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Quantum stream cipher by Yuen 2000 protocol: Design and experiment by intensity modulation scheme

Osamu Hirota, Masaki Sohma, Masaru Fuse, Kentaro Kato

TL;DR

This paper investigates the Yuen protocol (Y-00) as a quantum stream cipher that achieves high-rate encryption by randomizing quantum-noise–driven coherent-state modulations. It analyzes security against known/chosen plaintext attacks using heterodyne, indirect, and quantum unambiguous measurements, arguing that legitimate-key advantage preserved by a running key thwarts practical attacks within the PRNG period. The authors describe and implement an intensity-modulated Y-00 scheme, demonstrating 1 Gbps transmission over 20 km of fiber and showing that Bob retains lower error than an eavesdropper lacking the secret key. The work highlights a feasible path to information-theoretic security in symmetric-key cryptography using quantum noise, with promising implications for high-rate, long-distance secure communication and future enhancements like additional randomizations and amplification.

Abstract

This paper shall investigate Yuen protocol, so called Y-00, which can realize a randomized stream cipher with high bit rate(Gbps) for long distance(several hundreds km). The randomized stream cipher with randomization by quantum noise based on Y-00 is called quantum stream cipher in this paper, and it may have security against known plaintext attacks which has no analog with any conventional symmetric key ciphers. We present a simple cryptanalysis based on an attacker's heterodyne measurement and the quantum unambiguous measurement to make clear the strength of Y-00 in real communication. In addition, we give a design for the implementation of an intensity modulation scheme and report the experimental demonstration of 1 Gbps quantum stream cipher through 20 km long transmission line.

Quantum stream cipher by Yuen 2000 protocol: Design and experiment by intensity modulation scheme

TL;DR

This paper investigates the Yuen protocol (Y-00) as a quantum stream cipher that achieves high-rate encryption by randomizing quantum-noise–driven coherent-state modulations. It analyzes security against known/chosen plaintext attacks using heterodyne, indirect, and quantum unambiguous measurements, arguing that legitimate-key advantage preserved by a running key thwarts practical attacks within the PRNG period. The authors describe and implement an intensity-modulated Y-00 scheme, demonstrating 1 Gbps transmission over 20 km of fiber and showing that Bob retains lower error than an eavesdropper lacking the secret key. The work highlights a feasible path to information-theoretic security in symmetric-key cryptography using quantum noise, with promising implications for high-rate, long-distance secure communication and future enhancements like additional randomizations and amplification.

Abstract

This paper shall investigate Yuen protocol, so called Y-00, which can realize a randomized stream cipher with high bit rate(Gbps) for long distance(several hundreds km). The randomized stream cipher with randomization by quantum noise based on Y-00 is called quantum stream cipher in this paper, and it may have security against known plaintext attacks which has no analog with any conventional symmetric key ciphers. We present a simple cryptanalysis based on an attacker's heterodyne measurement and the quantum unambiguous measurement to make clear the strength of Y-00 in real communication. In addition, we give a design for the implementation of an intensity modulation scheme and report the experimental demonstration of 1 Gbps quantum stream cipher through 20 km long transmission line.

Paper Structure

This paper contains 15 sections, 37 equations, 2 figures.

Table of Contents

  1. Introduction
  2. Information theoretically secure stream cipher
  3. One time pad
  4. Randomized stream cipher
  5. Quantum communication for quantum cryptography
  6. Yuen protocol:Y-00
  7. Basic concept
  8. Signal design
  9. Known/chosen plaintext attack
  10. Heterodyne measurement
  11. Indirect measurement
  12. Quantum unambiguous measurement
  13. Communication distance
  14. Experimental result
  15. Conclusion

Figures (2)

  • Figure 1: Design of the basis for amplitude (intensity) modulation
  • Figure 2: (Color Online) Eye patterns of Bob(top) and Eve(bottom). The eye-pattern of Eve has no eye-opening, which makes it impossible to discriminate with all of the threshold for the M-ary signals.