  The paper deals with time-scaling transformations of dynamical systems. Such
scaling functions operate a change of coordinates on the time axis of the
system trajectories preserving its phase portrait. Exploiting this property, a
chaos encryption technique to transmit a binary signal through an analog
channel is proposed. The scheme is based on a suitable time-scaling function
which plays the role of a private key. The encoded transmitted signal is proved
to resist known decryption attacks offering a secure and reliable
communication.
