Cryptology ePrint Archive: Report 2021/986

Neon NTT: Faster Dilithium, Kyber, and Saber on Cortex-A72 and Apple M1

Hanno Becker and Vincent Hwang and Matthias J. Kannwischer and Bo-Yin Yang and Shang-Yi Yang

Abstract: We present new speed records on the Armv8-A architecture for the lattice-based schemes Dilithium, Kyber, and Saber. The core novelty in this paper is the combination of Montgomery multiplication and Barrett reduction resulting in “Barrett multiplication” which allows particularly efficient modular one-known-factor multiplication using the Armv8-A Neon vector instructions. These novel techniques combined with fast two-unknown-factor Montgomery multiplication, Barrett reduction sequences, and interleaved multi-stage butterflies result in significantly faster code. We also introduce “asymmetric multiplication” which is an improved technique for caching the results of the incomplete NTT, used e.g. for matrix-to-vector polynomial multiplication. Our implementations target the Arm Cortex-A72 CPU, on which our speed is 1.7× that of the state-of-the-art matrix-to-vector polynomial multiplication in Kyber [Nguyen–Gaj 2021]. For Saber, NTTs are far superior to Toom–Cook multiplication on the Armv8-A architecture, outrunning the matrix-to-vector polynomial multiplication by 2.1×. On the Apple M1, our matrix-vector products run 2.1× and 1.9× faster for Kyber and Saber respectively.

Category / Keywords: implementation / NIST PQC, Armv8-A, Neon, Dilithium, Kyber, Saber

Original Publication (with minor differences): IACR-CHES-2022

Date: received 23 Jul 2021, last revised 16 Nov 2021

Contact author: hanno becker at arm com, vincentvbh7 at gmail com, matthias at kannwischer eu, by at crypto tw, nick yang at chelpis com

Available format(s): PDF | BibTeX Citation

Version: 20211116:125153 (All versions of this report)

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