Sharding significantly enhances blockchain scalability by dividing the entire network into smaller shards that reach consensus and process transactions in parallel. Nevertheless, two new issues emerge with the adoption of sharding. One issue involves the shrinking size of consensus groups, which leads to vulnerability in consensus. Most existing works introduce periodic shuffle mechanisms to mitigate this problem. Nevertheless, these measures necessitate stronger security assumptions and can only offer a probabilistic assurance of consensus security. Another issue is the challenge in processing cross-shard transactions posed by the isolation of shards. Existing approaches utilize two-phase commit (2PC) or relay transaction mechanisms to handle cross-shard transactions. However, these approaches are vulnerable to double cross-shard attacks from malicious shards and are unable to achieve immediate atomicity. In this paper, to address the vulnerable consensus issue and achieve instant atomicity in cross-shard transactions, we design a hybrid consensus mechanism that embeds a lightweight global consensus into parallel intra-shard consensus processes. The global consensus allows all consensus nodes to jointly process cross-shard transactions, achieving cross-shard transaction instant atomicity. It also records shard snapshots to facilitate shard auditing to defend against malicious shards. Furthermore, we consider the performance of the proposed mechanism, and design a dynamic shard management mechanism. The dynamic shard management mechanism reduces transaction congestion and maintains an appropriate number of shards based on the system’s state. We conduct analyses of potential attacks and prove that our approach ensures safety and liveness even in the presence of malicious shards. We also evaluate the performance of our system and compare it with both non-sharded and classic blockchain-sharding systems. The evaluation results demonstrate the efficacy of our approach in dealing with transaction congestion while astutely controlling the number of shards.

中文翻译：

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通过混合共识和动态管理的安全高效的区块链分片方案


分片通过将整个网络划分为更小的分片来达成共识并并行处理交易，从而显着增强了区块链的可扩展性。然而，随着分片的采用，出现了两个新问题。其中一个问题涉及共识群体规模的缩小，这导致共识的脆弱性。大多数现有工作引入周期性洗牌机制来缓解这个问题。然而，这些措施需要更强的安全假设，并且只能提供共识安全的概率保证。另一个问题是分片隔离带来的处理跨分片交易的挑战。现有方法利用两阶段提交（2PC）或中继事务机制来处理跨分片事务。然而，这些方法容易受到恶意分片的双重跨分片攻击，并且无法实现即时原子性。在本文中，为了解决易受攻击的共识问题并实现跨分片交易中的即时原子性，我们设计了一种混合共识机制，将轻量级全局共识嵌入到并行的分片内共识过程中。全局共识允许所有共识节点共同处理跨分片交易，实现跨分片交易即时原子性。它还记录分片快照，以便于分片审计，以防御恶意分片。此外，我们考虑了所提出机制的性能，并设计了动态分片管理机制。动态分片管理机制减少了交易拥塞，并根据系统状态维持适当数量的分片。 我们对潜在攻击进行分析，并证明即使存在恶意分片，我们的方法也能确保安全性和活跃性。我们还评估了我们系统的性能，并将其与非分片和经典的区块链分片系统进行比较。评估结果证明了我们的方法在处理交易拥塞同时巧妙控制分片数量方面的有效性。