Side-Channel Analysis of Lattice-Based Post-Quantum Cryptography: Exploiting Polynomial Multiplication.

Polynomial multiplication algorithms such as Toom-Cook and the Number Theoretic Transform are fundamental building blocks for lattice-based post-quantum cryptography. In this work we present correlation power analysis based side-channel analysis methodologies targeting every polynomial multiplication strategy for all lattice-based post-quantum key encapsulation mechanisms in the final round of the NIST post-quantum standardization procedure. We perform practical experiments on real side-channel measurements demonstrating that our method allows to extract the secret key from all lattice-based post-quantum key encapsulation mechanisms. Our analysis shows that the used polynomial multiplication strategy can significantly impact the time complexity of the attack.