SERVER DEVICE, PRIVATE SEARCH PROGRAM, RECORDING MEDIUM, AND PRIVATE SEARCH SYSTEM

摘要

A server device 201 comprises a communication part 231, a search history storage region 213, a data storage part 210, and a checking part 220. The communication part receives a set of a trapdoor and a deterministic encrypted keyword from a search device 401. The search history storage region 213 stores the set of the trapdoor and the deterministic encrypted keyword. The data storage part 210 stores keyword information in which search target data and an encrypted keyword are associated with each other. If the deterministic encrypted keyword is obvious, a deterministic encrypted keyword corresponding to the encrypted keyword is additionally associated with the search target data and the encrypted keyword in the keyword information. The checking part 220 checks whether or not a deterministic encrypted keyword which matches the received deterministic encrypted keyword exists in the search history storage region 213. If the deterministic encrypted keyword exists, the checking part 220 executes a concealed search targeting the data storage part 210, based on a deterministic encryption scheme using the deterministic encrypted keyword existing in the search history storage region 213. If the deterministic encrypted keyword does not exist, the checking part 220 executes the concealed search targeting the data storage part 210, based on a probabilistic encryption scheme using the received trapdoor and the encrypted keyword stored in the data storage part 210.