HLOChain

Blockchain can effectively deal with the security and trust issues in Internet of Things (IoT) due to its salient features including decentralization, immutability, traceability, openness, and transparency. However, most IoT devices have too limited computing, storage, and bandwidth resources to maintain the complete operation of a blockchain system. To this end, we propose a hierarchical blockchain framework called HLOChain for IoT scenarios. First, according to computing and storage capabilities, the IoT devices are classified into three levels, i.e., high, medium, and low. They are deployed on different layers. In this way, a hierarchical blockchain architecture is designed. Second, we propose a lightweight proof of random (PoR) consensus mechanism to provide low-energy block mining, so that even the medium nodes can participate in the consensus task. Third, in order to reduce the ledger storage overhead, we design a blockchain storage optimization strategy based on the account model. Finally, the security analysis demonstrates that our HLOChain is secure against double-spend attack, Sybil attack, and so on. The experimental evaluation shows that our HLOChain achieves better performance in ledger storage cost, consensus computing cost, throughput, and transaction confirmation latency.