Usenix Security 26 Artifact: Streaming Function Secret Sharing and Its Applications

We introduce a new cryptographic primitive called {streaming function secret sharing} (SFSS), a new variant of function secret sharing (FSS) that is particularly suitable for secure computation over streaming messages. We formalize SFSS and propose concrete constructions, including SFSS for point functions, predicate functions, and feasibility results for generic functions. SFSS facilitates several promising applications in a simple and modular fashion, including conditional transciphering, policy-hiding aggregation, and attribute-hiding aggregation. In particular, our SFSS formalization and constructions identify security flaws and efficiency bottlenecks in existing solutions, and SFSS-powered solutions achieve the expected security goal with asymptotically and concretely better efficiency and/or enhanced functionality.

In this artifact evaluation, we provide implementation of SFSS primitives (including SDPF and SDCF) and applications (including window-based metadata-hiding aggregation).