JP2016012897A - Encryption data management system, proxy server, user terminal, encryption data management method, and computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a load related to encryption processing in the case of sharing encryption data by using a proxy re-encryption technology or a searchable encryption technology.SOLUTION: A user terminal 10 includes: a data encryption part 13 for generating the encryption data of data; a key encryption part 17 for generating the encryption data of the key of the encryption data; and a key generation part 12 for generating a re-encryption key related to a reception server 70. A storage server 30 includes an encryption data storage part 33 for storing the encryption data of the data and the encryption data of the key from the user terminal 10 in association. A proxy server 50 includes a re-encryption part 53 for performing re-encryption to the encryption data of the key from the storage server 30 by using the re-encryption key from the user terminal 10. The reception server 70 includes a decryption part 72 for decrypting the encryption data of the data from the storage server 30 by using a key obtained by decrypting the encryption data of the key subjected to the re-encryption from the proxy server 50.

Description

  The present invention relates to an encrypted data management system, a proxy server, a user terminal, an encrypted data management method, and a computer program.

  In recent years, the use of personal data has been studied. For example, by storing life log data, such as location information indicating the location where an individual is staying, in a location (for example, a cloud storage server) accessible to others via a communication network, It will be easier to use. However, it is important to handle life log data carefully from the viewpoint of privacy protection. For this reason, for example, enabling the access to only the other person permitted by the user with respect to the life log data stored in the cloud storage server by the user is cited as a privacy protection measure. In addition, it is desirable that the access control to life log data should be flexible. For example, even if position information is usually provided, position information when in a specific area is not provided. In addition, by concealing the life log data stored in the cloud storage server from the cloud storage company that manages the cloud storage server, the security of the user who keeps the life log data is increased. In order to solve these points, it is conceivable that life log data is encrypted and stored in a cloud storage server.

  As conventional encryption techniques, for example, encryption techniques such as a proxy re-encryption (PRE) technique and a searchable encryption technique are known. The proxy re-encryption technique is a technique for converting a file encrypted with another key while the file is encrypted (see, for example, Non-Patent Document 1). The searchable encryption technique is a technique for searching an encrypted file without decrypting it (see, for example, Non-Patent Document 2). Further, a technique called “Secure Indexes” that shortens the processing time of searchable encryption is known (see, for example, Non-Patent Document 3).

M. Blaze, G. Bleumer, and M. Strauss, “Divertible protocols and atomic proxy cryptography”, Advances in Cryptology EUROCRYPT'98, pp.127-144, Springer, 1998. D. Boneh, G. Di Crescenzo, R. Ostrovsky, and G. Persiano. “Public key encryption with keyword search.”, In EUROCRYPT '04, pp.506-522, 2004. E. Goh, “Secure Indexes”, Cryptology ePrint Archive, Report 2003/216, 2003.

  However, when the encrypted data is shared using the above-described conventional proxy re-encryption technique or searchable encryption technique, there is a problem that the load of encryption processing is heavy. In addition, the “Secure Indexes” technology can reduce the processing time of searchable encryption, but an erroneous search “False Positive” may occur.

  The present invention has been made in view of such circumstances, and can reduce the load on encryption processing when sharing encrypted data using proxy re-encryption technology or searchable encryption technology. An object is to provide an encrypted data management system, a proxy server, a user terminal, an encrypted data management method, and a computer program.

(1) One aspect of the present invention is an encrypted data management system including a user terminal, a storage server, a proxy server, and a receiving server, and the user terminal communicates with the storage server and the proxy server. A data encryption unit that generates encrypted data of the data, a key encryption unit that generates encrypted data of a key for the encrypted data of the data, and a re-encryption key for the receiving server A key generation unit, wherein the user terminal communication unit transmits the encrypted data of the data and the encrypted data of the key to the storage server, transmits the re-encryption key to the proxy server, and The storage server includes a storage server communication unit that communicates with the user terminal, the proxy server, and the receiving server, and the user. An encrypted data storage unit that associates and stores the encrypted data of the data acquired from the end and the encrypted data of the key, and the storage server communication unit transmits the encrypted data of the key to the proxy server The encrypted data of the data is transmitted to the receiving server, and the proxy server is obtained from the storage server, a proxy server communication unit that communicates with the user terminal, the storage server, and the receiving server. A re-encryption unit that re-encrypts the encrypted data of the key with the re-encryption key acquired from the user terminal, and the proxy server communication unit includes the re-encrypted key Receiving server communication for transmitting encrypted data to the receiving server, wherein the receiving server communicates with the storage server and the proxy server And decrypting the encrypted data of the re-encrypted key obtained from the proxy server to obtain the key, and decrypting the encrypted data of the data obtained from the storage server with the obtained key And a decryption unit.

(2) One aspect of the present invention is an encrypted data management system including a user terminal, a storage server, a proxy server, and a receiving server, and the user terminal communicates with the storage server and the proxy server. A data encryption unit that generates encrypted data of the data, an index generation unit that generates an index based on a tag for the data, a key generation unit that generates a re-encryption key for the receiving server, The user terminal communication unit transmits the encrypted data of the data and the index to the storage server, transmits the re-encryption key to the proxy server, and the storage server includes the user terminal and the Obtained from the storage server communication unit communicating with the proxy server and the user terminal An encrypted data storage unit that associates and stores the encrypted data of the data and the index, and an encryption search unit that retrieves the encrypted data associated with the index based on the trap door acquired from the proxy server; The storage server communication unit transmits encrypted data of the data as a result of the search to the proxy server, and the proxy server communicates with the user terminal, the storage server, and the receiving server. A server communication unit, a trap door generation unit that generates a trap door for a search keyword acquired from the receiving server, and encrypted data of data acquired from the storage server as a result of a search based on the trap door, To the receiving server acquired from the user terminal A re-encryption unit that performs re-encryption using the re-encryption key, wherein the proxy server communication unit transmits encrypted data of the re-encrypted data to the receiving server, and the receiving server Is an encrypted data management system comprising: a receiving server communication unit that communicates with the proxy server; and a decryption unit that decrypts the encrypted data of the re-encrypted data acquired from the proxy server. .

