Multi-Client Inner-Product Functional Encryption in the Random-Oracle Model

Michel Abdalla, Florian Bourse, Hugo Marival, David Pointcheval, Azam Soleimanian, and Hendrik Waldner

Abstract

Multi-client functional encryption (MCFE) is an extension of functional encryption (FE) in which the decryption procedure involves ciphertexts from multiple parties. In this paper, we consider MCFE schemes supporting encryption labels, which allow the encryptor to limit the amount of possible mix-and-match that can take place during the decryption. This is achieved by only allowing the decryption of ciphertexts that were generated with respect to the same label. This flexible form of FE was already investigated by Chotard et al. at Asiacrypt 2018 and Abdalla et al. at Asiacrypt 2019. The former provided a general construction based on different standard assumptions, but its ciphertext size grows quadratically with the number of clients. The latter gave a MCFE based on Decisional Diffie-Hellman (DDH) assumption which requires a small inner-product space. In this work, we overcome the deficiency of these works by presenting three constructions with linear-sized ciphertexts based on the Matrix-DDH (MDDH), Decisional Composite Residuosity (DCR) and Learning with Errors (LWE) assumptions in the random-oracle model. We also implement our constructions to evaluate their concrete efficiency.

Note: This paper has been accepted in SCN 2020.

Available format(s)
Category
Secret-key cryptography
Publication info
Published elsewhere. MAJOR revision.SCN 2020
DOI
10.1007/978-3-030-57990-6_26
Keywords
Functional encryptionmulti-clientinner-product functionalityrandom oracle.
Contact author(s)
michel abdalla @ ens fr
florian bourse @ ens fr
hmarival @ gmail com
david pointcheval @ ens fr
azam soleimanian @ ens fr
hendrik waldner @ ed ac uk
History
2020-12-11: revised
See all versions
Short URL
https://ia.cr/2020/788

CC BY

BibTeX

@misc{cryptoeprint:2020/788,
author = {Michel Abdalla and Florian Bourse and Hugo Marival and David Pointcheval and Azam Soleimanian and Hendrik Waldner},
title = {Multi-Client Inner-Product Functional Encryption in the Random-Oracle Model},
howpublished = {Cryptology ePrint Archive, Paper 2020/788},
year = {2020},
doi = {10.1007/978-3-030-57990-6_26},
note = {\url{https://eprint.iacr.org/2020/788}},
url = {https://eprint.iacr.org/2020/788}
}

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