PROCEEDINGS ARTICLE | October 19, 2004

Proc. SPIE. 5551, Quantum Communications and Quantum Imaging II

KEYWORDS: Modulation, Receivers, Cryptography, Optical communications, Quantum physics, Information security, Quantum information, Quantum communications, Quantum cryptography, Computer security

In 2000, an attractive new quantum cryptography was discovered by H.P.Yuen based on quantum communication theory. It is applicable to direct encryption, for example quantum stream cipher based on Yuen protocol(Y-00), with high speeds and for long distance by sophisticated optical devices which can work under the average photon number per signal light pulse: <n> = 1000 ~ 10000. In addition, it may provide information-theoretic security against known/chosen plaintext attack, which has no classical analogue.
That is, one can provide secure communication, even the system has H(K)<<H(X). This is a challenge to overcome Shannon limit in the cryptography theory.
In this paper, first, we give a brief review on the general logic of Yuen's theory. Then, we show concrete security analysis of quantum stream cipher to quantum individual measurement attacks. Especially by showing the analysis of Lo-Ko known plaintext attack, the feature of Y-00 is clarified. In addition, we give a simple experimental result on the scheme consisting of intensity modulation/direct detection optical communication.