Sharding Technologies in Blockchain: Basics, State of the Art, and Challenges

Sharding is one of the key technologies of blockchain scalable characteristics widely used in cryptocurrencies, Internet of Things, supply chain management and other fields. It can achieve high performance scaling without reducing the decentralization of blockchain, thus solving the problems of insufficient scalability and low throughput of blockchain. In this paper, the characteristics of some classical sharding technologies are analyzed in terms of performance and implementation. The key mechanisms of sharding are summarized, including sharding formation, reshuffle, intra-shard consensus protocol, and cross-shard protocol. Also, the advantages and shortcomings of typical scalability schemes are summarized, including state channel, DAG, and side chain. We summarize the current challenges faced by sharding technology from intra-shard, and cross-shard, and provide an outlook on the development prospects and future research directions in this field.