(3) One aspect of the present invention is the proxy server in an encrypted data management system including a user terminal, a storage server, a proxy server, and a receiving server, and a key for encrypted data of the data and the encrypted data of the data The user terminal that transmits the encrypted data of the data to the storage server, the storage server that stores the encrypted data of the data and the encrypted data of the key in association with each other, and the encrypted data of the data from the storage server A proxy server communication unit that communicates with the receiving server that acquires the encrypted data of the key acquired from the storage server, and re-encrypted with the re-encryption key for the receiving server acquired from the user terminal A re-encryption unit that performs the re-encryption. To transmitted key encrypted data to the receiving server is a proxy server.
(4) One aspect of the present invention is the proxy server according to (3), further including a trap door generation unit that generates a trap door for the search keyword acquired from the receiving server, wherein the proxy server communication unit includes The trap door is transmitted to the storage server storing an index based on the tag of the data in association with the encrypted data of the data and the encrypted data of the key, and a search based on the trap door is transmitted from the storage server. A proxy server that receives the resulting index and encrypted data of the key associated with the index, and transmits the received index and encrypted data of the re-encrypted key to the receiving server .
(5) In one aspect of the present invention, in the proxy server according to (4), the proxy server communication unit includes an encrypted data of a tag for the data, an index based on the tag, an encrypted data of the data, and The encrypted data of the tag as a result of the search based on the trap door is received from the storage server that is stored in association with the encrypted data of the key, and the proxy server receives the encrypted data of the received tag. The proxy server further includes a tag verification unit that performs tag verification based on a decryption result and the search keyword.

(6) One aspect of the present invention is the proxy server in an encrypted data management system including a user terminal, a storage server, a proxy server, and a receiving server, and an index based on encrypted data of the data and a tag for the data Provided to the storage server, the storage server storing the encrypted data and the index in association with each other, and the encrypted data of the data stored in the storage server. A proxy server communication unit that communicates with a receiving server, a trap door generation unit that generates a trap door for a search keyword acquired from the receiving server, and encrypted data of data acquired from the storage server by the proxy server communication unit On the other hand, A re-encryption unit that re-encrypts with the re-encryption key for the receiving server acquired from the terminal, and the proxy server communication unit transmits the trap door to the storage server, and the storage server A proxy server that receives encrypted data of data that is a result of a search based on the trapdoor from the server and transmits the encrypted data of the re-encrypted data to the receiving server.

(7) One aspect of the present invention is the user terminal in an encrypted data management system including a user terminal, a storage server, a proxy server, and a receiving server, and a user terminal communication unit that communicates with the storage server and the proxy server; A data encryption unit that generates encrypted data of the data, a key encryption unit that generates encrypted data of a key for the encrypted data of the data, and a key that generates a re-encryption key for the receiving server And the user terminal communication unit stores the encrypted data of the data and the encrypted data of the key in the storage server that stores the encrypted data of the data and the encrypted data of the key in association with each other. The encrypted data of the key acquired from the storage server is re-encrypted with the re-encryption key Transmitting said re-encryption key to Rokishisaba a user terminal.

(8) One aspect of the present invention is the user terminal in an encrypted data management system including a user terminal, a storage server, a proxy server, and a receiving server, and a user terminal communication unit that communicates with the storage server and the proxy server; A data encryption unit for generating encrypted data, an index generation unit for generating an index based on a tag for the data, and a key generation unit for generating a re-encryption key for the receiving server, The user terminal communication unit transmits the encrypted data of the data and the index to the storage server that associates and stores the encrypted data of the data and the index, and traps the search keyword of the receiving server The storage server as a search result based on doors Wherein transmitting said re-encryption key to the proxy server with respect et obtained data of the encrypted data to re-encrypted by the re-encryption key, a user terminal.

(9) One aspect of the present invention is an encrypted data management method in an encrypted data management system including a user terminal, a storage server, a proxy server, and a receiving server. The user terminal generates encrypted data of data. Generating encrypted data of the key for the encrypted data of the data, transmitting the encrypted data of the data and the encrypted data of the key to the storage server, and generating a re-encryption key for the receiving server The re-encryption key is transmitted to the proxy server, and the storage server stores the encrypted data of the data acquired from the user terminal in association with the encrypted data of the key, and the encryption of the key Send encrypted data to the proxy server, send encrypted data of the data to the receiving server, and the proxy server The encrypted data of the key acquired from the storage server is re-encrypted with the re-encryption key acquired from the user terminal, and the encrypted data of the re-encrypted key is transmitted to the receiving server. The receiving server decrypts the encrypted data of the re-encrypted key acquired from the proxy server to acquire a key, and encrypts the data acquired from the storage server with the acquired key. An encrypted data management method for decrypting data.

(10) One aspect of the present invention is an encrypted data management method in an encrypted data management system including a user terminal, a storage server, a proxy server, and a receiving server, and the user terminal generates encrypted data of data. Generating an index based on a tag for the data, transmitting the encrypted data of the data and the index to the storage server, generating a re-encryption key for the receiving server, and generating the re-encryption key The storage server stores the encrypted data of the data acquired from the user terminal and the index in association with each other, and the proxy server traps the search keyword acquired from the receiving server. Create a door and move the trap door to the storage server And the storage server searches the encrypted data associated with the index based on the trap door acquired from the proxy server, and transmits the encrypted data of the data as a result of the search to the proxy server. The proxy server performs re-encryption with the re-encryption key acquired from the user terminal on the encrypted data acquired from the storage server as a result of the search based on the trap door, Encrypted data management, wherein encrypted data of the re-encrypted data is transmitted to the receiving server, and the receiving server decrypts the encrypted data of the re-encrypted data acquired from the proxy server Is the method.

