Abstract :
In this paper, a secure communication technique, using a chaotic system with a single
adjustable parameter and a single observable time series, is proposed. The chosen chaotic
system, which is a variant of the famous Rikitake model, has a special structure for which
the adjustable parameter appears in the dynamic equation of the observable time series.
This particular structure is used to build a synchronization-based state observer that is
decoupled from the adaptive parameter identifier. A local Lyapunov function is used to
design the parameter identifier, with an adjustable convergence rate that guarantees the
stability of the overall system. A two-channel transmission method is used to exemplify
the suggested technique where the secret message is encoded using a nonlinear function
of both the chaotic states and the adjustable parameter of the chaotic system that acts
as a secret key. Simulations show that, at the receiver, the signal can be efficiently retrieved
only if the secret key is known, even when both the receiver and the transmitter are in perfect
synchronization. The proposed technique is demonstrated to have improved security
and privacy against intruders, when compared to other techniques reported in the literature,
while being simple to implement using both analog and digital hardware. In addition,
the chosen chaotic system is shown to be flexible in accommodating the transmission of
signals with variable bandwidths, which promotes the superiority and versatility of the
suggested secure communication technique.
