Research On Key Issues Of Blockchain For Internet Of Things

With the rapid development of 5G technology and the continuous acceleration of industrialization in China,the Internet of Things(IoT)is widely used in many industrial scenarios such as smart supply chains,smart grids,and smart healthcare,greatly improving information-processing and decision-making abilities when we facing massive amounts of data.At the same time,more and more attention has been paid to the security issues of IoT,and the security of information management in IoT has gradually become a key concern in the current academic and industrial communities.The traditional centralized information management solution is susceptible to single point of failure attack,and has security risks such as privacy data leakage and tampering.As a distributed ledger technology,blockchain has advantages such as decentralization,data traceability,and tamper resistance,which can effectively solve data security issues in IoT.Therefore,blockchain based IoT information management solutions have gradually become the mainstream solution.As the underlying supporting technology,the performance of blockchain will directly affect the application of blockchain based IoT information management solutions in various industrial scenarios.The IoT devices is highly distributed and the number of IoT devices is large,so a public chain solution can be used to securely manage IoT information.In addition,due to the large amount of data in IoT,sharding technology also has a good prospect in IoT information management.However,there are some issues when we deploy public chain and sharding system in IoT.Firstly,as a public consensus,the nodes in the Proof of Work(PoW)need to mine blocks,resulting in a high energy consumption.Since IoT devices have limited resources,they cannot perform mining for a long time,which will directly affect the security of blockchain.Secondly,Since the mining in PoW is competitive,there is only one node can win in each round.In this case,the resource utilization of devices is low and the devices also have a low enthusiasm to participate in maintaining the blockchain,which threats the blockchain security.Finally,most sharding method use random sharding algorithms to ensure the security of sharding systems.If the random sharding algorithms is used in IoT,it will lead an imbalance of the distribution of the resource strength and trust level between shards,affecting the security and throughput of sharding systems.Aiming at lightweight,cooperative and the applicability to IoT,we study the key issues which affect the performance of blockchain.The research contents and innovations mainly include the following aspects:(1)The research about the blockchain lightweight consensus for IoT.To solve the applicability and security problem caused by high energy consumption of PoW in IoT,we propose a Trust based Time Constrained PoW(TBTC-PoW).Firstly,in order to provide a security foundation for TBTC-PoW,we proposed Heterogeneity Considered Trust Mechanism(HCTM),where we calculate the trust value of the node based on its capability and quality.Secondly,in order to decrease the energy consumption of TBTC-PoW,a reasonable mining time window was allocated to the nodes based on their computing power,trust level,and the preset mining difficulty of the system.Finally,in order to reduce the centralization risk of TBTC-PoW,we set calm period parameter to limit the rounds of mining of the nodes which mine blocks frequently.The theoretical analysis and experimental results show that TBTCPoW has a lower energy consumption and higher security.(2)The research about the cloud-edge-end collaborative blockchain for IoT.To solve the low resource utilization rate,high energy consumption and low participation enthusiasm caused by competitive mining of PoW in IoT,we proposed a cloud-edge-end collaborative blockchain.Firstly,we proposed Relay mining based PoW(Relay-PoW),where nodes can mine block based on the PoW workloads of other nodes,improving the resource utilization rate of nodes.Secondly,we proposed parallel relay mining method,where nodes can parallelly mine blocks in a pipeline manner,improving the throughput of Relay PoW.Thirdly,we proposed Shapley-based Reward Allocation Strategy(SRAS),where edge servers can fairly allocate block revenue based on the marginal contribution of nodes,improving the participation enthusiasm of nodes.Finally,a supervision group mechanism was proposed to monitor the behavior of nodes in the network and ensure the system security.The theoretical analysis and experimental results show that the effectiveness of above methods.(3)The research about the blockchain sharding algorithm for IoT.To solve the problems that the existing sharding algorithms ignore he resource requirements,the resource heterogeneity of IoT devices and the closeness of the relationship between devices,we proposed a Sharding Algorithm based on Trust Field Model(STFM).Firstly,we improved the original trust field model to make it more suitable to IoT,where the definitions of trust quality and trust radius is expanded.Secondly,we clarified the requirements that sharding algorithms in IoT should meet and proposed STFM.The theoretical analysis and experimental results show that STFM makes the distribution of resource intensity and trust level between shards more balanced,and the relationship between nodes within shards is close,significantly improving the security and throughput of sharding systems.