(11) According to one aspect of the present invention, there is provided a computer of the proxy server in an encrypted data management system including a user terminal, a storage server, a proxy server, and a receiving server, about data encryption data and data encryption data. The user terminal that transmits encrypted data of a key to the storage server, the storage server that associates and stores the encrypted data of the data and the encrypted data of the key, and encryption of the data from the storage server A communication function for communicating with the receiving server for acquiring data, and re-encryption of the encrypted data of the key acquired from the storage server with a re-encryption key for the receiving server acquired from the user terminal. A computer program for realizing the re-encryption function to be performed. The communication function, transmits the encrypted data of said re-encrypted key to the receiving server is a computer program.

(12) One aspect of the present invention is based on encrypted data of data and a tag about the data in a computer of the proxy server in an encrypted data management system including a user terminal, a storage server, a proxy server, and a receiving server. Providing the user terminal for transmitting an index to the storage server, the storage server storing the encrypted data and the index in association with each other, and providing the encrypted data of the data stored in the storage server A communication function for communicating with a receiving server, a trap door generating function for generating a trap door for a search keyword acquired from the receiving server, and encrypted data of data acquired from the storage server by the communication function, From the user terminal A re-encryption function for performing re-encryption with the re-encryption key for the obtained receiving server, and the communication function transmits the trap door to the storage server, and A computer program that receives encrypted data of data that is a result of a search based on the trapdoor from a storage server, and transmits the encrypted data of the re-encrypted data to the receiving server.

  According to the present invention, when sharing encrypted data using proxy re-encryption technology or searchable encryption technology, it is possible to reduce the load on encryption processing.

It is a block diagram which shows the structure of the encryption data management system which concerns on 1st Embodiment of this invention. It is a sequence chart which shows the procedure of the encryption data management method which concerns on 1st Embodiment of this invention. It is a block diagram which shows the structure of the encryption data management system which concerns on 2nd Embodiment of this invention. It is a sequence chart which shows the procedure of the encryption data management method which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structure of the encryption data management system which concerns on 3rd Embodiment of this invention. It is a sequence chart which shows the procedure of the encryption data management method which concerns on 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, proxy re-encryption processing and searchable encryption processing will be described.

[Proxy re-encryption process]
The proxy re-encryption process is composed of algorithms PKG, E, D, RG, and R. The key generation algorithm PKG receives the security parameter k and outputs a key pair (pk, sk). The encryption algorithm E receives the key pk_A of the user A and the message m, and outputs a ciphertext c_A. Decryption algorithm D receives user A's key sk_A and ciphertext c_A, and outputs message m. The re-encryption key generation algorithm RG receives the key pk_A, sk_A of the user A and the key pk_B of the user B, and outputs a re-encryption key rk_ (A, B). The re-encryption algorithm R receives the re-encryption key rk_ (A, B) and the cipher text c_A, and outputs the re-encrypted cipher text c_B. Here, even if the re-encryption key rk_ (A, B) is owned, no information regarding the message m can be obtained. This proxy re-encryption process is described in Non-Patent Document 1, for example.

[Searchable cryptographic processing]
The searchable encryption process is composed of algorithms SKG, TD, BI, and SI. The key generation algorithm SKG receives the security parameter k and outputs a master key mk. The trap door generation algorithm TD receives the master key mk and the keyword w and outputs a trap door t_w. The index generation algorithm BI receives the master key mk and the document d and outputs an index i_d. The index search algorithm SI receives the trapdoor t_w and the index i_d as input, and outputs 1 if the keyword d is included in the document d, and outputs 0 if not. This searchable encryption process is described in Non-Patent Document 2, for example.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of an encrypted data management system according to the first embodiment of the present invention. In FIG. 1, a user terminal 10, a storage server 30, a proxy server 50, and a receiving server 70 are respectively connected to a communication network 90 so that data can be transmitted / received to / from each other via the communication network 90.

  The user terminal 10 requests the storage server 30 to store the encrypted data. The user terminal 10 includes a communication unit 11 (user terminal communication unit), a key generation unit 12, a data encryption unit 13, an index generation unit 14, a tag setting unit 15, and a data storage unit 16. The communication unit 11 exchanges data with other devices via the communication network 90. The key generation unit 12 generates a key. The data encryption unit 13 encrypts data. The index generation unit 14 generates an index. The tag setting unit 15 sets a tag. The data storage unit 16 stores data.

  The user terminal 10 includes a memory, a CPU (Central Processing Unit), and the like. The CPU executes a computer program for realizing the function of the user terminal 10 and realizes the function. The user terminal 10 may be configured using a general-purpose computer device, or may be configured as a dedicated hardware device. As the user terminal 10, a mobile communication terminal device such as a smartphone, a tablet computer device, a stationary personal computer device, or the like may be used.

  The storage server 30 includes a communication unit 31 (storage server communication unit), an encryption search unit 32, and an encrypted data storage unit 33. The communication unit 31 exchanges data with other devices via the communication network 90. The cryptographic search unit 32 searches the encrypted data stored in the encrypted data storage unit 33. The encrypted data storage unit 33 stores encrypted data.

  The storage server 30 is configured by a memory, a CPU, and the like, and the function is realized by the CPU executing a computer program for realizing the function of the storage server 30. The storage server 30 may be configured using a general-purpose computer device, or may be configured as a dedicated hardware device.

  The proxy server 50 includes a communication unit 51 (proxy server communication unit), a trap door generation unit 52, a re-encryption unit 53, an access right verification unit 54, and an access right storage unit 55. The communication unit 51 transmits and receives data to and from other devices via the communication network 90. The trap door generation unit 52 generates a trap door. The re-encryption unit 53 re-encrypts the encrypted data. The access right verification unit 54 verifies the access right to the encrypted data stored in the storage server 30. The access right storage unit 55 stores access right information for encrypted data stored in the storage server 30.

  The proxy server 50 is configured by a memory, a CPU, and the like, and the function is realized by the CPU executing a computer program for realizing the function of the proxy server 50. The proxy server 50 may be configured using a general-purpose computer device, or may be configured as a dedicated hardware device.

