Paper 2026/459

Naor-Yung Transform for IND-CCA Probing Security with Lattice Instantiations

Laurent Imbert, LIRMM, Univ. Montpellier, CNRS

Loïc Masure, LIRMM, Univ. Montpellier, CNRS

Laz Panard, LIRMM, Univ. Montpellier, CNRS

Abstract

In this work, we propose novel security notions for encryption schemes that simulate an adversary in the black-box model equipped with additional side-channel power. More concretely, the adversary is allowed to probe values of the secret-key sensitive algorithms, i.e. key generation and decryption. We then prove a generalization of the well-known Naor-Yung (NY) transform, generically lifting IND-CPA secure encryption schemes to IND-CCA ones in this new probing context. Moreover, we instantiate the resulting framework from lattices, constructing Rutile, a masking-friendly IND-CPA encryption scheme inspired by Kyber, and then Topaz its IND-CCA secure extension. In our proposal, the masking-unfriendly parts of Kyber, namely the central binomial distributions and the FO-transform, are replaced by masking-friendly counterparts (sum of uniforms and the aforementioned NY-transform).

@misc{cryptoeprint:2026/459,
      author = {Katharina Boudgoust and Laurent Imbert and Loïc Masure and Laz Panard},
      title = {Naor-Yung Transform for {IND}-{CCA} Probing Security with Lattice Instantiations},
      howpublished = {Cryptology {ePrint} Archive, Paper 2026/459},
      year = {2026},
      url = {https://eprint.iacr.org/2026/459}
}