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Scaling Zero Knowledge UNSAT Verification via Normalized Chaining

19 pages•Published: October 23, 2026

Abstract

Proofs of UNSAT are a standard primitive in formal verification and software assurance. In many real-world settings, the proof itself encodes proprietary or security-sensitive information, making public disclosure undesirable. Zero-knowledge certification of UNSAT addresses this tension: it enables a prover to convince a verifier that no satisfying assignment exists, without revealing anything about the underlying proof beyond its validity. Luo et al. recently introduced ZKUNSAT, a protocol that achieves this goal by proving the validity of a weakened resolution proof in zero knowledge. ZKUNSAT demonstrates the feasibility of zero-knowledge certification; however, its scalability to larger, real-world instances is constrained by substantial prover memory overhead, limiting its real-world applicability.
Motivated by advances in UNSAT proof formats such as LRAT, which enable efficient plain-text verification, we present a preprocessing technique that improves the efficiency of ZKUNSAT without introducing additional leakage. Our approach normalizes the proof so that each derived clause is justified by a resolution chain of fixed public length k. This eliminates chain-length leakage and reduces prover memory usage. With k = 16, our method certifies roughly 62% more instances than baseline ZKUNSAT on the SAT 2002 competition benchmarks. Furthermore, for an equivalent number of certified instances, the memory footprint drops to under 25% of that required by the baseline.

Keyphrases: proof checking, satisfiability, zero knowledge proofs

In: Erika Ábrahám, Nikolaj Bjørner and Michael Rawson (editors). Proceedings of the 26th Conference on Logic for Programming, Artificial Intelligence, and Reasoning, vol 112, pages 290-308.

BibTeX entry
@inproceedings{LPAR-26:Scaling_Zero_Knowledge_UNSAT,
  author    = {Ashwin Karthikeyan and Ethan Kharitonov and Kuldeep S. Meel and Anwar Hithnawi},
  title     = {Scaling Zero Knowledge UNSAT Verification via Normalized Chaining},
  booktitle = {Proceedings of the 26th Conference on Logic for Programming, Artificial Intelligence, and Reasoning},
  editor    = {Erika Ábrahám and Nikolaj Bjørner and Michael Rawson},
  series    = {EPiC Series in Computing},
  volume    = {112},
  publisher = {EasyChair},
  bibsource = {EasyChair, https://easychair.org},
  issn      = {2398-7340},
  url       = {/publications/paper/F5NK},
  doi       = {10.29007/g7v2},
  pages     = {290-308},
  year      = {2026}}
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