Registration device, search operation device, and data management device

A search operation device comprising:

• processing circuitry configured to:
• accept a search keyword and a user key;
• and
• generate a search query by using the search keyword and a user tag key included in the user key, wherein
• the user tag key has a plurality of flag values based on a plurality of attribute values which identify a plurality of attributes of a user and one or more tag attribute keys based on one or more aggregate values generated by aggregating the plurality of attribute values, and
• the processing circuitry further configured to:
• generate a search-purpose aggregate flag indicating one or more aggregate values each configured of one or more flag values, by aggregating the plurality of flag values included in the user tag key,
• generate, by using the search-purpose aggregate flag, search position information which identifies one or more attribute elements for use in searching among a plurality of attribute elements included in an encrypted tag registered together with ciphertext data in a database, and
• generate the search query by using the search keyword, the one or more tag attribute keys included in the user tag key, and the search position information.