Abstract:In order to reduce cost in data management and to outsource the data to cloud servers, data owners in more amounts are motivated in cloud computing. Before outsourcing for privacy requirements, confidential data must be encrypted and data utilization such as keyword-based document has to be retrieved. To support dynamic update operations such as deletion and insertion process, a secure multi-keyword ranked search scheme over encrypted cloud data is produced. In general, the index construction and query generation of the vector space model and TF_IDF model that is widely used are combined. "Greedy Depth-first Search", a special treebased index structure algorithm to provide multi-keyword ranked search that is efficient is proposed. To encrypt the index and query process, the secure KNN algorithm is used. Due to the use of our special tree-based index structure, the proposed scheme can achieve sub-linear search time and deal with the deletion and insertion of documents flexibly.