Hiba: Hierarchical High-Performance Blockchain Architecture

Sharding has the potential to overcome the scalability constraints of monolithic blockchains. However, some challenges are associated with sharding, such as optimizing the placement of transactions into shards to minimize cross-shard transactions, balancing workload as shard capacity increases, and identifying shards that process transactions maliciously. To address these challenges, we propose a hierarchical high-performance blockchain (Hiba) architecture. Hiba leverages inter-shard to facilitate cross-shard consensus, where a pre-selected subset of nodes from both transaction originating and receiving shards collaboratively participate in the validation process. This design ensures the validity of transactions and mitigates double-spending risks across various shards. Simultaneously, it reduces validation costs by eliminating the need for all nodes in both shards to actively participate in the consensus process. Additionally, Hiba implements a novel multi-tiered validation system. Following initial validation at the intra-shard and inter-shard levels, a subset of randomly chosen or suspicion-based transactions undergoes further validation through auxiliary consensus. This auxiliary consensus acts as a secondary validation layer, ensuring the integrity of the intra-shard/inter-shard consensus process. To improve transaction processing efficiency, we implement an optimized workload distribution scheme based on fitness functions to minimize the number of cross-shard transactions. The experimental results demonstrate that Hiba surpasses the existing works regarding throughput and latency.