We describe a simple method of interleaving a classical and quantum signal in a secure communication system at a single wavelength. The system transmits data encrypted via a one-time pad on a classical signal and produces a single photon reflection of the encrypted signal. This attenuated signal can be used to observe eavesdroppers and produce fresh secret bits. The system can be secured against eavesdroppers, detect simple tampering or classical bit errors, produces more secret bits than it

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... sumes and does not require any entanglement or complex wavelength division multiplexing, thus making continuous secure two-way communication via one-time pads practical.