Searchable encryption system, searchable encryption method, and non-transitory computer-readable recording medium

A searchable encryption method, wherein

• a registration device being a computer has stored therein a registration keyword, authorized-person attribute information indicating an attribute to be owned by an authorized person who has an authority to search for the registration keyword, and an index disclosure key to encrypt a registration keyword index corresponding to the registration keyword,
• the registration device generates the registration keyword index by using the registration keyword, the authorized-person attribute information, a user key function to generate a user key having incorporated therein searcher attribute information indicating an attribute that a searcher who searches for the registration keyword has, a search query function to generate a search query having the user key incorporated therein, the search query corresponding to a search keyword for the searcher to search for the registration keyword, and an index query function to generate an index query having the search query incorporated therein, the index query searching for the registration keyword index, and
• the registration device generates an encrypted index by encrypting the registration keyword index by using the index disclosure key.

A non-transitory computer-readable recording medium recorded with a searchable encryption program that causes a computer having stored therein a registration keyword, authorized-person attribute information indicating an attribute to be owned by an authorized person who has an authority to search for the registration keyword, and an index disclosure key to encrypt a registration keyword index corresponding to the registration keyword to:

• generate the registration keyword index by using the registration keyword, the authorized-person attribute information, a user key function to generate a user key having incorporated therein searcher attribute information indicating an attribute that a searcher who searches for the registration keyword has, a search query function to generate a search query having the user key incorporated therein, the search query corresponding to a search keyword for the searcher to search for the registration keyword, and an index query function to generate an index query having the search query incorporated therein, the index query being for searching for the registration keyword index;
• and
• generate an encrypted index by encrypting the registration keyword index by using the index disclosure key.