Research On Searchable Encryption Of Ciphertext Data In Cloud

With the rapid development of cloud computing and storage services,the number of users has been increasing,and thus the amount of data generated has been growing exponentially.In order to protect the confidentiality of data,users need to encrypt massive amounts of data into ciphertext and store them in the cloud,but this method could prevent data search.It is difficult that how data users search the interested files in the ciphertext.Searchable encryption technology has been proposed for the above problems.Furthermore,in order to achieve fine-grained access control,attribute-based encryption technology has been applied to searchable encryption schemes.Searchable encryption technology can solves the ciphertext search problem,but also faces some problems that need to be solved.Firstly,the leakage of key may cause the malicious user to search for the file stored in the cloud,and the cloud server cannot identify whether the search user is malicious.Secondly,since the data owner encrypts different files with different keys,they need to share a large number of key,which brings heavy key management problems.Finally,the data owner loses the right to manage the data that stored in the cloud,and The semi-trusted cloud server may maliciously tamper with the ciphertext,which cannot ensure that the data searched by the data user is complete.In response to the above problems,this paper presents the following two solutions:1.A verifiable and authenticated searchable encryption scheme with aggregate key is proposed.In the application scenario where the data owner encrypts different files with different keys,the aggregate key technology is used to realize that different users can search different files with the same keyword.By embedding the identity of the authorized user in the aggregation key,the cloud server can authenticate whether the search user is an authorized user,which can ensure that files stored in the cloud are not compromised.At the same time,the search user can verify whether the searched ciphertext is complete,which can prevent the cloud server from maliciously tampering with the ciphertext.In addition,the security analysis shows that the proposed scheme can achieve the security of selecting keyword attacks.Efficiency analysis shows that the scheme is efficient.2.Considering the scenario of electronic personal health record system,we put forward a searchable attribute-based signcryption scheme,which can support fine-grained access control,data privacy,data authenticity,and data searchability.Then we establish the security models and construct a searchable attribute-based signcryption scheme with hybrid access policy.According to the proposed security model frameworks,our scheme is proven to achieve:(i)ciphertext indistinguishability under the Decisional Bilinear Diffie-Hellman Exponent hardness assumption,(ii)existential unforgeability based on the hardness assumption of Computational Diffie-Hellman Exponent problem,(iii)selective security against chosen-keyword attack under the static assumption in the generic group model,(iv)keyword secrecy based on the one-way hardness of hash function.Furthermore,the experimental results show that the proposed scheme is efficient.