  The receiving server 70 is provided with encrypted data of data stored in the storage server 30. The receiving server 70 includes a communication unit 71 (receiving server communication unit) and a decoding unit 72. The communication unit 71 transmits and receives data to and from other devices via the communication network 90. The decryption unit 72 decrypts the encrypted data.

  The receiving server 70 is configured by a memory, a CPU, and the like, and realizes the function by the CPU executing a computer program for realizing the function of the receiving server 70. The receiving server 70 may be configured using a general-purpose computer device, or may be configured as a dedicated hardware device.

  Next, the operation of the encrypted data management system according to the first embodiment shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a sequence chart showing the procedure of the encrypted data management method according to the first embodiment of the present invention. Hereinafter, it is assumed that data exchange among any one of the user terminal 10, the storage server 30, the proxy server 50, and the receiving server 70 is performed via the communication network 90 by each communication unit.

  The user terminal 10 generates a key by the key generation unit 12 in advance. The key generation unit 12 executes the key generation algorithm PKG, receives the security parameter k, and acquires a key pair (pk_A, sk_A). The key sk_A is secretly acquired and securely held in the user terminal 10. The user terminal 10 discloses the key pk_A. Similarly, the receiving server 70 acquires the key pair (pk_B, sk_B). The key sk_B is secretly acquired and securely held in the receiving server 70. The receiving server 70 discloses the key pk_B.

  Further, the key generation unit 12 of the user terminal 10 executes the key generation algorithm SKG and acquires the master key mk. The user terminal 10 transmits the master key mk to the proxy server 50.

(Step S <b> 101) Data v stored in the storage server 30 is stored in the data storage unit 16 of the user terminal 10. The tag setting unit 15 of the user terminal 10 sets a tag for the data v. Here, for convenience of explanation, two tags u_1 and u_2 are set. For example, it is assumed that the data v is position information indicating the detailed stay location and stay time of the user. In this case, the tags u_1 and u_2 are set as information in which the stay location and the stay time are rough. For example, “Shibuya” as a tag related to the staying place and “Early January” as a tag related to the staying time are made ambiguous to a level that does not matter so much even if known to others.

  The data encryption unit 13 of the user terminal 10 executes the encryption algorithm E, encrypts the data v with its own public key pk_A, and obtains encrypted data E (pk_A, v). Further, the index generation unit 14 of the user terminal 10 sets all the tags u_1 and u_2 for the data v as one document d, executes the index generation algorithm BI for the document d using the master key mk, and sets the index i_d. To get.

  The user terminal 10 transmits the index i_d and the encrypted data E (pk_A, v) to the storage server 30. The storage server 30 associates the received index i_d with the encrypted data E (pk_A, v) and stores it in the encrypted data storage unit 33.

(Step S <b> 102) The user terminal 10 sets access right information for the proxy server 50. The access right information includes, for example, information indicating a business partner of a partner who is permitted to provide data deposited from the user terminal 10 to the storage server 30. The access right information includes, for example, a time zone during which data provision is not permitted and the location of the data provision partner. The proxy server 50 stores the access right information set from the user terminal 10 in the access right storage unit 55 in association with the identification information of the user terminal 10.

(Step S103) The receiving server 70 requests the proxy server 50 to search for encrypted data stored in the storage server 30. The receiving server 70 transmits a search keyword x for searching the encrypted data to the proxy server 50. When the proxy server 50 receives the search request, the proxy server 50 determines whether or not there is an access right for the receiving server 70 based on the access right information stored in the access right storage unit 55. Here, it is assumed that the receiving server 70 is determined to have access rights.

(Step S104) The trap door generation unit 52 of the proxy server 50 executes the trap door generation algorithm TD using the master key mk and the search keyword x received from the reception server 70, and acquires the trap door t_x. The proxy server 50 transmits the acquired trap door t_x to the storage server 30.

(Step S105) The cryptographic search unit 32 of the storage server 30 uses the trapdoor t_x received from the proxy server 50 as an index for all the encrypted data stored in the encrypted data storage unit 33. The search algorithm SI is executed. As a result, the index search algorithm SI outputs 1 for the index containing the search keyword x. The storage server 30 transmits the encrypted data associated with the index to which 1 is output to the proxy server 50. Here, since the search keyword x is equal to the tag u_1 and 1 is output for the index i_d, the encrypted data E (pk_A, v) associated with the index i_d is transmitted to the proxy server 50.

(Step S106) The proxy server 50 requests the re-encryption key for the receiving server 70 from the user terminal 10. The key generation unit 12 of the user terminal 10 executes the re-encryption key generation algorithm RG using its own key pk_A, sk_A and the public key pk_B of the receiving server 70 in response to the request for the re-encryption key. The re-encryption key rk_ (A, B) is acquired. The user terminal 10 transmits the acquired re-encryption key rk_ (A, B) to the proxy server 50.
Instead of step S106, the key generation unit 12 of the user terminal 10 generates a re-encryption key rk_ (A, B) for the receiving server 70 in advance, and the user terminal 10 transmits the re-encryption key rk_ (A, B) may be transmitted to the proxy server 50.

(Step S107) The re-encryption unit 53 of the proxy server 50 uses the re-encryption key rk_ (A, B) acquired from the user terminal 10 for the encrypted data E (pk_A, v) acquired from the storage server 30. The re-encryption algorithm R is used to execute the re-encrypted encrypted data E (pk_B, v). At this time, the proxy server 50 does not obtain any information about the data v. The proxy server 50 transmits the acquired encrypted data E (pk_B, v) to the receiving server 70. The decryption unit 72 of the receiving server 70 executes the decryption algorithm D, decrypts the encrypted data E (pk_B, v) with its own secret key sk_B, and acquires data v.

