 in this way, the validity verification (S211) of the newly received secret sharing data (m) is performed. That is, the above-described processing (S201 to S204) is performed. Thus, the process related to the validity verification of the secret sharing data acquired by the member terminal is completed.

As described above, each communication terminal that holds secret shared data performs validity verification of the distributed secret shared data, thereby reducing the risk of decryption using, for example, altered secret shared data Therefore, security can be improved. Also, when data held in the member terminal is an invalid data, since it is possible to obtain the re-secret sharing data through the communication terminal 10 ₁ as a host terminal and validity in each communication terminal 10 Proven secret sharing data can be held more reliably.

The process according to validity verification of the above may be embodiments also perform communication terminal 10 ₁ was host terminal. Further, secret sharing data communication terminal 10 ₁ is held, because it is originally data generated by the terminal itself, for example by electrons flag (e.g. the own terminal to indicate that this secret sharing data is generated by the own terminal (Signature) can be given to the secret sharing data, and if this flag is present, the validity can be verified.

(1-3. Decryption of data to be encrypted)
Next, processing related to decryption of data to be encrypted using secret sharing data held by a network member will be described with reference to FIGS. 10 and 11. FIG. 10 is a sequence diagram for explaining a series of processes related to decryption of data to be encrypted, and FIG. 11 is a flowchart for explaining a method for collecting secret shared data in the middle of decryption.

In 1-1 and 1-2, since the processing performed between the host terminal and the member terminal is different, the processing is described by clearly distinguishing between the host terminal and the member terminal. In the processing after 1-3, Similar processing is performed for both the host terminal and the member terminal. Thus, the 1-3 of the present embodiment, the processing of the communication terminal 10 ₁ to 10 _n are network members constituting the ad hoc network N1 to perform the decoding performed will be described. In the present embodiment, the communication terminal 10 _2, will be described a decoding terminal is a communication terminal that performs decryption of the encrypted target data (decoding apparatus).

First, the decryption terminal 10 ₂ searches for the communication terminal 10 (10 ₁ , 10 ₃ to 10 _m ) that can be a network member (having the ability to configure the ad hoc network N1), and can connect to the communication terminals 10 ₁ , 10 ₃ -10 _m is inquired as to whether or not connection can be made to the ad hoc network N1 (decomposition network) for decoding data (S301a, S301b, S301c). This process is the owner of the decoding terminal 10 ₂ is started by the case of the decoding of secret sharing data stored is distributed by encrypting operates the decoding terminal 10 _2. Inquiry from the communication terminal 10 ₁ that receives the from the decoding terminal 10 _2, by transmitting a response to the effect can be connected to the decoding terminal 10 ₂ (S302), the decoding terminal 10 ₂ and the communication terminal 10 ₁ A process related to the ad hoc network N1 connection is performed (S303). Similarly, the communication terminals 10 ₃ to 10 _m also respond to the decryption terminal 10 ₂ from each communication terminal 10 (S304, S306), whereby the communication terminals 10 ₃ to 10 _m and the decryption terminal 10 ₂ The ad hoc network N1 is connected between each other (S305, S307). In this way, it is assumed that an ad hoc network N1 including m communication terminals 10 is configured.

Here, the magnitude relationship between the terminal number m and the threshold value k for the ad-hoc network N1 including decoding terminal 10 ₂ is confirmed at the decoding terminal 10 ₂ (S308). Here, when the number of terminals m is smaller than the threshold value k, secret sharing data of the threshold value k or more cannot be collected, and the process related to decryption of the secret sharing data is stopped (S309). On the other hand, the terminal number m is is greater than the threshold value k is the decode terminal 10 _2, the process according to the collection of secret sharing data is (S310). This process will be described with reference to FIG. At this point, secret the decoding terminal 10 _2, the number m of communication terminals connected to the ad hoc network N1 has been confirmed that higher than the threshold value k, where all the communication terminals 10 is verified for correctness from that not holding distributed data, validity has been proved (i.e., electronic signature is attached) collecting process of the secret sharing data is performed by the decoding terminal 10 _2.

In Figure 11, first, it determines whether it is a secret sharing data number s is k or more holding the decoding terminal 10 ₂ to be subjected to decoding of secret sharing data is performed (S321). If k or more pieces of secret shared data are held at this time, it is not necessary to collect more secret shared data, but if the number of secret shared data s is less than k, the process proceeds to the next step. . That is, it is confirmed whether secret sharing data has been received from other network members that currently constitute the ad hoc network N1 (S322). Here, if all network subscribers have already received a secret shared data, since it is not possible to further increase the secret sharing data held in the decoding terminal 10 _2, it is impossible to perform decoding, the processing is aborted (S323).

On the other hand, if the still communication terminal 10 does not receive the secret shared data included in the network member, decoding terminal 10 _2, the communication terminal 10 (for example, the communication terminal 10 from the wireless communication unit 12 via the ad hoc network N1 ₃ ) A transmission request is transmitted to (S324). On the other hand, the communication terminal 10 ₃ that has received the transmission request transmits the secret sharing data to the decoding terminal 10 ₂ (S325). Decoding terminal 10 ₂ receives the secret sharing data from the communication terminal 10 ₃ in the wireless communication unit 12, to confirm whether there is an electronic signature to prove validity in the control unit 14 to the secret sharing data ( S326). Here, if that there is an electronic signature can be confirmed, increased by one secret sharing data number s which is held in the decoding terminal 10 ₂ (S328), it returns again to the initial processing. On the other hand, if the electronic signature is not added to the secret sharing data received at the decoding terminal 10 ₂ is not recognized the data as valid data (S327), first process without changing the secret sharing data number s Return to.

By repeating the above processing, when the secret sharing data number s which is held in the decoding terminal 10 ₂ is equal to or larger than k, the process ends in accordance with the recovery of the secret sharing data.

Returning to FIG. 10, k or more secret sharing data processing will be described after being recovered at the decoding terminal 10 _2. In the above secret sharing data recovery process (S310), k or more (that is, a threshold value or more) proven secret sharing data has been recovered, so that the decryption processing unit 16 of the decryption terminal 102 ₂ The encryption target data is decrypted using the secret sharing data (S311). Thereby, decrypted data is generated. Then, secret sharing data used for decoding is deleted by the decoding terminal 10 ₂ (S312). Decryption of the encrypted target data is performed by the above processing, the decoding terminal 10 ₂ can obtain the decoded data.

In the above processing, ₂ communication terminal 10 was a member terminal has been described a case where the decoding terminal in 1-1 and 1-2, also _{when one} communication terminal 10 was the host terminal is decoded terminal , decoded data is generated in the communication terminal 10 ₁ by the same process as described above.

