Paweł Kubczak

2023

1. Paweł Kubczak, Mieczysław Jessa, Michał Kasznia,
   Fast Synchronization Algorithm of High-Stability Oscillators to GNSS Signals,
   2023 Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium, EFTF/IFCS 2023, 15-19.05.2023, Toyama, Japan, Japan, 2023, pp. 1-4,
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2021

2. Paweł Kubczak, Wiktor Woźniak, Jakub Nikonowicz, Łukasz Matuszewski, Mieczysław Jessa,
   An Online Platform for Testing and Evaluating Random Number Generators,
   29th International Conference on Software, Telecommunications and Computer Networks, IEEE, Split, Hvar, Croatia, 23-25 Sept. 2021,
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   Abstract
   

   This article introduces a new online platform for testing binary random number generators. The growing share of low-complex devices in IoT networks increases the demand for basic authorization and authentication tools, the critical block of which is a secure random number generator. Communication devices, therefore, require designers to carry out time-consuming tests and acquire specialist knowledge of statistical testing in evaluation of their results. To meet the current requirements, we have created a test platform to assess the quality of random strings produced by the generator. The presented solution, based on the proprietary evaluation metric, provides feedback on the properties of the uploaded random sequences. Clear interface provides ease of use and by machine learning in the platform’s backend, along with the increase of processed data, the improved quality of the interpretation delivered by the system is ensured. The operation of the platform has been confirmed experimentally, based on the analysis of hardware generators producing random strings with known properties.

3. Łukasz Matuszewski, Jakub Nikonowicz, Paweł Kubczak, Wiktor Woźniak,
   Physical Unclonable Function Based on the Internal State Transitions of a Fibonacci Ring Oscillator,
   Sensors, Vol. 21, No. 11, 2021, pp. 3920/1-3920/13,
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   Abstract
   

   This article introduces a new class of physical unclonable functions (PUFs) based on the Fibonacci ring oscillator (FIRO). The research conducted here proves that before reaching the desired randomness, the oscillator shows a certain degree of repeatability and uniqueness in the initial sequence of internal state transitions. The use of an FIRO in conjunction with the restart method makes it possible to obtain a set of short boot sequences, which are processed with an innovative feature extraction algorithm that enables reliable device identification. This approach ensures the reuse of the existing random number generator (RNG), rather than multiplying ring oscillators in a dedicated structure. Moreover, the algorithm for the recovery of the device key from the boot set can be successfully implemented in the authorizing center, thus significantly releasing the resources of authorized low-complexity devices. The proposed methodology provides an easily obtainable key with identifiability, which was proven experimentally on FPGAs from different manufacturers.

4. Jakub Nikonowicz, Łukasz Matuszewski, Paweł Kubczak,
   Sequence Alignment Algorithm for Statistical Similarity Assessment,
   IEEE Access, Vol. 9, 2021, pp. 102153-102160,
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   Abstract
   

   This paper presents a new approach to statistical similarity assessment based on sequence alignment. The algorithm performs mutual matching of two random sequences by successively searching for common elements and by applying sequence breaks to matchless elements in the function of exponential cost. As a result, sequences varying significantly generate a high-cost alignment, while for low-cost sequences the introduced interruptions allow inferring the nature of sequences dependence. The most important advantage of the algorithm is an easy interpretation of the obtained results based on two parameters: stretch ratio and stretch cost. The operation of the method has been simulation tested and verified with the use of real data obtained from hardware random number generators. The proposed solution ensures simple implementation enabling the integration of hardware solutions, and operation based on only two sequences of any length predisposes the method to online testing.

2019

5. Paweł Kubczak, Jakub Nikonowicz, Łukasz Matuszewski,
   Kalman Filter Design for Fast Synchronization of a High-Stability Rubidium Oscillator,
   2019 Signal Processing: Algorithms, Architectures, Arrangements, and Applications (SPA), IEEE, Poznan, Poland, 18-20 Sept. 2019,
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   Abstract
   

   The article briefly describes the methodology of designing a Kalman filter that it is used in the phase lock loop (PLL). At the beginning the tools and the experimental environment are discussed, especially the structure of the synchronization loop. First, the characteristic of the 1PPS GNSS reference signal is obtained using superposition by gathering data when the oscillator is locked to GPS. This data is used to calculate a covariance matrix of the measurement noise for the Kalman filter. Next, a signal without noise from a very stable frequency source is applied as a reference signal, and the identification experiment of the oscillator is executed. Based on the identification data, one, two-, three- and four-dimensional space-state models of the rubidium clock are created and the process noise covariance matrix for the Kalman filter is calculated. At the end, the quality of Kalman filter tracking is examined. For this purpose, MSE between the real behavior of the phase and the estimation provided by the filter is calculated. Finally, the optimal dimensionality of the model is discussed. It is also shown how much the estimations of the phase prediction in Kalman filter can be trusted and how to adjust the process noise covariance matrix properly.

2018

6. Jakub Nikonowicz, Paweł Kubczak, Łukasz Matuszewski,
   Impact of the Decision Function on the Overall Performance of an Energy- and Entropy-Based Hybrid Detector,
   International Conference on Signals and Electronic Systems (ICSES 2018), IEEE, Krakow, Poland, 10-12 Sept. 2018, pp. 114-117,
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   Abstract
   

   The basic challenge in weak signal detection is not only to bring the signal to a useful form, but also to determine its presence in the surrounding background noise. One of the well-known and most commonly used methods is energy detection, extended in the following years to compound, hybrid solutions. In this article, the authors have shown that the improvement of detection can be achieved not only by extending already complex algorithms by additional processing branches, but simply by choosing a better decision criterion. For this purpose, the authors have defined a simulation model, which uses machine learning to redefine previously adopted decision thresholds and improve detection efficiency. The presented simulation results show significant improvement in detector performance in comparison with the classical approach.

7. Paweł Kubczak, Michał Kasznia, Mieczysław Jessa,
   Preprocessing for fast synchronization of high-stability oscillators disciplined by GNSS 1 PPS signal,
   2018 European Frequency and Time Forum (EFTF), IEEE, Turin, Italy, 10-12 April 2018, pp. 234-239,
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   Abstract
   

   This paper presents a novel algorithm for preprocessing of pulses coming from GNSS and signals produced locally by a rubidium oscillator to reduce synchronization time without changing the main algorithm of the control loop. Moving average and Kalman filtration were used as the preprocessing methods. The experimental results for different rubidium oscillators are presented.

2016

8. Jakub Nikonowicz, Paweł Kubczak, Łukasz Matuszewski,
   Hybrid detection based on energy and entropy analysis as a novel approach for spectrum sensing,
   International Conference on Signals and Electronic Systems (ICSES 2016), IEEE, Krakow, Poland, 5-7 Sept. 2016, pp. 206-211,
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   Abstract
   

   Detection of weak signals has become the study of particular importance as a consequence of the ongoing technology development in many different fields such as more efficient radio communication or reaching further exploration in astrophysics. Its main task still remains spectrum sensing, which is detecting the weak signals hidden in the noise. Among the well-known methods most commonly used remains energy detection, extended in the following years to double thresholding or cooperative sensing by multiple receivers. The authors of the article propose the innovative hybrid detection, where cooperation is realized on the basis of two independent methods within a single receiver. In the studied case of detection, the energy associated with equally simple analysis of entropy allows to improve the detection results in a changing radio environment. Reasonability of the proposed approach is confirmed by the results achieved in experimental detection system.