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 [KMS+16] and Gyges [JKS16]). Efficiency of such systems severely are dominated by efficiency of the underlying UC-secure zk-SNARK that is achieved using C\(\emptyset \)C\(\emptyset \) framework [KZM+15] 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.
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Notes
- 1.
A tutorial about the system can be found in http://cryptowiki.net/index.php?title=Privacy_preserving_smart_contracts:_Hawk_project.
- 2.
We use original construction of GM zk-SNARK that is published in Crypto 2017 [GM17] and implemented in \(\mathtt {Libsnark}\) library https://github.com/scipr-lab/libsnark. But one also can use the variation of GM zk-SNARK that recently is provided in full version of paper.
- 3.
Based on reported implementation on https://github.com/scipr-lab/libsnark.
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Acknowledgement
The author were supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No 780477 (project PRIViLEDGE), and by the Estonian Research Council grant (PRG49).
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Baghery, K. (2019). On the Efficiency of Privacy-Preserving Smart Contract Systems. In: Buchmann, J., Nitaj, A., Rachidi, T. (eds) Progress in Cryptology – AFRICACRYPT 2019. AFRICACRYPT 2019. Lecture Notes in Computer Science(), vol 11627. Springer, Cham. https://doi.org/10.1007/978-3-030-23696-0_7
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