  According to the first embodiment described above, the proxy server 50 generates a trap door for searching for encrypted data stored in the storage server 30, and the encrypted data of the search result based on the trap door is generated. The encrypted data received from the storage server 30 is re-encrypted with the re-encryption key for the receiving server 70. For this reason, the receiving server 70 can decrypt the re-encrypted encrypted data with its own key, so it is not necessary to have a key for the user terminal 10 that has deposited the encrypted data in the storage server 30. As a result, even if there are a plurality of user terminals 10 that deposit encrypted data in the storage server 30, the receiving server 70 that receives the data need not have a key for each of the plurality of user terminals 10. The effect that the load about a process can be reduced is acquired.

[Second Embodiment]
The second embodiment is a modification of the first embodiment described above.
FIG. 3 is a block diagram showing the configuration of the encrypted data management system according to the second embodiment of the present invention. In FIG. 3, parts corresponding to the parts in FIG. Hereinafter, differences from the first embodiment will be mainly described.

  In FIG. 3, the user terminal 10 further includes a key encryption unit 17 in addition to the configuration of FIG. The key encryption unit 17 performs key encryption.

  FIG. 4 is a sequence chart showing the procedure of the encrypted data management method according to the second embodiment of the present invention. In the following, with reference to FIG. 4, the operation of the encrypted data management system according to the second embodiment shown in FIG. 3 will be described mainly with respect to differences from the first embodiment. Hereinafter, it is assumed that data exchange among any one of the user terminal 10, the storage server 30, the proxy server 50, and the receiving server 70 is performed via the communication network 90 by each communication unit.

  First, similarly to the first embodiment, the user terminal 10 acquires a key pair (pk_A, sk_A) in advance, securely holds the key sk_A in the user terminal 10, and discloses the key pk_A. Similarly, the receiving server 70 acquires the key pair (pk_B, sk_B), securely holds the key sk_B in the receiving server 70, and discloses the key pk_B. The user terminal 10 acquires the master key mk and transmits the master key mk to the proxy server 50.

(Step S101a) The key generation unit 12 of the user terminal 10 generates a random number r as a key for encrypting the data v. The data encryption unit 13 of the user terminal 10 encrypts the data v with a random number r using a common key encryption method, and obtains encrypted data E (r, v). The key encryption unit 17 of the user terminal 10 executes the encryption algorithm E, encrypts the key (random number r) obtained by encrypting the data v with its own public key pk_A, and encrypts the data E (pk_A, r). To get. Further, as in the first embodiment, the user terminal 10 acquires the index i_d from the tags u_1 and u_2 for the data v.

  The user terminal 10 transmits the index i_d, the encrypted data E (pk_A, r), and the encrypted data E (r, v) to the storage server 30. The storage server 30 stores the received index i_d, encrypted data E (pk_A, r), and encrypted data E (r, v) in the encrypted data storage unit 33 in association with each other.

Next, steps S102, S103, and S104 are performed as in the first embodiment described above. Next, step S105a is performed.
(Step S105a) The cryptographic search unit 32 of the storage server 30 uses the trapdoor t_x received from the proxy server 50 as an index for all the encrypted data stored in the encrypted data storage unit 33. The search algorithm SI is executed. As a result, the index search algorithm SI outputs 1 for the index containing the search keyword x. The storage server 30 transmits the index and key encrypted data associated with the index from which 1 is output to the proxy server 50. Here, since the search keyword x is equal to the tag u_1 and 1 is output for the index i_d, the index i_d and the encrypted data E (pk_A, r) associated with the index i_d are sent to the proxy server 50. Suppose that it was sent.

Next, step S106 is performed as in the first embodiment described above. Instead of step S106, the re-encryption key rk_ (A, B) for the receiving server 70 may be transmitted from the user terminal 10 to the proxy server 50 in advance.
Next, step S107a is performed.
(Step S107a) The re-encryption unit 53 of the proxy server 50 uses the re-encryption key rk_ (A, B) acquired from the user terminal 10 for the encrypted data E (pk_A, r) acquired from the storage server 30. The re-encryption algorithm R is used to obtain the re-encrypted encrypted data E (pk_B, r). The proxy server 50 transmits the acquired encrypted data E (pk_B, r) and the index i_d acquired from the storage server 30 to the receiving server 70.

(Step S <b> 110) The receiving server 70 transmits the index i_d acquired from the proxy server 50 to the storage server 30. The storage server 30 transmits the encrypted data E (r, v) associated with the index i_d to the receiving server 70.

  The decryption unit 72 of the receiving server 70 executes the decryption algorithm D, decrypts the encrypted data E (pk_B, r) acquired from the proxy server 50 with its own private key sk_B, and acquires a key (random number r). To do. The decryption unit 72 of the receiving server 70 decrypts the encrypted data E (r, v) acquired from the storage server 30 using the acquired key (random number r), and acquires data v.

  According to the second embodiment described above, the key for the encryption of the data v is proxy re-encrypted and passed to the receiving server 70 (decryption side). Thereby, it is not necessary to perform proxy re-encryption processing for data v, and the encryption method for data v is not limited, and any encryption method can be used. For example, as in the second embodiment described above, the data v can be encrypted by a common key encryption method. In general, the common key cryptosystem can shorten the processing time compared to the public key cryptosystem. As a result, the load on cryptographic processing can be reduced.

  Further, according to the second embodiment, the proxy server 50 receives the encrypted data of the key from the storage server 30 and transmits the encrypted data obtained by re-encrypting the encrypted data of the key to the receiving server 70. This can reduce the amount of communication data compared to sending / receiving encrypted data of data or encrypted data obtained by re-encrypting encrypted data of data.

[Third Embodiment]
The third embodiment is a modification of the above-described second embodiment. In the third embodiment, “Secure Indexes” technology is used to shorten the processing time of searchable encryption. This “Secure Indexes” technology can reduce the processing time of searchable encryption, but may cause an erroneous search “False Positive”. “False Positive” is an error that erroneously determines that the index is generated from the document d even though the trap door is generated using a keyword that is not included in the document d. When this error occurs, there is a possibility that a document that the user terminal 10 does not permit to provide to the receiving server 70 is provided to the receiving server 70. In the third embodiment, when the “Secure Indexes” technology that shortens the processing time of searchable encryption is used, problems due to the occurrence of “False Positive” are prevented.

