Data storage apparatus, data updating system, data processing method, and computer readable medium

• US 10,116,442 B2
• Filed: 02/20/2015
• Issued: 10/30/2018
• Est. Priority Date: 02/20/2015
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Mori, Takumi, Kawai, Yutaka, Matsuda, Nori
• Primary Examiner(s): Powers, William S
• Application Number:
  US15/548,071
• Publication Number:
  US 20180026785A1
• Time in Patent Office: 1,348 Days
• CPC Class Codes: G06F 21/6218 to a system of files or objects, e.g. local or distributed file system or database
• CPC Class Codes: H04L 2209/76 Proxy, i.e. using intermediary entity to perform cryptographic operations network architectures or network communication protocols using hop-by-hop encryption H04L63/0464
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying
• CPC Class Codes: H04L 9/0894 Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage
• CPC Class Codes: H04L 9/30 Public key, i.e. encryption algorithm being computationally infeasible to invert or user's encryption keys not requiring secrecy

Abstract

A data storage unit (202) stores encrypted data while remaining in an encrypted state, and stores decryption conditions to define a user attribute of a decryption-permission user who is permitted to decrypt the encrypted data. In a case wherein revocation information to indicate a user attribute of a revoked user who is no longer the decryption-permission user has been added to the decryption condition when update timing arrives, a revocation information removing unit (206) removes the revocation information from the decryption condition while the encrypted data remains in the encrypted state. Further, the revocation information removing unit (206) transmits the encrypted data and the decryption conditions from which the revocation information has been removed to a re-encryption apparatus that performs re-encryption in a proxy re-encryption scheme, and receives, from the re-encryption apparatus, the encrypted data that has be re-encrypted in the proxy re-encryption scheme using the decryption condition from which the revocation information has been removed. A refresh processing unit (205) updates the encrypted data that has been re-encrypted and the decryption condition from which the revocation information has been removed.

Claims

1. A data storage apparatus comprising processing circuitry to:

store encrypted data that has been encrypted, while remaining in an encrypted state, and to store a decryption condition being a parameter to control permitted decryption of the encrypted data, where a decryption-permission user who is permitted to decrypt the encrypted data is defined in the decryption condition that does not require decryption of said encrypted data in order to read;

in a case where revocation information which identifies a revoked user who is no longer the decryption-permission user, has been added to the decryption condition when update timing to update the encrypted data and the decryption condition arrives, process the revocation information to remove the revoked user from the decryption condition while the encrypted data remains in an encrypted state, to transmit the encrypted data and the decryption condition from which the revocation information has been removed, to a re-encryption apparatus that performs re-encryption in a proxy re-encryption scheme, the transmission to the re-encryption apparatus being performed prior to decryption, and to receive from the re-encryption apparatus, the encrypted data that has been re-encrypted in the proxy re-encryption scheme using the decryption condition from which the revocation information has been removed; and

update the encrypted data that has been re-encrypted and received, and the decryption condition from which the revocation information has been removed.

2. The data storage apparatus as defined in claim 1, wherein the processing circuitry

updates the encrypted data that has been re-encrypted and received, and the decryption condition from which the revocation information has been removed, using update information used for update of a master public key being a master key of an encryption key used for encryption of the encrypted data, and a master secret key being a master key of a decryption key used for decryption of the encrypted data, and for update of the decryption key.

3. The data storage apparatus as defined in claim 2, wherein the processing circuitry

updates the encrypted data that has been re-encrypted and received, and the decryption condition from which the revocation information has been removed, using update information that is generated for updating the master public key and the master secret key by a key generation apparatus that updates the master public key and the master secret key.

