  We experimentally demonstrate a hybrid configuration for Quantum Key
Distribution, that combines the simplicity of Distributed Phase Reference
protocols with the self-referencing features and polarization insensitivity of
the so-called Plug & Play system. Additionally, all the components are arranged
in a server-client scheme to allow for practical key distribution. Blank,
coherent pulse pair trains are generated at the reception end of the link by
means of a pulse sequence and an unbalanced interferometer, and sent to the
other end. The emitter writes the qubits by erasing one of the pulses from the
pair as in a Coherent-One Way protocol. Detection, as well as eavesdropping
monitoring is performed at the receiver side, using the same interferometer
that was used to generate the initial phase-referenced pulses.
