Security of Y-00 and similar quantum cryptographic protocols

Abstract

It is claimed in Phys. Lett. A by T. Nishioka et. al. 327 (2004) 28-32, that the security of Y-00 is equivalent to that of a classical stream cipher. In this paper it is shown that the claim is false in either the use of Y-00 for direct encryption or key generation, in all the parameter ranges it is supposed to operate including those of the experiments reported thus far. The security of Y-00 type protocols is clarified.

V.2 is a comprehensive response to Nishioka et. al., and also contains a brief response to Lo and Ko (quant-ph/0309127). We have provided a concise, and hopefully understandable, description of the security characteristics of AlphaEta for both direct encryption as well as key generation. Submitted to Physics Letters A, Oct. 2004