MWPoW+: a strong consensus protocol for intra-shard consensus in blockchain sharding

Xu, Yibin, Shao, Jianhua ORCID: https://orcid.org/0000-0001-8461-1471, Slaats, Tijs and Düdder, Boris 2023. MWPoW+: a strong consensus protocol for intra-shard consensus in blockchain sharding. ACM Transactions on Internet Technology 23 (2) , 34. 10.1145/3584020

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Abstract

Blockchain sharding splits a blockchain into several shards where consensus is reached at the shard level rather than over the entire blockchain. It improves transaction throughput and reduces the computational resources required of individual nodes. But a derivation of trustworthy consensus within a shard becomes an issue as the longest-chain based mechanisms used in conventional blockchains can no longer be used. Instead, a vote-based consensus mechanism must be employed. However, existing vote-based Byzantine false tolerance consensus protocols do not offer sufficient security guarantees for sharded blockchains. First, when used to support consensus where only one block is allowed at a time (binary consensus), these protocols are susceptible to progress-hindering attacks, i.e., unable to reach a consensus. Second, when used to support a stronger type of consensus where multiple concurrent blocks are allowed (strong consensus), their tolerance of adversary nodes is low. This paper proposes a new consensus protocol to address all these issues. We call the new protocol MWPoW+ as its basic framework is based on the existing Multiple Winner Proof of Work (MWPoW) protocol but includes new mechanisms to address the issues mentioned above. MWPoW+ is a vote-based protocol for strong consensus, asynchronous in consensus derivation but synchronous in communication. We prove that it can tolerate up to f < n/2 adversary nodes in a shard using a binary consensus protocol, and does not suffer from progress-hindering attacks.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Computer Science & Informatics
Publisher:	Association for Computing Machinery (ACM)
ISSN:	1533-5399
Date of First Compliant Deposit:	13 April 2023
Date of Acceptance:	31 January 2023
Last Modified:	17 Nov 2023 09:29
URI:	https://orca.cardiff.ac.uk/id/eprint/158486

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