In the above-described FIGS. 10 and 11, it has described the case where the decoding terminal 10 ₂ performs decoding, the same processing as this, one communication terminal ₁₀ constituting the ad-hoc network _N1, 10 3 to 10 _m It is also possible to adopt a mode that is also performed in This is triggered by the inquiry about the ad hoc network N1 connection from the decryption terminal 10 ₂ to the communication terminals 10 ₁ , 10 ₃ to 10 _m , and the other 10 ₁ , 10 ₃ to 10 constituting the ad hoc network N1. The same processing (that is, recovery and decryption of secret sharing data) is performed in _m . In this case, decoded data is generated in each of all the communication terminals 10 ₁ to 10 _m configuring the ad hoc network N1.

By decrypting the data to be encrypted by the above processing, the communication terminals 10 ₁ to 10 _m constituting the ad hoc network N1 are not less than k threshold values, and the secrets are proved to be valid Since the decryption is performed only when the number of distributed data is equal to or more than the threshold value k, the data to be encrypted is decrypted under more strict conditions, so that the security is improved. In addition, since it is possible to perform decryption in the communication terminal 10 using only the secret shared data that has been proved valid, the data to be encrypted using the secret shared data that has been altered by the involvement of a third party or the like Compared with the case where the decryption is performed, it is possible to decrypt the data to be correctly encrypted more reliably.

(1-4. Deletion of Decrypted Data)
Next, processing related to deletion of decrypted data in the communication terminal 10 will be described with reference to FIG. FIG. 12 is a sequence diagram for explaining processing related to deletion of decrypted data. The data encryption system 1 according to the present embodiment is configured such that the decrypted data is deleted when the number of communication terminals 10 constituting the ad hoc network N1 becomes smaller than the threshold value k. Hereinafter, this process will be described. In 1-4, as a premise, all the communication terminals 10 ₁ to 10 _m constituting the ad hoc network N1 perform the above-described decryption of the data to be encrypted of 1-3 (generation of decrypted data). The processing in the case of the state is described. That is, it is assumed that all the communication terminals 10 ₁ to 10 _m constituting the ad hoc network N1 hold the decrypted data. And here, the communication terminal 10 ₁ may break the connection to adhoc network N1 (e.g., when moving the like to the communication is impossible area) will be described.

When the communication terminal 10 ₁ is a network member constituting the ad-hoc network N1 breaks its connection to the ad hoc network N1, in addition to the communication terminal 10 constituting the ad-hoc network N1 to the effect that the disconnection (communication terminals 10 ₂ to 10 _m ) via the short-range wireless communication unit 12 (S401a, S401b, S401c). Thereafter, the communication terminal 10 _1, cut off the connection to adhoc network N1 (S402), it deletes the decoded data stored in the communication terminal 10 ₁ of the storage unit 17 (S403). Thus, the communication terminal 10 _1, encryption target data is deleted as a trigger the disconnection from the ad hoc network N1.

On the other hand, in the disconnection notification other communication terminals ₁₀ 2 to 10, which has received the _m from the communication terminal 10 _1, in each of the communication terminals 10, confirmation of the number of members to be connected to the ad hoc network N1 is performed (S404~S406). If the number of members is equal to or less than k−1, that is, less than the threshold value k, the decrypted data stored in the storage unit 17 of each communication terminal 10 is deleted (S407 to S407). S409). It is possible to determine in advance in each communication terminal 10 that a series of processing (S407 to S409) that occurs when the number of members decreases is performed. As a result, the communication terminal 10 connected to the ad hoc network N1 has the number of network members currently connected to the ad hoc network N1 triggered by reception of a connection disconnection notification from another communication terminal 10 (communication terminal 10 ₁ in the present embodiment). When the number of members is smaller than k as a result, the decrypted data is deleted from each communication terminal 10. Thereby, when the number of communication terminals 10 connected to the ad hoc network N1 is less than the threshold value k, it is possible to adopt a configuration in which the decrypted data is deleted from each communication terminal 10.

  By performing the above processing, it is possible to prevent information leakage such as that the decrypted data decrypted by configuring the ad hoc network N1 is stolen by a third party or the like, and the security is further improved. .

  As described above, according to the configuration of the present embodiment, encryption of data to be encrypted, verification of validity, decryption of data to be encrypted (generation of decrypted data), and separation from an ad hoc network are performed. Security is improved at each stage of management of decrypted data, and information can be handled with higher security compared to conventional encryption processing.

<Second Embodiment>
(Configuration of data encryption system)
Next, a second embodiment of the present invention will be described. The second embodiment is different from the first embodiment in the following points. That is, in the first embodiment, when the communication terminal 10 encrypts the encryption target data and decrypts the distributed secret sharing data, the communication terminal 10 forms an ad hoc network N1 with the other communication terminal 10, and the ad hoc network N1 In contrast, in the second embodiment, one communication terminal 10 satisfies the condition indicated in the predetermined decryption condition, while k or more pieces of secret sharing data are collected via the decryption. Thus, k-1 pieces of secret shared data are obtained from the management server 20, and decryption is performed in the communication terminal 10 using the k-1 pieces of secret shared data and the secret shared data held in the own terminal. It is.

  Here, the decoding conditions used in the second embodiment will be described with reference to FIG. In FIG. 13, as a condition for decrypting the secret sharing data held by the communication terminal 10, the communication terminal 10 is required to reach the area P4 via the areas P1, P2, and P3 respectively at predetermined times. Is the case. In this case, the communication terminal 10 needs to move in each area as shown by the arrows in FIG. Whether or not the communication terminal 10 has passed through each area is determined based on GPS positioning information by the GPS satellite 30 connected to the communication terminal 10 by wireless communication. Then, when the communication terminal 10 transmits the GPS positioning result to the management server 20 via the wireless communication network N2, the management server 20 determines whether or not the communication terminal 10 satisfies the decoding condition. Thus, in the decryption of the data to be encrypted according to the present embodiment, the position information and time information of the communication terminal 10 are used as the decryption conditions, and the position information by the communication terminal 10 in the management server 20 is the decryption condition. When it is determined that the condition is satisfied, decoding in the communication terminal 10 is permitted. Hereinafter, a data encryption system having such an aspect will be described.

