Proof of Necessary Work: Succinct State Verification with Fairness Guarantees

Blockchain-based payment systems utilize an append-only log of transactions whose correctness can be verified by any observer. Classically, verification costs grow linearly in either the number of transactions or blocks in the blockchain (often both). Incrementally Verifiable Computation (IVC) can be used to enable constant-time verification, but generating the necessary proofs is expensive. We introduce the notion of Proof of Necessary Work (PoNW), in which proof generation is an integral part of the proof-of-work used in Nakamoto consensus, producing proofs using energy that would otherwise be wasted. We implement and benchmark a prototype of our system, enabling stateless clients to verify the entire blockchain history in about 40 milliseconds.