1. An unmanned aerial vehicle, comprising: a propulsion subsystem configured to propel the unmanned aerial vehicle between locations; and a transceiver configured to receive and transmit messages; an on-board computer system including: one or more processors; and memory that stores: a set of tasks to be completed by the unmanned aerial vehicle; and instructions that, when executed by the one or more processors, cause the on-board computer system to: determine a task for the set of tasks based at least in part a first message received via the transceiver; at a time after determining the task, cryptographically verifying that a second message received through the transceiver is trustworthy; recalculate the task based at least in part on information in the received second message; and control at least the propulsion subsystem to complete the recalculated task.