  FIG. 14 is a block diagram illustrating the configuration of the communication terminal 10 (10A) according to the present embodiment. As described above, the communication terminal 10 </ b> A according to the present embodiment has a function of acquiring position information of the own terminal from the GPS satellite 30. Specifically, as illustrated in FIG. 14, the communication terminal 10 </ b> A includes a position information acquisition unit (position information acquisition unit) 18 included in the communication unit 11, and the position information acquisition unit 18 is connected to the GPS satellite 30. In this way, information related to the current position of the communication terminal 10A is acquired. Thus, the location information of the communication terminal 10 acquired in the communication terminal 10A is transmitted from the long-distance wireless communication unit 13 of the communication terminal 10A to the management server 20 via the wireless communication network N2. Further, when the time when the communication terminal 10A stays at the specific position information is included in the decoding condition, the position information of the communication terminal 10A and the acquisition time (time information) of the position information are associated with each other and the communication terminal 10 to the management server 20. Then, the management server 20 confirms whether or not the position information and time information acquired in the communication terminal 10A satisfy the decryption condition of the data to be encrypted. The processing related to the acquisition of the position information by the position information acquisition unit 18 may be, for example, a mode in which the position information is periodically acquired in the communication terminal 10A, or the owner of the communication terminal 10A performs communication. It can also be set as the aspect performed by operating terminal 10A.

  Next, the decryption conditions for the encryption target data stored in the management server 20 will be described. FIG. 15 is a diagram illustrating an example of the decryption conditions for the encryption target data stored in the data storage unit 22 of the management server 20. As shown in FIG. 15, when the decoding condition is that the communication terminal 10A passes through a plurality of areas (for example, areas P1 to P4 in FIG. 13), the information related to each area and the area are passed. Decoding conditions can be indicated by a time and one condition, and a plurality of these conditions are listed. Note that the conditions relating to the time are not essential, and only the conditions relating to the place (designating the area to be routed) may be used. In order for the communication terminal 10A to satisfy the decoding conditions, the conditions must be satisfied in the order of condition 1, condition 2,. When the last condition (condition n in FIG. 15) is satisfied, the management server 20 determines that all conditions for decoding are satisfied, and the position that satisfies the last condition (that is, at location n in FIG. 15). The data to be encrypted can be decrypted at the position shown). As shown in FIG. 15, a range in which decoding can be performed (for example, a radius for defining a circular region drawn around a specific place is “distance 1”) is determined in advance. You can also. The decryption conditions are created for each piece of encryption target data by the host terminal that holds the encryption target data before encryption and transmitted to the management server 20, for example. Therefore, the management server 20 stores the decryption condition in association with the ID that specifies the data to be encrypted.

(About processing by data encryption system)
(2-1. Encryption of data to be encrypted)
Next, processing relating to encryption of data to be encrypted by the data encryption system 2 according to the present embodiment will be described with reference to FIG. In addition, about the part to which the process similar to 1st Embodiment is performed, the description which concerns on the detail is abbreviate | omitted.

In the present embodiment, the communication terminal 10A ₁ holds the data to be encrypted (S501), the communication terminal 10 ₁ as a host terminal in the case of performing the encryption of the encryption target data. Further, the communication terminal 10 ₁ as a host terminal, the threshold value k and the decoding conditions for performing encryption is determined (S502). Here, the threshold value k defined by the communication terminal 10A ₁ is a host terminal is the same as in the first embodiment. As for the decoding conditions, conditions shown in the table shown in FIG. 15 is determined by the communication terminal 10A ₁ is a host terminal, are combined as one data of decoded condition data.

Next, the communication terminal 10A ₁ is a host terminal searches the surroundings of the terminal, to the communication terminal _10A 2 10 A _n, querying whether connectable against ad hoc network N1 (S503a , S503b). In contrast, the communication terminal 10A ₂ that can be connected to the ad hoc network N1 performs a response to the effect which is connectable to the communication terminal 10A ₁ (S504). Furthermore, by the process according to the connection to adhoc network N1 between the communication terminal 10A ₁ and the communication terminal 10A ₂ is performed (S505~S506), the communication terminal 10A ₂ is connected to an ad hoc network N1. Also, with another communication terminal 10A including the communication terminal 10A _n, similar processing is performed (S507~S509), the communication terminal 10A _n are connected to an ad hoc network N1. By repeating this process, the ad hoc network N1 is configured by the n communication terminals 10A including the host terminal.

Here the communication terminal 10A ₁ is a host terminal checks whether the terminal number n to the ad-hoc network N1 is the threshold value k than the predetermined (S510), the terminal number n is the threshold k Is smaller, the number n of terminals is small, and the processing related to the encryption of the data to be encrypted is stopped (S511). On the other hand, the terminal number n in the case where more than the threshold value k, in the encryption processing section 15 of the communication terminal 10A ₁ is a host terminal, encrypting the encryption target data is performed (S512). Further, in the encrypted data, different secret sharing data distributed to n based on the number of terminals n are created (S513). Then, in relation to the secret sharing data, information for specifying the encryption target data (encryption target data ID), n secret sharing data generated from the encryption target data, and the secret sharing data Related data including information (network member ID) for identifying a network member that is a communication terminal 10A as a distribution destination, information (host ID) for identifying a host terminal, and a threshold value k is stored in the encryption processing unit 15. It is created (S514).

Thus secret sharing data related data and decoding condition data created by the communication terminal 10A ₂ 10 A is a member terminal from the wireless communication unit 12 of the communication terminal 10A ₁ of the communication unit 11 is a host terminal _is transmitted to _n (S515, S516). Thereby, the secret sharing data / related data and the decryption condition data are stored in the storage unit 17 of each communication terminal 10.

Further, the management server 20 from the communication terminal 10A ₁ is a host terminal, the series of data created or used in the encryption process described above is transmitted. That is, data to be encrypted, n pieces of secret sharing data, relevant data, and decrypted condition data is transmitted to the management server 20 from the communication terminal 10A ₁ of the long-distance wireless communication unit 13, is stored in the management server 20 (S517). Then, the communication terminal 10A _1, in order to ensure security, deletes the encryption target data and the secret shared data held in its own terminal ((2) ~ (n) ) (S518). Thereby, in the communication terminals 10A _{1 to} 10A _n configuring the ad hoc network N1, one piece of different secret sharing data and the decryption condition data are held. With the above processing, the processing related to encryption of the data to be encrypted ends.

(2-2. Decryption of data to be encrypted)
Next, processing related to decryption of data to be encrypted using secret sharing data held by a network member will be described with reference to FIG. FIG. 17 is a sequence diagram illustrating a series of processes related to decryption of data to be encrypted. In the process related to the decryption in the present embodiment, the process by one of the communication terminals 10A that are network members constituting the ad hoc network N1 for performing the decryption will be described as in 1-3. . Further, in the present embodiment, unlike the first embodiment, since it is possible to even be decrypted only one communication terminal 10A for holding secret sharing data, the communication terminal 10A _m are decoded terminal, the processing performed between the communication terminals 10A _m the management server 20 will be described. Further, in the present embodiment, as shown in the table of FIG. 15 described above, there are a plurality of conditions necessary for the communication terminal 10A to perform decoding, and data decoding is performed only when they are achieved in a specific order. The case where can be performed will be described.

