Oblivious Conjunctive Keyword Search

We study the problem of keyword search in which a server contains various multimedia contents and a user of server wishes to retrieve some multimedia item containing specific keywords without revealing to the server which item it is. Recently, Ogata and Kurosawa introduced an interesting keyword search scheme called oblivious keyword search by using the notion of oblivious transfer. However, only one keyword can be searched in each query, hence the scheme cannot provide a conjunctive keyword search which finds items containing each of several keywords. In this paper, we firstly design a conjunctive keyword search by using the oblivious transfer, and present oblivious conjunctive keyword search (for short, OCKS). We prove that OCKS protocol is secure under the intractability of RSA known target inversion problem.