Research And Implementation On Dynamic Searchable Encryption For Cloud Storage

Cloud storage technology provides massive storage resources for many enterprises,organizations and individuals.Network users can outsource data on the cloud servers to save local storage resources.However,cloud storage data is out of the physical control for users and can result in private data theft or data leakage.Dynamic searchable encryption technology has functions of update and keyword retrieval for encrypted data while ensuring the confidentiality of cloud storage data.However,most dynamic searchable encryption schemes are based on symmetric searchable encryption which requires pre-established secure key sharing channels and is difficult to be directly applied in cloud storage data sharing scenarios.In addition,some dynamic searchable encryption schemes only support document and index addition,and have limitations for deletion functions.To address the problems mentioned above,the main contributions of this dissertation are as follows.(1)For the secure sharing scenario of multi-party data in cloud storage platform,the dissertation proposes a dynamic multi-keyword searchable encryption scheme with hybrid encryption.In the scheme,the forward index is constructed by a cuckoo filter to realize the documents dynamic update function by data owners.The scheme supports conjunctive multi-keywords search by combining bilinear pairing with Lagrangian interpolation polynomials.To reduce the computational overhead in the ciphertext retrieval phase,a combination of inverted index and forward index is constructed to improve the retrieval efficiency of cloud server.This scheme is proved to be resistant the indistinguishability under chosen keyword attack by decision linear Diffie-Hellman problem.Simulation experiments are conducted to analyze the execution efficiency of the scheme for keyword search and index update in different datasets.The results show that the scheme effectively avoids the linear correlation between the retrieval time and the number of ciphertexts,and reduces the computational overhead in the update operation with a large amount of data.(2)The dissertation designs and implements a ciphertext retrieval system for cloud storage environment.With the starting point of supporting the addition and deletion of documents and indexes,a dynamic symmetric searchable encryption scheme is proposed by using pseudo-random functions and cuckoo filter.The scheme designs the inverted index with a linked list structure,users only upload the encrypted nodes in the linked list when updating,without reconstructing the complete index linked list corresponding to the keywords,which reduces the computational overhead in the update phase.The functional implementation of the cryptographic retrieval system is carried out using Flask development framework and Tencent Cloud Object Storage.Some test cases are written to test each functional module of the system,the results show that the system has good usability in core functions such as outsourced storage of encrypted documents,search and update of encrypted documents.