Concurrent Two-Party Key Exchange with Forward Unlinkability in Internet of Drones

By the drone capturing attacks, the adversaries can extract the long-Term secret keys stored in the drones. Therefore, it is necessary to consider forward secrecy and forward unlinkability to minimize the damage by the drone capturing attacks. Forward secrecy protects the secrecy of the past sessions between users and drones, and forward unlinkability guarantees the strong anonymity of users and drones participated in the past sessions, even when the long-Term secret keys are revealed to the attackers via the drone capturing attacks. In 2022 Jeong et el. suggested a three-party key agreement scheme for internet of drones which provides forward secrecy and forward unlikability. However, their scheme has some shortcomings. Especially, in their scheme a drone (or a user) cannot run concurrently multiple key exchange sessions with multiple users (or drones). And their scheme provides only weak forward secrecy, not standard forward secrecy. In this paper, we propose a key exchange protocol resolving all the shortcomings of the Jeong et al.'s scheme. That is, our key exchange protocol provides the standard forward secrecy and forward unlinkability. And a drone can run concurrently multiple sessions with users without communication with the server. We also suggest a formal model for the forward unlinkability, and prove the forward unlinkability of our scheme in the formal model.