First, at the time of starting the processing of the decoding, since one may not achieve the conditions for decoding by the decoding terminal 10A _m, condition p achieved by the decoding device 10A _m at this time is 0 (S601). Subsequently, the decoding terminal 10A _m refers to the decoding condition held in the storage unit 17 of its own terminal, and satisfies the condition indicated by p = p + 1 (that is, the condition 1 at this time). To the position indicated by (S602). This is done by the owner of the decryption device 10A _m refers to the information indicating the decoding condition stored in the decoding terminal 10A _m, to bring the decoded terminal 10A _m to the position indicated by the condition. Next, in the decoding terminal 10A _m arriving at the position indicated by the condition, the position information and the time information is acquired (S603). As described above, the decoding terminal 10A _m is by communicating with the GPS satellite 30 for example, it is possible to acquire the position information of the decoding terminals 10A _m. Then, the management server 20 from long-range wireless communication unit 13 of the decoding device 10A _m, position information and time information of the decoding terminals 10A _m is transmitted (S604).

The communication unit 21 of the management server 20 receives the position information and time information from the decoded terminal 10A _m, these pieces of information, to check whether meets the decoding of secret sharing data held in the decoding terminal 10A _m (S605). Specifically, the communication unit 21 by referring to the data storage unit 22, and which data to be encrypted secret sharing data that is held in the decoding terminal 10A _m is first source terminal is encrypted dispersed Identify what is. Next, the communication unit 21 compares the decoding conditions are stored in association with the encryption target data and (the table shown in FIG. 15), the position information and time information sent from the decoding terminal 10A _m Thus, it is determined whether these pieces of information satisfy the decoding condition (S606).

Here, information transmitted from the decoding terminal 10A _m is, if it is determined not to satisfy any of the n certain decoding conditions, in the management server 20, the decryption of the encrypted target data by the decoding terminal 10A _m The processing related to is stopped (S607). On the other hand, when the information sent from the decoding terminal 10A _m satisfies the decoding condition, then the decoding condition information sent from the decoding terminal 10A _m satisfies the plurality is decoded conditions It is determined whether the last condition is included (S608). Here, when the decoding condition satisfied by the information transmitted from the decoding terminal 10A _m is not the last of the series of decoding conditions, the communication unit 21 of the management server 20 sends the decoding terminal 10A _m to the decoding terminal 10A _m . A response to the next condition is instructed (S609). Then, in a long-range wireless communication unit 13 of the decoding device 10A _m when the corresponding indications to the following conditions is received, it repeats decoding satisfying process (S610). That is, the number of conditions p is increased by one and the same processing is performed (S602).

Further, the management server 20, the decoding condition satisfied by information sent from the decoding terminal 10A _m is, in the case when is the last condition (S611), the result is stored in the data storage unit 22 of the management server 20 among of n secret sharing data decoding terminal 10A _m is obtained by removing one held that, taken out k-1 pieces of secret sharing data arbitrarily. Then, k-1 pieces of secret sharing data is transmitted from the communication unit 21 on the decoded terminal 10A _m, it is received at the decoding terminal 10A _m (S612). Thus, the decoding at the terminal 10A _m order to be able to own terminal acquires the k pieces of secret sharing data including one secret sharing data held, the decoding processing unit of the decoding device 10A _m using this 16 Is decoded (S613). The secret sharing data used for decoding is deleted in the decoding terminal 10A _m (S614).

In the above embodiment, although not specifically described for validity verification for k-1 pieces of secret sharing data transmitted to the decoding terminal 10A _m from the communication unit 21 from the management server 20, the decoding terminal 10A _{In m} , after the secret sharing data is received, the management server 20 may be validated. The correctness verification method in this case is the same as 1-2 described above. That is, decoding and sends the secret sharing data to be verified to the management server 20 from the terminal 10A _m, using a k-1 pieces of secret sharing data stored in the management server 20 and the secret shared data to be verified In the case of decryption, confirmation is made based on whether or not the decrypted data matches the encryption target data stored in the management server 20. Then, only when secret sharing data validity is verified is maintained more than k at the decoding terminal 10A _m, it is possible to aspects decoding is performed.

As described above, in this embodiment, achieved by performing the decryption of the encrypted target data, even if the decoding terminal 10A _m does not constitute an ad hoc network N1, a predetermined decoding condition and, by the results achieved management server 20 to confirm, k-1 pieces of secret sharing data for decoding is sent to the decoding terminal 10A _m from the management server 20, in the decoding terminal 10A _m Decryption is performed. In this case, among the secret sharing data used for decoding, secret sharing data already than secret sharing data held in the decoding terminal 10A _m is one that is stored in advance in the management server 20, and the decoding since the condition is sent from only the management server 20 when it is achieved for the decoded terminal 10A _m, it is realized a high security.

(2-3. Deletion of Decoded Data)
Next, with reference to FIGS. 18 and 19, it will be described the process for deleting the decoded data decoded in the decoding terminal 10A _m. Figure 18 is a diagram explaining the case where decoding terminal 10A _m deletes the decrypted data, FIG. 19 is a diagram for explaining a process of deleting the decrypted data.

The decoding terminal 10A _m deletes the decoded data, as shown in FIG. 18, the decoding terminal 10A _m is a case where the movement from the area P4 that is specified as the last condition of the decoding conditions. At this time, the decoding terminal 10A _m, is carried out processing as shown in FIG. 19, decoded data held in the decoding terminal 10A _m is deleted.

Specifically, first, the position information is acquired in the position information acquisition unit 18 of the decoding device 10A _m (S701). Here, the position information acquired at the decoding terminal 10A _m, compared with the decrypted condition data stored in the storage unit 17 of the decoding device 10A _m, that is the position indicated by the positional information, the decoding It is confirmed in the control unit 14 whether or not it is out of a possible range (that is, the position indicated by the last condition and the area indicated by the decodable range from the position). At this time, if it is determined that the position indicated by the position information of the decoding terminal 10A _m is included in the range where decoding can be performed, the decoded data is not deleted and the position information is acquired again. The processing is repeated from (S701). On the other hand, when the decoding terminal 10A _m is determined to be out of the range that can be decoded, the decoded data is deleted to be held in the decoding terminal 10A _m (S703).

As described above, when the decryption terminal 10A _m holding the decrypted data is moved from a specific area by, for example, a third party, the decrypted data decrypted in the decryption terminal 10A _m is deleted. Information leakage can be prevented, and security can be further improved.

