Research On Keyword Feature Based Search Scheme Over Encrypted Cloud Data

Search over encrypted cloud data is a hot topic today. In recent years, much effort has been made to design efficient keyword based search scheme over encrypted cloud data. These schemes can support different search functions. However, those existing techniques find less practical significance in real world applications compared with the multi-keyword fuzzy search technique over encrypted data. And none of the keyword based search techniques take the semantic relationship between keywords into account. They regard the keywords that the user inputs as independent and irrelevant. In fact, the importance of each keyword is different, and this can be shown by the semantic relations between the query keywords. So, based on the problems mentioned above, two different search schemes over encrypted cloud data were proposed. The main works of this thesis are described as follows:(1) This thesis proposes a multi-keyword fuzzy search scheme over encrypted cloud data. In this scheme, develop a new method of keyword transformation based on the uni-gram, which will simultaneously improve the accuracy and creates the ability to handle other spelling mistakes.Additionally, keywords with same root can be queried using the stemming algorithm.Experiments using real-world data show that our scheme is practically efficient and achieve high accuracy(2) This thesis proposes a keyword weight based semantic extension search scheme over encrypted cloud data. In this scheme, we design a keyword weight algorithm to show the weight of each query keyword based on their relationships. Through the keyword weight, the search results will be more in line with the demand of users. Besides, we design a novel central keyword semantic extension ranked scheme based on the keyword weight. By extending the central querying keyword, not all keyword, our scheme makes tradeoff between the functionality and efficiency. In order to improve the efficiency of the scheme, we construct a sub-matrix based encryption scheme. Due to the application of sub-matrix, our search system supports updates. We propose two secure searchable encrypted schemes to meet different privacy requirements in two different threat models. Experiments on the real-world dataset show that our proposed scheme is efficient, effective and secure.