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arXiv:2506.10147 · Fluctuation and Noise Letters

Unconditionally Secure, Wireless-Wired Ground–Satellite–Ground Communication Networks Utilizing Classical & Quantum Noise

Lucas Truax, Sandip Roy, László B. Kish

Published Feb 15, 2025• 3 citations
arXivHTMLPDF

Abstract

In this paper, we introduce the Kirchhoff-Law-Johnson-Noise (KLJN) as an approach to securing satellite communications. KLJN has the potential to revolutionize satellite communication security through its combination of simplicity, cost-effectiveness, and resilience with unconditional security. Unlike quantum key distribution (QKD), which requires complex, fragile, and expensive infrastructure like photon detectors and dedicated optical links, KLJN operates using standard electronic components and wires, significantly reducing implementation costs and logistical hurdles. KLJN’s security, grounded in the fundamental laws of classical physics, is impervious to environmental and radiation-induced noise, making it highly reliable in the harsh conditions of satellite communications. This robustness, coupled with its ability to integrate seamlessly with existing infrastructure, positions KLJN as a revolutionary alternative to quantum solutions for ensuring secure, resilient satellite communications. The authors explore the value of achieving unconditionally secure communications in strategic ground-to-satellite networks which address vulnerabilities posed by advanced computational threats, including quantum computing. Our team has examined two leading approaches to unconditional security — the KLJN scheme and QKD — and analyzed the potential use of each for space systems. While QKD leverages quantum mechanics for security, it faces challenges related to cost, complexity, and environmental sensitivity. In contrast, the KLJN scheme utilizes classical physics principles to provide a simpler, more cost-effective, and resilient alternative, particularly for ground-based systems. Further, this paper highlights the potential for complementary roles of these technologies in hybrid networks: KLJN can facilitate secure key exchanges without QKD for ground communications connected via wire, and QKD could facilitate secure inter-island and direct-to-satellite communications. Through a detailed analysis of implementation challenges, key exchange speeds, and network architectures, this study concludes that KLJN offers significant advantages in simplicity, cost-efficiency, and robustness, making it a practical choice for many secure communication applications.

