MFPSE: Multi-user Forward Private Searchable Encryption with dynamic authorization in cloud computing

Dynamic Searchable Symmetric Encryption (DSSE) allows users to outsource data with ciphertext format to untrusted servers and supports the operations of data adding and deleting, which is adopted in common usage by government and business. Recently, the primitive of Forward Privacy in DSSE has drawn great public interest owing to its beneficial feature, which is that it can guard against the newly uploaded files from linking to previous search tokens. However, most of existing Forward Private Searchable Encryption (FPSE) schemes focus on single-user environment, which means that only the users themselves can utilize the data, greatly limits the wide application in cloud computing. To our knowledge, it is difficult to migrate the FPSE schemes to multi-user network. First, to realize forward privacy, the data owner should share the entire key group to the legitimate users, which means the users have the privilege of tampering or deleting data rather than query only; secondly, some FPSE schemes use the special structures and cannot be directly developed to multi-user network. Inspired by this, we present a scheme of multi-user forward private searchable encryption with dynamic authorization. The proposed scheme is based on a new structure of Multi-user State Chain and involves dynamic keyword-oriented authorization management. We prove our scheme can meet the secure characteristics, then conduct the performance evaluation and experiments. The results demonstrate that compared with the existing solutions, our scheme is superior in efficiency and practicability.