  A network of chaotic systems can be designed in such a way that the cluster
patterns formed by synchronous nodes can be controlled through the coupling
parameters. We present a novel approach to exploit such a network for covert
communication purposes, where controlled clusters encode the symbols
spatio-temporally. The cluster synchronization network is divided into two
subnetworks as transmitter and receiver. First, we specifically design the
network whose controlled parameters reside in the transmitter. Second, we
ensure that the nodes of the links connecting the transmitter and receiver are
not in the same clusters for all the control parameters. The former condition
ensures that the control parameters changed at the transmitter change the whole
clustering scheme. The second condition enforces the transmitted signals are
always continuous and chaotic. Hence, the transmitted signals are not modulated
by the information directly, but distributed over the links connecting the
subnetworks. The information cannot be deciphered by eavesdropping on the
channel links without knowing the network topology. The performance has been
assessed by extensive simulations of bit error rates under noisy channel
conditions.
