What Makes Fiat–Shamir zkSNARKs (Updatable SRS) Simulation Extractable?

Ganesh, C and Khoshakhlagh, H and Kohlweiss, M and Nitulescu, A and ZajÄ c, M (2022) What Makes Fiat–Shamir zkSNARKs (Updatable SRS) Simulation Extractable? In: 13th International Conference on Security and Cryptography for Networks, SCN 2022, 12 - 14 September 2022, Amalfi, pp. 735-760.

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Abstract

We show that three popular universal zero-knowledge SNARKs (Plonk, Sonic, and Marlin) are updatable SRS simulation extractable NIZKs and signatures of knowledge (SoK) out-of-the-box avoiding any compilation overhead. Towards this we generalize results for the Fiat–Shamir (FS) transformation, which turns interactive protocols into signature schemes, non-interactive proof systems, or SoK in the random oracle model (ROM). The security of the transformation relies on rewinding to extract the secret key or the witness, even in the presence of signing queries for signatures and simulation queries for proof systems and SoK, respectively. We build on this line of work and analyze multi-round FS for arguments with a structured reference string (SRS). The combination of ROM and SRS, while redundant in theory, is the model of choice for the most efficient practical systems to date. We also consider the case where the SRS is updatable and define a strong simulation extractability notion that allows for simulated proofs with respect to an SRS to which the adversary can contribute updates. We define three properties (trapdoor-less zero-knowledge, rewinding-based knowledge soundness, and a unique response property) that are sufficient for argument systems based on multi-round FS to be also simulation extractable in this strong sense. We show that Plonk, Sonic, and Marlin satisfy these properties, and conjecture that many other argument systems such as Lunar, Basilisk, and transparent variants of Plonk fall within the reach of our main theorem.

Item Type:	Conference Paper
Publication:	Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Publisher:	Springer Science and Business Media Deutschland GmbH
Additional Information:	The copyright for this article belongs to the Springer Science and Business Media Deutschland GmbH.
Keywords:	Authentication, Argument systems; Extractables; Fiat-Shamir; Interactive protocols; Non-interactive proof; Proof signature; Property; Random Oracle model; Signature Scheme; Zero knowledge, Network security
Department/Centre:	Division of Electrical Sciences > Computer Science & Automation
Date Deposited:	06 Oct 2022 11:25
Last Modified:	06 Oct 2022 11:25
URI:	https://eprints.iisc.ac.in/id/eprint/77242

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