CCA Updatable Encryption Against Malicious Re-encryption Attacks

Long Chen, Yanan Li, Qiang Tang

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Updatable encryption (UE) is an attractive primitive, which allows the secret key of the outsourced encrypted data to be updated to a fresh one periodically. Several elegant works exist studying various security properties. We notice several major issues in existing security models of (ciphertext dependent) updatable encryption, in particular, integrity and CCA security. The adversary in the models is only allowed to request the server to re-encrypt honestly generated ciphertext, while in practice, an attacker could try to inject arbitrary ciphertexts into the server as she wishes. Those malformed ciphertext could be updated and leveraged by the adversary and cause serious security issues. In this paper, we fill the gap and strengthen the security definitions in multiple aspects: most importantly our integrity and CCA security models remove the restriction in previous models and achieve standard notions of integrity and CCA security in the setting of updatable encryption. Along the way, we refine the security model to capture post-compromise security and enhance the re-encryption indistinguishability to the CCA style. Guided by the new models, we provide a novel construction ReCrypt+, which satisfies our strengthened security definitions. The technical building block of homomorphic hash from a group may be of independent interests. We also study the relations among security notions; and a bit surprisingly, the folklore result in authenticated encryption that IND-CPA plus ciphertext integrity imply IND-CCA security does not hold for ciphertext dependent updatable encryption.

Original languageEnglish (US)
Title of host publicationAdvances in Cryptology – ASIACRYPT 2020 - 26th International Conference on the Theory and Application of Cryptology and Information Security, 2020, Proceedings
EditorsShiho Moriai, Huaxiong Wang
PublisherSpringer Science and Business Media Deutschland GmbH
Pages590-620
Number of pages31
ISBN (Print)9783030648398
DOIs
StatePublished - 2020
Event26th International Conference on the Theory and Application of Cryptology and Information Security, ASIACRYPT 2020 - Daejeon, Korea, Republic of
Duration: Dec 7 2020Dec 11 2020

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume12493 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349

Conference

Conference26th International Conference on the Theory and Application of Cryptology and Information Security, ASIACRYPT 2020
Country/TerritoryKorea, Republic of
CityDaejeon
Period12/7/2012/11/20

All Science Journal Classification (ASJC) codes

  • Theoretical Computer Science
  • Computer Science(all)

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