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    Wyświetlanie 1-9 z 9
    Tytuł:
    Wykorzystanie funkcji skrótu do poprawy właściwości statystycznych ciągu liczb losowych
    Using a hash function to improve statistical properties of true random number sequences
    Autorzy:
    Matuszewski, Ł.
    Łoza, Sz.
    Jessa, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/152803.pdf
    Data publikacji:
    2014
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    generator liczb prawdziwie losowych
    generator pierścieniowy
    kryptografia
    funkcja skrótu
    losowość i pseudolosowość
    true random number generator
    ring oscillator
    cryptography
    hash function
    randomness and pseudo-randomness
    Opis:
    W pracy przedstawiono sposób wykorzystania funkcji skrótu, na przykładzie funkcji SHA-256 (ang. Secure Hash Algorithm), do poprawy właściwości statystycznych ciągów liczb losowych. W badaniach wykorzystano pakiet testów statystycznych NIST 800-22 do oceny właściwości wytwarzanego ciągu metodę restartów i test chi kwadrat, dzięki którym możliwe jest wykazanie, czy dany generator produkuje ciąg z przeważającymi elementami deterministycznymi czy niedeterministycznymi. Proponowany układ może być z powodzeniem zaimplementowany w każdym układzie FPGA (ang. Field Programmable Gate Array).
    Random sequences play a key role in many contemporary cryptographic systems. To increase the efficiency and robustness to attacks, it is recommended to integrate a source of random numbers with a cryptographic system using these numbers. Unfortunately, the list of non-deterministic physical phenomena available in digital circuits is rather short and practically includes jitter and metastable states. It is expected that the generator produces sequences that pass all known statistical tests and that the sequences are unpredictable and attack resistant. A generator that satisfies these expectations is named a true random number generator (TRNG). This paper presents a novel method for producing random bits with the use of jitter observed in ring oscillators. The method uses a Galois ring oscillator introduced recently and the hash function. To assess the quality of output sequences, the statistical test suite prepared by National Institute of Standards and Technology (NIST) and the restart mechanism were used. The proposed system can be implemented in any Field Programmable Gate Array (FPGA).
    Źródło:
    Pomiary Automatyka Kontrola; 2014, R. 60, nr 7, 7; 456-458
    0032-4140
    Pojawia się w:
    Pomiary Automatyka Kontrola
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Random Number Generator Using Ring Oscillators and SHA-256 as Post-Processing
    Autorzy:
    Łoza, S.
    Matuszewski, Ł.
    Jessa, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/963943.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    random numbers
    cryptography
    ring oscillators
    hash functions
    field programmable gate array (FPGA)
    Opis:
    Today, cryptographic security depends primarily on having strong keys and keeping them secret. The keys should be produced by a reliable and robust to external manipulations generators of random numbers. To hamper different attacks, the generators should be implemented in the same chip as a cryptographic system using random numbers. It forces a designer to create a random number generator purely digitally. Unfortunately, the obtained sequences are biased and do not pass many statistical tests. Therefore an output of the random number generator has to be subjected to a transformation called postprocessing. In this paper the hash function SHA-256 as postprocessing of bits produced by a combined random bit generator using jitter observed in ring oscillators (ROs) is proposed. All components – the random number generator and the SHA-256, are implemented in a single Field Programmable Gate Array (FPGA). We expect that the proposed solution, implemented in the same FPGA together with a cryptographic system, is more attack-resistant owing to many sources of randomness with significantly different nominal frequencies.
    Źródło:
    International Journal of Electronics and Telecommunications; 2015, 61, 2; 199-204
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A random number generator using ring oscillators and the Keccak as post-processing
    Autorzy:
    Łoza, S.
    Matuszewski, Ł.
    Jessa, M.
    Kubczak, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/114620.pdf
    Data publikacji:
    2015
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    true random number generator
    ring oscillator
    cryptography
    field programmable gate array (FPGA)
    hash function
    Opis:
    In cryptography, sequences of numbers with unpredictable elements are often required. Such sequences should pass all known statistical tests for random sequences. Because sequences produced in real circuits are biased, they do not pass many statistical tests, e.g., the distribution of numbers is not uniform. Such random number sequences should be subjected to a transformation called post-processing. In this paper, a true random number generator is considered. It uses ring oscillators and the Keccak hash function as post-processing. This paper presents only simulation conditions for this approach since the post-processing part was done using x86 architecture on a PC.
