Research And Design Of Lattice-based Searchable Encryption Scheme

To achieve the privacy security of and facilitate the effective use of outsourced data stored on a third-party cloud server,Searchable Encryption(SE)stands out and has attracted more and more attention because of its security and high efficiency.As one of the important branches of SE,Public-key Encryption with Keyword Search(PEKS)has become a current research hotspot.However,most of current PEKS schemes are designed based on the hard problems in the number theory,which can not resist the quantum attacks.The advent of the quantum era will bring a fatal blow to the traditional PEKS and even the whole traditional public-key cryptography.For solving the problem,Lattice Cryptography is applied to PEKS to achieve post-quantum security.Although lattice-based PEKS has been developed for many years,and a series of excellent schemes have been proposed,which can be well applied to some common scenarios,there are still some key problems to be solved.(1)In multi-user scenarios,the generation and storage of keyword ciphertext require high time and storage overhead.(2)Untrusted servers may have malicious behaviors,such as incomplete or wrong search results returned to data users,and how can we efficiently verify the correctness of search results.For the sake of resolving the above problems,we mainly make the following works:(1)Aiming to tackle the problem that lattice-based PEKS schemes supporting conjunctive keyword search incur a huge cost in a multi-user scenario,we proposed a novel lattice-based PEKS scheme which borrows the idea of broadcast encryption.For all data users,our scheme only needs to generate one keyword ciphertext,which greatly reduces the time cost and storage cost that needs to be spent.In addition,all data users in our scheme are still relatively independent,and each data user can use his private key to generate trapdoors to meet his retrieval needs.(2)In order to achieve the efficient verification of search results,we proposed two solutions for two different application scenarios.One is the HV-PEKS scheme,which applies Hash Table to store verification vectors and uses the hash values of keywords as the Key of Hash Table to ensure the corresponding relationship of keywords and verification vectors and speed up the retrieval of the verification vector.This scheme is suitable for scenarios with small keyword space.The other is the BV-PEKS scheme,which applies a bloom filter to verify the search results.Thanks to the high efficiency of the bloom filter in storage and query,the BV-PEKS scheme has more significant advantages in scenarios with large keyword space.There are 14 figures,8 tables and 61 references.