HCV: Practical Multi-Keyword Conjunctive Query with Little Result Pattern Leakage

Multi-keyword conjunctive query is the most common searchable encryption (SE) scheme and gives practical search capability. This paper focuses on constructing a conjunctive query scheme with high privacy and accurate query result. For efficiency, this paper introduces a novel counter vector (CV) data structure instead of inverted index and builds the CV index database with three-tuple keywords. We use two kinds of cryptography primitives to encrypt the CV index database, respectively. One is symmetric encryption for efficiency, which gives two schemes, CVX and ICV. Experiments show that both CVX and ICV have much higher efficiency than the existing schemes. The other is BGN homomorphic encryption for privacy and gives the scheme HCV. HCV reduces much RP information leakage and even achieves “ideal” leakage for 3-keyword query. Experiments show that the HCV scheme achieves high privacy while compromising not so much storage.