AMSA: Adaptive Merkle Signature Architecture

Hash-based signatures (HBS) are promising candidates for quantum-secure signatures on embedded IoT devices because they only use fast integer math, are well understood, produce small public keys, and offer many design parameters. However, HBS can only sign a limited amount of messages and produce - similar to most post-quantum schemes - large signatures of several kilo bytes.In this paper, we explore possibilities to reduce the size of the signatures by 1. improving the Winternitz One-Time Signature with a more efficient encoding and 2. offloading auxiliary data to a gateway.We show that for similar security and performance, our approach produces 2.6 % smaller signatures in general and up to 17.3 % smaller signatures for the sender compared to the related approaches LMS and XMSS. Furthermore, our open-source implementation allows a wider set of parameters that allows to tailor the scheme to the available resources of an embedded device, which is an important factor to overcome the security challenges in IoT.