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Hash functions - characteristics, implementation and collisions
Karásek, Jan ; Sobotka, Jiří (referee) ; Lambertová, Petra (advisor)
Hash functions belong to elements of modern cryptography. Their task is to transfer the data expected on the entry into a unique bite sequence. Hash functions are used in many application areas, such as message integrity verification, information authentication, and are used in cryptographic protocols, to compare data and other applications. The goal of the master’s thesis is to characterize hash functions to describe their basic characteristics and use. Next task was to focus on one hash function, in particular MD5, and describe it properly. That means, to describe its construction, safety and possible attacks on this function. The last task was to implement this function and collisions. The introductory chapters describe the basic definition of hash function, the properties of the function. The chapters mention the methods preventing collisions and the areas were the hash functions are used. Further chapters are focused on the characteristics of various types of hash functions. These types include basic hash functions built on basic bit operations, perfect hash functions and cryptographic hash functions. After concluding the characteristics of hash functions, I devoted to practical matters. The thesis describes the basic appearance and control of the program and its individual functions which are explained theoretically. The following text describes the function MD5, its construction, safety risks and implementation. The last chapter refers to attacks on hash functions and describes the hash function tunneling method, brute force attack and dictionary attack.
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Vliv aktivních bezpečnostních prvků na dopravu
Chmelíček, Patrik
The bachelor’s thesis deals with influence of active safety features on traffic. It describes their current condition and specifies technological possibilities of the features given the current trends in this branch and presents their use in agricultural machinery. Emphasis is placed mainly on modern assistive systems such as blind spot monitoring, emergency braking etc, lane keeping assistence etc. Second part of the thesis pursues sorting and analysis of the accident rate in Czech republic, European union and giving comparison to a countries from a different parts of the world, such as United states or Kazachstan. This research is followed by potential capability of active safety systems to reduce those accidents. Based on theese data, effectivity of active car safety features given economical aspects in traffic is judged.
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Species-specific and individual predictors of birds' collisions with glass obstacles in the Czech Republic
Semeráková, Anna ; Sedláček, Ondřej (advisor) ; Viktora, Lukáš (referee)
Recent landscape transformation is associated with the emergence of various artificial obstacles that change the natural form of habitats and biocorridors of free-ranging animals. Glass obstacles represent a particular problem due to their transparency and reflectivity. Collisions with glass represent one of the most significant causes of bird mortality worldwide, accounting for over hundreds of millions bird deaths annually. Many authors consider this source of mortality to be completely non-selective. In that case, total collisions mortality would represent a function of population size. However, here I assume that the relationship between collision mortality and population size is more complex and that certain avian ecological groups may be differently susceptible to glass collisions based on their specific ecological characteristics. Long-term records of bird-glass collisions in the Czech Republic were provided by the Czech faunistic databases. These records were compared with the population size of analysed species and with selected ecological and morphological species characteristics. Consistently with the premise, I found out that the greatest amount of collision mortality is explained by the species' population size. However, other species characteristics, such as higher body weight,...
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Bird mortality at transparent barriers
Houdová, Monika ; Reif, Jiří (advisor) ; Koleček, Jaroslav (referee)
Bird mortality at transparent barriers (noise barriers or common house windows) is undoubtedly very important environmental issue, because of the rapid development of human society and even more rapid growth of very dangerous places for birds. At this time there is no review article yet, that would synthesize each sub-study on the extent to which individuals can die on those obstacles, which factors are critical for the ability of obstacle avoiding, how much collision threaten the vitality of bird populations and if we can prevent such unintended damage. This bachelor thesis handle with these questions as a literary review. From the available information we can suggests that the most important factor is migration behavior of birds, individuals migrating through the night are much more at risk than those migrating during the day, mostly because of light pollution, which can confuse them. The most dangerous time of year in this direction is clearly autumn, and that also relates with migration. Population losses caused by collision to the transparent barriers can be up to 20 % of the total population per year. Thesis in addition to a summary of available information on the issue proposes and evaluates possible preventive aplications, which may further serve to effective conservation for birds among...
