| 摘要 |
[Problem] To provide an encrypted database system and the like that, in relation to encrypted columns, enable the natural joining of a plurality of tables without performing processing that decodes column data. [Solution] A client terminal (10) is provided with: a column encryption unit (21) that, from an encryption key, a table identifier, and a column identifier, generates a column private key, a column public key, and a comparison value, from which the unit generates a concealed comparison value and a ciphertext, thus encrypting a particular column; and an encrypted table natural joining request unit (22) that issues a natural joining request text (71) that requests natural joining related to the column encrypted from the encryption key, table identifier, and column identifier. The natural joining request text contains as a table joining key the column public key and column private key that were generated by the encryption key from the table identifier of a first and second table and the column identifier of the a-th column and b-th column. Then, an encrypted database server (50) executes natural joining using the table joining key, and returns the result (81). |