<Third Embodiment>
(Configuration of data encryption system)
Next, a third embodiment of the present invention will be described. The third embodiment is different from the second embodiment in the following points. That is, in the second embodiment, when the communication terminal 10 encrypts the data to be encrypted and decrypts the distributed secret shared data, one communication terminal 10 is indicated by the predetermined decryption condition. When the condition is satisfied, k-1 pieces of secret shared data are acquired from the management server 20, and the communication terminal 10 decrypts the k-1 pieces of secret shared data and the secret shared data held in the own terminal. Is done. On the other hand, in the third embodiment, decryption conditions are individually given to a plurality of communication terminals 10 holding secret sharing data, and the number of communication terminals 10 satisfying the individual decryption conditions is the threshold value k. When this is the case, k−1 pieces of secret sharing data are transmitted from the management server 20 to the k communication terminals 10 that satisfy the individual decryption conditions. Decoding is performed using k pieces of secret sharing data including secret sharing data to be held.

  Here, the decoding conditions used in the third embodiment will be described with reference to FIG. In FIG. 20, as a condition for decrypting the secret sharing data held by the communication terminals 101 to 104, the communication terminals 101, 102, 103, and 104 are individually located in the areas P1, P2, P3, and P4 at predetermined times, respectively. Is required as a decoding condition. In this case, each of the communication terminals 101 to 104 acquires the GPS positioning information by the GPS satellite 30 as the position information of the own terminal, and the time information indicating the time when the position information and the GPS positioning information are acquired is transmitted to the wireless communication network N2. The GPS positioning result is transmitted to the management server 20 via the network. Thereby, in the management server 20, it is determined whether the communication terminals 101-104 satisfy | filled the decoding conditions defined separately, respectively. As described above, in the decryption of the data to be encrypted according to the present embodiment, the position information and time information of the communication terminals 101 to 104 are used as individual decryption conditions, and the individual decryption conditions are set in the management server 20. When it is determined that there are k or more communication terminals 10 that satisfy the threshold, decoding in the communication terminal 10 that satisfies the individual decoding conditions is permitted.

  FIG. 21 is a diagram illustrating an example of individual decoding conditions associated with a plurality of communication terminals 10 (10A) configuring the ad hoc network N1 in the present embodiment. FIG. 21 (A) is similar to the table shown in FIG. 6 (B), for example, for the network member ID that identifies the communication terminal that is a network member, and for each communication terminal 10 indicated by this network member ID. The secret sharing data to be transmitted is associated with the validity verification result of the secret sharing data. The table shown in FIG. 21A is further associated with the individual decoding conditions shown in FIG. Specifically, in FIG. 21B, as the decoding conditions to be satisfied by the communication terminal 10 specified as “terminal ID 1”, the location “location 1”, the time “time 1”, and the location indicated by the location 1 are A range “distance 1” in which decoding can be performed is shown as the center. Therefore, when the communication terminal 10 specified by the terminal ID 1 satisfies the conditions shown in FIG. 21B, the management server 20 determines that the decoding conditions individually assigned to the communication terminal 10 are satisfied. . Individual decoding conditions as shown in FIG. 21B are individually determined for each communication terminal 10. This individual decryption condition is determined by the host terminal that holds the data to be encrypted before encryption.

  Also, the individual decryption conditions determined by the host terminal are the same for the communication terminal 10 (network member) connected to the ad hoc network N1 that encrypts the data to be encrypted, as in the second embodiment. Sent. Thereby, the individual decoding conditions which should be satisfied in each communication terminal 10 can be grasped.

  As described above, since the position information of the communication terminal 10 is used for the individual decryption condition, the communication terminal 10 (10A) used in the data encryption system 3 according to the present embodiment is the second implementation. The position information acquisition unit 18 is included as in the form. And it has the function to acquire the positional information on a self-terminal by communicating with the GPS satellite 30, and to transmit to the management server 20.

(About processing by data encryption system)
(3-1. Encryption of data to be encrypted)
Next, processing related to encryption of data to be encrypted by the data encryption system 1 according to the present embodiment will be described with reference to FIG. In addition, about the part to which the process similar to 1st Embodiment and 2nd Embodiment is performed, the description which concerns on the detail is abbreviate | omitted.

In the present embodiment, the communication terminal 10A ₁ holds the data to be encrypted (S801), the communication terminal 10 ₁ as a host terminal in the case of performing the encryption of the encryption target data. Further, the communication terminal 10 ₁ as a host terminal is determined threshold k in performing encryption (S802). Here, the threshold value k defined by the communication terminal 10A ₁ is a host terminal is the same as the first embodiment and the second embodiment.

Next, the communication terminal 10A ₁ is a host terminal searches the surroundings of the terminal, to the communication terminal _10A 2 10 A _n, querying whether connectable against ad hoc network N1 (S803a , S803b). In contrast, the communication terminal 10A ₂ that can be connected to the ad hoc network N1 performs a response to the effect which is connectable to the communication terminal 10A ₁ (S804). Furthermore, by the process according to the connection to adhoc network N1 between the communication terminal 10A ₁ and the communication terminal 10A ₂ is performed (S805~S806), the communication terminal 10A ₂ is connected to an ad hoc network N1. The same processing is performed with other communication terminals 10A including the communication terminal 10A _n (S807 to S809), and the communication terminal 10A _n is connected to the ad hoc network N1. By repeating this process, the ad hoc network N1 is configured by the n communication terminals 10A including the host terminal.

Here the communication terminal 10A ₁ is a host terminal checks whether the terminal number n to the ad-hoc network N1 is the threshold value k than the predetermined (S810), the terminal number n is the threshold k Is smaller, the number n of terminals is small, and the process related to the encryption of the data to be encrypted is stopped (S811). On the other hand, the terminal number n in the case where more than the threshold value k, in the encryption processing section 15 of the communication terminal 10A ₁ is a host terminal, encrypting the encryption target data is performed (S812). Further, in the encrypted data, different secret sharing data distributed to n based on the number n of terminals are created (S813). Then, in relation to the secret sharing data, information for specifying the encryption target data (encryption target data ID), n secret sharing data generated from the encryption target data, and the secret sharing data Related data including information (network member ID) for identifying a network member that is a communication terminal 10A as a distribution destination, information (host ID) for identifying a host terminal, and a threshold value k is stored in the encryption processing unit 15. It is created (S814). Furthermore, in the present embodiment, at this point, the individual decoding condition data includes individual decoding conditions in each communication terminal 10A is created by the communication terminal 10A ₁ is a host terminal (S815). Specifically, data such as the table shown in FIG. 21 is generated by the communication terminal 10A _1.

