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

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.

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.