# Blockchain Technology for Secure Communication and Formation Control in Smart Drone Swarms
## 2 Related Works  
The concept of leveraging blockchain technology to address problems with identification, security, and storage in UAV clusters is not new. There have been studies that have used novel methods to examine how we can use the benefits of blockchain technology to lessen these issues. A more theoretical prospect of blockchain applications in UAV swarms can be found in [12; 13; 14]. A detailed explanation of how blockchain technology can be applied to drone clusters through various scenarios and examples is provided. Also, a thorough examination of the advantages of applying blockchain technology to these systems is conducted. Moreover, the potential problems and limitations of such applications are described. Works with specific results and contributions related to the technical aspects of this area are presented below. For example, in [15], a lightweight blockchain is proposed, along with an interesting mechanism for message routing between UAV nodes to enhance the security of routing in 5G NR cellular networks. In addition, a way of identifying and managing malicious nodes is included. Proof of Traffic (PoT) is utilized for reaching a consensus, while the synchronization of the updated blocks is performed passively within the energy consumption limits. As it is based on the results of this work, the proposed scheme is very efficient and capable of ensuring the smooth operation of the swarm, even if there are malicious intrudes inside it. A novel approach in which a UAV swarm is able to conduct surveillance missions at specific points of interest (POIs) by utilizing blockchain technology is proposed in [16]. It is essentially a tangled-based model (IOTA), which relies on a decision-making strategy (smart contract) for the coordination of UAVs. The described idea is based on autonomous swarm operation (without the existence of some control center), in contrast to most of the published research. The blockchain is embedded in the UAVs, while there are some more nodes on the ground that have specific functionalities (route planning, financial transactions). The above-mentioned research is the only one that shares some components (smart contracts and autonomous decision making) with our suggested scheme. The UAV-TIEN system is a blockchain-based data transmission model proposed in [17]. This specific scheme is secure due to the nature of blockchain technology and also robust against line-of-sight blocking problems. Monte Carlo simulations were carried out in order to evaluate the efficiency of the proposed model. The results were very promising due to the model's ability to increase the data broadcasting range. Scalability-related issues may arise due to the broadcasting mechanism that was used in the study (broadcasting to every UAV inside the range). However, by selecting a different mechanism and utilizing some ground station nodes, this problem can be solved. Also, by optimizing parameters such as the maximum blockchain length (MBL) and broadcasting frequency (BF), channel congestion can be improved. In order to ensure security in UAV networks during surveillance and identify potentially compromised UAVs based on trust policies, [18] suggests a method that utilizes blockchain principles. The method allows for the accurate detection of false data when an official UAV is compromised. To validate the suggested strategy, ABS-SecurityUAV,a unique agent-based simulator, was employed. In the conducted tests, the majority of the UAVs were able to confirm information about a person moving through a regulated area, and none of them confirmed false information from a UAV that had been hijacked. In [19], a blockchain-based data acquisition procedure is shown in which data are collected from IoTs utilizing a UAV as a relay and securely stored in a blockchain on an MEC (Mobile Edge Computing) server. Data are encrypted using the proposed technique before being sent to the MEC server with the help of a UAV.