Gergely Vadai

What Kind of Noise Guarantees Security for the Kirchhoff-Law–Johnson-Noise Key Exchange?

This paper is a supplement to our recent one about the analysis of the noise properties in the Kirchhoff-law–Johnson-noise (KLJN) secure key exchange system [Gingl and Mingesz, PLOS ONE 9 (2014) e96109, doi: 10.1371/journal.pone.0096109]. Here, we use purely mathematical statistical derivations to prove that only normal distribution with special scaling can guarantee security. Our results are in agreement with earlier physical assumptions [Kish, Phys. Lett. A 352 (2006) 178–182, doi: 10.1016/j.physleta.2005.11.062]. Furthermore, we have carried out numerical simulations to show that the communication is clearly unsecure for improper selection of the noise properties. Protection against attacks using time and correlation analysis is not considered in this paper. Related simulations are available at http://www.noise.inf.u-szeged.hu/Research/kljn/.

Analysis of an Attenuator Artifact in an Experimental Attack by Gunn-Allison-Abbott Against the Kirchhoff-Law-Johnson-Noise (KLJN) Secure Key Exchange System

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 GAAs 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 GAAs 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 GAAs scheme via an elementary current comparison attack which yields negligible error probability for Eve even without averaging over the correlation time of the noise.

Generalized Kirchhoff-Law-Johnson-Noise (KLJN) secure key exchange system using arbitrary resistors

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.

Generalized Attack Protection in the Kirchhoff-Law-Johnson-Noise Secure Key Exchanger

The Kirchhoff-Law-Johnson-Noise unconditionally secure key exchanger is a promising, surprisingly simple, very low cost and efficient electronic alternative to quantum key distribution. A few resistors, switches, and interconnecting cables can provide unconditionally secure data transmission in the ideal case by utilizing the thermal noise of the resistors. The key problems regarding practical realizations are related to the resistance tolerance, finite cable resistance, and other non-ideal properties that can cause information leak. In this paper, we present robust protection from cable resistance and resistance mismatch attacks against the system. Our theoretical results show that all resistive inaccuracies, parasitic resistances, cable resistance, and temperature dependence can be compensated; therefore, the practical implementation becomes much easier. The generalized method provides inherent protection against the so-called second law attack as well.

Power Spectral Density Estimation for Wireless Fluctuation Enhanced Gas Sensor Nodes

Fluctuation enhanced sensing (FES) is a promising method to improve the selectivity and sensitivity of semiconductor and nanotechnology gas sensors. Most measurement setups include high cost signal conditioning and data acquisition units as well as intensive data processing. However, there are attempts to reduce the cost and energy consumption of the hardware and to find efficient processing methods for low cost wireless solutions. In this paper, we propose highly efficient signal processing methods to analyze the power spectral density of fluctuations. These support the development of ultra-low-power intelligent fluctuation enhanced wireless sensor nodes while several further applications are also possible.

Can the fluctuations of motion be used to estimate the performance of kayak paddlers

Today many compact and efficient on-water data acquisition units help the modern coaching by measuring and analyzing various inertial signals during kayaking. One of the most challenging problems is how these signals can be used to estimate performance and to develop the technique. Recently we have introduced indicators based on the fluctuations of the inertial signals as promising additions to the existing parameters. In this work we report about our more detailed analysis, compare new indicators and discuss the possible advantages of the applied methods. Our primary aim is to draw the attention to several exciting and inspiring open problems and to initiate further research even in several related multidisciplinary fields. More detailed information can be found on a dedicated web page, this http URL

Security and performance analysis of the Kirchhoff-Law-Johnson-Noise secure key exchange protocol

The Kirchhoff-Law-Johnson-(like)-Noise (KLJN) key exchange system is a promising low-cost alternative to the quantum key distribution and is based solely on the laws of classical physics. Although several papers have been published in the field, there is still an ongoing debate about the security of the method. In our paper we will give an overview the most important findings about the security of the KLJN system and show the effects of the non-idealities of the system on the information leak. We will also analyze different methods of proposed cracking the KLJN protocol, including the latest directional coupler attack.

Enhanced time-domain detection of the activation frequency of atrial fibrillation

Atrial fibrillation is the most common sustained cardiac arrhythmia. To determine the activation frequency of the atrial fibrillation the frequency-domain analysis is used mostly, however it is unreliable in several cases. This insufficiency led to the demand of using time-domain analysis. Although these attempts seemed to be promising, there have remained several limitations. In our research we developed an enhanced algorithm for time-domain analysis. We defined two indicators which characterized the signals and the reliability of the method well. As compared to the frequency-domain analysis our algorithm can widen the applicability of time-domain analysis since in several cases - when the results of the frequency-domain analysis are unreliable - it can be applied still reliably. As a complementation of the frequency-domain analysis our algorithm can be an extremely helpful tool in medical practice.

Fluctuation enhanced gas detector for wireless sensor networks

Fluctuation enhanced sensing (FES) is a promising method to improve information extraction from noisy sensor signal especially in the rapidly growing field of semiconductor and nanotechnology gas sensors. Some attempts were made to support the application of the principle in low power, battery powered devices and partial results are available. In this paper we present a complete mixed-signal system that contains a low power analog and digital signal processing part as well. Besides theoretical investigations we have carried out measurements and simulations to optimize the performance and achieve high accuracy. Including all components and processing the system needs only 2mA of active supply current working from a 3V battery and a coin cell battery can provide 250 days of operation at sample rate of 6 samples per hour.

Real-Time Demonstration of the Main Characteristics of Chaos in the Motion of a Real Double Pendulum.

Several studies came to the conclusion that chaotic phenomena are worth including in high school and undergraduate education. The double pendulum is one of the simplest systems that is chaotic; therefore, numerical simulations and theoretical studies of it have been given large publicity, and thanks to its spectacular motion, it has become one of the most famous demonstration tools of chaos, either through simulations or in real experiments. Although several attempts have been made to use the experiment in laboratory exercises, as the friction in the real experiment changes the nature of the motion and the values of characteristic parameters during the motion, examining the measured (dissipative) motion and comparing it with theoretical results raises several questions. In our review, we present a measurement system which is able to analyse these questions. The system, which consists of simple yet precise data acquisition electronics, easily attainable sensors, a Bluetooth module (to communicate with the PC) and open-source software, demonstrates on-line the main characteristics of chaos and the methods of its study and allows us to analyse the dissipative motion. Further information (including downloadable software) is provided on a dedicated page, http://www.inf.u-szeged.hu/noise/Research/DoublePendulum/.