SECRET RETRIEVAL SYSTEM, PUBLIC PARAMETER GENERATION DEVICE, ENCRYPTION DEVICE, USER SECRET KEY GENERATION DEVICE, QUERY ISSUE DEVICE, RETRIEVAL DEVICE, COMPUTER PROGRAM, SECRET RETRIEVAL METHOD, PUBLIC PARAMETER GENERATION METHOD, ENCRYPTION METHOD, USER SECRET KEY GENERATION METHOD, QUERY ISSUE METHOD, AND RETRIEVAL METHOD

摘要

Provided is a secret retrieval system for a plurality of users, in which the size of a cipher text is reduced, to eliminate the necessity of generating a new cipher text even in the case where a new user is added. A public parameter generation device (100) generates a pair of a public parameter and a master secret key. An encryption device (400) uses the public parameter, to encrypt a keyword and thus generate a cipher text. A user secret key generation device (200) uses the master secret key, to generate a user secret key of a query issue device (300). The query issue device (300) uses the user secret key, to generate a query for retrieving the keyword. A retrieval device (500) judges whether a hit is obtained or not by the retrieval on the basis of the cipher text and the query.