Conjunctive Keyword Forward Secure Ranked Dynamic Searchable Encryption Over Outsourced Encrypted Data

Cloud Computing enables individuals and organizations with extensive computing capabilities along with scalable storage services. However the security of outsourced data brings about privacy concerns when confidential data is outsourced to third party service providers. The Searchable Symmetric Encryption (SSE) is a solution towards enabling data owners to securely outsource and later retrieve the matching documents based on encrypted queries. Majority of existing SSE schemes lack support for relevance based retrieval of matching documents to queried keywords, expressive queries, and privacy of query terms and documents. In this paper we present a novel dynamic SSE scheme which retrieves documents ranked based on their relevance to the queries, and ensures forward and backward privacy definitions given by R Bost et al. Our scheme is lightweight as it allows the server to compute document-query relevance in a secure manner without affecting the entire outsourced index, especially during update operations, which is normally the case in existing state of the art. We employ an indexing mechanism which is alternate to the most frequently used Inverted Index structure but overcomes drawbacks of such an index. Experimental analysis of our scheme on RFC dataset demonstrated a sub-linear search time and efficient update operations. The proposed scheme also ensures forward and backward security during search and update operations.