4. A data updating system comprising:

a data storage apparatus including;

first processing circuitry to

store encrypted data which has been encrypted, while remaining in an encrypted state, and to store a decryption condition being a parameter to control permitted decryption of the encrypted data, where a decryption-permission user who is permitted to decrypt the encrypted data is defined in the decryption condition that does not require decryption of said encrypted data in order to read,

determine, when update timing to update the encrypted data and the decryption condition arrives, whether revocation information that identifies a revoked user who is no longer the decryption-permission user, has been added to the decryption condition, and in a case wherein the revocation information has been added to the decryption condition, to remove the revoked user from the decryption condition while the encrypted data remains in an encrypted state, to transmit the encrypted data and the decryption condition from which the revocation information has been removed, to a re-encryption apparatus that performs re-encryption in a proxy re-encryption scheme, the transmission to the re-encryption apparatus being performed prior to decryption, and to receive from the re-encryption apparatus, the encrypted data that has been re-encrypted in the proxy re-encryption scheme using the decryption condition from which the revocation information has been removed, and

update the encrypted data that has been re-encrypted and received, and the decryption condition from which the revocation information has been removed; and

a key update apparatus including second processing circuitry to update a decryption key used for decryption of the encrypted data when the update timing arrives.

5. The data updating system as defined in claim 4, wherein

in the data storage apparatus, the first processing circuitry updates the encrypted data that has been re-encrypted and received, and the decryption condition from which the revocation information has been removed, using update information used for update of a master public key being a master key of an encryption key used for encryption of the encrypted data, and a master secret key being a master key of the decryption key, and wherein

in the key update apparatus, the second processing circuitry updates the decryption key using the update information.

6. The data updating system as defined in claim 5,

wherein in the key update apparatus, the second processing circuitry

receives the update information from a key generation apparatus that generates the update information and updates the master public key and the master secret key using the update information;

and

transmits the update information that has been received, to the data storage apparatus, and

updates the decryption key using the update information received,

and wherein, in the data storage apparatus, the first processing circuitry receives the update information from the key update apparatus, and updates the encrypted data that has been re-encrypted and received, and the decryption condition from which the revocation information has been removed, using the update information received.

7. The data updating system as defined in claim 4, wherein

in the key update apparatus, the second processing circuitry

determines whether or not to deem-consider a decryption key to be an object of update, and

updates only a decryption key that has been determined as the object of update.

8. The data updating system as defined in claim 5, wherein

in the key update apparatus, in accordance with a date and time when a decryption key has been updated last, the second processing circuitry selects update information used for updating the decryption key, and updates the decryption key using the update information selected.

9. A data processing method, comprising

by a computer that stores encrypted data that has been encrypted, while remaining in an encrypted state, and stores a decryption condition being a parameter to control permitted decryption of the encrypted data, where a decryption-permission user who is permitted to decrypt the encrypted data is defined in a decryption condition that does not require decryption of said encrypted data in order to read,

in a case where revocation information which identifies a revoked user who is no longer the decryption-permission user, has been added to the decryption condition when update timing to update the encrypted data and the decryption condition arrives, processing the revocation information to remove the revoked user from the decryption condition while the encrypted data remains in an encrypted state, transmitting the encrypted data and the decryption condition from which the revocation information has been removed, to a re-encryption apparatus that performs re-encryption in a proxy re-encryption scheme prior to decryption, receiving from the re-encryption apparatus, the encrypted data that has been re-encrypted in the proxy re-encryption scheme using the decryption condition from which the revocation information has been removed, and

updating the encrypted data that has been re-encrypted and received, and the decryption condition from which the revocation information has been removed.

10. A non-transitory computer readable medium storing a data processing program that causes a computer that stores encrypted data that has been encrypted while remaining in an encrypted state, and stores a decryption condition being a parameter to control permitted decryption of the encrypted data, where a decryption-permission user who is permitted to decrypt the encrypted data is defined in the decryption condition that does not require decryption of said encrypted data in order to read;

a revocation information removing processing to remove, in a case where revocation information identifies a revoked user who is no longer the decryption-permission user, has been added to the decryption condition when update timing to update the encrypted data and the decryption condition arrives, processing the revocation information to remove the revoked user from the decryption condition while the encrypted data remains in an encrypted state, to transmit the encrypted data and the decryption condition from which the revocation information has been removed, to a re-encryption apparatus that performs re-encryption in a proxy re-encryption scheme, the transmission to the re-encryption apparatus being performed prior to decryption, and to receive from the re-encryption apparatus, the encrypted data that has been re-encrypted in the proxy re-encryption scheme using the decryption condition from which the revocation information has been removed; and

a refresh processing to update the encrypted data that has been re-encrypted and received by the revocation information removing processing, and the decryption condition from which the revocation information has been removed.