Improved Attribute-Based Encryption Scheme in Fog Computing Environment for Healthcare Systems

In today's smart healthcare system, medical records of patients are exposed to a large number of users for various purposes, from monitoring the patients' health to data analysis. Preserving the privacy of a patient has become an important and challenging issue. outsourced Ciphertext-Policy Attribute-Based Encryption (CP-ABE) provides a solution for the data sharing and privacy preservation problem in the healthcare system in fog environment. However, the high computational cost in case of frequent attribute updates renders it infeasible for providing access control in healthcare systems. In this paper, we propose an efficient method to overcome the frequent attribute update problem of outsourced CP-ABE. In our proposed approach, we generate two keys for each user (a static key and a dynamic key) based on the constant and changing attributes of the users. Therefore, in case of an attribute change for a user, only the dynamic key is updated. Also, the key update is done at the fog nodes without compromising the security of the system. Thus, both the communication and the computational overhead associated with the key update in the outsourced CP-ABE scheme are reduced, making it an ideal solution for data access control in healthcare systems. The efficacy of our proposed approach is shown through theoretical analysis and experimentation.