Paper 2025/2036
On new variants of funcCPA security and related CCA-secure constructions
Abstract
FuncCPA is a recent security notion in which the CPA game is extended by a functional re-encryption oracle in order to model setups in which a server performing FHE computations is allowed to interactively delegate part of the computation back to the client. In this paper, we study funcCPA-style variants of several CCA security notions, including CCA1 and the more recent vCCA security. Contrary to the CPA case where a strict separation holds between CPA and funcCPA, we show that these new variants are equivalent to their respective originating CCA security notions. Interestingly, funcCPA-style security notions also model setups where, rather than delegating part of the encrypted domain computation all the way back to the client, the server has the ability to perform this delegation towards a honest or semi-honest client proxy it hosts, such as a secure enclave. We then provide a number of blueprints for achieving both FHE-like capabilities and advanced CCA security properties which may then meaningfully be implemented by leveraging on the combination of a partially homormophic scheme and a semi-honest non-colluding enclave hosted within the server performing the encrypted domain calculations itself.
Note: Accepted to PKC 2026. This version includes the appendix that will not be included in the proceedings version.
Metadata
- Available format(s)
-
PDF
- Category
- Public-key cryptography
- Publication info
- A major revision of an IACR publication in PKC 2026
- Contact author(s)
-
caroline fontaine @ cnrs fr
marc renard @ lmf cnrs fr
renaud sirdey @ cea fr
oana stan @ cea fr - History
- 2026-03-02: last of 4 revisions
- 2025-11-03: received
- See all versions
- Short URL
- https://ia.cr/2025/2036
- License
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CC BY
BibTeX
@misc{cryptoeprint:2025/2036,
author = {Caroline Fontaine and Marc Renard and Renaud Sirdey and Oana Stan},
title = {On new variants of {funcCPA} security and related {CCA}-secure constructions},
howpublished = {Cryptology {ePrint} Archive, Paper 2025/2036},
year = {2025},
url = {https://eprint.iacr.org/2025/2036}
}
