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Unconditionally secure key distribution without quantum channel

Hua-Lei Yin

TL;DR

This work proposes probability key distribution (PKD), an unconditional-secure key-distribution scheme that does not require exchanging quantum signals over a quantum channel. PKD relies on a provable quantum one-way function realized via discrete phase-randomized weak coherent states produced by a random mapping from true randomness; as the phase granularity grows and mean photon number is kept small, Eve cannot extract information about the underlying bit substrings, effectively decoupling phase information. The authors show a zero phase-error rate in an entanglement-based view, establish universal composable security with a precise secret-key-length bound $\ell$, and provide a practical simulation framework for gains, detection events, and error rates. By combining random information negotiation with fixed and per-session secret keys, PKD achieves information-theoretic security without relying on a global quantum network, potentially enabling scalable global deployment of unconditionally secure cryptography.

Abstract

Key distribution plays a fundamental role in cryptography. Currently, the quantum scheme stands as the only known method for achieving unconditionally secure key distribution. This method has been demonstrated over distances of 508 and 1002 kilometers in the measurement-device-independent and twin-field configurations, respectively. However, quantum key distribution faces transmission distance issues and numerous side channel attacks since the basic physical picture requires the use of quantum channels between users. Even when quantum repeater and quantum constellation are used, commercializing quantum cryptography on a large scale remains unattainable due to the considerable expense and significant technical hurdles associated with establishing a global quantum network and facilitating mobile quantum communication. Here, by discovering the provable quantum one-way function, we propose another key distribution scheme with unconditional security, named probability key distribution, that promises users between any two distances to generate a fixed and high secret key rate. There are no quantum channels for exchanging quantum signals between two legitimate users. Non-local entangled states can be generated, identified and measured in the equivalent virtual protocol and can be used to extract secret keys. We anticipate that this discovery presents a paradigm shift in achieving unconditionally secure cryptography, thereby facilitating its widespread application on a global scale.

Unconditionally secure key distribution without quantum channel

TL;DR

This work proposes probability key distribution (PKD), an unconditional-secure key-distribution scheme that does not require exchanging quantum signals over a quantum channel. PKD relies on a provable quantum one-way function realized via discrete phase-randomized weak coherent states produced by a random mapping from true randomness; as the phase granularity grows and mean photon number is kept small, Eve cannot extract information about the underlying bit substrings, effectively decoupling phase information. The authors show a zero phase-error rate in an entanglement-based view, establish universal composable security with a precise secret-key-length bound , and provide a practical simulation framework for gains, detection events, and error rates. By combining random information negotiation with fixed and per-session secret keys, PKD achieves information-theoretic security without relying on a global quantum network, potentially enabling scalable global deployment of unconditionally secure cryptography.

Abstract

Key distribution plays a fundamental role in cryptography. Currently, the quantum scheme stands as the only known method for achieving unconditionally secure key distribution. This method has been demonstrated over distances of 508 and 1002 kilometers in the measurement-device-independent and twin-field configurations, respectively. However, quantum key distribution faces transmission distance issues and numerous side channel attacks since the basic physical picture requires the use of quantum channels between users. Even when quantum repeater and quantum constellation are used, commercializing quantum cryptography on a large scale remains unattainable due to the considerable expense and significant technical hurdles associated with establishing a global quantum network and facilitating mobile quantum communication. Here, by discovering the provable quantum one-way function, we propose another key distribution scheme with unconditional security, named probability key distribution, that promises users between any two distances to generate a fixed and high secret key rate. There are no quantum channels for exchanging quantum signals between two legitimate users. Non-local entangled states can be generated, identified and measured in the equivalent virtual protocol and can be used to extract secret keys. We anticipate that this discovery presents a paradigm shift in achieving unconditionally secure cryptography, thereby facilitating its widespread application on a global scale.
Paper Structure (15 sections, 54 equations, 1 figure)

This paper contains 15 sections, 54 equations, 1 figure.

Table of Contents

  1. I. Review of quantum measurements
  2. A. Unambiguous state discrimination
  3. B. Minimum error discrimination
  4. II. Proof of the first observation
  5. A. Random mapping rule
  6. B. Discrete phase-randomized coherent state
  7. III. Proof of the second observation
  8. A. Types of attack utilized in cryptanalysis
  9. B. One-time pad encryption and perfect secrecy
  10. C. The security of random information negotiation with $\vec{R}_{n}(\vec{x}_{a})$
  11. IV. Secret key rate
  12. A. Proof of zero phase error
  13. B. Universally composable framework
  14. C. Entropic uncertainty relation
  15. V. Simulation formula

Figures (1)

  • Figure S1: The random mapping rule of some one PKD session. The basic unit of the phase row is $2\pi/1024$; thus, 1023 denotes that the phase $\theta=2\pi/1024\times1023$. The bit substring $\vec{x}=1111011010=\vec{c}_{0}$ is the first to appear, so it corresponds to phase $\theta=0$. The bit substring $\vec{x}=1001101010=\vec{c}_{1023}$ is the last to appear, so it corresponds to the phase $\theta=2\pi/1024\times1023$.