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It has been pointed out by Yuen that the security theory of quantum keydistribution(QKD) guided by Shor-Preskill theory has serious defects, inparticular their key rate theory is not correct. Theory groups of QKD tried toimprove several defects. Especially, Renner employed trace distance and quantumleftover Hash Lemma. However, the present theory encountered a problem of aquantitative evaluation of security. To cope with it, he uses a wronginterpretation on the trace distance and its level epsilon_{sec}, and justifiesthe unconditional security of own system when epsilon_{sec} is 10^{-6 } ~10^{-20}. In this paper, we discuss the following problems. What is the originof the misconception of the present theory? How does the present theory lead tothe misconception?. To show their process toward the misconception,Koashi-Preskill's theory which has a typical misconception is examined. A mainpoint of our comment is that QKD theory ignores the security requirementagainst attacker which is necessary to compare whole encryption schemes fromclassical to quantum. To clarify it, we emphasize that the trace distanceitself cannot have any operational meaning such as failure probability, and itis only mathematical tool as a measure of closeness. As a result, it is giventhat the security with above values derived from their formulation meansnothing in the general cryptological sense. In addition, I point out that acomment by Bennett and Riedel on unconditional security of QKD is not correct.Also, I point out that the experimental systems of groups of Los Alamos,Toshiba-UK, NICT, and others cannot have security guarantee even in future.

Misconception in Theory of Quantum Key Distribution -Reply to Renner-