ZETH: On Integrating Zerocash on Ethereum

TL;DR

ZETH adapts the Zerocash privacy protocol for Ethereum, enabling private transfers of Ether and digital assets without altering the underlying blockchain, and analyzes its privacy guarantees and potential information leakages.

Contribution

This paper introduces ZETH, a novel adaptation of Zerocash for Ethereum, allowing private transactions on an account-based blockchain without modifying the base layer.

Findings

ZETH can transfer Ether and smart contract assets privately.

Privacy promises of ZETH are well-defined and controlled.

ZETH is viable for private transactions on public and permissioned chains.

Abstract

Transaction privacy is a hard problem on an account-based blockchain such as Ethereum. While Ben-Sasson et al. presented the Zerocash protocol [BCG+14] as a decentralized anonymous payment (DAP) scheme standing on top of Bitcoin, no study about the integration of such DAP on top of a ledger defined in the account model was provided. In this paper we aim to fill this gap and propose ZETH, an adaptation of Zerocash that can be deployed on top of Ethereum without making any change to the base layer. Our study shows that not only ZETH could be used to transfer Ether, the base currency of Ethereum, but it could also be used to transfer other types of smart contract-based digital assets. We propose an analysis of ZETH's privacy promises and argue that information leakages intrinsic to the use of this protocol are controlled and well-defined, which makes it a viable solution to support private transactions in the context of public and permissioned chains.