Thus secret sharing data related data and individual decoding condition data created is a member terminal from the wireless communication unit 12 of the communication terminal 10A ₁ of the communication unit 11 is a host terminal communication terminals 10A ₂ ~ 10A _{n is} transmitted (S816, S817). Thereby, the secret sharing data / related data and the individual decryption condition data are stored in the storage unit 17 of each communication terminal 10. At this time, the individual decoding condition data to be transmitted to the communication terminals 10A _{2 to} 10A _n includes a decoding condition of the other communication terminal 10A as included in the table shown in FIG. Alternatively, the individual decoding condition may be extracted according to the communication terminal 10A as the transmission destination. When the individual decoding condition data is transmitted to the communication terminal 10A in a state including the decoding conditions of the other communication terminal 10A, which individual decoding condition needs to be determined depends on the communication terminal that has received this data It is determined at 10A.

Further, the management server 20 from the communication terminal 10A ₁ is a host terminal, the series of data created or used in the encryption process described above is transmitted. That is, data to be encrypted, n pieces of secret sharing data, related data, and individual decryption condition data are transmitted from the long-range wireless communication unit 13 of the communication terminal 10A ₁ to the management server 20 and stored in the management server 20. (S818). Then, the communication terminal 10A _1, in order to ensure security, deletes the encryption target data and the secret shared data held in its own terminal ((2) ~ (n) ) (S819). Thereby, in the communication terminals 10A _{1 to} 10A _n configuring the ad hoc network N1, one piece of different secret sharing data and individual decryption condition data are held. With the above processing, the processing related to encryption of the data to be encrypted ends.

(3-2. Decryption of data to be encrypted)
Next, processing related to decryption of data to be encrypted using secret sharing data held by a network member will be described with reference to FIG. FIG. 23 is a sequence diagram illustrating a series of processes related to decryption of data to be encrypted. Note that the decryption process in the present embodiment is also described as a process by one of the communication terminals 10A that are network members constituting the ad hoc network N1 for performing the decryption, similar to 1-3. . Also, in this embodiment, unlike the second embodiment, decryption is performed when there are k or more communication terminals 10A that hold secret shared data and satisfy the individual decryption conditions. since the process is common to be performed in 10A, a decoding terminal single communication terminal 10A _m, decoding according to the embodiment using the process performed between the decoding terminal 10A _m the management server 20 Processing related to the conversion will be described. In the present embodiment, as shown in the table of FIG. 21 described above, a condition (individual decoding condition) that the communication terminal 10A needs to satisfy in order to perform decoding is determined for each communication terminal 10A. A case will be described in which data can be decrypted only when there are k or more communication terminals 10A that satisfy the conversion condition.

First, the management server 20 is in a standby state in order to receive position information / time information from the communication terminal 10A (S901). Here, the decoding terminal 10A _m refers to the individual decoding condition is held in the storage unit 17 of its own terminal to check the condition of the decoding to be satisfied by its own terminal, it moves to the position indicated by the condition ( S902). This is done by the owner of the decryption device 10A _m refers to the information indicating the individual decoding conditions stored in the decoded terminal 10A _m, to bring the decoded terminal 10A _m to the position indicated by the condition. Next, in the decoding terminal 10A _m arriving at the position indicated by the condition, the position information and the time information is acquired (S903). As described above, the decoding terminal 10A _m is by communicating with the GPS satellite 30 for example, it is possible to acquire the position information of the decoding terminals 10A _m. Then, the management server 20 from long-range wireless communication unit 13 of the decoding device 10A _m, position information and time information of the decoding terminals 10A _m is transmitted (S904).

The communication unit 21 of the management server 20 receives the position information and time information from the decoded terminal 10A _m, these pieces of information, to check whether individual decoding satisfy the secret sharing data held in the decoding terminal 10A _m (S905). Specifically, the communication unit 21 by referring to the data storage unit 22, and which encryption target data is secret sharing data decoding terminal 10A _m holds a first source terminal is encrypted dispersed Identify what is. Next, the communication unit 21, in connection with the encryption target data, and the individual decoding conditions are stored in association with the information specifying the decoding terminal 10A _m (network subscriber ID), from the decoded terminal 10A _m By comparing the transmitted position information and time information, it is determined whether these pieces of information satisfy the decoding condition (S906).

Here, information transmitted from the decoding terminal 10A _m is, if it is determined not to satisfy any of the individual decoding conditions stored in the data storage unit 22, the management server 20, the encryption performed by the decoding device 10A _m The process related to the decryption of the data to be processed is stopped (S907). On the other hand, when the information sent from the decoding terminal 10A _m satisfies the decoding condition, the process proceeds to the next step, satisfy the individual decoding condition associated with the same encryption target data and the decoded terminal 10A _m It is confirmed whether there are k or more communication terminals 10A (S908). Here, when there are less than k communication terminals 10A that satisfy the individual decryption conditions associated with the same encryption target data as the decryption terminal 10A _m (S909), the management server 20 uses the same encryption target data. Since the decryption cannot be performed without receiving the position information and the time information related to the individual decryption condition from the other communication terminal 10A that stores the secret sharing data, the process returns to the standby state (S901) again.

On the other hand, if the communication terminal 10A satisfying the individual decoding condition associated with the same encryption target data and the decoded terminal 10A _m is not less than k stand has been confirmed, the decoded terminal 10A _m, decoding while being notified that allow to perform, secret sharing data held k-1 pieces of secret sharing data used to perform the decoding (although the decoding terminal 10A _m in the decoding terminal 10Am (m) is divided Is transmitted) (S910). Although not shown in FIG. 23, when there are k or more communication terminals 10A that satisfy the decoding conditions, each of k-1 or more communication terminals 10A that satisfy the individual decoding conditions is also simultaneously received. K-1 pieces of secret shared data different from the secret shared data held by the communication terminal 10A are transmitted from the management server 20 to the communication terminal 10A.

Accordingly, since the decryption terminal 10A _m can acquire k pieces of secret shared data including one secret share data held by the own terminal, the decryption processing unit of the decryption terminal 10A _m can be obtained using them. 16 is decoded, and decoded data is generated (S911). The secret sharing data used for decoding is deleted in the decoding terminal 10A _m (S912).

In the above embodiment, although not specifically described for validity verification for k-1 pieces of secret sharing data transmitted to the decoding terminal 10A _m from the communication unit 21 from the management server 20, the decoding terminal 10A _{In m} , after the secret sharing data is received, the management server 20 may be validated. The correctness verification method in this case is the same as 1-2 described above. That is, decoding and sends the secret sharing data to be verified to the management server 20 from the terminal 10A _m, using a k-1 pieces of secret sharing data stored in the management server 20 and the secret shared data to be verified In the case of decryption, confirmation is made based on whether or not the decrypted data matches the encryption target data stored in the management server 20. Then, only when secret sharing data validity is verified is maintained more than k at the decoding terminal 10A _m, it is possible to aspects decoding is performed.

