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arXiv:1405.2034 · Metrology and Measurement Systems

On the “Cracking” Scheme in the Paper “A Directional Coupler Attack Against the Kish Key Distribution System” by Gunn, Allison and Abbott

Hsien-Pu Chen, László B. Kish, Claes G. Granqvist, Claes G. Granqvist

Published Aug 20, 2014• 39 citations
arXivHTMLPDF

Abstract

Abstract Recently, Gunn, Allison and Abbott (GAA) [http://arxiv.org/pdf/1402.2709v2.pdf] proposed a new scheme to utilize electromagnetic waves for eavesdropping on the Kirchhoff-law-Johnson-noise (KLJN) secure key distribution. We proved in a former paper [Fluct. Noise Lett. 13 (2014) 1450016] that GAA’s mathematical model is unphysical. Here we analyze GAA’s cracking scheme and show that, in the case of a loss-free cable, it provides less eavesdropping information than in the earlier (Bergou)-Scheuer-Yariv mean-square-based attack [Kish LB, Scheuer J, Phys. Lett. A 374:2140-2142 (2010)], while it offers no information in the case of a lossy cable. We also investigate GAA’s claim to be experimentally capable of distinguishing—using statistics over a few correlation times only—the distributions of two Gaussian noises with a relative variance difference of less than 10-8. Normally such distinctions would require hundreds of millions of correlations times to be observable. We identify several potential experimental artifacts as results of poor KLJN design, which can lead to GAA’s assertions: deterministic currents due to spurious harmonic components caused by ground loops, DC offset, aliasing, non-Gaussian features including non-linearities and other non-idealities in generators, and the timederivative nature of GAA’s scheme which tends to enhance all of these artifacts.

DOI
10.2478/mms-2014-0033

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ON THE "CRACKING" EXPERIMENTS IN GUNN, ALLISON, ABBOTT, "A DIRECTIONAL COUPLER ATTACK AGAINST THE KISH KEY DISTRIBUTION SYSTEM"

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Recently Gunn, Allison and Abbott (GAA) [http://arxiv.org/pdf/1402.2709v2.pdf] proposed a new scheme to utilize electromagnetic waves for eavesdropping on the Kirchhoff-law‐Johnson-noise (KLJN) secure key distribution. In a former paper [http://vixra.org/pdf/1403.0964v4.pdf], we proved that CAA's wave-based attack is unphysical. Here we address their experimental results regarding this attack. Our analysis shows that GAA virtually claim that they can identify, in a few correlation times that, from two Gaussian distributions with zero mean, which one is wider when their relative width difference is <10 -4 . Normally, such decision would need millions of correlations times to observe. We identify the experimental artifact causing this situation: existing DC current and/or ground loop (yielding slow deterministic currents) in the system. It is important to note that, while the GAA's cracking scheme, the experiments and the analysis are invalid, there is an important benefit of their attempt: our analysis implies that, in practical KLJN systems, DC currents ground loops or any other mechanisms carrying a deterministic current/voltage component must be taken care of to avoid information leak about the key.

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Do Electromagnetic Waves Exist in a Short Cable at Low Frequencies? What Does Physics Say?

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We refute a physical model, recently proposed by Gunn, Allison and Abbott (GAA) [ http://arxiv.org/pdf/1402.2709v2.pdf ], to utilize electromagnetic waves for eavesdropping on the Kirchhoff-law–Johnson-noise (KLJN) secure key distribution. Their model, and its theoretical underpinnings, is found to be fundamentally flawed because their assumption of electromagnetic waves violates not only the wave equation but also the second law of thermodynamics, the principle of detailed balance, Boltzmann's energy equipartition theorem, and Planck's formula by implying infinitely strong blackbody radiation. We deduce the correct mathematical model of the GAA scheme, which is based on impedances at the quasi-static limit. Mathematical analysis and simulation results confirm our approach and prove that GAA's experimental interpretation is incorrect too.

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A recent paper by Gunn–Allison–Abbott (GAA) [L. J. Gunn et al., Scientific Reports 4 (2014) 6461] argued that the Kirchhoff-law–Johnson-noise (KLJN) secure key exchange system could experience a severe information leak. Here we refute their results and demonstrate that GAA's arguments ensue from a serious design flaw in their system. Specifically, an attenuator broke the single Kirchhoff-loop into two coupled loops, which is an incorrect operation since the single loop is essential for the security in the KLJN system, and hence GAA's asserted information leak is trivial. Another consequence is that a fully defended KLJN system would not be able to function due to its built-in current-comparison defense against active (invasive) attacks. In this paper we crack GAA's scheme via an elementary current-comparison attack which yields negligible error probability for Eve even without averaging over the correlation time of the noise.

