ARMed SPHINCS computing a 41KB signature in 16KB of RAM

Abstract

This paper shows that it is feasible to implement the stateless hash-based signature scheme SPHINCS-256 on an embedded microprocessor with memory even smaller than a signature and limited computing power. We demonstrate that it is possible to generate and verify the 41KB signature on an ARM Cortex M3 that only has 16KB of memory available. We provide benchmarks for our implementation which show that this can be used in practice. To analyze the costs of using the stateless SPHINCS scheme instead of its stateful alternatives, we also implement XMSSMT on this platform and give a comparison.