Anotace:
In this article, we describe the principles and advantages of using the Number-Theoretic Transform (NTT) in post-quantum cryp-tography. We deal with usages of NTT in post-quantum algorithms included in the competition announced by the National Institute ofStandards and Technology. Attention is paid to the fast multiplication of polynomials using NTT and negacyclic convolution. We alsofocus on the existing implementation of NTT and its modifications to analyze the effectiveness of individual modifications. Separateattention is paid to the Constant Time implementation of NTT because the constant computation time of the transformation decreasesa possibility of side channel attack. We describe measurements performed on OS Linux Ubuntu 20.04 LTS environment in Linux kernelmode, with the highest attention to the measurement executed on a microcontroller with an ARM 32-bit core. Measurements performedon microcontroller units are done using 32-bit and 16-bit arithmetic to demonstrate how to achieve constant computation time of thetransformation. We present the results and analysis of measurements performed using modified implementations