Title: On Replacing Cryptopuzzles with Useful Computation in Blockchain Proof-of-Work Protocols

Abstract: Proof-of-Work (PoW) blockchains have emerged as a robust and effective consensus mechanism in open environments like the Internet, leading to widespread deployment with numerous cryptocurrency platforms and substantial investments. However, the current PoW implementation primarily focuses on validating the discovery of a winning nonce. Exploring the notion of replacing cryptographic puzzles with useful computing tasks becomes compelling, given the substantial computational capacity of blockchain networks and the global pursuit of a more sustainable IT infrastructure. In this study, we conduct a comprehensive analysis of the prerequisites for alternative classes of tasks, examining proposed designs from existing literature in light of these requirements. We distill pertinent techniques and address gaps in the current state-of-the-art, providing valuable insights into the evolution of consensus mechanisms beyond traditional PoW.