Efficient Software Implementation of Ring-LWE Encryption

Abstract. Present-day public-key cryptosystems such as RSA and Elliptic Curve Cryptography (ECC) will become insecure when quantum computers become a reality. This paper presents the new state of the art in efficient software imple-mentations of a post-quantum secure public-key encryption scheme based on the ring-LWE problem. We use a 32-bit ARM Cortex-M4F microcontroller as the tar-get platform. Our contribution includes optimization techniques for fast discrete Gaussian sampling and efficient polynomial multiplication. This implementation beats all known software implementations, on any architecture, by at least one or-der of magnitude. We further show that our scheme beats all ECC-based public-key encryption schemes by at least one order of magnitude. At 128-bit security we require 121166 cycles per encryption and 43324 cycles per decryption, while at a 256-bit security we require 261939 cycles per encryption and 96520 cycles per decryption. Gaussian sampling is done at an average of 28.5 cycles per sam-ple.