Abstract
Decentralized ledger-based cryptocurrencies like Bitcoin present a way to construct payment systems without trusted banks. However, the anonymity of Bitcoin is fragile. Many altcoins and protocols are designed to improve Bitcoin on this issue, among which Zerocash is the first full-fledged anonymous ledger-based currency, using zero-knowledge proof, specifically zk-SNARK, to protect privacy. However, Zerocash suffers two problems: poor scalability and low efficiency. In this paper, we address the above issues by constructing a micropayment system in Zerocash called Z-Channel. First, we improve Zerocash to support multisignature and time lock functionalities, and prove that the reconstructed scheme is secure. Then we construct Z-Channel based on the improved Zerocash scheme. Our experiments demonstrate that Z-Channel significantly improves the scalability and reduces the confirmation time for Zerocash payments.
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Notes
- 1.
The work of BOLT (Blind Off-chain Lightweight Transactions) [26] mentions Zerocash, claiming that if a BOLT is built on Zerocash, it would provide better channel privacy than built on other currencies. However, BOLT focuses on solving the linkability issue in channels, and does not specify the concrete construction over Zerocash.
- 2.
We neglect the transaction fees.
- 3.
This procedure may be executed distributedly, where the input \(\mathsf {sk}_{\mathsf {dst},i}\) is shared by more than one parties, and \(\sigma _{i}\) is synthesized from the shared signatures.
- 4.
In Z-Channel, the public output is always zero, so we neglect it in the sequel.
- 5.
When the channel is already established, to abort means executing the \(\mathsf {Close}\) protocol.
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Acknowledgement
The authors are supported by the National Natural Science Foundation of China (Grant No. 61572318, 61672339, 61672347).
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Zhang, Y., Long, Y., Liu, Z., Liu, Z., Gu, D. (2018). Z-Channel: Scalable and Efficient Scheme in Zerocash. In: Susilo, W., Yang, G. (eds) Information Security and Privacy. ACISP 2018. Lecture Notes in Computer Science(), vol 10946. Springer, Cham. https://doi.org/10.1007/978-3-319-93638-3_39
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