  Secure communication based on message encryption might be performed by
combining the message with controlled noise (called pseudo-noise) as performed
in Spread-Spectrum communication used presently in Wi-Fi and Smartphone
Telecommunication systems. Quantum communication based on entanglement is
another route for securing communications as demonstrated by several important
experiments described in this work. The central role played by the photon in
unifying the description of Classical and Quantum noise as major ingredients of
secure communication systems is highlighted and described on the basis of the
classical and quantum fluctuation dissipation theorems.
