Abstract: In traditional medical information system,medical health data security storage and sharing have been becoming a challenging task.There are many restrictions in process of health data accessing and sharing for different people of identity,which spends a lot of resources and time on identity verification and data authentication.Aiming at these problems such as storage of the high concentration,unreliable data sharing security and the difficulty of reaching agreement,this paper proposed an alliance blockchain-based medical health data security model.According to the distribution of medical resources in reality,the medical institutions are ranked in the security model,and then combine DPOS with PBFT to ensure that the medical institutions can reach an agreement rapidly without a central node and share medical data in alliance.The security model has the advantages of decentralization,high security and tamper resistance,so it can store data records and other important information on the blockchain,but the original medical data is stored in Distributed database.The use’s medical health data is stored securely,meanwhile the sharing efficiency among the medical institutions is improved.Security analysis shows that the proposed model can protect medical health data within the scope of fault tolerance,prevent the data from tampering and the collusion problem.The proposed model has a 99% probability to ensure that the medical institutions can reach a consensus and share medical data in alliance by the consistency analysis.

Key words: Blockchain, Hybrid consensus mechanism, Medical health data, Proxy re-encryption, Security model