Cryptology ePrint Archive: Report 2019/480

On the Efficiency of Privacy-Preserving Smart Contract Systems

Karim Baghery

Abstract: Along with blockchain technology, smart contracts have found intense interest in lots of practical applications. A smart contract is a mechanism involving digital assets and some parties, where the parties deposit assets into the contract and the contract redistributes the assets among the parties based on provisions of the smart contract and inputs of the parties. Recently, several smart contract systems are constructed that use zk-SNARKs to provide privacy-preserving payments and interconnections in the contracts (e.g. Hawk [IEEE S&P, 2016] and Gyges [ACM CCS, 2016]). Efficiency of such systems severely are dominated by efficiency of the underlying UC-secure zk-SNARK that is achieved using COCO framework [Kosba et al., 2015] applied on a non-UC-secure zk-SNARK. In this paper, we show that recent progresses on zk-SNARKs, allow one to simplify the structure and also improve the efficiency of both systems with a UC-secure zk-SNARK that has simpler construction and better efficiency in comparison with the currently used ones. More precisely, with minimal changes, we present a variation of Groth and Maller's zk-SNARK from Crypto 2017, and show that it achieves UC-security and has better efficiency than the ones that currently are used in Hawk and Gyges. We believe, new variation can be of independent interest.

Category / Keywords: applications / privacy-preserving smart contracts, zk-SNARKs, UC-security, CRS model

Original Publication (in the same form): AFRICACRYPT 2019

Date: received 10 May 2019, last revised 12 May 2019

Contact author: baghery karim at gmail com

Available format(s): PDF | BibTeX Citation

Version: 20190513:215822 (All versions of this report)

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