The Kirchhoff-Law-Johnson-Noise (KLJN) secure key exchange scheme leverages statistical physics to enable secure communication with zero average power flow in a wired channel. While the original KLJN scheme requires significant power for operation, a recent wireless modification, TherMod, proposed by Basar claims a “low power” implementation. This paper critically examines this claim. We explain that the additional components inherent in the wireless adaptation substantially increase power consumption, rendering the “low power” assertion inappropriate. Furthermore, we clarify that the security claims of the original KLJN scheme do not directly translate to this wireless adaptation, implying significant security breach. Finally, the scheme looks identical to one of the stealth communicators from 2005, which was shown not to be secure.
The Kirchhoff-Law-Johnson-Noise (KLJN) secure key exchange scheme leverages statistical physics to enable secure communication with zero average power flow in a wired channel. While the original KLJN scheme requires significant power for operation, a recent wireless modification, TherMod, proposed by Basar claims a “low power” implementation. This paper critically examines this claim. We explain that the additional components inherent in the wireless adaptation substantially increase power consumption, rendering the “low power” assertion inappropriate. Furthermore, we clarify that the security claims of the original KLJN scheme do not directly translate to this wireless adaptation, implying significant security breach. Finally, the scheme looks identical to one of the stealth communicators from 2005, which was shown not to be secure.
not-yet-known not-yet-known not-yet-known unknown This commentary critically reviews the 2024 article ”Kirchhoff meets Johnson: In pursuit of unconditionally secure communication” by Ertugrul Basar, focusing on claims regarding the originality, security, and energy efficiency of thermal noise-based secure communication systems. The article presents the Kirchhoff-law-Johnson-noise (KLJN) key exchange scheme and wireless noise modulation as breakthroughs in security; this review clarifies their historical foundation, practical limitations, and security vulnerabilities. Key issues discussed include proper attribution to pioneering work by Kish (2005–2006), feasibility of unconditional security for wireless adaptations, and exaggerated claims of low-power operation. The aim is to contextualize this field’s evolution for engineering audiences and stimulate more precise scholarship and realistic expectations for future research directions.
Abstract We introduce two new Kirchhoff-law-Johnson-noise (KLJN) secure key distribution schemes which are generalizations of the original KLJN scheme. The first of these, the Random-Resistor (RR-) KLJN scheme, uses random resistors with values chosen from a quasi-continuum set. It is well-known since the creation of the KLJN concept that such a system could work in cryptography, because Alice and Bob can calculate the unknown resistance value from measurements, but the RR-KLJN system has not been addressed in prior publications since it was considered impractical. The reason for discussing it now is the second scheme, the Random Resistor Random Temperature (RRRT-) KLJN key exchange, inspired by a recent paper of Vadai, Mingesz and Gingl, wherein security was shown to be maintained at non-zero power flow. In the RRRT-KLJN secure key exchange scheme, both the resistances and their temperatures are continuum random variables. We prove that the security of the RRRT-KLJN scheme can prevail at a non-zero power flow, and thus the physical law guaranteeing security is not the Second Law of Thermodynamics but the Fluctuation-Dissipation Theorem. Alice and Bob know their own resistances and temperatures and can calculate the resistance and temperature values at the other end of the communication channel from measured voltage, current and power-flow data in the wire. However, Eve cannot determine these values because, for her, there are four unknown quantities while she can set up only three equations. The RRRT-KLJN scheme has several advantages and makes all former attacks on the KLJN scheme invalid or incomplete.
Salem et al. proposed an asymmetric Kirchhoff-Law-Johnson-Noise (KLJN) scheme using four resistors, termed P-Ther-Mod, for wired and wireless thermal noise modulation in low-power IoT applications. While the authors correctly derive bit error probability (BEP) expressions and demonstrate improved BER performance, the core idea of using multiple resistors with a truth table for bit interpretation to enhance security and reliability is not novel, for it was introduced in 2013 as the "multiple" KLJN (MKLJN) protocol. Furthermore, the claimed "low-power" advantage is questionable, as the four-resistor design consumes at least four times the power per exchanged bit compared to the classical two-resistor KLJN, without reducing the energy per bit. These aspects warrant clarification to properly contextualize the contributions of the P-Ther-Mod scheme.
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.
Recently, Bennett and Riedel (BR) (http://arxiv.org/abs/1303.7435v1) argued that thermodynamics is not essential in the Kirchhoff-law-Johnson-noise (KLJN) classical physical cryptographic exchange method in an effort to disprove the security of the KLJN scheme. They attempted to demonstrate this by introducing a dissipation-free deterministic key exchange method with two batteries and two switches. In the present paper, we first show that BR's scheme is unphysical and that some elements of its assumptions violate basic protocols of secure communication. All our analyses are based on a technically unlimited Eve with infinitely accurate and fast measurements limited only by the laws of physics and statistics. For non-ideal situations and at active (invasive) attacks, the uncertainly principle between measurement duration and statistical errors makes it impossible for Eve to extract the key regardless of the accuracy or speed of her measurements. To show that thermodynamics and noise are essential for the security, we crack the BR system with 100% success via passive attacks, in ten different ways, and demonstrate that the same cracking methods do not function for the KLJN scheme that employs Johnson noise to provide security underpinned by the Second Law of Thermodynamics. We also present a critical analysis of some other claims by BR; for example, we prove that their equations for describing zero security do not apply to the KLJN scheme. Finally we give mathematical security proofs for each BR-attack against the KLJN scheme and conclude that the information theoretic (unconditional) security of the KLJN method has not been successfully challenged.
This paper introduces a new attack against the Kirchhoff–Law–Johnson-Noise (KLJN) secure key exchange scheme. The attack is based on the nonlinearity of the noise generators. We explore the effect of total distortion ([Formula: see text]) at the second order ([Formula: see text]), third order ([Formula: see text]) and a combination of the second and third orders ([Formula: see text]) on the security of the KLJN scheme. It is demonstrated that as little as 1% results in a notable power flow along the information channel, which leads to a significant information leak. We also show that decreasing the effective temperature (that is, the wire voltage) and, in this way reducing nonlinearity, results in the KLJN scheme approaching perfect security.