Kavach: Lightweight masking techniques for polynomial arithmetic in lattice-based cryptography

Lattice-based cryptography has laid the foundation of various modern-day cryptosystems that cater to several applications, including post-quantum cryptography. For structured lattice-based schemes, polynomial arithmetic is a fundamental part. In instances, performance optimizations come from implementing compact multipliers due small range secret coefficients. However, this optimization does not easily translate side-channel protected implementations since masking requires coefficients be distributed over large range. work, we address problem and propose two novel generalized techniques, one for number theoretic transform (NTT) based another non-NTT-based arithmetic. Both these proposals enable masked multiplication while utilizing retaining property.For demonstration, used proposed technique instantiated schoolbook as well NTT-based multiplication. can utilize in unmasked implementations. The an extra accumulation along with multiplications first-order implementation. cost nothing compared area saved by existing cheap units. We also extensively test resistance design through TVLA guarantee its security.