Research On Technologies Of Multi-Dimensional Keyword Search Over Encrypted Data In Cloud Computing

With the rapid development of information technology,cloud computing has emerged as a hot research area in both industry and academia.As a new computing paradigm,cloud computing can provide tremendous storage and computing resources to resource-constrained users by means of outsourcing,alleviating the cost of software development and hardware maintenance.Despite of plenty of powerful advantages,data privacy is one of the primary obstacles which prevent the widespread adoption of cloud computing.The data are required to be encrypted before being outsourced to the cloud server to protect the sensitive data of the users.However,it is important and challenging to achieve efficient multi-keyword search over encrypted data.Searchable encryption(SE)can directly perform efficient keyword search on encrypted data,while ensuring the confidentiality of data.As an important branch of searchable encryption,multi-dimensional keyword search can achieve complex data search through the conjunction of diffident dimensions and has been widely used in of scenario of the medical record for quick search,in which all the keywords are divided into many dimensions.Although the existing multi-dimensional keyword search schemes support multiple data search modes,such as range query,subset query and so on,there are still deficiencies in efficiency and security.Firstly,in the existing multi-dimensional keyword search schemes,the search trapdoor submitted by the user is generated in a deterministic way such that the server can carry out statistical analysis on the keywords and retrieve the private information about the keywords.Secondly,among the dynamic multi-dimensional keyword search schemes,the existing schemes only achieve the linear search complexity and suffer from inefficiency in initiation,generation of trapdoor and search phases,such that they cannot satisfy the application requirements for quick search over large-scale data.Thirdly,none of the existing multidimensional keyword search schemes support of the verifiability of the search results,that is,the user cannot verify the correctness and completeness of the search results.In this dissertation,we focus on the key issues of multi-dimensional keyword search over the encrypted data in cloud computing.The main contents include:(1)how to design multidimensional keyword search scheme supporting flexible and expressive queries;(2)how to design multi-dimensional keyword search scheme supporting the dynamic update operations;(3)how to design verifiable multi-dimensional keyword search scheme.The main contributions are three-fold.1.We propose a flexible multi-dimensional keyword search scheme supporting equality,range and subset queries in each dimensional.Moreover,attribute hierarchy is utilized to shorten the length of index vectors and query vectors,such that the search efficiency is improved.Moreover,random numbers and nonlinear spitting of vectors are introduced into trapdoor generation algorithm,achieving the indistinguishability of trapdoor and ensuring the privacy of the query keywords.The proposed scheme has less computation overhead in initialization,encryption of the index,the trapdoor generation and query and is more suitable for large scale of data search scenarios.(Chapter 3)2.We propose a sub-linear multi-dimensional keyword search scheme supporting the dynamic update operations.We achieve the insertion and deletion operations of the documents by the way of updating nodes in the index tree,solving the problem that the existing sub-linear multi-dimensional keyword search schemes do not support dynamic update operations of documents.In addition,we propose a novel index structure based on multiple attribute tree,achieving sub-linear search complexity.Experiments and theoretical analysis show that the proposed scheme achieves better efficiency advantages in initialization,trapdoor generation and search.(Chapter 4)3.We propose a multi-dimensional keyword search scheme supporting the verification of search results.In the proposed scheme,a semi-trusted authority is introduced to help finishing the keys generation and authorization query and fine-grained permission authorization operations for query users,such that search can also be carried out when the data owner is not online.In addition,we utilize dual orthonormal bases to generate search index and trapdoor.By using the dual system encryption methodology,the proposed scheme can achive the properties of adaptively index-hiding and queryhiding against chosen plaintext attack(CPA).Besides,the proposed scheme supports the verification of search results.(Chapter 5).