Methods of Using Existing Wire Lines (power lines, phone lines, internet   lines) for Totally Secure Classical Communication Utilizing Kirchoff's Law   and Johnson-like Noise
  We outline some general solutions to use already existing and currently used wire lines, such as power lines, phone lines, internet lines, etc, for the unconditionally secure communication method based on Kirchoff's Law and Johnson-like Noise (KLJN). Two different methods are shown. One is based on filters used at single wires and the other one utilizes a common mode voltage superimposed on a three-phase powerline. 
Laszlo B. Kish