PPFilter: Provider Privacy-Aware Encrypted Filtering System

Filtering refers to an operation to determine whether the concerned data should be accepted and transferred, or be blocked and marked as a malicious traffic flow. It mitigates the inter-domain bandwidth overhead, local computational cost and storage cost for data identification. In many sensitive applications, the identity of the data provider needs to be hidden. This creates challenges how to filter the transmitted data packet with an encrypted form. It is non-trivial to hide this data provider's identity while enabling filtering, as the policy used as a matching criteria will need to determine whether the data needs to be transferred or not without knowing the origin of that data. In this work, we design PPFilter, a privacy-aware encrypted filtering mechanism which allows the filtering to be conducted without the need to know the identity of the data provider. PPFilter achieves the integrity protection of the data packets and the provider privacy Level 3. PPFilter is built on top of a novel notion called identity-based encryption with sender search (IESS), which supports anonymous sender identity in an encrypted searching. We present a provably secure IESS instantiation, and apply it to achieve a PPFilter protocol. PPFilter allows the data provider's identity to be hidden from both the transferred data and policy while enabling the filtering capability, which solves the aforementioned problem. The analysis and evaluation show that PPFilter maintains cost-reasonable filtering while preserving provider privacy, and hence it guarantees its practicality.