# Efficient Security Scheme for Disaster Surveillance UAV Communication Networks
## 5 The Proposed Security Scheme
### Setup Phase  
The setup phase is responsible for preparing the air drones for their missions and assigning the required security parameters for different parties. Figure 2 shows the setup phase. * _Issuing Key Parameters_ TA provides the keying parameters for each party in the connection: TA issues a public/private key pair for \(CS\); \(\tilde{r}_{2 cs}\) as a private key and \((\tilde{a}_{cs},\tilde{p}_{cs})\) as public key, and then sends the key pair to \(CS\) via secure channel. \[TA\ \frac{\tilde{r}_{2 cs}(\tilde{a}_{cs},\tilde{p}_{cs})}{\tilde{r}_{2 cs}( \tilde{a}_{cs},\tilde{p}_{cs})}\ CS.\]  
Figure 2: Setup phase. TA assigns a set of unique secret IDs and secret session keys Ks and sends it securely to the _CS_. _CS_ then provides a unique secret ID = \(D_{w}\) and a secret session key K = \(k_{w}\) for each drone, which uses \(D_{w}\) to prove its identity to _CS_. While the \(k_{w}\) is utilized during the round that the drone plays the cluster head role to organize the joining/leaving groups process: \[TA\xrightleftharpoons[]{\cup(D,k)}CS.\] _CS_ assigns these security parameters for the drones before releasing them to begin their missions (_CS assign \(<D_{w},k_{w}>\) to \(D\)_). * _Forming the Groups_ The whole disaster area is divided into subareas As; each subarea \(\mathbb{A}_{j}\) is monitored by certain number of air drones \(m\) that are arranged in \(k\) groups; the number of the groups in the subarea is varied according to the size and importance of the subarea. For instance, the city downtown usually is more crucial than uptown, as downtown is crowded by people and has most of the business and important buildings. Drones can join or leave the group at any time as they can fly to the group or fly back to the _CS_ to recharge their batteries. When the drones are flying over the subarea to collect information about the subarea, forward messages from the earth, or take photos/videos; they are called _Monitoring Drones_. While the drones are flying back to the substation, they are working as _Relaying Drones_ to forward the messages from the cluster heads to the base station _CS_. In other words, the monitoring drone is converted to a relaying drone once it leaves its group to recharge the battery. For each group \(G_{l}\), the _CS_ assigns a different number of cluster heads \(D_{1},\ldots,D_{\beta}\) for each reading round, where \(\beta\) is varied for each group per reading round. For example, substation _CS_ connects to four groups in the subarea \(A_{1}\); each group has 20 drones. For group \(G_{1}\), substation chooses drones \(D_{2}\) and \(D_{15}\) to be two cluster heads for round 1; drones \(D_{20}\), \(D_{18}\), and \(D_{13}\) to be three cluster heads for round 2; and so on. The chain of cluster heads for each group is assigned by the corresponding _CS_, i.e., the _CS_ operator. The groups in the same subarea are using different frequency channels to reduce the interference with other groups' connections. * _Programming the Drones_ At _CS_, the drones' operator prepares each drone for its assigned task. The object _Mission_ is assigned for each drone; _Mission_ includes which subarea the drone has to scan, at what level it will fly, which group to enroll, and what mission to accomplish, such as taking photos/videos for the subarea, connecting with and forwarding the messages from the earth, or transferring first aid medical equipment. In addition, the operator determines when that specific drone works as a cluster head of its group. Consequently, the drone's path is pre-planned, i.e., the drones are tracked by GPS, so that, if a drone is redirected from the specified path, a suspicious action alarm is declared. For instance, the operator assigns _Mission_\({}_{r}\) for the drone \(D_{r}\) The operator sets two fingerprints' features [32] for each drone; these features extract characteristics from transmitted signals from the wireless devices and their environments to generate non-forgeable signatures.