Security of Y-00 and Similar Quantum Cryptographic Protocols

摘要

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.