Accelerating Cross-Shard Blockchain Consensus via Decentralized Coordinators Service With Verifiable Global States

Sharding is a promising technique to improve the scalability of blockchain systems via processing transactions in parallel. However, there is an overwhelmingly high proportion of cross-shard transactions requiring complicated cross-shard consensus among the involved shards. To solve the problem, most state-of-the-art works adopt a centralized or decentralized coordinator to harmonize the cross-shard consensus. Nevertheless, they usually incur a confirmation latency of at least three consensus rounds and fail to avoid unnecessary communication costs for invalid and conflicting cross-shard transactions. Therefore, we propose DCchain that fully eliminates computation and communication latency for invalid or conflicting transactions. Specifically, DCchain introduces a decentralized coordinator (DC) that maintains verifiable global states. DC directly identifies and aborts invalid and conflicting cross-shard transactions, avoiding additional cross-shard computation and communication overhead. Besides, we present a robust two-tier consensus protocol. It commits valid cross-shard transactions through efficient interaction between DC and involved shards while defeating Byzantine behaviors. Finally, our performance evaluations demonstrate that DCchain's efficiency is superior to a popular existing work by nearly three times at best.