Fine-Grained Proxy Re-encryption: Definitions and Constructions from LWE

Yunxiao Zhou, Shengli Liu, Shuai Han*, Haibin Zhang

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

3 Citations (Scopus)

Abstract

Proxy re-encryption (PRE) allows a proxy with a re-encryption key to translate a ciphertext intended for Alice (delegator) to another ciphertext intended for Bob (delegatee) without revealing the underlying message. However, with PRE, Bob can obtain the whole message from the re-encrypted ciphertext, and Alice cannot take flexible control of the extent of the message transmitted to Bob. In this paper, we propose a new variant of PRE, called Fine-Grained PRE (FPRE), to support fine-grained re-encryptions. An FPRE is associated with a function family F, and each re-encryption key rkA→Bf is associated with a function f∈ F. With FPRE, Alice now can authorize re-encryption power to proxy by issuing rkA→Bf to it, with f chosen by herself. Then the proxy can translate ciphertext encrypting m to Bob’s ciphertext encrypting f(m) with such a fine-grained re-encryption key, and Bob only obtains a function of message m. In this way, Alice can take flexible control of the message spread by specifying functions. For FPRE, we formally define its syntax and formalize security notions including CPA security, ciphertext pseudo-randomness, unidirectionality, non-transitivity, collusion-safety under adaptive corruptions in the multi-user setting. Moreover, we propose a new security notion named ciphertext unlinkability, which blurs the link between a ciphertext and its re-encrypted ciphertext to hide the proxy connections between users. We establish the relations between those security notions. As for constructions, we propose two FPRE schemes, one for bounded linear functions and the other for deletion functions, based on the learning-with-errors (LWE) assumption. Our FPRE schemes achieve all the aforementioned desirable securities under adaptive corruptions in the standard model. As far as we know, our schemes provide the first solution to PRE with security under adaptive corruptions in the standard model.

Original languageEnglish
Title of host publicationAdvances in Cryptology – ASIACRYPT 2023 - 29th International Conference on the Theory and Application of Cryptology and Information Security, Proceedings
EditorsJian Guo, Ron Steinfeld
PublisherSpringer Science and Business Media Deutschland GmbH
Pages199-231
Number of pages33
ISBN (Print)9789819987351
DOIs
Publication statusPublished - 2023
Event29th Annual International Conference on the Theory and Application of Cryptology and Information Security, Asiacrypt 2023 - Guangzhou, China
Duration: 4 Dec 20238 Dec 2023

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume14443 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349

Conference

Conference29th Annual International Conference on the Theory and Application of Cryptology and Information Security, Asiacrypt 2023
Country/TerritoryChina
CityGuangzhou
Period4/12/238/12/23

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