[Resource Topic] 2021/977: Shorter and Faster Post-Quantum Designated-Verifier zkSNARKs from Lattices

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Title:
Shorter and Faster Post-Quantum Designated-Verifier zkSNARKs from Lattices

Authors: Yuval Ishai, Hang Su, David J. Wu

Abstract:

Zero-knowledge succinct arguments of knowledge (zkSNARKs) enable efficient privacy-preserving proofs of membership for general NP languages. Our focus in this work is on post-quantum zkSNARKs, with a focus on minimizing proof size. Currently, there is a 1000\times gap in the proof size between the best pre-quantum constructions and the best post-quantum ones. Here, we develop and implement new lattice-based zkSNARKs in the designated-verifier preprocessing model. With our construction, after an initial preprocessing step, a proof for an NP relation of size 2^{20} is just over 16 KB. Our proofs are 10.3\times shorter than previous post-quantum zkSNARKs for general NP languages. Compared to previous lattice-based zkSNARKs (also in the designated-verifier preprocessing model), we obtain a 42\times reduction in proof size and a 60\times reduction in the prover’s running time, all while achieving a much higher level of soundness. Compared to the shortest pre-quantum zkSNARKs by Groth (Eurocrypt 2016), the proof size in our lattice-based construction is 131\times longer, but both the prover and the verifier are faster (by 1.2\times and 2.8\times, respectively). Our construction follows the general blueprint of Bitansky et al. (TCC 2013) and Boneh et al. (Eurocrypt 2017) of combining a linear probabilistically checkable proof (linear PCP) together with a linear-only vector encryption scheme. We develop a concretely-efficient lattice-based instantiation of this compiler by considering quadratic extension fields of moderate characteristic and using linear-only vector encryption over rank-2 module lattices.

ePrint: https://eprint.iacr.org/2021/977

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