# US 2018/0025172 A1 · Data storage apparatus, data processing method, and computer readable medium > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0025172 A1 - Document ID: US20180025172A1 - Status: Published application - Kind: A1 - Application number: 15/548,064 - Filed: 2015-02-20 - Published: 2018-01-25 - Earliest claimed: 2015-02-20 - Assignees: Mitsubishi Electric Corporation - Applicants: Mitsubishi Electric Corporation - Inventors: Takumi MORI; Yutaka KAWAI; Nori MATSUDA - Web page: https://patentgrep.com/patent/US20180025172A1 ## CPC - G06F 21/6218: {to a system of files or objects, e.g. local or distributed file system or database} - H04L 9/0847: {involving identity based encryption [IBE] schemes} - H04L 9/0894: {Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage} - H04L 9/30: Public key, i.e. encryption algorithm being computationally infeasible to invert or user's encryption keys not requiring secrecy - H04L 2209/76: Proxy, i.e. using intermediary entity to perform cryptographic operations - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract An encrypted data receiving unit (201) receives encrypted data which has been encrypted, in which a decryption condition to define a user attribute of a decryption-permission user who is permitted to decrypt the encrypted data is embedded. A data storage unit (202) stores the encrypted data received by the encrypted data receiving unit (201) in an encrypted state. A revocation processing unit (209) adds revocation information in which a user attribute of a revoked user who is no longer the decryption-permission user is indicated, to an embedded decryption condition that is embedded in the encrypted data, while the encrypted data remains in an encrypted state. ## Claims ### Claim at position 1 1-15. (canceled) ### Claim 16 A data storage apparatus comprising processing circuitry to: receive encrypted data which has been encrypted, in which a decryption condition, whereby a user attribute of a decryption-permission user who is permitted to decrypt the encrypted data is defined, is embedded; store the encrypted data that has been received, in an encrypted state; and add revocation information in which a user attribute of a revoked user who is no longer the decryption-permission user is indicated, to an embedded decryption condition that is embedded in the encrypted data, while the encrypted data remains in the encrypted state. ### Claim 17 (depends on 16) The data storage apparatus as defined in claim 16, wherein the processing circuitry receives, along with the encrypted data, a decryption condition with a same content as the embedded decryption condition, as an external decryption condition, and adds the revocation information to the external decryption condition, along with addition of the revocation information to the embedded decryption condition. ### Claim 18 (depends on 16) The data storage apparatus as defined in claim 16, wherein the processing circuitry receives the encrypted data that has been encrypted in an encryption scheme using a basis vector, and generates a basis vector corresponding to the revocation information, and adds the revocation information to the embedded decryption condition while the encrypted data remains in an encrypted state. ### Claim 19 (depends on 18) The data storage apparatus as defined in claim 18, wherein the processing circuitry adds the revocation information to the embedded decryption condition while the encrypted data remains in an encrypted state, by changing a span program of the embedded decryption condition corresponding to addition of the revocation information, generating a ciphertext element corresponding to the revocation information based on a share according to secret sharing of the user attribute of the decryption-permission user and the user attribute of the revoked user, and adding the ciphertext element corresponding to the revocation information to a ciphertext element corresponding to the user attribute of the decryption-permission user. ### Claim 20 (depends on 17) The data storage apparatus as defined in claim 17, wherein the processing circuitry removes the revocation information from the external decryption condition, transmits the encrypted data and the external 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, and receives the encrypted data that has been re-encrypted in the proxy re-encryption scheme with the external decryption condition from which the revocation information has been removed, from the re-encryption apparatus. ### Claim 21 (depends on 16) The data storage apparatus as defined in claim 16, wherein the processing circuitry adds revocation information in which a user attribute of a revoked user who is no longer the decryption-permission user due to a personnel transfer is indicated, to the embedded decryption condition. ### Claim 22 (depends on 20) The data storage apparatus as defined in claim 20, wherein the processing circuitry removes revocation information in which a user attribute of a user who has been restored to the decryption-permission user from the revoked user due to a personnel transfer is indicated, from the external decryption condition. ### Claim 23 (depends on 16) The data storage apparatus as defined in claim 16, wherein the processing circuitry adds revocation information in which a user attribute of a revoked user who is no longer the decryption-permission user due to loss of an access right to the encrypted data is indicated, to the embedded decryption condition. ### Claim 24 (depends on 20) The data storage apparatus as defined in claim 20, wherein the processing circuitry removes revocation information in which a user attribute of a user who has been restored to the decryption-permission user from the revoked user due to re-acquisition of an access right to the encrypted data is indicated, from the external decryption condition. ### Claim 25 (depends on 16) The data storage apparatus as defined in claim 16, wherein the processing circuitry adds revocation information being a logical formula wherein a NOT operator and the user attribute of the revoked user are combined, to the embedded decryption condition being a logical formula whereby the user attribute of the decryption-permission user is defined. ### Claim 26 (depends on 25) The data storage apparatus as defined in claim 25, wherein the processing circuitry operates distinguishing a logical formula from the revocation information when the logical formula wherein a NOT operator and any user attribute are combined is other than the revocation information, and is made to correspond to the encrypted data. ### Claim 27 (depends on 20) The data storage apparatus as defined in claim 20, wherein the processing circuitry adds revocation information being a logical formula wherein a NOT operator and the user attribute of the revoked user are combined, to the external decryption condition being a logical formula whereby the user attribute of the decryption-permission user is defined, and operates distinguishing a logical formula from the revocation information when the logical formula wherein a NOT operator and any user attribute are combined is other than the revocation information, and is made to correspond to the encrypted data. ### Claim 28 (depends on 16) The data storage apparatus as defined in claim 16, wherein the processing circuitry receives encrypted data that has been encrypted in an encryption scheme, which can be decrypted only with a decryption key whereto a user attribute matching the user attribute of the decryption-permission user is set. ### Claim 29 A data processing method comprising: receiving encrypted data which has been encrypted, in which a decryption condition, whereby a user attribute of a decryption-permission user who is permitted to decrypt the encrypted data is defined, is embedded, storing the encrypted data that has been received, in an encrypted state, and adding revocation information in which a user attribute of a revoked user who is no longer the decryption-permission user is indicated, to an embedded decryption condition that is embedded in the encrypted data, while the encrypted data remains in the encrypted state. ### Claim 30 A non-transitory computer readable medium storing a data processing program that causes a computer to execute: an encrypted data receiving processing to receive encrypted data which has been encrypted, in which a decryption condition, whereby a user attribute of a decryption-permission user who is permitted to decrypt the encrypted data is defined, is embedded; a data storage processing to store the encrypted data that has been received by the encrypted data receiving processing, in an encrypted state; and a revocation processing to add revocation information in which a user attribute of a revoked user who is no longer the decryption-permission user is indicated, to an embedded decryption condition that is embedded in the encrypted data, while the encrypted data remains in the encrypted state.