This paper presents the security analysis on the quantum stream cipher so called Yuen-2000 protocol (or $αη$ scheme) against the fast correlation attack, the typical attack on stream ciphers. Although a very simple experimental model of the quantum stream cipher without a random mapper may be decrypted in the information theoretic sense by the fast correlation algorithm, it is not a basic feature of Yuen 2000 protocol. In fact, we clarify that there exists a randomization scheme which attains the perfect correlation immunity against such attacks under an approximation. And in this scheme, the running key correlation from the second randomization that determines the mapping patterns is dismissed also by quantum noise. In such a case, any fast correlation attack does not work on the quantum stream cipher.This paper presents the security analysis on the quantum stream cipher so called Yuen-2000 protocol (or $αη$ scheme) against the fast correlation attack, the typical attack on stream ciphers. Although a very simple experimental model of the quantum stream cipher without a random mapper may be decrypted in the information theoretic sense by the fast correlation algorithm, it is not a basic feature of Yuen 2000 protocol. In fact, we clarify that there exists a randomization scheme which attains the perfect correlation immunity against such attacks under an approximation. And in this scheme, the running key correlation from the second randomization that determines the mapping patterns is dismissed also by quantum noise. In such a case, any fast correlation attack does not work on the quantum stream cipher.

arXiv:quant-ph/0604036Apr 6, 20061 citation

A quantum stream cipher by Yuen 2000 protocol with nonlinear random number generator

Kentaro Kato, Osamu Hirota

A quantum stream cipher by Yuen 2000 (Y-00) protocol with a feedback shift register - a linear feedback shift register (LFSR) or a nonlinear feedback shift register - is very attractive in implementing a secure high-speed optical data transmission system for next-generation optical networking. So far, a LFSR has been used in a quantum stream cipher by Y-00 as a running key generator, rather than a nonlinear feedback shift register. But, it is well-known that an appropriately designed nonlinear feedback shift register has larger period and linear complexity than the corresponding quantities of a LFSR driven by a secret key of the same length. Although large linear complexity of a key generator does not immediately guarantee the security of the key generator itself, it forces the eavesdropper at least to collect more measurement data to carry out the attacks. This motivates us to use a nonlinear feedback shift register as a running key generator in a quantum stream cipher by Y-00. The purpose of this study is to make a quantum stream cipher more costly in terms of cryptoanalysis, enhancing the advantages of using a nonlinear feedback shift register. For this purpose, we propose a new randomization technique for a running key generator in this paper. First, we state the basics of a quantum stream cipher by Y-00. Second, we propose the randomization on a running key consisting of two different type of basis converter. To evaluate the effect of the randomization in terms of the amount of information that is extracted by her measurement, numerical simulation is performed in the cases of an optical heterodyne receiver and a quantum optimal receiver under the assumption that the eavesdropper knows plaintext. Finally, we summarize the results.A quantum stream cipher by Yuen 2000 (Y-00) protocol with a feedback shift register - a linear feedback shift register (LFSR) or a nonlinear feedback shift register - is very attractive in implementing a secure high-speed optical data transmission system for next-generation optical networking. So far, a LFSR has been used in a quantum stream cipher by Y-00 as a running key generator, rather than a nonlinear feedback shift register. But, it is well-known that an appropriately designed nonlinear feedback shift register has larger period and linear complexity than the corresponding quantities of a LFSR driven by a secret key of the same length. Although large linear complexity of a key generator does not immediately guarantee the security of the key generator itself, it forces the eavesdropper at least to collect more measurement data to carry out the attacks. This motivates us to use a nonlinear feedback shift register as a running key generator in a quantum stream cipher by Y-00. The purpose of this study is to make a quantum stream cipher more costly in terms of cryptoanalysis, enhancing the advantages of using a nonlinear feedback shift register. For this purpose, we propose a new randomization technique for a running key generator in this paper. First, we state the basics of a quantum stream cipher by Y-00. Second, we propose the randomization on a running key consisting of two different type of basis converter. To evaluate the effect of the randomization in terms of the amount of information that is extracted by her measurement, numerical simulation is performed in the cases of an optical heterodyne receiver and a quantum optimal receiver under the assumption that the eavesdropper knows plaintext. Finally, we summarize the results.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIESep 5, 20083 citations

Quantum Stream Cipher for Secure Communication

Fumio Futami, Osamu Hirota

Jan 1, 20140 citations

This paper presents the security analysis on the quantum stream cipher so called Yuen-2000 protocol (or

αη

scheme) against the fast correlation attack, the typical attack on stream ciphers. Although a very simple experimental model of the quantum stream cipher without a random mapper may be decrypted in the information theoretic sense by the fast correlation algorithm, it is not a basic feature of Yuen 2000 protocol. In fact, we clarify that there exists a randomization scheme which attains the perfect correlation immunity against such attacks under an approximation. And in this scheme, the running key correlation from the second randomization that determines the mapping patterns is dismissed also by quantum noise. In such a case, any fast correlation attack does not work on the quantum stream cipher.