A Decentralized Multi-authority ABE Scheme in Cooperative Medical Care System.

In this paper, we propose an attribute-based encryption (ABE) scheme that can be used in cooperative medical care systems with multiple distrusted principles. Unlike prior multi-authority ABEs, this scheme distributes secret key generation to different medical care centers, which enables distributed authorization and access control. By separating the key generation process among medical care centers and data owners (DOs), our scheme is resilient to collusion between malicious their parties and users. This new Cooperative Medical Care System (CMCS) distinguishes between DO principal and medical care centers: DOs own the data but allows medical care centers to arbitrate access by providing attribute labels to users. The data is protected by access policy encryption over these attributes. Unlike prior systems, attributes generated by medical centers are not user-specific, and neither is the system susceptible to collusion between users who try to escalate their access by sharing keys. We prove our CMCS scheme correct under the Decisional Bilinear Diffie-Hellman (DBDH) assumption; we also include a complete end-to-end implementation that demonstrates the practical efficacy of our technique.