  FIG. 5 is a block diagram showing a configuration of an encrypted data management system according to the third embodiment of the present invention. In FIG. 5, portions corresponding to the respective portions in FIG. 3 are denoted by the same reference numerals. Hereinafter, differences from the second embodiment will be mainly described.

  In FIG. 5, the user terminal 10 further includes a tag encryption unit 18 in addition to the configuration of FIG. 3. The tag encryption unit 18 encrypts the tag. The proxy server 50 further includes a tag verification unit 56 in addition to the configuration of FIG. The tag verification unit 56 performs tag verification.

  FIG. 6 is a sequence chart showing the procedure of the encrypted data management method according to the third embodiment of the present invention. In the following, with reference to FIG. 6, the operation of the encrypted data management system according to the third embodiment shown in FIG. 5 will be described mainly with respect to differences from the second embodiment. Hereinafter, it is assumed that data exchange among any one of the user terminal 10, the storage server 30, the proxy server 50, and the receiving server 70 is performed via the communication network 90 by each communication unit.

  First, similarly to the first embodiment, the user terminal 10 acquires a key pair (pk_A, sk_A) in advance, securely holds the key sk_A in the user terminal 10, and discloses the key pk_A. Similarly, the receiving server 70 acquires the key pair (pk_B, sk_B), securely holds the key sk_B in the receiving server 70, and discloses the key pk_B. The user terminal 10 acquires the master key mk and transmits the master key mk to the proxy server 50. In the third embodiment, the proxy server 50 executes a general public key encryption key generation algorithm, acquires the key sk_P secretly, securely holds it in the proxy server 50, and acquires the acquired key pk_P. Publish.

(Step S101b) The key generation unit 12 of the user terminal 10 generates a random number r as a key for encrypting the data v. The data encryption unit 13 of the user terminal 10 encrypts the data v with a random number r using a common key encryption method, and obtains encrypted data E (r, v). The key encryption unit 17 of the user terminal 10 executes the encryption algorithm E, encrypts the key (random number r) obtained by encrypting the data v with its own public key pk_A, and encrypts the data E (pk_A, r). To get. Further, as in the first embodiment, the user terminal 10 acquires the index i_d from the tags u_1 and u_2 for the data v.

  The tag encryption unit 18 of the user terminal 10 encrypts each tag u_1, u_2 with the public key pk_P of the proxy server 50, and acquires encrypted data E (pk_P, u_1) and encrypted data E (pk_P, u_2). . The user terminal 10 makes an index i_d, encrypted data E (pk_A, r), encrypted data E (r, v), encrypted data E (pk_P, u_1), and encrypted data E (to the storage server 30. pk_P, u_2) is transmitted. The storage server 30 receives the received index i_d, encrypted data E (pk_A, r), encrypted data E (r, v), encrypted data E (pk_P, u_1), and encrypted data E (pk_P, u_2). Are stored in the encrypted data storage unit 33 in association with each other.

Next, steps S102, S103, and S104 are performed as in the first embodiment described above. Next, step S105b is performed.
(Step S105b) The cryptographic search unit 32 of the storage server 30 uses the trapdoor t_x received from the proxy server 50 as an index for all the encrypted data stored in the encrypted data storage unit 33. The search algorithm SI is executed. As a result, the index search algorithm SI outputs 1 for the index containing the search keyword x. The storage server 30 transmits to the proxy server 50 the index, the key encrypted data, and the tag encrypted data associated with the index from which 1 is output. Here, since the search keyword x is equal to the tag u_1 and 1 is output for the index i_d, the encrypted data E (pk_A, r) and the encrypted data E ( It is assumed that pk_P, u_1) and encrypted data E (pk_P, u_2) are transmitted to the proxy server 50.

Next, step S106 is performed as in the first embodiment described above. Instead of step S106, the re-encryption key rk_ (A, B) for the receiving server 70 may be transmitted from the user terminal 10 to the proxy server 50 in advance.
Next, step S120 is performed.
(Step S120) The tag verification unit 56 of the proxy server 50 decrypts the encrypted data E (pk_P, u_1) and the encrypted data E (pk_P, u_2) using its own secret key sk_P, and tags u_1, u_2 is acquired. Next, the tag verification unit 56 determines whether the search keyword x acquired from the receiving server 70 in step S103 matches either of the tags u_1 and u_2. As a result of this determination, if the search keyword x matches either of the tags u_1 and u_2, it is considered that “False Positive” has not occurred. In this case, similarly to the second embodiment described above, step S107a is performed, and the proxy server 50 transmits the encrypted data E (pk_B, r) and the index i_d to the receiving server 70.

  On the other hand, as a result of the determination, if the search keyword x does not match either of the tags u_1 and u_2, it is considered that “False Positive” has occurred. In this case, the proxy server 50 stops the process. Accordingly, the encrypted data E (pk_B, r) and the index i_d are not transmitted to the receiving server 70.

  If the search keyword x matches either of the tags u_1 and u_2 in step S120, and the encrypted data E (pk_B, r) and the index i_d are transmitted to the receiving server 70 in step S107a, the above-described second Step S110 is performed as in the embodiment. By this step S110, the receiving server 70 acquires the data v.

  According to the third embodiment described above, it is possible to detect an erroneous search “False Positive” that occurs when using the “Secure Indexes” technology that can reduce the processing time of searchable encryption. Accordingly, it is possible to prevent a problem that a document that the user terminal 10 does not permit to be provided to the receiving server 70 is provided to the receiving server 70 due to the occurrence of “False Positive”.

  Further, the proxy server 50 performs tag verification (step S120) before re-encrypting the encrypted data E (pk_A, r) acquired from the storage server 30. As a result, when the tag verification fails (when “False Positive” occurs), it is possible to prevent re-encryption of the encrypted data E (pk_A, r). The load about can be reduced.

