Abstract:

In most searchable encryption schemes,the cloud server would compare the trapdoor with all secure indexes in the database during the search operation,which will cause excessive overhead.To address this problem,an efficient multi-keyword search encryption scheme supporting flexible access control is proposed.Before the sensitive data is encrypted and uploaded to the cloud server,it is clustered using the k-means to get several segmentation clusters,each of which would be given a different index through the Latent Dirichlet Allocation.In the search phase,the cloud server finds the cluster with the highest correlation through the Jaccard distance between the key set in the trapdoor and each cluster index,and searches the matched clusters in order to reduce the comparisons between the trapdoor and the index.And then the cloud server obtains the file list using the B+ tree-based data structure to improve the search efficiency.In addition,the scheme achieves encrypted file sharing by combining the broadcast encryption mechanism,which allows users to search for keywords in the authorized file subset,and takes the keyword set of each cluster as the user access rights.The performance comparison and experimental analysis show that a constant size of the user private key would be provided,and the communication cost and storage cost are independent of the number of authorized users,with the precision of search reaching about 90%.

Key words: searchable encryption, k-means clustering algorithm, broadcast encryption, access control