Paper 2018/407

Goshawk: A Novel Efficient, Robust and Flexible Blockchain Protocol

Cencen Wan, Shuyang Tang, Yuncong Zhang, Chen Pan, Zhiqiang Liu, Yu Long, Zhen Liu, and Yu Yu

Abstract

Proof of Work (PoW), a fundamental blockchain protocol, has been widely applied and thoroughly testifed in various decentralized cryptocurrencies, due to its intriguing merits including trustworthy sustainability, robustness against sybil attack, delicate incentive-compatibility, and openness to any participant. Meanwhile, PoW-powered blockchains still suffer from poor efciency, potential selfsh mining, to-be-optimized fairness and extreme inconvenience of protocol upgrading. Therefore, it is of great interest to design new PoW-based blockchain protocol to address or relieve the above issues so as to make it more applicable and feasible. To do so, frstly we take advantage of the basic framework (i.e., two-layer chain structure) adopted in Bitcoin-NG which was introduced by Eyal et al. to extend the throughput of Bitcoin-derived blockchains signifcantly via blocks of a two-layer structure, inheriting the high throughput merit while ridding off the vulnerability to the attack of microblock swamping in Bitcoin-NG as well as attaining a better fairness property, by presenting two-level mining mechanism and incorporating this mechanism into the two-layer chain structure. Furthermore, to tackle the selfsh mining issue, strengthen the robustness against the “51%” attack of PoW miners, and offer the flexibility for future protocol updating effectively, we borrow the idea of ticket-voting mechanism from DASH and Decred, and combine it with our improved structure elaborately to build a novel efcient, robust and flexible blockchain protocol (named Goshawk). Last but not the least, this scheme has been implemented and deployed in the testnet of the public blockchain project Hcash for months, and has demonstrated its stability and high efciency with such real-world test.

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