As described above, in the present embodiment, by performing the decryption of the encrypted target data, even if the decoding terminal 10A _m does not constitute an ad hoc network N1, advance individual decryption determined for each terminal when the communication terminal 10A which has achieved conditions there are more than k stand including decoding terminal 10A _m, transmits k-1 pieces of secret sharing data for decoding the decoded terminal 10A _m from the management server 20 is, decoding is performed at the decoding terminal 10A _m. In this case, among the secret sharing data used for decoding, secret sharing data already than secret sharing data held in the decoding terminal 10A _m is one that is stored in advance in the management server 20, and individually decodes since the communication terminal 10A which conditions are attained is sent on the decoded terminal 10A _m from the management server 20 only when there is more than k base is realized a high security.

(3-3. Deletion of Decrypted Data)
In the present embodiment, the process of deleting the decrypted data generated at the decoding terminal 10A _m are the same as the second embodiment. That is, it compares the position information acquired in the location information acquiring unit 18 of the decoding device 10A _m, and an individual decryption condition stored in the storage unit 17 of the decoding device 10A _m, is the position indicated by the positional information, decoding It is confirmed in the control unit 14 whether or not it is out of the range that can be converted (that is, the position indicated by the individual decoding conditions and the area indicated by the decoding range from the position). At this time, if the position indicated by the position information of the decoding terminals 10A _m is determined to be included in the range that can be decoded, the deletion of the decoded data is not performed. However, if the decoding terminal 10A _m is determined to be out of the range that can be decoded, the decoded data held in the decoding terminal 10A _m is deleted.

As described above, when the decryption terminal 10A _m holding the decrypted data is moved from a specific area by, for example, a third party, the decrypted data decrypted in the decryption terminal 10A _m is deleted. Information leakage can be prevented, and security can be further improved.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made. For example, in the first embodiment, the mode in which only the secret sharing data whose validity has been verified is used for the decryption has been described. However, it is also possible to omit the process related to the verification of the validity.

Further, in the above-described embodiment, when data is encrypted and decrypted by the communication terminal 10, an aspect in which encryption or decryption is performed after the ad hoc network N1 is configured with another communication terminal 10 will be described. However, encryption or decryption is performed using another network that can determine that the communication terminals 10 are physically close to each other and can share the information between the communication terminals 10. May be. Specifically, for example, each of the communication terminals 10 receives the position information of its own terminal by GPS positioning or the like, and this information is a network composed of the communication terminals 10 ₁ to 10 _n (the network here is an ad hoc network) The network is not limited to this, and may be a network constructed via the wireless communication network N2.

Moreover, in the said embodiment, the aspect which the specific communication terminal 10 (decoding terminal 10 ₂ ) makes the inquiry which concerns on the ad hoc network N1 connection with respect to the other communication terminal 10 as an opportunity that the communication terminal 10 decodes data. However, other embodiments can be used. For example, a configuration in which the ad hoc network N1 is configured, and the communication terminals 10 ₁ to 10 _{n of} the network members that store the secret sharing data monitor whether or not the other communication terminals 10 are in an environment that can configure the ad hoc network N1. An environment in which the communication terminal 10 _m that has confirmed that the number of communication terminals 10 that can form the ad hoc network N1 is equal to or greater than the threshold value k becomes the decryption terminal 10 _{m and} can also form the ad hoc network N1. It can be set as the aspect which performs the inquiry which concerns on the structure of the ad hoc network N1 with respect to the other communication terminal 10 in this. In this case, another communication terminal 10 can release the monitoring state at the stage where the inquiry has been received according to the configuration of the ad-hoc network N1 from the decoding terminal 10 _m, it starts the process according to the decoding.

Further, as a modification of the above-described aspect, for example, the communication terminal 10 (for example, the number 1 to n is assigned to n pieces of secret shared data and the secret shared data (1) having the smallest number is assigned (for example, The communication terminal 10 ₁ ) monitors the other communication terminals 10 (10 ₂ to 10 _n ), and when the number of communication terminals 10 exceeding the threshold value k is in a state that can form the ad hoc network N1, the decoding terminals 10 ₁ may be a mode in which processing related to decoding is started.

Further, in the 2-3 and 3-3 of the above embodiment, when deleting the decoded data decoded terminal 10A _m is decoded, the decoding terminal 10A _m itself in the decoding condition (individual decoding condition) Although it has been described in the aspect of deleting the decoded data held in its own terminal when it is detected that it is out of the position indicated by the position shown and the decodable range from the position, The management server 20 may be involved in the deletion of the decrypted data. Specifically, the decoding terminal 10A _m are periodically acquires position information of the terminal after the decoding of the data, keep the advertise the information to the management server 20. Then, the management server 20, the position information transmitted from the decoded terminal 10A _m determines whether or meets the decoding condition of the decoding terminal 10A _m. Here, if, when the decoding position information transmitted from the terminal 10A _m is out from the area indicated by the decoding range from the position and the position indicated by the decoding condition of the decoding terminal 10A _m the management server the decoded terminal 10A _m from 20 sends a delete command of the decoded data may be a mode for deleting the decoded data based on the instruction at the decoding terminal 10A _m.

  In the third embodiment, an aspect in which each communication terminal 10 has one individual decoding condition has been described. However, as in the second embodiment, an aspect including a plurality of conditions may be employed. In this case, the management server 20 determines that the individual decoding condition for the communication terminal 10 is satisfied only when the plurality of conditions given to each communication terminal 10 can be completely satisfied. .

  DESCRIPTION OF SYMBOLS 1, 2, 3 ... Data encryption system 10, 10A ... Communication terminal (decryption terminal), 11 ... Communication part, 12 ... Short-distance wireless communication part, 13 ... Long-distance wireless communication part, 14 ... Control part, 15 ... Encryption processing unit, 16 ... Decryption processing unit, 17 ... Storage unit, 18 ... Location information acquisition unit, 20 ... Management server, 21 ... Communication unit, 22 ... Data storage unit, 23 ... Validity verification unit, 30 ... GPS satellite.

