Security with Functional Re-encryption from CPA

Yevgeniy Dodis, Shai Halevi, Daniel Wichs

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


The notion of functional re-encryption security (funcCPA) for public-key encryption schemes was recently introduced by Akavia et al. (TCC’22), in the context of homomorphic encryption. This notion lies in between CPA security and CCA security: we give the attacker a functional re-encryption oracle instead of the decryption oracle of CCA security. This oracle takes a ciphertext ct and a function f, and returns fresh encryption of the output of f applied to the decryption of ct ; in symbols, ct= Enc (f(Dec (ct) ) ). More generally, we even allow for a multi-input version, where the oracle takes an arbitrary number of ciphertexts ct1, … ct and outputs ct= Enc (f(Dec (ct1), …, Dec (ct) ) ). In this work we observe that funcCPA security may have applications beyond homomorphic encryption, and set out to study its properties. As our main contribution, we prove that funcCPA is “closer to CPA than to CCA”; that is, funcCPA secure encryption can be constructed in a black-box manner from CPA-secure encryption. We stress that, prior to our work, this was not known even for basic re-encryption queries corresponding to the identity function f. At the core of our result is a new technique, showing how to handle adaptive functional re-encryption queries using tools previously developed in the context of non-malleable encryption, which roughly corresponds to a single non-adaptive parallel decryption query.

Original languageEnglish (US)
Title of host publicationTheory of Cryptography - 21st International Conference, TCC 2023, Proceedings
EditorsGuy Rothblum, Hoeteck Wee
PublisherSpringer Science and Business Media Deutschland GmbH
Number of pages27
ISBN (Print)9783031486173
StatePublished - 2023
Event21st International conference on Theory of Cryptography Conference, TCC 2023 - Taipei, Taiwan, Province of China
Duration: Nov 29 2023Dec 2 2023

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume14370 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference21st International conference on Theory of Cryptography Conference, TCC 2023
Country/TerritoryTaiwan, Province of China

ASJC Scopus subject areas

  • Theoretical Computer Science
  • General Computer Science


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