Abstract: A searchable encrypted electronic medical record data sharing scheme in blockchain is proposed for the problems of data security,storage,and data sharing existing in electronic medical records.Firstly,the proposed scheme uses a cloud server to store electronic medical records and re-encrypts the corresponding ciphertexts to ensure data sharing among different medical institutions.Secondly,the blockchain is used to store indices.In the search phase,a smart contract is invoked on the consortium blockchain to execute keyword ciphertext search,which realizes secure storage of indexes and reduces the risk of malicious searches by semi-honest third parties.At the same time,this scheme hides conditions in re-encryption keys to ensure data confidentiality,ensuring that agents cannot learn any information about the conditions.Finally,analysis shows that the scheme is lightweight and has great advantages in terms of computational and communication overhead.

Key words: electronic medical record, blockchain, searchable encryption, proxy re-encryption