Untappable communication channels over optical fibers from quantum-optical noise

Coherent light, as produced by lasers, gives rise to an intrinsic noise, known as quantum noise, optical noise or shot noise. AlphaEta is a protocol which exploits this physical phenomenon to obtain secure data encryption or key distribution over a fiber-optic channel in the presence of an eavesdropper. In this paper we focus on the cryptographic aspects of AlphaEta and its variants. Moreover, we propose a new protocol for which we can provide a rigorous proof that the eavesdropper obtains neglible information. In comparison to singlephoton quantum cryptography, AlphaEta provide much higher throughputs combined with a well-known technology.