    Źródło:
    Measurement Automation Monitoring; 2015, 61, 7; 290-292
    2450-2855
    Pojawia się w:
    Measurement Automation Monitoring
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Aplikacje RIA w systemach CMS oraz e-commerce
    RIA applications based on CMS and e-commerce systems
    Autorzy:
    Łoza, M.
    Kowalski, P. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/277300.pdf
    Data publikacji:
    2012
    Wydawca:
    Sieć Badawcza Łukasiewicz - Przemysłowy Instytut Automatyki i Pomiarów
    Tematy:
    RIA
    CMS
    e-commerce
    aplikacje internetowe
    aplikacje wekowe
    PHP
    JavaScript
    internet applications
    web applications
    Opis:
    Aplikacje RIA zyskują popularność w szerokim świecie Internetu. Ich główną zaletą jest bardzo duży stopień przystępności dla użytkownika, przede wszystkim ze względu na eliminację konieczności "przeładunku" strony po dokonaniu pewnych jej modyfikacji. RIA jest idealną technologią do współpracy z środowiskiem CMS. System CMS umożliwia zarządzanie stronami w bardzo łatwy sposób, nawet dla osób z relatywnie małą znajomością języka HTML. Technologia RIA jest wymarzonym rozwiązaniem dla właścicieli małych firm, które nie mogą sobie pozwolić na zatrudnienie dodatkowej osoby tylko do zarządzania stroną internetową. Skomplikowane systemy, takie jak CMS, stają się nawet prostsze niż pisanie strony w zwykłym - klasycznym kodzie HTML. Do głównych celów realizowanych w powyższym systemie można zaliczyć uproszczenie wszystkich skomplikowanych operacji oraz zapewnienie przyjaznego dla użytkownika interfejsu, który "poprowadzi" za rękę użytkowników. System CMS musi być bardzo elastyczny, aby dostosować się do użytkowników. Innym bardzo ważnym aspektem jest bieżące utrzymanie systemu, gdyż każdy błąd zagrażający bezpieczeństwu danych musi zostać wyeliminowany. Dla środowiska rozwijającego oprogramowanie ważnym wątkiem jest również rejestracja wszystkich błędów, tak aby w przyszłości móc go odtworzyć w zależności od kierunku rozwoju oprogramowania.
    RIA applications are gaining popularity over the internet. They are very user friendly because we are eliminating page reloading after making actions. It's ideal technology for making backend for CMS. A CMS system makes managing of website very easy for people with zero HTML skills. It's perfect for owners of small business which can't afford for hire another person, just for managing website. But such complex systems as CMS are very complicated, even if it's simpler than writing website in plain HTML it still may be too hard to understand for people. And it is developer's work to simplify all complex operation, provide user friendly interface which will take users hand and bring him safely to the other side. CMS systems must be also very flexible to adjust themselves to users. We must also remember about keeping system up to date, because every bug which is threaten for data safety must be eliminated. For developer it's also important to log all errors, so in future he or she can recreate the error on develop environment.
    Źródło:
    Pomiary Automatyka Robotyka; 2012, 16, 7-8; 102-106
    1427-9126
    Pojawia się w:
    Pomiary Automatyka Robotyka
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Various designs of the two-stroke engine heads with the valve flushed system
    Autorzy:
    Łoza, Ł.
    Kaźmierczak, A.
    Borkowska, J.
    Skorupa, P.
    Krakowian, K.
    Cienciała, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/242546.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Techniczny Wojsk Lotniczych
    Tematy:
    engine
    two-stroke
    internal combustion
    valve flushed system
    piston-controlled cam
    high petrol consumption
    oil in the petrol
    toxic by-products
    loud noise
    uneven running
    low efficiency
    Opis:
    The two-stroke engines have never acquired the popularity of the four-stroke engines due to their inherent performance limitations. The tasks of many engineering teams were to find the basic causes, which resulted in the inferior performance of these engines. Today’s task is to build a two-stroke engine whose performance could match that of a four-stroke engine in areas of common use. The most typical performance problems of a two-stroke engine are high petrol consumption caused by low efficiency, toxic by-products of combustion being emitted into the atmosphere (caused by oil present in the petrol), and uneven and loud engine noise. The greatest challenge is to achieve a good chamber purge during one stroke in which the fresh fuel mixture flows through the piston-controlled inlet port while at the same time the fumes are being exhausted through the outlet port. This in contrast with the four-stroke engines where the intake and exhaust are each done with two separate strokes. From the energy point of view, the two-stroke engine is not efficient because a certain amount of fresh fuel is being wasted in the exhaust fumes. We propose to replace the piston-controlled cam with the valve-flushed system, which will cause the combustion process to become more efficient. The purpose of this paper is to present various designs of the engine heads and analyse their performance. The goal of this proposal is to choose the best combination of these engine heads in order to achieve the optimum overall engine performance.
