A protected and Lively Multi Keyword Hierarchical Search Arrangement over Encoded Cloud data

Research focus on a secure multi-keyword ranked search scheme over encrypted cloud data, which simultaneously supports dynamic update operations like deletion and insertion of documents. The research propose a “Greedy Depth- �rst Search� algorithm to provide efficient multi-keyword ranked search. A secure tree-based search scheme over the encrypted cloud data, which supports multi- keyword ranked search and dynamic operation on the document collection. Specially the vector space model and the widely-used “term frequency (TF) × inverse document frequency (IDF)� model are combined in the index construction and query generation to provide multi-keyword ranked search. In order to obtain high search efficiency, construct a tree-based index structure and propose a “Greedy Depth-�rst Search� algorithm based on this index tree. Due to the special structure of our tree-based index, the proposed search scheme can flexibly achieve sub-linear search time and deal with the deletion and insertion of documents. The secure algorithm is utilized to encrypt the index and query vectors, and meanwhile ensure accurate relevance score calculation between encrypted index and query vectors. In order to resist statistical attacks, phantom terms are added to the index vector for blinding search results. Moreover, parallel search can be flexibly performed to further reduce the time cost of search process. Extensive experiments are conducted to demonstrate the efficiency of the proposed scheme.