Cryptology ePrint Archive: Report 2019/035

Using TopGear in Overdrive: A more efficient ZKPoK for SPDZ

Carsten Baum and Daniele Cozzo and Nigel P. Smart

Abstract: The HighGear protocol (Eurocrypt 2018) is the fastest currently known approach to preprocessing for the SPDZ Multi-Party Computation scheme. Its backbone is formed by an Ideal Lattice-based Somewhat Homomorphic Encryption Scheme and accompanying Zero-Knowledge proofs. Unfortunately, due to certain characteristics of HighGear such current implementations use far too low security parameters in a number of places. This is mainly due to memory and bandwidth consumption constraints. In this work we present a new approach to the ZKPoKs as introduced in the HighGear work. We rigorously formalize their approach and show how to improve upon it using a different proof strategy. This allows us to increase the security of the underlying protocols, all while maintaining roughly the same performance in terms of memory and bandwidth consumption.

Category / Keywords: cryptographic protocols / SPDZ, HighGear, ZKPoK

Original Publication (with minor differences): To appear SAC 2019

Date: received 15 Jan 2019, last revised 19 Mar 2020

Contact author: nigel smart at kuleuven be,daniele cozzo@kuleuven be,carsten baum@biu ac il

Available format(s): PDF | BibTeX Citation

Note: Minor correction

Version: 20200319:081735 (All versions of this report)

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