Searchable Encryption with Conjunctive Field Free Keyword Search Scheme

Prior Searchable Symmetric Encryption (SSE) works focus on single keyword search. Conjunctive Keyword Searches (CKS) schemes enhance system usability by retrieving the matching files. Most of existing conjunctive keyword works that use conjunctive keyword searches with fixed position keyword fields are not useful for many applications, such as the body of e-mail and unstructured text. The recipients have to repeatedly perform the search protocol for many times. In our paper, we propose a new symmetric key encryption scheme which supports a keyword field free method for conjunctive keyword search on encrypted file without needing to specify the positions of the keywords where the keywords can be in any arbitrary order. In this scheme, the recipients can give the server one trapdoor for multi keywords. In other words, the proposed method will retrieve the data in one round of communication between the recipients and server, and the search process could not leak any information about the number of keywords in query. Furthermore, we introduced an efficient secure index construction based on pseudorandom functions and Bloom filters. Through analysis section, we determine how such scheme could be used to guarantee fast, low storage overhead and secure access to the database.