## 1 Introduction
### Related Work  
In the scientific literature, various authentication methods for IoD systems have been suggested. These approaches fall into different categories, such as identity-based cryptography ([1, 2]), certifiateless ([3, 4, 5]), signcryption ([6, 7]), blockchain-based ([8, 9, 10]), or physical unclonable function (PUF)-based solutions ([11, 12]). In [13], the aims are to create a centralized IoD scheme, where MEC (mobile edge computing) operators are only in contact with one central UAV service provider (USP). In their proposition, when a drone (\(D_{1}\)) intends to connect to \(MEC_{2}\) from \(MEC_{1}\), the system's flexibility and the drone's freedom of movement are restricted. Since \(MEC_{1}\) and \(MEC_{2}\) belong to different service providers, \(D_{1}\) must be authorized to connect to \(MEC_{2}\). In such a scenario, the drones' access rights stored by \(MEC_{1}\) and \(MEC_{2}\)'s may fall out of sync, leading to a deadlock where \(MEC_{1}\) permits the drone to enter the territory or join the network while \(MEC_{2}\) blocks the action. A unique aspect of a PUF is that the drone does not store any keys physically. The storage of keys in non-volatile memory typically exposes ICs to hardware attacks, enabling adversaries to read the memory content. In contrast, applying PUF, the drone does not store the key at all. Even if someone tries to probe PUFs, their response to a challenge can be significantly affected. Therefore, managing a key using PUFs is highly secure and resistant to physical attacks, and physical unclonable function (PUF)-based authentication for drones can offer several advantages. Moreover, it provides protection against forgery or impersonation by using unique bitstrings based on physical characteristics during the authentication process. Another advantage of PUFs over other hardware-based security systems is that even if a hacker has physical access to the device, he or she cannot clone its internal features. [PERSON] et al. introduced an anonymous authentication system ([14]) for UAV applications utilizing radio frequency identification (RFID) and PUFs. The scheme consists of two entities: a UAV with a tag and a server. The proposed scheme provides mutual authentication and scalability, and the security of their scheme is based on [PERSON] and [PERSON]'s security model. In contrast to our proposition, their registration phase is based on a secure communication channel between the drone and the server, which increases the time complexity. Moreover, in later communication, the drones cannot communicate with each other, only the server. Another PUF-based authentication scheme for drones, proposed by [PERSON] et al. ([15]), is where the usage of PUFs provides a lightweight and secure method to authenticate the IoD parties and achieve UAV-to-ground station and UAV-to-UAV communications. The scheme includes a system model with a ground station, legitimate UAVs, and an adversary drone. The proposed scheme has security features, in  
Figure 1: Internet of Drones architecture. cluding key agreement, mutual authentication, and forward secrecy. Using Mao Boyd logic, formal security analysis has shown that this scheme is secure. The work of [PERSON] et al. is similar in many ways to our proposal, but the essential differences are that in their scheme, the base station generates the session key between the two drones, and the base station stores the PUF values in a central database. Since IoD systems are distributed, applying private blockchains to store, share and manage these values may be desirable. In [16], proposed by [PERSON] et al. a new blockchain-based framework (BSD2C-IoD) for secure data management among communication entities in IoD environments is presented. Their approach can effectively withstand various potential attacks, and the formal security analysis of BSD2C-IoD is conducted through the ROR oracle model, while formal security verification is carried out by utilizing the AVISPA tool. This solution uses the blockchain to store and validate the data.