Paper 2021/1615

High-order Polynomial Comparison and Masking Lattice-based Encryption

Jean-Sébastien Coron and François Gérard and Simon Montoya and Rina Zeitoun

Abstract

The main protection against side-channel attacks consists in computing every function with multiple shares via the masking countermeasure. For IND-CCA secure lattice-based encryption schemes, the masking of the decryption algorithm requires the high-order computation of a polynomial comparison. In this paper, we describe and evaluate a number of different techniques for such high-order comparison, always with a security proof in the ISW probing model. As an application, we describe the full high-order masking of the NIST finalists Kyber and Saber, with a concrete implementation.