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Security and usability of standard has hfunctions, in particular MD-5, SHA-1 and SHA-2
Galaczová, Barbora ; Tůma, Jiří (advisor) ; Joščák, Daniel (referee)
Title: Security and usability of standard hash functions, in particular MD-5, SHA-1 and SHA-2 Author: Galaczová Barbora Department: Department of Algebra Supervisor: Doc. RNDr. Tůma Jiří, DrSc., Department of Algebra Consultant: Ing. Budiš Petr, Ph.D. Abstract: In the present work we try to digestedly describe standard hash functions, in particular MD-5, SHA-1 and SHA-2. We describe resume of existing attacks on these hash functions. We closely focused on MD-5 collision attacks, because the other hash function collision attacks result from these. Next we describe posibilities of practical usage of hash function collisions, in particular into the qualified certificates area and possible threats. At the end to the present work we describe new hash functions, which could replace current hash functions. This work also contains software to calculate MD-5 hash and search it`s collisions. The software is based on method invented by Czech cryptoanalytist Vlastimil Klíma. Keywords: hash function, collision, qualified certificate, security.
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Properties of near-horizon geometry of spacetimes
Daněk, Jiří ; Žofka, Martin (advisor) ; Svítek, Otakar (referee)
Nowadays, the near-horizon regions of black holes have enjoyed great attention thanks to their role in the popular AdS/CFT correspondence and their specific geometry suitable for formulations of uniqueness theorems in higher dimensions. A strictly general-relativistic point of view reveals also many interesting phenomena taking place near black-hole horizons. Our aim was to investigate how horizon multiplicity affects near-horizon geometry, geodesical distance, radial motion of photons and massive, charged particles, and also the possibility of collision processes leading to unbound collision energies near the horizon. We chose the Reissner-Nordström-de Sitter metric, which, on the one hand, is simple thanks to being static and spherically symmetric but which, on the other hand, is rich enough to enable the existence of up to a doubly degenerate ultra-extreme horizon. After discussing the physical feasibility of the near-horizon limit, we applied it to single, double, and triple horizons, their near-horizon geometries, and local collision processes. We found continuous coordinate systems covering all types of horizons and analytic solutions for motion of radial photons and special or critical, massive, charged particles in their vicinity. We addressed particle collisions in the immediate vicinity of horizons...
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Ecological and ethological aspects of bird-building collisions
Semeráková, Anna ; Sedláček, Ondřej (advisor) ; Koleček, Jaroslav (referee)
Collisions with artificial structures represent one of the most significant cause of bird mortality worldwide. Accounting for hundreds of millions bird deaths each year, bird-building collisions represent a particular problem. Although the bird's vision system is perfectly adapted to the orientation during fast flight, birds are often confused due to the transparency or reflectivity of the glass. Moreover, light pollution of urban areas interferes with the physiological geomagnetic and polarized light compass in birds, which causes the night migrants to disorient. The bird-building collision frequency variates in time and space. Throughout the day, largest number of fatal collisions occurs during early morning. Throughout the year, the peak in the numbers of fatal strikes appears in the course of autumn migration. Local species abundance did not appear to be the most important predictor of collision probability. Species traits making birds highly prone to collisions are small body size, high flight speed, long distance of migration and feeding strategy requiring rare and temporary food sources. Aggressive males during the mating period and inexperienced post-fledging juveniles are among the most vulnerable individuals. Based on taxon-specific ecological traits, some bird families were identified to...
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Predictive software for Earth collision with Near Eartch Objects
Stopka, Jiří ; Daněk, Vladimír (referee) ; Bartoněk, Jaroslav (advisor)
Aim of this bachelor’s thesis is to research and discuss the basics of orbital mechanics and their application on a real problem. The application of orbital mechanics is made by creating a software for predicting Earth’s collision with Near-Earth Objects in Borland Delphi 7 development enviroment. The created software should be able to predict close approaches of Earth and Near-Earth Objects in a time scale selected by user and issue a warning in case of a dangerous close approach.
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Better Chaperone Bounds Using 3D Sensors
Tinka, Jan ; Beran, Vítězslav (referee) ; Najman, Pavel (advisor)
Room-scale tracking encourages users to move more freely and even walk. Even though there has been much research on making the limited physical workspace feel larger in the VR, these approaches have their limitations and require certain conditions to be met. This thesis proposes an alternative approach to the conventional play-area boundaries of high-end VR products such as the HTC Vive and Oculus Rift which are set by the user in a 2-D fashion as a means of enhance workspace utilization. A 3-D scanner is used to make a 3-D point-cloud model of the play area's surroundings. This model is then used to detect collisions and provide feedback to the user. Evaluation based on user tests showed that this approach can be useful, is well accepted by users and might be worth further research.
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