In recent years, the medical industry is generating a large amount of data. How to securely store and reliably share these medical data has been a hot research topic. Cloud storage technology can be applied to the medical industry to adapt to the rapid growth of medical data. However, cloud-based data storage and sharing systems face a series of security issues: whether the integrity of outsourced medical data can be guaranteed, and malicious access between different medical institutions may leak user's privacy. This article proposes a system that simultaneously solves the integrity auditing of medical data and securely data sharing between different medical institutions under the terminal-edge-cloud framework. Specifically, patients/doctors are treated as terminal users, medical institutions are viewed as edge nodes, and medical clouds form the central storage layer. In the process of data auditing, third-party auditor can achieve integrity auditing of medical cloud storage data. Moreover, different medical institutions use private-set-intersection technology to share the common user's electronic medical data, while for other users not in intersection set, their data does not need to be shared. Finally, security and performance analyses show that our proposed system is provable secure and has high computational and communication efficiency.

Vehicular ad hoc network (VANET), as an important part of intelligent transportation system, attracts more and more attention since it can provide communication about traffic and vehicle conditions, and optimize the transportation. It is noted that it also faces a series of security challenges. One of core issues is how to achieve secure data sharing and access control. Ciphertext-policy attribute-based encryption (CP-ABE) technique is often used to achieve these goals simultaneously. However, in the execution process of applying CP-ABE to VANET, there are two crucial issues that need to be resolved. One is key-escrow issue, which means that all vehicles’ secret keys will be leaked once if the central attribute authority (CAA) is compromised, and another is the revocation issue of departing vehicles from current region. In order to resolve these two issues simultaneously, in this paper, we propose an efficient data sharing protocol for VANET with the key-escrow-free and vehicle-revocable properties. More specifically, we design a sub-protocol between CAA and vehicles, which interactively issues secret keys for these vehicles. But CAA does not know any user’s true secret key, which guarantees that it is still secure even if CAA is compromised. In addition, we additionally introduce an entity named group manager, which manages and updates the unrevoked users in the current group. In order to improve the efficiency of the whole system, we adopt the online/offline encryption method for data owner and outsourced decryption technique for the resource-constraint data users. Finally, the performance analysis show that our proposed protocol is competitive in the phases of online encryption, key generation and CAA-setup, and thus is useful in the practical applications of VANET.