    Źródło:
    Journal of KONES; 2015, 22, 4; 187-190
    1231-4005
    2354-0133
    Pojawia się w:
    Journal of KONES
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On the nature of silver ions in complex media
    Autorzy:
    Loza, K.
    Diendorf, J.
    Sengstock, C.
    Koller, M.
    Epple, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/286036.pdf
    Data publikacji:
    2014
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Polskie Towarzystwo Biominerałów
    Tematy:
    silver ions
    biocides
    biomaterials
    Opis:
    Antimicrobial biocides are commonly used to present the growth of bacteria on surfaces and within materials. They are typically added in small quantities to many applications to prevent bacterial growth on the treated object. Silver is increasingly used in many applications due to the aim to replace organic chemical agents by inorganic additives. Examples of applications are bacteriostatic water filters for household use or swimming pool algaecides and numerous devices, ranging from consumer commodities like mobile phones, refrigerators, and clothes to medical devices like catheters, implant surfaces, and plasters. To meet the diversity of application types, many different forms of silver compounds have been developed to serve this market. In particular, there is little information on the types of transformations that silver nanoparticles will undoubtedly undergo in real, complex environments during long-term aging, and the impact of these transformations on their distribution in the environment, bioavailability, and toxicity potential. The biocidal action results from the interaction of silver ions with bacteria. The most potent compounds for a high silver release are soluble silver salts like silver nitrate or silver acetate. These are fully water soluble with a high silver ion release rate. Therefore they are often used as control in cell experiments to elucidate the biological effect of silver nanoparticles. However, in the case of free silver nanoparticles the interactions can be more complex and catalytic reactions on the particle surface which depend on the size and shape of the nanoparticles can render the system very complex. If AgNO3 is used as control, it is tacitly assumed, that the free silver ion concentration is the same as that in the added AgNO3. This obviously cannot be true because of the presence of a whole set of proteins, biomolecules and inorganic ions like Cl- and H2PO4- in the biological medium. These will react with the silver ions in one or the other way. We report on experiments on the behaviour of silver ions in biologically relevant concentrations in different media, from physiological salt solution over phosphate-buffered saline solution to cell culture media. For dissolution and immersion experiments PVP-coated silver nanoparticles were synthesized by reduction with glucose in the presence of PVP. The final silver concentration in all dispersions was determined by atomic absorption spectroscopy. The dissolution of silver nanoparticles was followed in long-term experiments out of a dialysis tube which was permeable only for silver ions. In case of immersion experiments, the nanoparticles and all precipitates were isolated by ultracentrifugation, redispersed in pure water and again subjected to ultracentrifugation. The particles were analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray powder diffraction. The dissolution requires the presence of dissolved oxygen. If no oxygen is present, only a very small fraction of silver is dissolved, possibly by traces of oxygen in the experimental setup. An oxidizing agent like H2O2 clearly enhances the dissolution. The presence of NaCl, either in pure form or as PBS, strongly slows down the dissolution, probably due to silver chloride formation. Cysteine has a clearly inhibiting effect with almost no dissolution of the silver nanoparticles whereas glucose has a decelerating effect but leads to a similar final dissolved fraction. This suggests that cysteine adsorbs onto the silver nanoparticle surface with its thiol group and prevents the oxidation. In contrast, glucose slows down the dissolution, but clearly did not prevent the oxidation on a longer time scale. We have extended the studies by mixing silver nanoparticle dispersions with different media of increasingly biological nature. The solutions/dispersions were stirred for equilibration and then subjected to ultracentrifugation. All precipitates and nanoparticles were isolated by this way and then analyzed. The results show that both initially present silver ions and released silver ions are mainly precipitated as AgCl if chloride is present. Only in the absence of chloride, glucose is able to reduce Ag+ to Ag0. The initially present silver nanoparticles were recovered in all cases. Silver phosphate was not observed in any case, probably due to the moderate pH (around 7) at which phosphate is mostly protonated to hydrogen phosphate and dihydrogen phosphate. We can conclude that released silver ions precipitate mostly as AgCl in biological media, and that most cell culture studies where silver ions are used as control are in fact studying the effect of colloidal silver chloride on the cells. To prove this assumption, human mesenchymal stem cells (hMSC) were cultured in the presence of silver chloride nanoparticles (diameter 120 nm), and the viability of the cells was analyzed by fluorescence microscopy. In general, we clearly observed that pure silver nanoparticles have lower toxicity to hMSC compared to silver chloride nanoparticles with a comparable total silver dose. Silver acetate in the biological medium had a comparable toxicity to hMSC compared to silver chloride nanoparticles with the same total silver dose.
