Cloud-fog-assisted electronic health record (EHR) systems offer promising solutions for large-scale medical data storage and processing. However, they also raise critical privacy concerns, particularly regarding secure computation over sensitive data, fine-grained bilateral access control, dynamic revocation, and decryption key exposure. Existing cryptographic primitives, such as functional encryption and matchmaking encryption, address some of these challenges individually but fail to offer a unified solution. In this work, we design a revocable and privacy-preserving data computing system with bilateral access control (RPDC-BAC) for cloud-fog-assisted EHR sharing by proposing a novel cryptographic primitive, called server-aided revocable attribute-based matchmaking functional encryption (SR-AB-MFE). Specifically, the proposed scheme supports expressive bilateral access control and computation over encrypted data. In addition, it incorporates time-evolving decryption keys and a server-aided revocation mechanism to mitigate key exposure and efficiently revoke users. To further reduce receiver-side overhead, fog nodes assist in ciphertext authentication and partial decryption. We formally define the proposed primitive and prove its security under static assumptions. Finally, extensive experimental results demonstrate the efficiency and practicality of our design.

The integration of cloud-edge computing with Internet of Things (IoT) healthcare greatly improves medical service efficiency and reduces home monitoring costs. However, in an untrusted and open environment, it still faces significant privacy and security challenges, especially in terms of confidentiality and authenticity of medical data, as well as bilateral access control between patients and healthcare providers. At present, there are few solutions capable of addressing the aforementioned issues efficiently, as they typically come with significant communication and computational overhead. This poses a substantial challenge for IoT devices that are usually resource-constrained. To address the above issues, this paper proposes an efficient and verifiable fine-grained bilateral access control scheme for cloud-edge IoT healthcare. The scheme adopts flexible attribute-based threshold bilateral access control to provide data confidentiality and authenticity at the same time. In addition, our scheme achieves constant-size ciphertexts, utilizes offline/online technology to accelerate ciphertext generation, and outsources the data authenticity verification and partial decryption process to edge nodes, thereby improving the communication and computational efficiency. Furthermore, our scheme implements verification of outsourced results to resist attacks from malicious edge nodes. The formal security proof and experimental evaluation show that our scheme is more functional and practical than other bilateral access control schemes for IoT healthcare.