Claims (16)

A data encryption system comprising a plurality of communication devices including one host device that holds encryption target data that is an object to be encrypted, and a plurality of member devices different from the host device,
The host device is
When the number of the plurality of communication devices is n and the threshold value is k, n> k and information specifying the plurality of communication devices is notified to each other, and these pieces of information are assigned to the plurality of communication devices. A procedure for collecting partial data related to the data to be encrypted at the time of decryption when it is specified that the plurality of communication devices constitute the same network by holding each in the communication device. Encryption means for creating encrypted data obtained by encrypting the encryption target data using an encryption method including:
A distribution unit that distributes the encrypted data and generates n different secret sharing data that are partial data related to the data to be encrypted;
a distribution means for distributing different n-1 secret sharing data to the n-1 member devices;
A data encryption system comprising:   The data encryption system according to claim 1, wherein the network is an ad hoc network.   The encryption unit is configured such that each of the plurality of communication devices acquires the position information of the communication device and shares the position information in a network configured between the plurality of communication devices, so that the plurality of communication devices 2. The data encryption system according to claim 1, wherein the encrypted data is created when it is determined that they are physically close to each other.   The data encryption system according to any one of claims 1 to 3, wherein the encryption method is a threshold secret sharing scheme. A management server connected to the plurality of communication devices via a wireless communication network;
The host device is
Data transmission means for transmitting the data to be encrypted and the n different secret sharing data to the management server;
The management server
The data encryption according to any one of claims 1 to 4, further comprising: received data storage means for storing the data to be encrypted from the host device and the n different pieces of secret sharing data. system. The member device is
Storage means for storing secret sharing data distributed from the host device;
The secret sharing data stored in the storage means is transmitted to the management server, the verification of the validity of the secret sharing data is requested, and the verification result of the validity transmitted from the management server is displayed. A secret sharing data verification means for receiving,
The management server
Validity of the secret sharing data from the member device based on the n different secret sharing data and the data to be encrypted received from the host device and receiving the secret sharing data from the member device 6. The data encryption system according to claim 5, further comprising a validity verification unit that verifies and transmits the result to the member device. The validity verification means includes
Of the n different secret sharing data transmitted from the host device, k−1 secret sharing data different from the secret sharing data from the member device, the secret sharing data from the member device, and , The decrypted data is compared with the encryption target data from the host device, and when the encryption target data matches the decrypted data, the member device The data encryption system according to claim 6, wherein the validity of the secret sharing data is determined to have been verified. A decryption device that is included in the plurality of communication devices and decrypts the data to be encrypted,
In order to determine that the decryption device and other communication devices that hold the secret sharing data are composed of k or more, and that the decryption device and the other communication device are physically close to each other Secret sharing data acquisition means configured to acquire k−1 or more secret sharing data from other communication devices via the decoding network,
Decryption means for performing decryption using the acquired secret sharing data and the secret sharing data held in the decrypting device, and generating decrypted data;
The data encryption system according to claim 1, further comprising: A decryption device that is included in the plurality of communication devices and decrypts the data to be encrypted,
In order to determine that the decryption device and other communication devices that hold the secret sharing data are composed of k or more, and that the decryption device and the other communication device are physically close to each other Secret decoding data acquisition means for acquiring k-1 or more secret sharing data whose validity has been verified from other communication devices via the decoding network,
Decryption means for performing decryption using the acquired secret sharing data and the secret sharing data held in the decrypting device, and generating decrypted data;
The data encryption system according to claim 6 or 7, further comprising:   10. The data encryption system according to claim 8, wherein the decryption network is an ad hoc network.   The decoding device further includes a deletion unit that deletes the decoded data held by the decoding device when the number of communication devices constituting the decoding network becomes k or less. The data encryption system according to any one of claims 8 to 10. The decryption device
Position information acquisition means for acquiring position information of the decoding device;
A positional information transmitting means for transmitting the positional information to the management server;
The management server
In the storage means, the decryption device further stores a decryption condition indicating position information, which is a condition under which the decryption device can perform the decryption using the secret sharing data,
It is determined whether or not the position information from the decryption device satisfies the decryption condition, and if it is determined that the decryption condition is satisfied, k−1 different from the secret sharing data held by the decryption device Further comprising decryption condition determination means for transmitting the pieces of secret sharing data to the decryption device,
The decryption unit of the decryption device performs decryption using the secret sharing data transmitted from the management server and the secret sharing data held in the decryption device, and generates decryption data. Item 8. The data encryption system according to any one of Items 5 to 7 . The decryption device
Position information acquisition means for acquiring position information of the decoding device;
A positional information transmitting means for transmitting the positional information to the management server;
The management server
In the storage means, the decryption condition that allows the decryption device to perform the decryption using the secret sharing data, and the individual decryption condition that indicates different position information for each communication device that holds the secret sharing data Further store
When the position information from the decoding device determines whether or not the dedicated decoding condition is satisfied, and there are k or more communication devices that are determined to satisfy the dedicated decoding condition, including the decoding device, Further comprising decryption condition judging means for transmitting k-1 secret shared data different from the secret shared data held by the decryption device to the decryption device;
The decryption unit of the decryption device performs decryption using the secret sharing data transmitted from the management server and the secret sharing data held in the decryption device, and generates decryption data. Item 8. The data encryption system according to any one of Items 5 to 7 .   The decoding device further comprises a deletion unit that deletes the decoded data held by the decoding device when the decoding device no longer satisfies the decoding condition after decoding. 14. The data encryption system according to any one of items 13. A host device included in a data encryption system including a plurality of communication devices including one host device that holds encryption target data that is an object to be encrypted and a plurality of member devices different from the host device. There,
When the number of the plurality of communication devices is n and the threshold value is k, n> k and information specifying the plurality of communication devices is notified to each other, and these pieces of information are assigned to the plurality of communication devices. A procedure for collecting partial data related to the data to be encrypted at the time of decryption when it is specified that the plurality of communication devices constitute the same network by holding each in the communication device. Encryption means for creating encrypted data obtained by encrypting the encryption target data using an encryption method including:
A distribution unit that distributes the encrypted data and generates n different secret sharing data that are partial data related to the data to be encrypted;
a distribution means for distributing different n-1 secret sharing data to the n-1 member devices;
A host device comprising: A data encryption method by a data encryption system comprising a plurality of communication devices comprising one host device that holds encryption target data to be encrypted and a plurality of member devices different from the host device Because
When the number of the plurality of communication devices is n and the threshold value is k, the encryption means of the host device informs each other that n> k and specifies the plurality of communication devices. By holding these pieces of information in each of the plurality of communication devices, if it is specified that the plurality of communication devices constitute the same network, the data to be encrypted is included in the data to be encrypted at the time of decryption. An encryption step of creating encrypted data obtained by encrypting the data to be encrypted using an encryption method including a procedure of collecting related partial data;
A distribution step of distributing the encrypted data by a distribution unit of the host device and generating n different secret sharing data that are partial data related to the data to be encrypted;
A distribution step of distributing different n-1 pieces of secret sharing data to n-1 member devices by a distribution unit of the host device;
A data encryption method comprising:

Images