A lattice-based searchable encryption scheme with the validity period control of files

In recent years, with the dramatic increase in the use of multimedia data, rapid retrieval and sharing of the multimedia data have become major trends. The validity period control function widely used in daily softwares, which enables multimedia data to be shared from a specific time and revokes the authorization of shared data at another specific time, thereby effectively enhancing the personalized experience of multimedia data users. At the same time, to protect privacy, databases usually store data in an encrypted form and use searchable encryption technology to retrieve keywords on the ciphertext to quickly extract the required multimedia data. However, the existing searchable encryption scheme cannot control the reading of multimedia data by using validity period. To solve this problem, we propose a lattice-based searchable encryption scheme with the validity period control of files. In order that the data owners have flexible and fine-grained control over the files, we convert the time information into a lattice vector for setting a different valid time for each file. Meanwhile, we embed the time information into the ciphertext, so that the data owner only needs to set the validity period once to automatically maintain the life cycle of the files over encrypted data, instead of manually withdrawing each expired file. Furthermore, we combine searchable encryption and time-distance so that our scheme returns valid files only if the keywords match correctly and the search time matches the file’s validity period. This scheme is a candidate for time-controlled searchable encryption technology in the post-quantum era because our scheme constructed on learning with error (LWE) problem which has been proven to resist quantum attacks.