Single-Query Verifiable Proof-of-Sequential-Work

TL;DR

This paper introduces a new proof-of-sequential-work protocol that allows a verifier with no parallelism to efficiently verify sequential computations with just a single oracle query per challenge, improving verification simplicity.

Contribution

The proposed PoSW enables verification with a single query per challenge without requiring verifier parallelism, unlike prior protocols that need multiple oracle queries.

Findings

Verifier can confirm sequential work with one query per challenge.

Verification complexity is reduced to a single oracle query per challenge.

The protocol maintains security against adversaries with polynomial parallelism.

Abstract

We propose a proof-of-sequential-work (PoSW) that can be verified with only a single query to the random oracle for each random challenge. Proofs-of-sequential-work are protocols that facilitate a verifier to efficiently verify if a prover has executed a specified number of computations sequentially. Denoting this number of sequential computations with N , the prover with poly(N) parallelism must take $\Omega(N)$-sequential time while the verifier verifies the computation in O(log N)-sequential time using upto O(log N) parallelism. We propose a PoSW that allows any verifier, even the one with no parallelism, to verify using just a single sequential computation on a single challenge. All the existing PoSWs [10, 5, 2, 6] mandate a prover to compute a sequence of responses from a random oracle against N-rounds of queries. Then the prover commits this sequence using a commitment scheme (e.g., Merkle root (like) commitment) predefined in the PoSWs. Now the verifier asks the prover to provide a set of proofs against t randomly chosen checkpoints, called challenges, in the computed sequence. The verifier finds out the commitment from each of these proofs spending O(log N) rounds of queries to the oracle. It can be reduced to a single round of queries only if the verifier owns O(log N) parallelism [6]. The verifier in our PoSW demands no parallelism but uses a single query to the random oracle in order to verify each of the t challenges. The key observation is that the commitment schemes themselves in the prior works demand O(log N ) oracle queries to verify.