Due to its security, transparency, and flexibility in verifying virtual assets, blockchain has been identified as one of the key technologies for Metaverse. Unfortunately, blockchain-based Metaverse faces serious challenges such as massive resource demands, scalability, and security concerns. To address these issues, this paper proposes a novel sharding-based blockchain framework, namely MetaShard, for Metaverse applications. Particularly, we first develop an effective consensus mechanism, namely Proof-of-Engagement, that can incentivize MUs' data and computing resource contribution. Moreover, to improve the scalability of MetaShard, we propose an innovative sharding management scheme to maximize the network's throughput while protecting the shards from 51% attacks. Since the optimization problem is NP-complete, we develop a hybrid approach that decomposes the problem (using the binary search method) into sub-problems that can be solved effectively by the Lagrangian method. As a result, the proposed approach can obtain solutions in polynomial time, thereby enabling flexible shard reconfiguration and reducing the risk of corruption from the adversary. Extensive numerical experiments show that, compared to the state-of-the-art commercial solvers, our proposed approach can achieve up to 66.6% higher throughput in less than 1/30 running time. Moreover, the proposed approach can achieve global optimal solutions in most experiments.

翻译：由于其在验证虚拟资产方面的安全性、透明性和灵活性，区块链已被视为元宇宙的关键技术之一。然而，基于区块链的元宇宙面临着资源需求巨大、可扩展性及安全性等严峻挑战。为解决这些问题，本文提出了一种面向元宇宙应用的新型分片区块链框架——MetaShard。具体而言，我们首先开发了一种有效的共识机制，即“参与证明”，该机制可激励移动用户贡献数据和计算资源。此外，为提升MetaShard的可扩展性，我们提出了一种创新的分片管理方案，旨在最大化网络吞吐量的同时保护分片免受51%攻击。由于该优化问题属于NP完全问题，我们开发了一种混合方法，通过二分搜索法将原问题分解为若干子问题，并利用拉格朗日方法高效求解。由此，所提方法能够在多项式时间内获得解，从而实现灵活的分片重配置，并降低攻击者篡改的风险。大量数值实验表明，与现有最先进的商业求解器相比，我们的方法在不到1/30的运行时间内可实现高达66.6%的吞吐量提升。此外，在大多数实验中，该方法能够获得全局最优解。