Abstract: In order to realize the sharing of patient data and to query patient medical records more conveniently, electronic medical records have become indispensable data in the medical system. In order to solve the problem of fine-grained access control between doctors and patients and patient privacy protection, an encryption and decryption outsourcing solution supporting attribute update in a smart medical environment is proposed. By outsourcing encryption and decryption operations to fog nodes, the solution effectively reduces the computational burden of data owners and data users and improves efficiency. In addition, the program supports the updating of patients’ medical records, which is more in line with actual application conditions. At the same time, when the ciphertext is updated, the authorized institution transmits the hash value related to the attribute to the medical cloud server, which effectively protects the user privacy. Finally, the solution is proved to be safe based on the difficult problem of DBDH, and the analysis of experimental data shows that the solution has certain advantages in computational efficiency. 

Key words: smart medical, multi-authority, property update, fog computing, outsourced computing