MVSS: Blockchain Cross-shard Account Migration Based on Multi-version State Synchronization

The cross-shard account migration mechanism is one of the most advanced solutions to the unbalanced load problem in blockchain sharding systems. Existing solutions employ locking schemes to ensure the atomicity of transactions and the consistency of account states. However, these methods suffer from high transaction locking rates, degraded system performance, and disordered transaction execution sequences. To overcome these limitations, this paper proposes the first cross-shard account migration mechanism based on Multi-Version State Synchronization (MVSS), which ensures sequential execution of transactions while reducing the locking rate and latency, thereby enhancing system throughput. Specifically, MVSS divides related transactions into two categories based on their arrival time, and innovates to have the source shard and the destination shard process each category of transactions, instead of blocking all transactions at the source shard as in the existing schemes. Furthermore, in the special timestamp interleaving scenario, MVSS synchronizes the multiple version states of the account among the related shards according to the fine-grained order, which effectively maintains the consistency of the transaction sequence and the account state. Additionally, this paper delves into the security aspects of MVSS, proposing effective solutions to combat double-spending and replay attacks. Finally, We conducted extensive experiments based on a blockchain sharding simulator using over 2000 lines of Go to evaluate the performance of MVSS. The experimental results indicate that, compared to the state-of-the-art solutions such as Fine-tuned scheme, MVSS reduces locking time by 23.4%, decreases transaction latency by 7.5%, and improves throughput by 2.3%.