Proof-of-Hashing: A Novel HMAC-Based Cryptographic Puzzle with Dual-Purpose Output

This paper introduces Proof-of-Hashing (PoH), a novel cryptographic puzzle mechanism that extends traditional proof-of-work systems by leveraging HMAC (Hash-based Message Authentication Code) with key variation instead of nonce iteration. Unlike conventional approaches where the computational effort produces only a validity proof, the proposed method yields a cryptographic key that can be subsequently reused for message authentication. This dual-purpose output—simultaneously demonstrating computational work and providing an authentication capability—represents a fundamental departure from existing proof-of-work paradigms. The theoretical foundations, security analysis, implementation details, and practical applications of this approach are presented herein. Experimental results demonstrate that Proof-of-Hashing maintains comparable computational characteristics to traditional methods while offering enhanced functionality through the cryptographic binding between the discovered key and the authenticated message.