Towards Globally Optimized Hybrid Homomorphic Encryption - Featuring the Elisabeth Stream Cipher

Orel Cosseron; Clément Hoffmann; Pierrick Méaux; François-Xavier Standaert

Paper 2022/180

Towards Globally Optimized Hybrid Homomorphic Encryption - Featuring the Elisabeth Stream Cipher

Orel Cosseron, École Normale Supérieure de Lyon, Télécom ParisTech

Clément Hoffmann

, Université Catholique de Louvain

Pierrick Méaux

, University of Luxembourg

François-Xavier Standaert

, Université Catholique de Louvain

Abstract

Hybrid Homomorphic Encryption (HHE) reduces the amount of computation client-side and band- width usage in a Fully Homomorphic Encryption (FHE) framework. HHE requires the usage of specific sym- metric schemes that can be evaluated homomorphically efficiently. In this paper, we introduce the paradigm of Group Filter Permutator (GFP) as a generalization of the Improved Filter Permutator paradigm introduced by M ́eaux et al. From this paradigm, we specify Elisabeth , a family of stream cipher and give an instance: Elisabeth-4 . After proving the security of this scheme, we provide a Rust implementation of it and ensure its performance is comparable to state-of-the-art HHE. The true strength of Elisabeth lies in the available opera- tions server-side: while the best HHE applications were limited to a few multiplications server-side, we used data sent through Elisabeth-4 to homomorphically evaluate a neural network inference. Finally, we discuss the improvement and loss between the HHE and the FHE framework and give ideas to build more efficient schemes from the Elisabeth family

Note: Corrected small affiliation mistake

Metadata

Available format(s): PDF
Category: Secret-key cryptography
Publication info: A minor revision of an IACR publication in ASIACRYPT 2022
Keywords: homomorphic encryption hybrid homomorphic encryption Elisabeth stream-ciphers Group Filter Permutator TFHE
Contact author(s): orel cosseron @ ens-lyon fr
clement hoffmann @ uclouvain be
pierrick meaux @ uni lu
fstandae @ uclouvain be
History: 2022-09-21: last of 4 revisions; 2022-02-20: received; See all versions
Short URL: https://ia.cr/2022/180
License: CC BY

BibTeX

@misc{cryptoeprint:2022/180,
      author = {Orel Cosseron and Clément Hoffmann and Pierrick Méaux and François-Xavier Standaert},
      title = {Towards Globally Optimized Hybrid Homomorphic Encryption - Featuring the Elisabeth Stream Cipher},
      howpublished = {Cryptology {ePrint} Archive, Paper 2022/180},
      year = {2022},
      url = {https://eprint.iacr.org/2022/180}
}