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Comments on “A New Transient Attack on the Kish Key Distribution System”

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Abstract A recent IEEE Access Paper by Gunn, Allison and Abbott (GAA) proposed a new transient attack against the Kirchhoff-law-Johnson-noise (KLJN) secure key exchange system. The attack is valid, but it is easy to build a defense for the KLJN system. Here we note that GAA’s paper contains several invalid statements regarding security measures and the continuity of functions in classical physics. These deficiencies are clarified in our present paper, wherein we also emphasize that a new version of the KLJN system is immune against all existing attacks, including the one by GAA.

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ANALYSIS OF THE ATTENUATOR-ARTIFACT IN THE EXPERIMENTAL ATTACK OF GUNN-ALLISON-ABBOTT AGAINST THE KLJN SYSTEM

László B. Kish, Zoltán Gingl, Róbert Mingesz +3 more

After briefly summarizing our general theoretical arguments, we show that, the experienced strong information leak at the Gunn-Allison-Abbott attack [Scientific Reports 4 (2014) 6461] against the Kirchhoff-law-Johnson-noise (KLJN) secure key exchange scheme, resulted from a serious design flaw of the system. The attenuator broke the single Kirchhoff-loop into two coupled loops. This is an illegal operation because the single loop is essential for the security, thus the observed leak is obvious. We demonstrate this by cracking the system with an elementary current comparison attack yielding close to 1 success probability for Eve even without averaging within a sub-correlation-time measurement window. A fully defended KLJN system would not be able to function, at all, due to its built-in current-comparison defense against active (invasive) attacks.

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Long Response to Scheuer-Yariv: "A Classical Key-Distribution System based on Johnson (like) noise - How Secure?", physics/0601022

László B. Kish

This is the longer (partially unpublished) version of response; the shorter version (http://arxiv.org/abs/physics/0605013) is published in Physics Letters A. We point out that the claims in the comment-paper of Scheuer and Yariv are either irrelevant or incorrect. We first clarify what the security of a physically secure layer means. The idealized Kirchoff-loop-Johnson-like-noise (KLJN) scheme is totally secure therefore it is more secure than idealized quantum communication schemes which can never be totally secure because of the inherent noise processes in those communication schemes and the statistical nature of eavesdropper detection based on error statistics. On the other hand, with sufficient resources, a practical/non-ideal realization of the KLJN cipher can arbitrarily approach the idealized limit and outperform even the idealized quantum communicator schemes because the non-ideality-effects are determined and controlled by the design. The cable resistance issue analyzed by Scheuer and Yariv is a good example for that because the eavesdropper has insufficient time window to build a sufficient statistics and the actual information leak can be designed. We show that Scheuer's and Yariv's numerical result of 1% voltage drop supports higher security than that of quantum communicators. Moreover, choosing thicker or shorter wires can arbitrarily reduce this voltage drop further; the same conclusion holds even according to the equations of Scheuer and Yariv.

