| In the cloud-edge computing scenario,where edge servers are deployed,including base stations,routers,gateways,and other facilities,is publicly accessible infrastructure.Private data of users are vulnerable to huge threats,and measures need to be taken to ensure users’privacy and security.In edge cloud,due to the need to provide support for numerous edge devices,a large number of services will be deployed.It is an urgent task to select the optimal service composition scheme from a large number of services.In addition,it is difficult for existing cloud service providers to bear the responsibility of protecting users’privacy,and users do not actually own their data.Therefore,it is necessary to design a data access control scheme to protect users’data from illegal access and tampering.In view of the above three problems,this thesis focuses on blockchain technology,and studies blockchain technology and related applications in the cloud-edge computing environment.The main work includes the following aspects:(1)In order to solve the privacy and security issues in cloud-edge computing,a lightweight blockchain called LBlockchainE for cloud-edge computing is proposed in this thesis.Considering the limitation of edge server resources,a data placement strategy is proposed.The storage resource consumption is considered as an influencing parameter,and servers with rich resources are selected for preferential storage.The access delay between servers is taken into account in the data placement strategy,and nodes with the lowest access and storage cost will be selected as the preferred storage choice.LBlockchainE adopts the low-energy consumption feature of the Proof of Stake,and determines the ownership of bookkeeping rights through a small amount of competitive computing and node resources.The experimental results show that,compared with Ethereum,LBlockchainE consumes less energy and occupies less storage space.The average data transmission delay of LBlockchainE is reduced by 1.6%,and the power consumption is reduced by 78%.Compared with random storage,best storage and optimal data storage strategies,the strategy proposed in this thesis maintains the same message cost.(2)Aiming at the problem of service composition in edge cloud,a trusted service composition optimization scheme for cloud-edge computing called TSC-ECFA is proposed.Services with the same input and output are grouped into a class by a predation strategy,reducing the number of combinations to find feasible solutions.The step size factor and attractiveness formula of firefly algorithm are also improved,so as to give full play to the detection ability of the step size factor in the early stage of the algorithm,and balance the local search and the global search.Then,considering that the QoS attribute value of the service is easy to be tampered with,the blockchain is used to store the QoS attribute value to ensure the immutability and reliability of the QoS attribute value.Finally,the iteration times and optimization of the three algorithms are tested in the simulation experiment.The experimental results show that the comprehensive performance of TSC-ECFA is better than other algorithms.(3)The medical scenario is selected from scenarios supported by cloud-edge computing.Aiming at its existing problems,an attribute-based encryption scheme for cloud-edge computing called CEC-ABE is proposed.In this scheme,the agreement process between the patient and the hospital is added before the attribute-based encryption stage,and the diagnosis and treatment time,diagnosis and treatment doctor and other diagnosis and treatment information are confidentially transmitted through the encryption algorithm.Then,the uploaded encrypted data is stored in the blockchain in the form of transaction records to ensure the integrity of the data,and the access to the electronic health records is controlled through the attribute encryption scheme based on the outsourced ciphertext strategy.Finally,through the experimental test of the CEC-ABE with CP-ABE and other algorithms,the computational cost of each stage of the algorithm and the computational delay of each role are compared,and the overall comprehensive performance is better than other algorithms.(4)The above algorithm is applied and an electronic health record access control system is constructed.Based on the demand analysis of the system,the electronic health record access control system is designed and planned from the overall structure,and the functions that the system should contain are analyzed in the demand analysis part.Class diagrams are given for the client and the server.Secondly,every class and interface involved in the system is analyzed and explained.Finally,in the system implementation,the medical scene information is displayed with the help of the Android terminal development technology. |
