The current supply chain traceability system based on centralized design has many disadvantages.Besides its performance improvement depending on the central server,other problems such as difficulty in supervision and accountability,excessive intermediate circulation nodes and opaque data also exist.Therefore,we design and implement a supply chain traceability system based on side chain technology.The system can achieve the goods management,information sharing and product traceability through Ethereum smart contract.At the same time,we use the side chain technology to expand the Ehtereum to meet the needs of practical applications.Experimental results show that the proposed system can trace the whole life circle of products in the supply chain,facilitating user verification query and third-party supervision.Besides,the throughput of the system reaches 200 TPS,and the cost of each transaction is reduced to 0.07 yuan.

Due to the large volume,various types and high security requirements of power data,its disaster tolerance and backup scheme should provide scalability and privacy protection.Blockchain is tamper-resistant,decentralized and traceable,which caters to such requirements.Therefore,this paper proposes a new blockchain-based disaster recovery and backup scheme of power data,integrating AONT,threshold secret sharing and other cryptographic technologies.The prototype system is implemented on an open-source blockchain platform,Ethereum.Experimental and Analysis results show that the scheme can ensure the consistency,tamper resistance and confidentiality of backup data.It is highly scalable,reducing the construction cost of infrastructure as well as the risk of single point of failure.

To improve the security of Wireless Mesh Network(WMN),this paper proposes a Smart Contract-based Security Architecture(SCSA) that integrates blockchain technology.The proposed architecture builds blockchains on routing nodes.Three types of smart contracts are deployed to provide hierarchical management for public keys of nodes,including public key updating,public key cancellation and user access authentication.Also,the Elliptic Curve Diffie-Hellman(ECDH) and symmetric encryption are used to implement secure communication between nodes.Experimental results show that SCSA can efficiently resist node clone attacks or node forgery attacks,key compromise attacks and denial of service attacks,ensuring the security and efficiency of network communication.

Traditional defense system based on Domain Name System(DNS) is vulnerable to saturated traffic attacks and DNS hijacking attacks.To address the problem,this paper performs theoretical analysis and research on key factors in preventing network attacks,and constructs a model for network flows and state transitions.On this basis,a DNS collaborative defense system based on hyperledger is proposed.In the system,multi-lateral resources are integrated through consortium blockchains for collaborative resistance to network attacks.The channel architecture and endorsement policies of hyperledger are used to implement privacy protection and network information sharing.Analysis results show that the collaborative defense system is highly safe at the data level and the service level,providing a feasible solution to security threats in the domain name industry.

The alliance chain is a kind of blockchain that allows authorized nodes to join in the network.However,when the network condition is poor,the nodes will join and exit dynamically.Therefore,on the basis of ring signature theory,ElGamal digital signature algorithm and PBFT algorithm,we propose a ring signature scheme based on ElGamal digital signature algorithm to cope with this problem.First,we analyze the correctness and anonymity of the ring signature algorithm.Then,we use the ring signature scheme to improve the signature and verification process of the PBFT algorithm.Finally,we adopt Caliper,the blockchain performance testing framework in Fabric,to test the performance of the improved scheme.Experimental results show that the improved,ring signature-based PBFT consensus algorithm can solve the dynamic joining and exiting problem of nodes in the network while reaching the fault-tolerant rate of the Byzantine node of the original PBFT algorithm,which has certain practical values.

Based on the blockchain overall architecture,the technology stack hierarchy is introduced.Bitcoin is used as an example to analyze the blockchain working principle.The blockchain ledger storage model and ledger classification are described from the perspective of distributed ledger.The data in the blockchain is spread across the network through consensus algorithms,reaches a consensus and is stored.In the absence of a trusted third party,this paper uses smart contracts to achieve independent operation of transactions,bussinesses and distributed applications to ensure the integrity,security and legitimacy of blockchain data.It combines the hash algorithm with the Merkel tree to reduce the blockchain storage space,provide anonymous identity proof for the blockchain participants based on the digital signature algorithm,and further protect the blockchain data privacy by using encryption and decryption technology.In view of blockchain security,privacy protection,wallet management and other issues,the deficiencies of the current research and the direction of future research are analyzed and forecasted.

To meet the needs of protecting the integrity of log data in computer operation system,this paper designs and implements a blockchain-based trusted log storage and verification system.During the storage phase,user uploads the date fingerprint of the local log to the blockchain and saves the returned credentials.During the verification phase,user fetches the stored fingerprint from blockchain,and compares it with the data fingerprint computed from local log to verify the integrity.Analysis result shows that with the advantages of decentralization,transparency,tamper-resistant and so on,this system can effectively detect the tampering behavior on the log data.

Aiming at the problems of learning record opaque,easy to credit tampering and low efficiency of learning results certification and conversion faced by credit bank mode,a management and control model of blockchain learning achievementd is proposed.It presented the structure of the model,introduces the related implementation principles.And proposes an improved Practical Byzantine Fault Tolerance(PBFT) consensus mechanism to achieve efficient,low cost and scalable learning results management and control mode,and designed the learning achievement certification standard and the conversion standard smart contract to ensure the automation and transparent execution of the model.Experimental results show that the model can provide new ideas and technical support for the management of learning outcomes under the credit bank mode.

As a decentralized distributed ledger technology,the main function of blockchain is to reach a consensus among untrusted nodes.In the blockchain,a suitable consensus mechanism can improve the blockchain performance and guarantee transaction data security.This paper proposes a new solution strategy for the “nothing at stake” problem in the Proof of Stakes(PoS).This strategy allows voting nodes to send agreement disagreement votes.If the node votes for a fork and the fork wins,the node will gain the profit.Otherwise,if the node votes against a fork and the fork fails,the node will also gain the profit.A smart contract is deployed on the Ethereum platform to validate the voting strategy.Results show that the proposed strategy can run normally and the nodes finally reach consensus.

Point-to-point encryption is an encryption method widely used in online communication software,and is mostly implemented by asymmetric encryption,but the public key distribution scheme relies on a centralized server.If the centralized server is attacked,there is a risk that chat information will be leaked due to a Man-in-the-Middle Attack(MITM).Therefore,this paper uses blockchain technology for auditing to build a decentralized public key distribution scheme.The scheme saves summary of all the public key modification records in the blockchain maintained by the CA through the smart contract,so that it can track and verify the maliciously modified records.The scheme also abopts the improved consensus algorithm based on Practical Byzantine Fault Tolerance(PBFT) to achieve low energy consymption,and efficient Byzantine fault tolerance.Experimental results show that compared with the algorithm,the scheme has high security.