[Resource Topic] 2020/822: Efficient Multi-Client Functional Encryption for Conjunctive Equality and Range Queries

Welcome to the resource topic for 2020/822

Title:
Efficient Multi-Client Functional Encryption for Conjunctive Equality and Range Queries

Authors: Kwangsu Lee

Abstract:

In multi-client functional encryption (MC-FE) for predicate queries, clients generate ciphertexts of attributes x_1, \ldots, x_n binding with a time period T and store them on a cloud server, and the cloud server receives a token corresponding to a predicate f from a trusted center and learns whether f(x_1, \ldots, x_n) = 1 or not by running the query algorithm on the multiple ciphertexts of the same time period. MC-FE for predicates can be used for a network event or medical data monitoring system based on time series data gathered by multiple clients. In this paper, we propose efficient MC-FE schemes that support conjunctive equality or range queries on encrypted data in the multi-client settings. First, we propose an efficient multi-client hidden vector encryption (MC-HVE) scheme in bilinear groups and prove the selective strong attribute hiding security with static corruptions. Our MC-HVE scheme is very efficient since a token is composed of four group elements, a ciphertext consists of O(n) group elements, and the query algorithm only requires four pairing operations. Second, we propose an efficient multi-client range query encryption (MC-RQE) scheme and prove the weak attribute hiding security with static corruptions. Since our MC-RQE scheme uses a binary tree, it is efficient since a ciphertext consists of O(n \log D) group elements and a token consists of O(n \log D) group elements where D is the maximum value of the range.

ePrint: https://eprint.iacr.org/2020/822

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