  According to the first, second, and third embodiments described above, the security and convenience of the encrypted data of the data deposited from the user terminal 10 to the storage server 30 is improved by proxy re-encryption. For example, since an administrator of the storage server 30 (for example, a cloud storage operator) cannot decrypt the encrypted data, the leakage of the data to the administrator of the storage server 30 can be prevented. On the other hand, the user of the receiving server 70 re-encrypts the encrypted data of the data or the encrypted data of the key of the encrypted data of the data with the re-encryption key of the receiving server 70. Can be obtained and decoded, so that the data can be obtained.

  Furthermore, according to the above-described first, second, and third embodiments, the search can be performed as it is without decrypting the encrypted data stored in the storage server 30 by the searchable encryption. The content of the encrypted data can be kept secret from 30 managers. Further, the search keyword can be kept secret from the administrator of the storage server 30.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the specific structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

For example, a computer program for realizing the steps shown in FIGS. 2, 4, and 6 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed. You may do it. Here, the “computer system” may include an OS and hardware such as peripheral devices.
“Computer-readable recording medium” refers to a flexible disk, a magneto-optical disk, a ROM, a writable nonvolatile memory such as a flash memory, a portable medium such as a DVD (Digital Versatile Disk), and a built-in computer system. A storage device such as a hard disk.

Further, the “computer-readable recording medium” means a volatile memory (for example, DRAM (Dynamic DRAM) in a computer system that becomes a server or a client when a program is transmitted through a network such as the Internet or a communication line such as a telephone line. Random Access Memory)), etc., which hold programs for a certain period of time.
The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

DESCRIPTION OF SYMBOLS 10 ... User terminal, 11 ... Communication part (user terminal communication part), 12 ... Key generation part, 13 ... Data encryption part, 14 ... Index generation part, 15 ... Tag setting part, 16 ... Data storage part, 17 ... Key Encryption unit, 18 ... tag encryption unit, 30 ... storage server, 31 ... communication unit (storage server communication unit), 32 ... cryptographic search unit, 33 ... encrypted data storage unit, 50 ... proxy server, 51 ... communication unit (Proxy server communication unit), 52 ... trap door generation unit, 53 ... re-encryption unit, 54 ... access right verification unit, 55 ... access right storage unit, 56 ... tag verification unit, 70 ... receiving server, 71 ... communication unit (Receiving server communication unit) 72, Decoding unit

Claims (12)

