Enabling Central Keyword-Based Semantic Extension Search Over Encrypted Outsourced Data

In practice, search keywords have quite different importance when users take search operations. In addition, such keywords may have a certain grammatical relationship among them, which reflect the importance of keywords from the user's perspective intuitively. However, the existing search techniques regard the search keywords as independent and unrelated. In this paper, for the first time, we take the relation among query keywords into consideration and design a keyword weighting algorithm to show the importance of the distinction among them. By introducing the keyword weight to the search protocol design, the search results will be more in line with the user's demand. On top of this, we further design a novel central keyword semantic extension ranked scheme. By extending the central query keyword instead of all keywords, our scheme makes a good tradeoff between the search functionality and efficiency. To better express the relevance between queries and files, we further introduce the TF-IDF rule when building trapdoors and the index. In particular, our scheme supports both data set and keywords updates by using the sub-matrix technique. Our work first gives a basic idea for the design of the central keyword semantic extension ranked scheme, and then presents two secure searchable encryption schemes to meet different privacy requirements under two different threat models. Experiments on the real-world data set show that our proposed schemes are efficient, effective, and secure.