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IEICE Technical Report; IEICE Tech. Rep.

Security evaluation system for quantum stream cipher by Y-00 protocol

Osamu Hirota, Kiichi Yamashita, Katsuyoshi Harasawa, Masaru Fuse, Kenichi Ohhata

Published Jun 7, 2007• 0 citations
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Quantum Stream Cipher for Secure Communication

Fumio Futami, Osamu Hirota

•Jan 1, 2014•0 citations

Structural Vulnerability in Y00 Protocols

Kentaro Imafuku

This paper critically analyzes the Y00 protocol, a quantum noise-based stream cipher proposed to enhance classical cryptographic methods through quantum mechanical properties. Despite its promise, we reveal a structural vulnerability that enables the leakage of secret information from measurement outcomes. To systematically evaluate its security, we first formalize the claims of previously proposed Y00 protocols, clarifying their achievements and limitations. We then identify the structural vulnerability through an intuitive explanation and rigorous formulation using maximum likelihood estimation. Our findings demonstrate that Y00's structural weaknesses allow for the unique determination of the shared secret, leading to significant information leakage. Using the "Toy protocol" as a reference model, we contextualize these results within the broader field of security technology. Furthermore, we generalize our findings to a wider class of quantum-based stream cipher protocols, identifying a fundamental security condition that Y00 fails to satisfy. This condition serves as a critical benchmark for ensuring the security of any stream cipher protocol relying on physical states, whether quantum or classical. These findings underscore the importance of rigorous security evaluations, particularly in systems intended for practical applications. Unexamined vulnerabilities not only undermine trust but also expose systems to avoidable risks, making rigorous analysis indispensable for ensuring resilience and security.

arXiv:2412.07300•Dec 10, 2024•1 citation

Quantum Stream Cipher Based on Holevo–Yuen Theory: Part II

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This paper discusses the foundation of security theory for the Quantum stream cipher based on the Holevo-Yuen theory, which allows the use of "optical amplifiers". This type of cipher is a technology that provides information-theoretic security (ITS) to optical data transmission by randomizing ultrafast optical communication signals with quantum noise. In general, the quantitative security of ITS is evaluated in terms of the unicity distance in Shannon theory. However, the quantum version requires modeling beyond the Shannon model of a random cipher to utilize the characteristics of the physical layer. Therefore, as the first step, one has to develop a generalized unicity distance theory and apply it to the evaluation of security. Although a complete theoretical formulation has not yet been established, this paper explains a primitive structure of a generalization of the Shannon random cipher and shows that the realization of this is the generalized quantum stream cipher. In addition, we present several implementation methods of generalized quantum stream ciphers and their security.

Entropy•Nov 15, 2024•0 citations

Randomization of running key for quantum stream cipher Y-00

Tetsuya Shimizu, Osamu Hirota

IEICE Technical Report; IEICE Tech. Rep.•Jun 7, 2007•1 citation

Randomization techniques for the intensity modulation-based quantum stream cipher and progress of experiment

Kentaro Kato, Osamu Hirota

The quantum noise based direct encryption protocol Y-OO is expected to provide physical complexity based security, which is thought to be comparable to information theoretic security in mathematical cryptography, for the. physical layer of fiber-optic communication systems. So far, several randomization techniques for the quantum stream cipher by Y-OO protocol have been proposed, but most of them were developed under the assumption that phase shift keying is used as the modulation format. On the other hand, the recent progress in the experimental study on the intensity modulation based quantum stream cipher by Y-OO protocol raises expectations for its realization. The purpose of this paper is to present design and implementation methods of a composite model of the intensity modulation based quantum stream cipher with some randomization techniques. As a result this paper gives a viewpoint of how the Y-OO cryptosystem is miniaturized.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Sep 1, 2011•14 citations

A possibility of information theoretic security of quantum stream cipher Y-00

Osamu Hirota

IEICE Technical Report; IEICE Tech. Rep.•Jun 5, 2008•0 citations
This paper critically analyzes the Y00 protocol, a quantum noise-based stream cipher proposed to enhance classical cryptographic methods through quantum mechanical properties. Despite its promise, we reveal a structural vulnerability that enables the leakage of secret information from measurement outcomes. To systematically evaluate its security, we first formalize the claims of previously proposed Y00 protocols, clarifying their achievements and limitations. We then identify the structural vulnerability through an intuitive explanation and rigorous formulation using maximum likelihood estimation. Our findings demonstrate that Y00's structural weaknesses allow for the unique determination of the shared secret, leading to significant information leakage. Using the "Toy protocol" as a reference model, we contextualize these results within the broader field of security technology. Furthermore, we generalize our findings to a wider class of quantum-based stream cipher protocols, identifying a fundamental security condition that Y00 fails to satisfy. This condition serves as a critical benchmark for ensuring the security of any stream cipher protocol relying on physical states, whether quantum or classical. These findings underscore the importance of rigorous security evaluations, particularly in systems intended for practical applications. Unexamined vulnerabilities not only undermine trust but also expose systems to avoidable risks, making rigorous analysis indispensable for ensuring resilience and security.
This paper discusses the foundation of security theory for the Quantum stream cipher based on the Holevo-Yuen theory, which allows the use of "optical amplifiers". This type of cipher is a technology that provides information-theoretic security (ITS) to optical data transmission by randomizing ultrafast optical communication signals with quantum noise. In general, the quantitative security of ITS is evaluated in terms of the unicity distance in Shannon theory. However, the quantum version requires modeling beyond the Shannon model of a random cipher to utilize the characteristics of the physical layer. Therefore, as the first step, one has to develop a generalized unicity distance theory and apply it to the evaluation of security. Although a complete theoretical formulation has not yet been established, this paper explains a primitive structure of a generalization of the Shannon random cipher and shows that the realization of this is the generalized quantum stream cipher. In addition, we present several implementation methods of generalized quantum stream ciphers and their security.
The quantum noise based direct encryption protocol Y-OO is expected to provide physical complexity based security, which is thought to be comparable to information theoretic security in mathematical cryptography, for the. physical layer of fiber-optic communication systems. So far, several randomization techniques for the quantum stream cipher by Y-OO protocol have been proposed, but most of them were developed under the assumption that phase shift keying is used as the modulation format. On the other hand, the recent progress in the experimental study on the intensity modulation based quantum stream cipher by Y-OO protocol raises expectations for its realization. The purpose of this paper is to present design and implementation methods of a composite model of the intensity modulation based quantum stream cipher with some randomization techniques. As a result this paper gives a viewpoint of how the Y-OO cryptosystem is miniaturized.