Paper 2026/285 Original: eprint.iacr.org/2026/285 ↗
How (not) to Switch FHE Schemes: Framework and Attacks in the IND-CPA-D Model
Abstract
In this paper, we study the IND-CPA-D security of FHE schemes combined via scheme switching. We introduce a formal framework for capturing security in this setting and identify sufficient conditions under which such combined schemes achieve IND-CPA-D security. We then focus on the specific case of scheme switching from CKKS to exact FHE schemes. We show that the PEGASUS construction [LHHMQ21] does not achieve IND-CPA-D security, and provide a proof-of-concept implementation of a key-recovery attack against the CKKS-to-FHEW switching mechanism in the OpenFHE library.
Metadata
- Available format(s)
PDF- Category
- Public-key cryptography
- Publication info
- Preprint.
- History
- 2026-06-17: last updated
- 2026-02-17: published
- Short URL
- https://ia.cr/2026/285
- License
- https://creativecommons.org/licenses/by/4.0/
BibTeX
@misc{cryptoeprint:2026/285,
author = {Giacomo Santato and Riccardo Zanotto},
title = {How (not) to Switch FHE Schemes: Framework and Attacks in the IND-CPA-D Model},
howpublished = {Cryptology {ePrint} Archive, Paper 2026/285},
year = {2026},
url = {https://eprint.iacr.org/2026/285}
}