  Cloud computing system based on data centers has recently attracted
considerable attention. In that system, all data are communicated via a high
speed optical network between a customer and data center or between data
centers. There is a serious threat so called "Eavesdropper data center
business", which means the eavesdropper can get all data from the transmission
line and sell specific data selected by the protocol analyzer to malicious
people who want to get the secret data. So we need to consider cyber attack
against Layer-1 (physical layer). Quantum cryptography has been developed to
protect such an attack. In order to apply such a new security technologies, the
communication performance is very important as well as its security, because
the data speed is more than several Gbit/sec. This research note III will
discuss communication performances of quantum key distribution (QKD) and
quantum enigma cipher, and explaines that QKD based on single photon signals
cannot realize appropriate data speed, but quantum enigma cipher can.
