Cross-shard Transaction Processing in Sharding Blockchains

Sharding blockchains could improve the transaction throughput and achieve scalibility, making the application fields of the blockchain technology more extensive. Cross-shard transactions account for a large fraction of transactions in a sharding blockchain, so the processing method of cross-shard transactions is of vital importance to the system efficiency. In this paper, we focus on the study of cross-shard transaction processing methods. Firstly, a summary of cross-shard transaction processing methods for sharding blockchains is given. Secondly, we propose RSTBP, which is built on the basis of a two phase commit protocol. In RSTBP, an input shard runs an intra-shard consensus algorithm, i.e., a Byzantine fault tolerance (BFT) algorithm, to process multiple inputs of different transactions simultaneously. For each input, a corresponding proof of availability is generated and sent to the relevant shards. Compared with previous schemes, the number of BFT calls is reduced by hundreds of times when processing the same number of transactions. Thirdly, RSTSBP is designed by making some modifications to RSTBP. The proofs of availability are constructed according to different shards. The Merkel tree structure is different from that of RSTBP to cut down message complexity of the proofs. Both of the two schemes are proved to satisfy the consistency, liveness and responsiveness properties, and improve the cross-shard transaction processing efficiency.