| 摘要 |
An encrypted-data reception unit (201) receives encrypted data, i.e. data which has been encrypted, that has, embedded therein, decoding conditions in which user attributes of decoding-permitted users for whom decoding of the encrypted data is permitted are defined. A data storage unit (202) stores the encrypted data received by the encrypted-data reception unit (201), while maintaining the encrypted data in an encrypted state. An invalidation processing unit (209) adds, to the embedded decoding conditions embedded in the encrypted data, while the encrypted data is in an encrypted state, invalidation information in which user attributes of invalidated users who are no longer decoding-permitted users are described. |