DOI
10.1142/s0219477525500324

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In this paper, we introduce the Kirchhoff-Law-Johnson-Noise (KLJN) as an approach to securing satellite communications. KLJN has the potential to revolutionize satellite communication security through its combination of simplicity, cost-effectiveness, and resilience with unconditional security. Unlike quantum key distribution (QKD), which requires complex, fragile, and expensive infrastructure like photon detectors and dedicated optical links, KLJN operates using standard electronic components and wires, significantly reducing implementation costs and logistical hurdles. KLJN’s security, grounded in the fundamental laws of classical physics, is impervious to environmental and radiation-induced noise, making it highly reliable in the harsh conditions of satellite communications. This robustness, coupled with its ability to integrate seamlessly with existing infrastructure, positions KLJN as a revolutionary alternative to quantum solutions for ensuring secure, resilient satellite communications. The authors explore the value of achieving unconditionally secure communications in strategic ground-to-satellite networks which address vulnerabilities posed by advanced computational threats, including quantum computing. Our team has examined two leading approaches to unconditional security — the KLJN scheme and QKD — and analyzed the potential use of each for space systems. While QKD leverages quantum mechanics for security, it faces challenges related to cost, complexity, and environmental sensitivity. In contrast, the KLJN scheme utilizes classical physics principles to provide a simpler, more cost-effective, and resilient alternative, particularly for ground-based systems. Further, this paper highlights the potential for complementary roles of these technologies in hybrid networks: KLJN can facilitate secure key exchanges without QKD for ground communications connected via wire, and QKD could facilitate secure inter-island and direct-to-satellite communications. Through a detailed analysis of implementation challenges, key exchange speeds, and network architectures, this study concludes that KLJN offers significant advantages in simplicity, cost-efficiency, and robustness, making it a practical choice for many secure communication applications.
Abstract Noise: an enemy to be dealt with and a major factor limiting communication system performance. However, what if there is gold in that garbage? In conventional engineering, our focus is primarily on eliminating, suppressing, combating, or even ignoring noise and its detrimental impacts. Conversely, could we exploit it similarly to biology, which utilizes noise‐alike carrier signals to convey information? In this context, the utilization of noise, or noise‐alike signals in general, has been put forward as a means to realize unconditionally secure communication systems in the future. In this tutorial article, we begin by tracing the origins of thermal noise‐based communication and highlighting one of its significant applications for ensuring unconditionally secure networks: the Kirchhoff‐law‐Johnson‐noise (KLJN) secure key exchange scheme. We then delve into the inherent challenges tied to secure communication and discuss the imperative need for physics‐based key distribution schemes in pursuit of unconditional security. Concurrently, we provide a concise overview of quantum key distribution schemes and draw comparisons with their KLJN‐based counterparts. Finally, extending beyond wired communication loops, we explore the transmission of noise signals over‐the‐air and evaluate their potential for stealth and secure wireless communication systems.
The Kirchhoff-Law-Johnson-Noise (KLJN) secure key exchange system has been introduced as a simple, very low cost and efficient classical physical alternative to quantum key distribution systems. The ideal system uses only a few electronic components-identical resistor pairs, switches and interconnecting wires-in order to guarantee perfectly protected data transmission. We show that a generalized KLJN system can provide unconditional security even if it is used with significantly less limitations. The more universal conditions ease practical realizations considerably and support more robust protection against attacks. Our theoretical results are confirmed by numerical simulations.
Abstract There is an ongoing debate about the fundamental security of existing quantum key exchange schemes. This debate indicates not only that there is a problem with security but also that the meanings of perfect, imperfect, conditional and unconditional (information theoretic) security in physically secure key exchange schemes are often misunderstood. It has been shown recently that the use of two pairs of resistors with enhanced Johnsonnoise and a Kirchhoff-loop ‒ i.e., a Kirchhoff-Law-Johnson-Noise (KLJN) protocol ‒ for secure key distribution leads to information theoretic security levels superior to those of today’s quantum key distribution. This issue is becoming particularly timely because of the recent full cracks of practical quantum communicators, as shown in numerous peer-reviewed publications. The KLJN system is briefly surveyed here with discussions about the essential questions such as (i) perfect and imperfect security characteristics of the key distribution, and (ii) how these two types of securities can be unconditional (or information theoretical).
There is an ongoing debate about the fundamental security of existing quantum key exchange schemes. This debate indi cates not only that there is a problem with security but also that the meanings of perfect, imperfect, conditional and unconditional (information theoretic) security in physically secure key exchange schemes are often misunderstood. It has been shown recently that the use of two pairs of resistors with enhanced Johnsonnoise and a Kirchhoff-loop ‒ i.e ., a Kirchhoff-Law-Johnson-Noise (KLJN) protocol ‒ for secure key distribution leads to information theoretic security levels superior to those of today’s quan tum key distribution. This issue is becoming particularly timely because of the recent full cracks of practical quantum communicators, as shown in numerous peer- reviewed publications. The KLJN system is briefly surveyed here with discussions about the essential questions such as ( i) perfect and imperfect security characteristics of the key distribution, and ( ii ) how these two types of securities can be unconditional (or information theoretical).
The imperative need for unconditionally secure key exchange is caused by the increasing connectivity of networks and by the increasing number and level of sophistication of cyberattacks. Two concepts that are information theoretically secured are quantum key distribution (QKD) and Kirchhoff-Law-Johnson-Noise (KLJN). However, these concepts require a dedicated connection between hosts in peer-to-peer (P2P) networks which can be impractical and/or cost prohibitive. A practical and cost effective method is to have each host share their respective cable(s) with other hosts such that two remote hosts can realize a secure key exchange without the need of an additional cable or key exchanger. \n \nWe introduce a protocol for linear chain networks with a reconfigurable filter system to create non-overlapping single loops in the smart power grid for the realization of the Kirchhoff-Law-Johnson-(like)-Noise secure key distribution system. The protocol is valid for one-dimensional daisy chain networks (chain-like power line) which are typical of the electric distribution network between the utility and the customer. The speed of the protocol (the number of steps needed) versus grid size is analyzed. When properly generalized, such a system has the potential to achieve unconditionally secure key distribution over the smart power grid of arbitrary geometrical dimensions. \n \nIn this work we also analyze the cost complexities of cable, key exchangers, and time required in the star network. We mention the reliability of the star network and compare it with other network geometries. We also conceived a protocol and equation for the number of secure bit exchange periods needed in a star network. We then outline other network geometries and trade-off possibilities that seem interesting to explore. \n \nWe also propose a new key exchange trust evaluation for peer-to-peer sensor networks, where part of the network has unconditionally secure key exchange. As the utilization of sensor networks continues to increase, the importance of security becomes more profound. Many industries depend on sensor networks for critical tasks, and a malicious entity can potentially cause catastrophic damage. For a given sensor, the higher the portion of channels with unconditionally secure key exchange, the higher the trust value. We give a brief introduction to unconditionally secured key exchange concepts and mention current trust measures in sensor networks. We demonstrate the new key exchange trust measure on a hypothetical sensor network using both wired and wireless communication channels.
A secure key distribution (exchange) scheme is unconditionally secure if it is unbreakable against arbitrary technological improvements of computing power and/or any development of new algorithms. There are only two families of experimentally realized and tested unconditionally secure key distribution technologies: quantum key distribution (QKD), the base of quantum cryptography, which utilizes quantum physical photonic features, and the Kirchhoff-Law–Johnson-Noise (KLJN) system that is based on classical statistical physics (fluctuation–dissipation theorem). The focus topic of this paper is the thermodynamical situation of the KLJN system. In all the original works, the proposed KLJN schemes required thermal equilibrium between the devices of the communicating parties to achieve perfect security. However, Vadai et al., in (Nature) Sci. Rep. 5, 13653 (2015) show a modified scheme, where there is a non-zero thermal noise energy flow between the parties, yet the system seems to resist all the known attack types. We introduce an attack type against their system. The attack utilizes coincidence events between the line current and voltages. We show that there is a non-zero information leak toward the Eavesdropper, even under idealized conditions. As soon as the thermal equilibrium is restored, the system becomes perfectly secure again. In conclusion, perfect unconditional security requires thermal equilibrium.