云存储中多授权多关键字属性基可搜索加密方案OA

To protect the security of private data stored in cloud servers,encryption is commonly used to process sensitive data.However,ciphertext data in the cloud impedes subsequent retrieval and sharing by users.Meanwhile,unauthorized access may cause privacy leakage of user data,and the traditional single-authorization mechanism is faced with perfor-mance bottlenecks and single point of failure risks.To solve the above problems,this paper proposes a multi-authority multi-keyword attribute-based searchable encryption scheme for cloud storage.Ciphertext-policy attribute-based encryption(CP-ABE)is adopted to ensure data confidentiality and implement fine-grained access control in the system.In addition,online/offline encryption technology is introduced.Complex operations such as symmetric key generation,share calculation of access policy matrix M and ciphertext component generation are executed in the offline phase,while only dot product operations are needed in the online encryption phase to generate the final ciphertext,which reduces the online encryption computational overhead on user clients.A cryptographic accumulator is used to construct keyword indices and verify key-words submitted by users during the search process,lowering the cost of complex cryptographic computations and improving the operational efficiency of the scheme.A result verification process is also added in the user decryption phase.The correctness of returned results is judged based on user attributes and access policies,so as to guarantee the integrity and validity of data returned by cloud servers.In terms of security,the proposed scheme is proven secure under selective keyword indistinguishability.Finally,simulation experiments are carried out.Experimental results demonstrate that compared with similar existing schemes,the proposed scheme improves the efficiency by 52.34%,62.23%and 53.97%in the stages of index generation,trapdoor generation and search respectively.