Searchable encryption: A survey on privacy-preserving search schemes on encrypted outsourced data

摘要

Outsourcing confidential data to cloud storage leads to privacy challenges that can be reducedusing encryption. However, with encryption in place, the utilization of the data is reduced, whichleads to reduced quality of experience of the users. To overcome this, searchable encryption(SE) schemes are utilized, which allow the end users to retrieve the relevant documents fromthe cloud, for which various researchers have worked utilizing different techniques. Despite thepopularity of the searchable encryption schemes, most of the surveys either do not provide orpresent an incomplete taxonomy of SE schemes. Hence, in this paper, we attempt to presenta complete taxonomy/classification of the searchable encryption schemes in terms of the typeof search, type of index, results retrieved, implementation type, multiplicity of users, and thetechnique used. From the literature, it is observed that inner product similarity is widely adoptedby researchers to compute the similarity of the query and the document index as it providesboth conjunctive and disjunctive searching (ie, have better search capability) but requires highsearch time (ie, have lower search efficiency). On the other hand, schemes based on binarycomparisons exist, which require less search time (ie, have better search efficiency) but supportonly conjunctive searching (ie, have limited search capability). Thus, a major conclusion drawnfrom our work is that there is an imbalance between search capability and search efficiency,ie, in the existing schemes, search capability can be improved at the cost of search time only.Therefore, we suggest that one direction where researchers should work on is to provide abalance between search capability and search efficiency.