Full-Accessible Multiparty Searchable Encryption Scheme for Shared Cloud Storage

To securely share the data between users, encryption schemes with keyword searches in various settings have been proposed. Many studies design schemes in a designated receiver setting where a data owner specifies which receivers could download the data in advance at the time the data are uploaded. In this setting, it is not easy to extend the scheme to support environments with multiple data owners. Moreover, there was no scheme considering the situation in which a newly enrolled user accesses data that were uploaded prior to his enrollment. On the other hand, schemes designed in an undesignated receiver setting support multiple data owners and allow data to be accessed by all users in the system, regardless of the time the data were uploaded. However, most of them are not secure against collusion attacks involving an untrusted server and revoked users. In this paper, we propose a full-accessible multiparty searchable encryption (FA-MPSE) scheme for data-sharing systems. Our scheme supports the property that we call full-accessibility, and any users in the system can access all data in the storage. In addition, our scheme is secure against collision attacks so that the revoked users who collaborate with the server can not access the stored data. Furthermore, our scheme provides all the essential properties of MPSE, such as query privacy, query unforgeability, full-revocability, and unlinkability, and its security is proven in a formal security model. We provide the comparison result with the related schemes to show that our scheme has a comparative advantage.