This paper is the part-II of the previous paper and introduces the world of
Yuen’s concept. In the theory of cryptology, the Shannon impossibility theorem
states that the upper bound of the security of a plaintext against a
ciphertext-only attack is the entropy of the secret key. At the same time, it
gives the upper bound of the unicity distance against a known plaintext attack.
Hence the development of a new symmetric key cipher requires finding a way to
undo or lift this theorem. Such challenges have been attempted with quantum
stream cipher and quantum data locking as block cipher. Both ciphers are
designed by means of differentiating the receiving performance of Bob with key
and Eve without key according to the principle of quantum communication theory.
Thus, the origin of security of both ciphers come from the principle of keyed
communication in quantum noise (KCQ) proposed by Yuen. In this paper, we
explain and compare the principles and features of both cipher and assist to
improve the quantum data locking scheme. Then we will introduce experimental
research on quantum stream cipher towards commercialization, which has
performance superior to conventional cipher.

Este artículo explora los viajes en el tiempo y sus implicaciones.

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