arXiv:physics/0602013•Feb 2, 2006•0 citations
Abstract Recently, Gunn, Allison and Abbott (GAA) [http://arxiv.org/pdf/1402.2709v2.pdf] proposed a new scheme to utilize electromagnetic waves for eavesdropping on the Kirchhoff-law-Johnson-noise (KLJN) secure key distribution. We proved in a former paper [Fluct. Noise Lett. 13 (2014) 1450016] that GAA’s mathematical model is unphysical. Here we analyze GAA’s cracking scheme and show that, in the case of a loss-free cable, it provides less eavesdropping information than in the earlier (Bergou)-Scheuer-Yariv mean-square-based attack [Kish LB, Scheuer J, Phys. Lett. A 374:2140-2142 (2010)], while it offers no information in the case of a lossy cable. We also investigate GAA’s claim to be experimentally capable of distinguishing—using statistics over a few correlation times only—the distributions of two Gaussian noises with a relative variance difference of less than 10-8. Normally such distinctions would require hundreds of millions of correlations times to be observable. We identify several potential experimental artifacts as results of poor KLJN design, which can lead to GAA’s assertions: deterministic currents due to spurious harmonic components caused by ground loops, DC offset, aliasing, non-Gaussian features including non-linearities and other non-idealities in generators, and the timederivative nature of GAA’s scheme which tends to enhance all of these artifacts.
Recently Gunn, Allison and Abbott (GAA) [http://arxiv.org/pdf/1402.2709v2.pdf] proposed a new scheme to utilize electromagnetic waves for eavesdropping on the Kirchhoff-law‐Johnson-noise (KLJN) secure key distribution. In a former paper [http://vixra.org/pdf/1403.0964v4.pdf], we proved that CAA's wave-based attack is unphysical. Here we address their experimental results regarding this attack. Our analysis shows that GAA virtually claim that they can identify, in a few correlation times that, from two Gaussian distributions with zero mean, which one is wider when their relative width difference is <10 -4 . Normally, such decision would need millions of correlations times to observe. We identify the experimental artifact causing this situation: existing DC current and/or ground loop (yielding slow deterministic currents) in the system. It is important to note that, while the GAA's cracking scheme, the experiments and the analysis are invalid, there is an important benefit of their attempt: our analysis implies that, in practical KLJN systems, DC currents ground loops or any other mechanisms carrying a deterministic current/voltage component must be taken care of to avoid information leak about the key.
We refute a physical model, recently proposed by Gunn, Allison and Abbott (GAA) [ http://arxiv.org/pdf/1402.2709v2.pdf ], to utilize electromagnetic waves for eavesdropping on the Kirchhoff-law–Johnson-noise (KLJN) secure key distribution. Their model, and its theoretical underpinnings, is found to be fundamentally flawed because their assumption of electromagnetic waves violates not only the wave equation but also the second law of thermodynamics, the principle of detailed balance, Boltzmann's energy equipartition theorem, and Planck's formula by implying infinitely strong blackbody radiation. We deduce the correct mathematical model of the GAA scheme, which is based on impedances at the quasi-static limit. Mathematical analysis and simulation results confirm our approach and prove that GAA's experimental interpretation is incorrect too.
A recent paper by Gunn–Allison–Abbott (GAA) [L. J. Gunn et al., Scientific Reports 4 (2014) 6461] argued that the Kirchhoff-law–Johnson-noise (KLJN) secure key exchange system could experience a severe information leak. Here we refute their results and demonstrate that GAA's arguments ensue from a serious design flaw in their system. Specifically, an attenuator broke the single Kirchhoff-loop into two coupled loops, which is an incorrect operation since the single loop is essential for the security in the KLJN system, and hence GAA's asserted information leak is trivial. Another consequence is that a fully defended KLJN system would not be able to function due to its built-in current-comparison defense against active (invasive) attacks. In this paper we crack GAA's scheme via an elementary current-comparison attack which yields negligible error probability for Eve even without averaging over the correlation time of the noise.
Abstract A recent IEEE Access Paper by Gunn, Allison and Abbott (GAA) proposed a new transient attack against the Kirchhoff-law-Johnson-noise (KLJN) secure key exchange system. The attack is valid, but it is easy to build a defense for the KLJN system. Here we note that GAA’s paper contains several invalid statements regarding security measures and the continuity of functions in classical physics. These deficiencies are clarified in our present paper, wherein we also emphasize that a new version of the KLJN system is immune against all existing attacks, including the one by GAA.
After briefly summarizing our general theoretical arguments, we show that, the experienced strong information leak at the Gunn-Allison-Abbott attack [Scientific Reports 4 (2014) 6461] against the Kirchhoff-law-Johnson-noise (KLJN) secure key exchange scheme, resulted from a serious design flaw of the system. The attenuator broke the single Kirchhoff-loop into two coupled loops. This is an illegal operation because the single loop is essential for the security, thus the observed leak is obvious. We demonstrate this by cracking the system with an elementary current comparison attack yielding close to 1 success probability for Eve even without averaging within a sub-correlation-time measurement window. A fully defended KLJN system would not be able to function, at all, due to its built-in current-comparison defense against active (invasive) attacks.
This is the longer (partially unpublished) version of response; the shorter version (http://arxiv.org/abs/physics/0605013) is published in Physics Letters A. We point out that the claims in the comment-paper of Scheuer and Yariv are either irrelevant or incorrect. We first clarify what the security of a physically secure layer means. The idealized Kirchoff-loop-Johnson-like-noise (KLJN) scheme is totally secure therefore it is more secure than idealized quantum communication schemes which can never be totally secure because of the inherent noise processes in those communication schemes and the statistical nature of eavesdropper detection based on error statistics. On the other hand, with sufficient resources, a practical/non-ideal realization of the KLJN cipher can arbitrarily approach the idealized limit and outperform even the idealized quantum communicator schemes because the non-ideality-effects are determined and controlled by the design. The cable resistance issue analyzed by Scheuer and Yariv is a good example for that because the eavesdropper has insufficient time window to build a sufficient statistics and the actual information leak can be designed. We show that Scheuer's and Yariv's numerical result of 1% voltage drop supports higher security than that of quantum communicators. Moreover, choosing thicker or shorter wires can arbitrarily reduce this voltage drop further; the same conclusion holds even according to the equations of Scheuer and Yariv.