报告人：张心轩

报告地点：淦昌苑D座320，线上腾讯会议ID：310-537-944

报告时间：2024-04-08 10:30-11:30

报告题目：Zero-Knowledge Functional Elementary Databases

报告摘要：Zero-knowledge elementary databases (ZK-EDBs) enable a prover to commit a database $D$ of key-value $(x,v)$ pairs and later provide a convincing answer to the query ``send me the value $D(x)$ associated with $x$'' without revealing any extra knowledge (including the size of $D$). After its introduction, several works extended it to allow more expressive queries, but the expressiveness achieved so far is still limited: only a relatively simple queries--range queries over the keys and values-- can be handled by known constructions.

In this paper we introduce a new notion called zero knowledge functional elementary databases (ZK-FEDBs), which allows the most general functional queries. Roughly speaking, for any Boolean circuit $f$, ZK-FEDBs allows the ZK-EDB prover to provide convincing answers to the queries of the form ``send me all records $(x,v)$ in $D$ satisfying $f(x,v)=1$,'' without revealing any extra knowledge (including the size of $D$). We present a construction of ZK-FEDBs in the random oracle model and generic group model, whose proof size is only linear in the length of record and the size of query circuit, and is independent of the size of input database $D$.

Our technical constribution is two-fold. Firstly, we introduce a new variant of zero-knowledge sets (ZKS) which supports combined operations on sets, and present a concrete construction that is based on groups with unknown order. Secondly, we develop a tranformation that tranforms the query of Boolean circuit into a query of combined operations on related sets, which may be of independent interest.

eprint：https://eprint.iacr.org/2023/156

报告人简介：张心轩，2018年于山东大学泰山学堂获得数学学士学位，现于中国科学院信息工程研究所攻读网络空间安全博士学位。研究方向为密码协议，具体包括零知识证明、零知识数据库、zk-SNARK、不经意传输等。在ASIACRYPT上发表论文三篇。

邀请人：胡思煌

审核人：魏普文