Efficient Strong Privacy-Preserving Conjunctive Keyword Search Over Encrypted Cloud Data

TL;DR

This paper introduces a novel dynamic searchable symmetric encryption scheme that ensures strong privacy-preserving conjunctive keyword search, eliminating result pattern leakage and improving efficiency by scaling with keyword update frequency.

Contribution

It presents the first DSSE scheme that achieves strong privacy for conjunctive search, eliminating KPRP leakage and reducing search complexity based on keyword update frequency.

Findings

Eliminates keyword pair result pattern leakage

Maintains forward and backward privacy

Achieves efficient search scaling with update frequency

Abstract

Searchable symmetric encryption (SSE) supports keyword search over outsourced symmetrically encrypted data. Dynamic searchable symmetric encryption (DSSE), a variant of SSE, further enables data updating. Most DSSE works with conjunctive keyword search primarily consider forward and backward privacy. Ideally, the server should only learn the result sets involving all keywords in the conjunction. However, existing schemes suffer from keyword pair result pattern (KPRP) leakage, revealing the partial result sets containing two of query keywords. We propose the first DSSE scheme to address aforementioned concerns that achieves strong privacy-preserving conjunctive keyword search. Specifically, our scheme can maintain forward and backward privacy and eliminate KPRP leakage, offering a higher level of security. The search complexity scales with the number of documents stored in the database in several existing schemes. However, the complexity of our scheme scales with the update frequency of the least frequent keyword in the conjunction, which is much smaller than the size of the entire database. Besides, we devise a least frequent keyword acquisition protocol to reduce frequent interactions between clients. Finally, we analyze the security of our scheme and evaluate its performance theoretically and experimentally. The results show that our scheme has strong privacy preservation and efficiency.