In 2016, the National Institute of Standards and Technology (NIST) announced a standardization process for quantum-secure cryptographic primitives. The goal was to find secure key encapsulation mechanisms (KEM) and signature schemes. One unique approach was the PICNIC signature scheme, a scheme utilizing the MPC-in-the-Head (MPCitH) paradigm. This made PICNIC an interesting approach, since its security relies on well researched block ciphers and hash functions. PICNIC was announced as an alternative candidate by NIST. A lot of follow-up schemes based on PICNIC, like BBQ, Banquet, and FEAST, were proposed using different block ciphers and variations on the original construction paradigm. In 2022, NIST announced a second call specifically for signature schemes. MPC-in-the-Head-based signature schemes became their own category, with multiple submissions in this call. This articel explains the core idea and functionality of early MPCitH based signature schemes and how we at Fraunhofer AISEC make use of the concepts.

To ensure the security of embedded systems, the integrity and authenticity of the software must be verified, for example through signatures. However, targeted hardware attacks enable malware to be used to take over the system. What risks are modern cryptographic implementations exposed to? What countermeasures need to be taken? To answer these questions, Fraunhofer AISEC was commissioned by the German Federal Office for Information Security (BSI) to carry out a study of laser-based fault attacks on XMSS. The focus is on a hash-based, quantum-secure scheme for creating and verifying signatures based on the Winternitz One-Time-Signature (WOTS) scheme.