Paper 2024/1194

Hardware Implementation and Security Analysis of Local-Masked NTT for CRYSTALS-Kyber

Abstract

The rapid evolution of post-quantum cryptography, spurred by standardization efforts such as those led by NIST, has highlighted the prominence of lattice-based cryptography, notably exemplified by CRYSTALS-Kyber. However, concerns persist regarding the security of cryptographic implementations, particularly in the face of Side-Channel Attacks (SCA). The usage of operations like the Number Theoretic Transform (NTT) in CRYSTALS-Kyber introduces vulnerabilities to SCA, especially single-trace ones, such as soft-analytical side-channel attacks. To address this threat, Ravi et al. proposed local masking as a countermeasure by randomizing the NTT’s twiddle factors, but its implementation and security implications require further investigation. This paper presents a hardware implementation of the NTT with local masking, evaluating its performance, area utilization, and security impacts. Additionally, it analyzes the vulnerabilities inherent in local masking and assesses its practical security effectiveness through non-specific t-tests, showing that there are configurations of local masking that are more prone to leakage than others.