Paper 2025/2304

Streaming Function Secret Sharing and Its Applications

Jianli Bai, Singapore Management University

Ye Dong, National University of Singapore

Yijian Liu, Institute of Information Engineering, Chinese Academy of Sciences & School of Cyber Security, University of Chinese Academy of Sciences

Yu Zhang, Institute of Information Engineering, Chinese Academy of Sciences & School of Cyber Security, University of Chinese Academy of Sciences

Xianhui Lu, Institute of Information Engineering, Chinese Academy of Sciences & School of Cyber Security, University of Chinese Academy of Sciences

Tianwei Zhang, Nanyang Technological University

Abstract

Collecting statistics from users of software and online services is crucial to improve service quality, yet obtaining such insights while preserving individual privacy remains a challenge. Recent advances in function secret sharing (FSS) make it possible for scalable privacy-preserving measurement (PPM), which leads to ongoing standardization at the IETF. However, FSS-based solutions still face several challenges for streaming analytics, where messages are continuously sent, and secure computation tasks are repeatedly performed over incoming messages. We introduce a new cryptographic primitive called streaming function secret sharing (SFSS), a new variant of 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 powers 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.

BibTeX

@misc{cryptoeprint:2025/2304,
author = {Xiangfu Song and Jianli Bai and Ye Dong and Yijian Liu and Yu Zhang and Xianhui Lu and Tianwei Zhang},
title = {Streaming Function Secret Sharing and Its Applications},
howpublished = {Cryptology {ePrint} Archive, Paper 2025/2304},
year = {2025},
url = {https://eprint.iacr.org/2025/2304}
}