Möbius: an Atomic State Sharding Design for Account-Based Blockchains

This paper presents Mobius, the first cost-efficient state sharding design that remains consensus mechanism agnostic and guarantees atomicity for cross-shard smart contract transactions. In particular, to address the challenges posed by the growing blockchain state, Mobius enables its participants to verify all transactions while only storing a partial state. Unlike previous state sharding systems, the proposed protocol uses a novel vector commitment data structure to reduce the network bandwidth overhead via proof aggregation. Further, it utilizes a novel epoch-based multi-phase commitment technique for guaranteeing atomicity in cross-shard transactions. Experiments presented here show that Mobius reduces the disk requirement of each participant linearly with respect to the number of shards. Further, it presents a 4.7-7.3x lower network bandwidth overhead when compared to existing state-of-the-art state sharding systems. The outcomes also confirm that existing smart contracts can operate on Mobius in cross-shard scenarios without modifications.