Synced Hash-Based Signatures: Post-Quantum Authentication in a Blockchain

A new post-quantum, hash-based signature (HBS) scheme is introduced. In known HBS, the size and cost of each signature increase as the total number of messages one wishes to authenticate increase. In real-world applications, requiring large volumes of signatures, they can become impractical. This paper studies HBS in a blockchain: a public, decentralized database. The proposed HBS scheme shows that, when all signatures are known, quite the opposite is possible: the signatures can become more efficient as the number of signatures grows. Authenticating large volumes of messages results less costly on average than authenticating only a few