The public parameter PK is a transmission device 100 that generates and transmits an encryption tag that is an encrypted keyword, and a server 200 that receives and stores the encryption tag and executes a secret search in response to a request for the secret search. And a secret search system 1000 including a receiving device 300 that generates a trapdoor, which corresponds to the digital signature of the keyword and that requests data for a secret search, transmits the trap door to the server 200, and receives the search result. Key information. The public parameter PK includes a true public parameter PP and a protection key PK ′. The transmitting device 100 and the receiving device 300 require both the public parameter PP and the protection key PK ′, but the server 200 does not require the protection key PK ′. Therefore, the key generation device 300 generates the true public parameter PP included in the public parameter PK and the protection key PK ′ separately.
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