Grstl Implementation Guide

The Grstl hash function is a nalist in the SHA-3 competition organized by NIST. In this paper, we describe a number of implementation techniques and tricks for Grstl . They allow us to develop a range of ecient implementations for various platforms, from 8-bit microcontrollers to modern desktop processors using 256-bit AVX instructions. These results demonstrate the implementation exibility of the algorithm and we hope will inspire further optimizations and ports to other platforms. The information in this paper will also be useful for developers planning to implement Grstl eciently on the platform of their choice. Furthermore, we believe also hardware implementations may benet from the optimization techniques presented in this paper.