Research On Revocable And Searchable Attribute-based Encryption Algorithms

Cloud computing has attracted wide attentions from all walks of life with its powerful storage space and fast computing services.Since data are stored in the cloud,the data owner loses the direct control of data,and the confidentiality and access control of data cannot be guaranteed.Attribute-based encryption can realize fine-grained and non-interactive access control of ciphertext data,and thus it is considered to be one of the most effective encryption techniques to solve the above problems.In attribute-based encryption,the user's key may be stolen,lost or the user leaves the system.At this time,the user's access permission should be revoked in time to ensure the confidentiality of data.In addition,data are stored in the cloud server after encryption,where the confidentiality of data is protected.However,when the user needs to search for data,the ciphertext data must be downloaded,decrypted and searched,which will cause a waste of bandwidth and resources.In order to ensure that the cloud server can search and query the data required by the user on the ciphertext,as well as it cannot obtain any information of data,searchable attribute-based encryption technology arises.However,the existing searchable attribute-based encryption algorithms still have some problems,such as low search efficiency,low accuracy,and inability to verify the integrity of ciphertext data.These problems hinder the application of searchable attribute-based encryption in practical scenarios.In order to solve the above problems,this thesis mainly does the following work:(1)To propose an attribute-based encryption algorithm that can support user revocation and multi-keyword search for the medical health system.The proposed algorithm uses the minimum subset coverage algorithm KUNodes to achieve efficient user revocation.At the same time,the algorithm can provide multi-keyword search,and effectively avoid the return of a large number of irrelevant documents.In addition,the proposed algorithm can calculate the hash value of the random key hash value and the symmetric ciphertext in parallel,which can quickly verify the integrity of the returned result.Finally,under the general group model,it is proved that the algorithm is resistant to selective plaintext attacks and selective keyword attacks.Performance analysis shows that the proposed algorithm is practical in the medical health systems.(2)To present an attribute-based encryption algorithm that can provide multi-keyword search and fast decryption.The algorithm utilizes the LSSS access policy in the encryption of the keywords,so that the attribute needs to match with the access strategy during the retrieval process,which can improve the accuracy of the retrieval.At the same time,in the process of re-encryption,the public key of the data receiver is embedded in the ciphertext.After receiving the new ciphertext,the data receiver only needs to perform an exponential operation to recover the plaintext information,which can improve the efficiency of decryption.Finally,it is proved that the proposed algorithm can resist the selective plaintext attack and the selective keyword attack under the selective access structure.Performance analysis shows that the proposed algorithm has high efficiency in the electronic personal health record system.