An encrypted data management system comprising a user terminal, a storage server, a proxy server, and a receiving server,
The user terminal is
A user terminal communication unit that communicates with the storage server and the proxy server;
A data encryption unit that generates encrypted data;
A key encryption unit for generating encrypted data of a key for the encrypted data of the data;
A key generation unit for generating a re-encryption key for the receiving server,
The user terminal communication unit transmits the encrypted data of the data and the encrypted data of the key to the storage server, and transmits the re-encryption key to the proxy server.
The storage server
A storage server communication unit for communicating with the user terminal, the proxy server and the receiving server;
An encrypted data storage unit that stores the encrypted data of the data acquired from the user terminal and the encrypted data of the key in association with each other,
The storage server communication unit transmits the encrypted data of the key to the proxy server, transmits the encrypted data of the data to the receiving server,
The proxy server is
A proxy server communication unit that communicates with the user terminal, the storage server, and the receiving server;
A re-encryption unit that re-encrypts the encrypted data of the key acquired from the storage server with the re-encryption key acquired from the user terminal,
The proxy server communication unit transmits encrypted data of the re-encrypted key to the receiving server,
The receiving server is
A receiving server communication unit that communicates with the storage server and the proxy server;
Decrypting the encrypted data of the re-encrypted key acquired from the proxy server to acquire the key, and decrypting the encrypted data of the data acquired from the storage server with the acquired key And comprising
Encrypted data management system. An encrypted data management system comprising a user terminal, a storage server, a proxy server, and a receiving server,
The user terminal is
A user terminal communication unit that communicates with the storage server and the proxy server;
A data encryption unit that generates encrypted data;
An index generator for generating an index based on a tag for the data;
A key generation unit for generating a re-encryption key for the receiving server,
The user terminal communication unit transmits the encrypted data of the data and the index to the storage server, and transmits the re-encryption key to the proxy server.
The storage server
A storage server communication unit that communicates with the user terminal and the proxy server;
An encrypted data storage unit that stores the encrypted data of the data acquired from the user terminal in association with the index;
A cryptographic search unit that searches for encrypted data associated with the index based on the trapdoor acquired from the proxy server,
The storage server communication unit transmits encrypted data of the data as a result of the search to the proxy server,
The proxy server is
A proxy server communication unit that communicates with the user terminal, the storage server, and the receiving server;
A trap door generation unit for generating a trap door for the search keyword acquired from the receiving server;
A re-encryption unit that re-encrypts the encrypted data of the data acquired from the storage server as a result of the search based on the trapdoor with a re-encryption key for the receiving server acquired from the user terminal; With
The proxy server communication unit transmits encrypted data of the re-encrypted data to the receiving server,
The receiving server is
A receiving server communication unit that communicates with the proxy server;
A decryption unit that decrypts encrypted data of the re-encrypted data acquired from the proxy server,
Encrypted data management system. The proxy server in an encrypted data management system comprising a user terminal, a storage server, a proxy server, and a receiving server,
The user terminal that transmits the encrypted data of the data and the encrypted data of the key for the encrypted data of the data to the storage server, the encrypted data of the data and the encrypted data of the key are stored in association with each other A proxy server communication unit that communicates with the storage server and the receiving server that obtains encrypted data of the data from the storage server;
A re-encryption unit that re-encrypts the encrypted data of the key acquired from the storage server with a re-encryption key for the receiving server acquired from the user terminal,
The proxy server communication unit transmits encrypted data of the re-encrypted key to the receiving server;
Proxy server. A trap door generating unit that generates a trap door for the search keyword acquired from the receiving server;
The proxy server communication unit transmits the trap door to the storage server that stores an index based on the tag of the data in association with the encrypted data of the data and the encrypted data of the key, and from the storage server Receiving an index as a result of a search based on the trapdoor and encrypted data of the key associated with the index, and receiving the received index and encrypted data of the re-encrypted key in the receiving server; Send to
The proxy server according to claim 3. The proxy server communication unit stores the encrypted data of the tag for the data in association with the index based on the tag, the encrypted data of the data, and the encrypted data of the key from the storage server. Receives encrypted tag data that is the result of a search based on
The proxy server further includes a tag verification unit that performs tag verification based on the decrypted result of the encrypted data of the received tag and the search keyword.
The proxy server according to claim 4. The proxy server in an encrypted data management system comprising a user terminal, a storage server, a proxy server, and a receiving server,
The user terminal that transmits encrypted data of data and an index based on a tag for the data to the storage server, the storage server that associates and stores the encrypted data of the data and the index, and the storage server A proxy server communication unit that communicates with a receiving server that receives provision of encrypted data of the data stored in
A trap door generation unit for generating a trap door for the search keyword acquired from the receiving server;
A re-encrypting unit that re-encrypts the encrypted data of the data acquired from the storage server by the proxy server communication unit with a re-encryption key for the receiving server acquired from the user terminal; Prepared,
The proxy server communication unit transmits the trap door to the storage server, receives encrypted data of data that is a result of a search based on the trap door from the storage server, and transmits the re-encrypted data Sending encrypted data to the receiving server;
Proxy server. The user terminal in an encrypted data management system comprising a user terminal, a storage server, a proxy server, and a receiving server,
A user terminal communication unit that communicates with the storage server and the proxy server;
A data encryption unit that generates encrypted data;
A key encryption unit for generating encrypted data of a key for the encrypted data of the data;
A key generation unit for generating a re-encryption key for the receiving server,
The user terminal communication unit transmits the encrypted data of the data and the encrypted data of the key to the storage server that associates and stores the encrypted data of the data and the encrypted data of the key, and the storage server Transmitting the re-encryption key to the proxy server that re-encrypts with the re-encryption key the encrypted data of the key obtained from
User terminal. The user terminal in an encrypted data management system comprising a user terminal, a storage server, a proxy server, and a receiving server,
A user terminal communication unit that communicates with the storage server and the proxy server;
A data encryption unit that generates encrypted data;
An index generator for generating an index based on a tag for the data;
A key generation unit for generating a re-encryption key for the receiving server,
The user terminal communication unit transmits the encrypted data of the data and the index to the storage server that stores the encrypted data of the data in association with the index, and serves as a trap door for the search keyword of the receiving server. Transmitting the re-encryption key to the proxy server that re-encrypts the encrypted data of the data acquired from the storage server as a result of the search based on the re-encryption key;
User terminal. An encrypted data management method in an encrypted data management system comprising a user terminal, a storage server, a proxy server, and a receiving server,
The user terminal generates encrypted data of data, generates encrypted data of a key for the encrypted data of the data, and transmits the encrypted data of the data and the encrypted data of the key to the storage server Generating a re-encryption key for the receiving server, sending the re-encryption key to the proxy server,
The storage server stores the encrypted data of the data acquired from the user terminal in association with the encrypted data of the key, transmits the encrypted data of the key to the proxy server, and encrypts the data Sending data to the receiving server;
The proxy server re-encrypts the encrypted data of the key acquired from the storage server with the re-encryption key acquired from the user terminal, and the encrypted data of the re-encrypted key To the receiving server,
The receiving server obtains a key by decrypting the encrypted data of the re-encrypted key obtained from the proxy server, and uses the obtained key to obtain the encrypted data of the data obtained from the storage server. Decrypt,
Encrypted data management method. An encrypted data management method in an encrypted data management system comprising a user terminal, a storage server, a proxy server, and a receiving server,
The user terminal generates encrypted data of the data, generates an index based on a tag for the data, transmits the encrypted data of the data and the index to the storage server, and re-registers for the receiving server. Generate an encryption key, send the re-encryption key to the proxy server,
The storage server stores the encrypted data of the data acquired from the user terminal in association with the index;
The proxy server generates a trap door for a search keyword acquired from the receiving server, and transmits the trap door to the storage server.
The storage server searches the encrypted data associated with the index based on the trap door acquired from the proxy server, and transmits the encrypted data of the data as a result of the search to the proxy server,
The proxy server re-encrypts the encrypted data acquired from the storage server as a result of the search based on the trap door with the re-encryption key acquired from the user terminal, and Sending encrypted data of the encrypted data to the receiving server;
The receiving server decrypts the encrypted data of the re-encrypted data obtained from the proxy server;
Encrypted data management method. In the computer of the proxy server in the encrypted data management system comprising a user terminal, a storage server, a proxy server, and a receiving server,
The user terminal that transmits the encrypted data of the data and the encrypted data of the key for the encrypted data of the data to the storage server, the encrypted data of the data and the encrypted data of the key are stored in association with each other A communication function for communicating with the storage server and the receiving server for obtaining encrypted data of the data from the storage server;
A computer program for realizing a re-encryption function for re-encrypting the encrypted data of the key acquired from the storage server with a re-encryption key for the receiving server acquired from the user terminal And
The communication function transmits encrypted data of the re-encrypted key to the receiving server.
Computer program. In the computer of the proxy server in the encrypted data management system comprising a user terminal, a storage server, a proxy server, and a receiving server,
The user terminal that transmits encrypted data of data and an index based on a tag for the data to the storage server, the storage server that associates and stores the encrypted data of the data and the index, and the storage server A communication function for communicating with a receiving server that receives provision of encrypted data of the data stored in
A trap door generation function for generating a trap door for the search keyword acquired from the receiving server;
To realize a re-encryption function for re-encrypting encrypted data of data acquired from the storage server by the communication function with a re-encryption key for the receiving server acquired from the user terminal. Computer program
The communication function transmits the trap door to the storage server, receives encrypted data of data that is a search result based on the trap door from the storage server, and encrypts the re-encrypted data. Sending data to the receiving server;
Computer program.

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