Certificateless Broadcast Encryption with Authorization Suitable for Storing Personal Health Records.

The article focuses on a privacy-preserving certificateless broadcast encryption scheme with authorization (PPCBE-wA) designed for securely storing and sharing personal health records (PHR) in cloud environments. This scheme enables patients to outsource encrypted PHR data to cloud servers and selectively authorize a group of receivers (e.g., healthcare providers) to decrypt the data without exposing sensitive information or receiver identities, thereby addressing key escrow and privacy concerns. The construction is proven secure against adaptive chosen ciphertext attacks under the Decision Diffie–Hellman (DDH) assumption in the random oracle model and demonstrates improved computational and communication efficiency compared to related schemes. While the ciphertext size scales linearly with the number of authorized users, the scheme offers a practical and secure solution for dynamic, privacy-preserving access control in cloud-based medical data systems.