The Security And Privacy Of Blockchain-enabled EMR Storage Management Scheme

The sharing of electronic medical record(EMR)data is the key method to improve the quality of medical services and reduce medical costs.However,the decentralized storage of EMR hinders data sharing,and medical service providers have too much access to EMR,resulting in the disclosure of patients’ privacy,and non professional doctors have the right to modify EMR,resulting in unreliable EMR information.At the same time,the length of signature and key of EMR ciphertext is large,and the signature scheme is vulnerable to bypass attack,which also affects the healthy development of EMR.In order to solve these problems,this paper proposes a blockchain based searchable electronic medical record data sharing scheme and a blockchain based EMR secure storage and sharing scheme supporting permission separation and attribute revocation.The specific research contents are as follows:Firstly,fine-grained access control is realized by keyword search based on ciphertext policy attribute,and fine-grained access control of encrypted data is realized by specifying expressive access policy with Boolean formula on attribute,so as to further minimize bandwidth and communication consumption.Secondly,the ciphertext length increases flexibly and linearly with the number of clauses in DNF form or the size of Boolean formula in access structure.In addition,the threshold signature mechanism converts multiple signatures generated by the threshold number of data owners into a single threshold signature,which further reduces the length of the ciphertext.Then,a fast(outsourcing)decryption scheme is proposed,which allows the private chain server to perform the most time-consuming pairing operation by using its key,leaving a small number of lightweight operations on the data user side.The cost of outsourcing decryption will not change with the number of clauses in DNF form or the size of accessing Boolean formula,which further speeds up the search process.Public verifiers are allowed to check the correctness of search results on behalf of data users without divulging privacy,which reduces the computing needs of data users with limited resources.Finally,the idea of lattice theory,linear secret sharing and binary revocation tree is introduced,and a lattice based signature scheme is proposed by using attribute based encryption and NTRU cryptography.