| Researchers have been studying digital currency for decades.In 2008,Satoshi Nakamoto proposed Bitcoin based on blockchain technology[1].On January 3,2009,the genesis block with the serial number of 0 was created.On January 9,2009,the block with the serial number of 1 appeared.It was connected to the genesis block to form a chain,which marked the birth of the blockchain.In the past 11 years,digital currency schemes including Bitcoin have gradually attracted widespread attention from the entire soci-ety.More than 5,000 cryptocurrency schemes or smart contract platform schemes based on blockchain technology have been proposed to meet differ-ent application needs.In many application scenarios,the rapidly developing Internet of Things(IoT)in recent years is one promising application scenario for adopting blockchain technology.In the IoT scenario,there may be many smart termi-nals,such as smart bracelets,smart refrigerators,etc.Those smart devices may need to carry out transactions or even execute some smart contracts between each other.The history of these smart terminals executing transac-tions or contracts may need to be recorded to ensure that the transaction can take effect or the contract can be monitored.In such a scenario,traditional financial trading systems are difficult to meet their application needs.A blockchain-based payment system or smart contract platform may be a potential solution to the above requirements.However,for the following reasons,most existing blockchain solutions are not suitable for IoT scenarios.Some blockchain solutions do not support smart contracts,so the functions that smart terminals can achieve are extremely limited.Some blockchain solutions support smart contracts,but they rely on Po W or Po C to make consensus,while smart terminals often have little computing electricity or storage space to perform such energy-consuming consensus.In addition,since IoT devices are often closely associated with physical entities,how to ensure the privacy of IoT devices is also an important research topic.To solve the above problems,this work will study the blockchain scheme for the Internet of Things environment.Among many blockchain solutions,we think that Chainspace[2]has the potential to be applied to IoT scenarios.Chainspace is a sharded smart con-tracts platform.Chainspace does not use resource-intensive consensus pro-tocols such as Po W or Po C so that nodes with limited resources can also participate in transaction verification.It also improves network scalability through sharding strategy,enabling more nodes to join the network.In ad-dition,it separates the execution and verification of smart contracts,thereby enhancing the privacy of smart contracts.But Chainspace can still be improved.In Chainspace,the emergence of malicious shards will cause security problems.Nodes cannot dynamically join the network or exit from the network.The auditability in Chainspace is not perfect.Therefore,we improve Chainspace and design a more secure and efficient blockchain solution,VChain,on the basis of Chainspace.Firstly,we apply the sharded structure to enhance the network scalabil-ity.A transaction is just verified by a part of the whole nodes in the network.When there are more nodes in the network,more transactions can be veri-fied,which means the transaction throughput will be higher.Then we design the two-layer consensus structure so that a certain percentage of malicious shards can be tolerated.It means that an honest consensus result can still be reached even when not all the shards are honest.Also,we adopt the strategy in Chainspace to set apart the transaction execution and transaction verification.The privacy of the smart contract can be guaranteed because the verification nodes needn't run the contracts but only need to verify the execution results.Moreover,we design a Po W-free and Po C-free audit mechanism to provide security.Even nodes lack of resources can play a role in the transaction verification.It guarantees that honest nodes are encouraged to maintain the system function well and dishonest nodes will pay a high price for doing evil.At last,we analyze the security of VChain.Not only do we design VChain for the Internet of Things environment,but also we attempt to apply it to the actual environment.At present,elec-tricity quota allocation in most countries or regions is uniformly dispatched by centralized institutions.We try to realize peer-to-peer energy trading,so as to make full use of the electricity generation capacity of small and micro nodes.Moreover,in the traditional electricity system,the data on electricity generation equipment is mainly stored locally.We believe that these data can be shared across the entire network to provide”raw materials”for the superstructure of the Internet of Things.In order to achieve these goals,we need to break the barrier between the physical world and the digital world by combining blockchain technology and the Internet of Things technology to provide a potential solution for peer-to-peer energy transactions.Through the Internet of Things,we can collect physical data,process physical data,transmit electricity,and authorize IoT devices.Through the blockchain,we can record transaction ledgers,query transaction ledgers,audit transaction ledgers,and update participating nodes.Based on such a design principle,we design a system for electricity In-ternet of Things,VChain Electricity,based on VChain.Firstly,we define the main objects in VChain Electricity.Then,we design the basic structure of VChain Electricity.Besides,we elaborate on the design ideas and design methods of the experiments.Finally,we present the experimental results,showing that VChain Electricity has the potential to be applied in the elec-tricity IoT environment. |
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