    Źródło:
    Engineering of Biomaterials; 2014, 17, no. 128-129; 80
    1429-7248
    Pojawia się w:
    Engineering of Biomaterials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Digital random bit generators implemented in FPGAs offered by various manufacturers
    Autorzy:
    Kubczak, P.
    Matuszewski, Ł.
    Jessa, M.
    Łoza, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/114475.pdf
    Data publikacji:
    2015
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    true random number generator
    ring oscillator
    cryptography
    field programmable gate array (FPGA)
    Opis:
    In cryptography, we require that a random sequence should have excellent statistical properties as well as non-deterministic character. Combining multiple independent sources of randomness using the modulo two operation, significantly improves the statistical properties of the generated sequences and also affects the accumulation of true randomness generated in the oscillator sources. This is a very promising method of producing random sequences. In this paper, we compare the implementations of the RO-based combined random generator in various FPGAs technologies offered by various manufactures (Xilinx, Altera, Lattice). In this research, we used a NIST 800-22 statistical test suite to assess the statistical properties. The results show that the method of producing strings with a combined generator is the method stable in terms of technology. The results are similar for implementation in all FPGA used in the experiment. So, the proposed generator can be implemented in various programmable structures together with other components of a cryptographic system.
    Źródło:
    Measurement Automation Monitoring; 2015, 61, 7; 293-295
    2450-2855
    Pojawia się w:
    Measurement Automation Monitoring
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The impact of the energy state of the surface of friction pairs on the friction and wear in internal combustion engines
    Autorzy:
    Borkowska, J.
    Kaźmierczak, A.
    Krakowian, K.
    Cienciała, M.
    Skorupa, P.
    Łoza, Ł.
    Powiązania:
    https://bibliotekanauki.pl/articles/245015.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Techniczny Wojsk Lotniczych
    Tematy:
    friction pairs
    top layer of surface
    sealing function
    piston ring
    cylinder sleeve
    combustion engine
    tangential force
    friction coefficient
    molecular structure
    bond
    tribology
    Opis:
    The elements creating a friction pairs are described to be very difficult in terms of defining all optimal parameters in an unequivocal way. The research on stability of friction pairs is focused on the surface and the top layer of surface in the parts concerned. The main goal is to find new design solutions and materials, thereby achieving one million kilometers of mileage to main repair in the case of internal combustion engines. The biggest structural difficulties are noticeable in friction pairs where it can be observed sliding and returning motion, which is also connected with sealing function. A typical example of such pair is piston ring – cylinder sleeve in piston – rings - cylinder unit in an internal combustion engine. Engineers are currently seeking an additional factor, which would enable gaining the reduction of tangential force by reducing the friction coefficient in elements of friction pair during operations. The surface free energy may be such factor - it results from molecular structure and nature of the bonds between the molecules present in the material. Components of surface free energy determine the tribological properties of the material, which is reflected in the stability of the units. Energy state of the surface, which is connected with chemistry and characteristics in the material, is the first step to consider about the impact on wearing in internal combustion engine. This is the main topic of this article.
    Źródło:
    Journal of KONES; 2015, 22, 4; 37-41
    1231-4005
    2354-0133
    Pojawia się w:
    Journal of KONES
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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