On the Design of Hardware Building Blocks for Modern Lattice-Based Encryption Schemes

We present both a hardware and a software implementation variant of the learning with errors (LWE) based cryptosystem presented by Lindner and Peikert. This work helps in assessing the practicality of lattice-based encryption. For the software implementation, we give a comparison between a matrix and polynomial based variant of the LWE scheme. This module includes multiplication in polynomial rings using Fast Fourier Transform (FFT). In order to implement lattice-based cryptography in an efficient way, it is crucial to apply the systems over polynomial rings. FFT speeds up multiplication in polynomial rings, which is the most critical operation in lattice-based cryptography, from quadratic to quasi-linear runtime. For the hardware variant, we show how this fundamental building block of lattice-based cryptography can be implemented and evaluated in terms of performance. A second important component for lattice-based cryptosystems is the sampling from discrete Gaussian distributions. We examine three different variants for sampling Gaussian distributed integers, namely rejection sampling, a rounding based approach, and a look-up table based approach in hardware.