Distributed and Parallel Blockchain: Towards a Multi-Chain System With Enhanced Security

Isolatability and scalability are two critical issues faced by blockchain. Blockchain interoperability addresses isolatability between heterogeneous blockchains, while sharding-based blockchain achieves scalability by solving isolatability of homogeneous blockchains running in different shards. To ensure atomicity between different blockchains, they both need to overcome two significant problems: 1) how to handle cross-chain transactions without trusting any third parties; 2) how to enhance the resistance to double-spending attacks of participating blockchains. To this end, this work presents a two-tier multi-zone architecture, Distributed and Parallel Blockchain (DP-Chain), where Consensus Zone in tier-1 features blockchain interoperability and sharding-based blockchain by allowing homogeneous or heterogeneous blockchains run in different zones, while Coordination Layer in tier-2 allows them to interoperate as a Direct Acyclic Graph (DAG) without trusting any third parties. Meanwhile, the coordination scheme between the two tiers is designed to resist potential double-spending attacks. Then, stochastic models are used to capture DP-Chain consensus process and analyze the probability of successful double-spending attacks. These analyses can help understand DP-Chain easily and offer theoretical guidelines for further implementations. Finally, based on the proposed architecture, a practical system is realized with C++ and open in Github for testing. Extensive experiments show correctness and effectiveness of this design.