  Drone security is currently a major topic of discussion among researchers and
industrialists. Although there are multiple applications of drones, if the
security challenges are not anticipated and required architectural changes are
not made, the upcoming drone applications will not be able to serve their
actual purpose. Therefore, in this paper, we present a detailed review of the
security-critical drone applications, and security-related challenges in drone
communication such as DoS attacks, Man-in-the-middle attacks, De-Authentication
attacks, and so on. Furthermore, as part of solution architectures, the use of
Blockchain, Software Defined Networks (SDN), Machine Learning, and Fog/Edge
computing are discussed as these are the most emerging technologies. Drones are
highly resource-constrained devices and therefore it is not possible to deploy
heavy security algorithms on board. Blockchain can be used to cryptographically
store all the data that is sent to/from the drones, thereby saving it from
tampering and eavesdropping. Various ML algorithms can be used to detect
malicious drones in the network and to detect safe routes. Additionally, the
SDN technology can be used to make the drone network reliable by allowing the
controller to keep a close check on data traffic, and fog computing can be used
to keep the computation capabilities closer to the drones without overloading
them.
