Jiafan Wang (Data61, CSIRO), Sherman S. M. Chow (The Chinese University of Hong Kong)

Searchable encryption lets an untrusted cloud server store keyword-document tuples encrypted by writers and conduct keyword searches with tokens from readers. Multi-writer schemes naturally offer broad applicability; however, it is unclear how to achieve the distinctive features of single-writer systems, namely, optimal search traversing only the result set and forward privacy invalidating old search tokens against any new data. Cutting-edge results by Wang and Chow (Usenix Security 2022) incur extra traversal over existing keywords and weaken forward privacy that only invalidates previous-issued search tokens periodically.

We propose delegatable searchable encryption (DSE) with optimal search time for the multi-writer multi-reader setting. Beyond forward privacy, DSE supports security measures countering new integrity threats by malicious clients and keyword-guessing attacks inherent to public-key schemes. These are simultaneously made conceivable via one-time delegations of updating and/or searching power from the data owner and our tailored notion of shiftable multi-recipient counter encryption. DSE also benefits from the hybrid searchable encryption idea of Wang and Chow but at a microscopic level. Our evaluation confirms the order-of-magnitude improvement in search time over real-world datasets.

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Zitao Chen (University of British Columbia), Karthik Pattabiraman (University of British Columbia)

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Zhengxiong Luo (Tsinghua University), Kai Liang (Central South University), Yanyang Zhao (Tsinghua University), Feifan Wu (Tsinghua University), Junze Yu (Tsinghua University), Heyuan Shi (Central South University), Yu Jiang (Tsinghua University)

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