CVCQ: Off-Chain Committee-Based Verifiable Cross-Chain Query Scheme for Large-Scale BIoT

Blockchain with the Internet of Things (BIoT) denotes that the blockchain system is used for managing node identities in centerless IoT. Large-scale BIoT (L-BIoT) means many blockchains are used for managing node identities from different IoTs. The verifiable query scheme for BIoT was widely discussed in real-time IoT system. However, the query scheme will require cross-chain operations when BIoT expands into L-BIoT. Cross-chain verifiable query schemes for BIoT exist two issues. 1) Multiround Consensus: Cross-chain query requires the relay chain and related chains to participate in consensus, and each interaction requires initiating one consensus round. 2) High-Overhead Verification: Each data item returned by various blockchains requires individual integrity verification. We propose CVCQ, an off-chain committee (OC)-based verifiable cross-chain query scheme for L-BIoT. CVCQ achieves only one-round consensus by shifting the on-chain data query and consensus to an OC. Meanwhile, the aggregation accumulator and proofs are utilized to verify data integrity, ensuring the low-overhead verification. We proved that CVCQ reduces complexity of consensus from $O(m^{\lambda +1}+m\cdot N^{\lambda })$ to $O(m^{\lambda })$ , and decreases the computational complexity of verification from $O(m\log n)$ to $O(1)$ , when cross-chain data query involving m regional IoTs with N nodes and n data. The experiment results show that CVCQ outperforms the existing schemes by achieving higher on-chain throughput and lower latency.