Abstract:
Hash-based signature schemes are digital-signature families grounded in the security of cryptographic hash functions. They rely on minimal assumptions and are believed to resist known quantum attacks. They are commonly categorized into three groups: one-time signatures (OTS), few-time signatures, and many-time signatures.
NIST has standardized the stateful LMS and XMSS and, more recently, the stateless SPHINCS+. In this talk, I will review Lamport OTS (LOTS) and Winternitz OTS (WOTS) as core one-time signature schemes, explain the central role of Merkle trees in building multi-message schemes from OTS, and, finally, review XMSS and SPHINCS+ as two major standardized designs. In particular, I focus on SPHINCS+, which is built from WOTS+ (a variant of WOTS), FORS (a ew-time signature scheme), and a hypertree of Merkle trees.