Research On Blockchain Cross-Chain Technology For Medical Big Data

With the continuous development of blockchain technology,more and more blockchain platform projects have been implemented,and there are many applications in the medical field.Platforms for different medical institutions or regions often adopt different architectures,and it is difficult to have efficient and reliable collaboration.Blockchain cross-chain technology is usually used to realize information transmission,interconnection and value transfer between value islands.However,the current research and application of cross-chain technology pays more attention to security than privacy,and the mechanisms in all aspects are not perfect.In response to these problems,this thesis studies the privacy,functionality,stability etc.of blockchain and cross-chain technology.The thesis first proposes a privacy protection scheme based on group signature technology,analyzes cross-chain requirements and privacy requirements,and proposes an overall scheme architecture.Various group signature algorithms are researched and compared,the BLS signature algorithm is applied and improved among them,a Dynamic m-of-n Signature Scheme(Dm SS)is proposed,and a specific process and algorithm are designed.On the basis of dividing the group,Dm SS realizes the dynamic adjustment of the multi-signature strategy according to the group size,so that the BLS group signature algorithm can be adaptively adjusted dynamically according to the change of the number of group nodes,which is more flexible,easier to expand,and improves overall efficiency.This scheme replaces individual signatures and public keys with group aggregated signatures and aggregated public keys,which protects the privacy of individual identities.After that,the thesis studies the key issues of cross-chain smart contract technology.The first is to design and implement a cross-chain smart contract call scheme for medical scenarios.According to different types of cross-chain smart contracts,rich cross-chain functions are realized,which expand the functionality of cross-chain;and the result data of smart contracts is used to replace the original cross-chain transmission of full-text data,reducing the scope of transmission of specific sensitive data and enhancing privacy.The second is to propose a cross-chain relay fault handling mechanism suitable for a single node cross-chain relay mode,and design the DN-BDN election algorithm and related processes to realize automatic and rapid switching in the event of a fault,with higher operating efficiency.Finally,the thesis designs and implements a blockchain platform system for medical alliance scenarios,applies the above research results to the system,and develops a "blockchain medical data management system" client,which realizes login-registration,blockchain various functional modules such as data addition,deletion,modification,and query,cross-chain data query,etc.Then,the platform is used to test the research of this thesis.The test results show that the privacy protection scheme based on the group signature algorithm not only provides privacy protection but also improves the overall system efficiency and improves the flexibility when the number of nodes changes.The cross-chain smart contract call scheme improves the functionality and privacy of crosschain applications,and at the same time,it runs well and is feasible.While the cross-chain relay fault handling mechanism realizes failover,it is more efficient than the PBFT consensus nodes.The research of this thesis achieves the design expectations as a whole and provides ideas for the practical application of blockchain cross-chain technology in the field of medical big data.