  We propose a design that uses the principle of chaos for UAV secure
communication. A UAV identified as an aerial base station communicates with a
ground base station over an RF channel. The communication units have dynamics
based on the logistic map. The map is chaotic in the appropriate parameter
space. Its states are non-periodic, broadband, and noise-like in the frequency
domain. They are useful for spreading information during transmission, making
it difficult for an eavesdropper to recover the modulated message since state
prediction is ultimately impossible. To retrieve it, we propose a variable
feedback controller. It asymptotically stabilizes the error dynamics when the
information source is off. During transmission, the controller synchronizes the
units such that the error contains signatures of the information signal.
Therefore, the information signal is retrievable by a suitable detection
mechanism. Security depends on the confidentiality of the map, the variable
feedback controller, including its scale factor and bounded feedback gain, and
the designer`s choice of invertible function for use in the scrambling and
descrambling process. Also, the method is less prone to jamming attacks and
multipath effects as the broadband spectrum can be used to randomly select RF
channels. It uses only a few simple algorithms, including a correlation
summation and a detection mechanism. The algorithms collect subsamples of the
received signal sequences and averages over each subsample length. The method
requires minimal programming efforts and low hardware resource utilization. It
is energy-efficient, which is a vital consideration for any UAV security model.
Moreover, we realize a prototype of the communication system on
field-programmable gate arrays. We presented a digital design of the secure
communication system involving the transmission of bitstreams between the ABS
and GBS.
