International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Moz$\mathbb{Z}_{2^k}$zarella: Efficient Vector-OLE and Zero-Knowledge Proofs Over $\mathbb{Z}_{2^k}$

Carsten Baum , Aarhus University
Lennart Braun , Aarhus University
Alexander Munch-Hansen , Aarhus University
Peter Scholl , Aarhus University
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Presentation: Slides
Conference: CRYPTO 2022
Abstract: Zero-knowledge proof systems are usually designed to support computations for circuits over $\mathbb{F}_2$ or $\mathbb{F}_p$ for large $p$, but not for computations over $\mathbb{Z}_{2^k}$, which all modern CPUs operate on. Although $\mathbb{Z}_{2^k}$-arithmetic can be emulated using prime moduli, this comes with an unavoidable overhead. Recently, Baum et al. (CCS 2021) suggested a candidate construction for a designated-verifier zero-knowledge proof system that natively runs over $\mathbb{Z}_{2^k}$. Unfortunately, their construction requires preprocessed random vector oblivious linear evaluation (VOLE) to be instantiated over $\mathbb{Z}_{2^k}$. Currently, it is not known how to efficiently generate such random VOLE in large quantities. In this work, we present a maliciously secure, VOLE extension protocol that can turn a short seed-VOLE over $\mathbb{Z}_{2^k}$ into a much longer, pseudorandom VOLE over the same ring. Our construction borrows ideas from recent protocols over finite fields, which we non-trivially adapt to work over $\mathbb{Z}_{2^k}$. Moreover, we show that the approach taken by the QuickSilver zero-knowledge proof system (Yang et al. CCS 2021) can be generalized to support computations over $\mathbb{Z}_{2^k}$. This new VOLE-based proof system, which we call QuarkSilver, yields better efficiency than the previous zero-knowledge protocols suggested by Baum et al. Furthermore, we implement both our VOLE extension and our zero-knowledge proof system, and show that they can generate 13-50 million VOLEs per second for 64 to 256 bit rings, and evaluate 1.3 million 64 bit multiplications per second in zero-knowledge.
Video from CRYPTO 2022
  title={Moz$\mathbb{Z}_{2^k}$zarella: Efficient Vector-OLE and Zero-Knowledge Proofs Over $\mathbb{Z}_{2^k}$},
  author={Carsten Baum and Lennart Braun and Alexander Munch-Hansen and Peter Scholl},