Unmanned aerial vehicles (UAVs) or drones have the potential to supplant helicopters in real-time highway surveillance applications due to cost, form factor, and other considerations. The wireless medium used for communication has the potential to expose a fleet of drones en route to surveillance to link failures and attacks on passed messages. Given the sparse topology, messages among UAVs, vehicles, and trusted authority could be transmitted through collaboration among UAVs and vehicles. Since vehicles and drones in a highway environment are mobile, related ad hoc network is continuously updated to account for reachability of transmitted signals. It is also necessary to authenticate the drones and vehicles to ensure that the transmitted messages are uncorrupted and trusted. To accommodate processing power and mobility constraints, we develop lightweight authentication protocols that facilitate secure message transfer. We also evaluate the security properties of these protocols.