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Methods of steganography
Obdržálková, Karolína ; Blažek, Petr (referee) ; Člupek, Vlastimil (advisor)
This bachelor thesis deals with steganography, its types and methods. Steganography is generally described in this work. A significant part of this thesis is devoted to the development of steganography and also describes how is steganography used for malware and copyright protection. The next part describes the types of steganography according to the type of carrier, their methods and properties of steganographic methods. Based on theoretical knowledge, an application with a graphical user interface was created to hide and reveal secret information using steganographic method LSB. This application is described in the final part together with the evaluation of security of hidden information.
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Sensitivity analysis of different forms of state observers
Kadlec, Milan ; Findura, Milan (referee) ; Vavřín, Petr (advisor)
This master thesis is focused on the sensitivity analysis of selected kinds of state reconstructors. They are realized in a general form, via direct and parallel programing. Quantity that determines the quality of sensitivity is output signal difference of the reconstructor with the general form of the system. Testing will be based on different initial state conditions and on the parameters change of the feedback A matrix due to the rested reconstructors.
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Improving Robustness of Speaker Recognition using Discriminative Techniques
Novotný, Ondřej ; Ferrer, Luciana (referee) ; Pollák, Petr (referee) ; Černocký, Jan (advisor)
Tato práce pojednává o využití diskriminativních technik v oblasti rozpoznávání mluvčích za účelem získání větší robustnosti těchto systémů vůči vlivům negativně ovlivňující jejich výkonnost. Mezi tyto vlivy řadíme šum, reverberaci nebo přenosový kanál. Práce je rozdělena do dvou hlavních částí. V první části se věnujeme teoretickému úvodu do problematiky rozpoznávání mluvčích. Popsány jsou jednotlivé kroky rozpoznávacího systému od extrakce akustických příznaků, extrakce vektorových reprezentací nahrávek, až po tvorbu finálního rozpoznávacího skóre. Zvláštní důraz je věnován technikám extrakce vektorové reprezentace nahrávky, kdy popisujeme dvě rozdílná paradigmata možného přístupu, i-vektory a x-vektory. Druhá část práce se již více věnuje diskriminativním technikám pro zvýšení robustnosti. Techniky jsou organizovány tak, aby odpovídaly postupnému průchodu nahrávky rozpoznávacím systémem. Nejdříve je věnována pozornost předzpracování signálu pomocí neuronové sítě pro odšumění a obohacení signálu řeči jako univerzální technice, která je nezávislá na následně použitém rozpoznávacím systému. Dále se zameřujeme na využití diskriminativního přístupu při extrakci příznaků a extrakci vektorových reprezentací nahrávek. Práce rovněž pokrývá přechod od generativního paradigmatu k plně diskriminativnímu přístupu v systémech pro rozpoznávání mluvčích. Veškeré techniky jsou následně vždy experimentálně ověřeny a zhodnocen jejich přínos. V práci je navrženo několik přístupů, které se osvědčily jak u generativního přístupu v podobě i-vektorů, tak i u diskriminativních x-vektorů, a díky nim bylo dosaženo významného zlepšení. Pro úplnost jsou, v oblasti problematiky robustnosti, do práce zařazeny i další techniky, jako je normalizace skóre, či více-scénářové trénování systémů. Závěrem se práce zabývá problematikou robustnosti diskriminativních systému z pohledu dat využitých při jejich trénování.
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A Tool for Robustness Testing of Web-Services
Zelinka, Tomáš ; Očenášek, Pavel (referee) ; Rychlý, Marek (advisor)
This project deals with testing of web services. The result of this work will be a tool for load testing of web services using fault injection in their communication. The first part of the project discusses the basic aspects of testing web services. The second part of the work is more focused on testing high loads in combination with fault injection. The tool will allow automated run of the tests. The distributed model of the tool was designed to simulate real loads. In the last chapter are summarized achieved results.
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Digital Image Steganography
Kolarčík, Tomáš ; Šimek, Václav (referee) ; Strnadel, Josef (advisor)
This bachelor thesis deals with digital image steganography and implements some of the available methods. This thesis describes steganography on a general level, it's history and it's current form. It also shows it's classification according to the type of carrier, the classification of the methods according to the style of hiding data and the influence of the hidden information. The primary subject of this thesis is image steganography, where facts that allow imperceptibly hide data inside image are described. A great part of this thesis is dedicated to the characteristics of the methods, which we observe and to the methods themselves. All of the methods described are implemented in a graphical and console application. The created application provides multiple image formats for hiding. In the last part, testing is performed in terms of capacity, imperceptibility and robustness.
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Digital Image Steganography
Mazánek, Antonín ; Šimek, Václav (referee) ; Strnadel, Josef (advisor)
This bachelor's thesis introduces the steganography scientific discipline. It presents its ancient and relative recent history, mentions its current use and outlines the possible directions for steganography future. It introduces steganography into context of hiding information superior domain and highlights differences between other methods in this domain. It describes steganography subdivisions and closer deals with digital image steganography. It presents some known methods and types of digital image data. The thesis also contains more detailed description of image data in PNG format. It describes the implementation of LSB and PVD steganography methods with images in PNG format as cover object and evaluates their key properties, namely: imperceptibility, capacity and robustness. At the end of the thesis, the author's reflection on the results and possibilities of further modifications of the mentioned methods is given.
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Identification of AC induction motor parameters
Křížek, Tomáš ; Václavek, Pavel (referee) ; Blaha, Petr (advisor)
This thesis describes and realizes (in program Matlab/Simulink and in the microcontroller Freescale 56F8346) one off-line identification method of AC Induction motor parameters which are necessary to implement the field-oriented control strategy. The identification metod identify leakage inductance, magnetizing inductance and secondary time constants. The presented method is evaluted, advantages and disadvantages of this method are evaluated with reference to their possible use in real-machine. The experimental results and schemes which are presented demonstrate the feasibility methods. The thesis is dividend in seven chapters. Second chapter describes the basic principle and model AC induction motor. Third chapter generally describes identification methods. Fourth, fifth and sixth chapters deal with method which is based on a previous work of the authors [4] and [5].
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Image watermarking
Štágl, Luboš ; Zezula, Radek (referee) ; Číka, Petr (advisor)
This diploma thesis is concerned in static pictures Security problems. That means, additional informations (watermark) are embedded to the original picture in a specific way. This complex picture structure (watermark) should be unremoval by different attacks runing processes. The main goal of this diploma thesis is realize two separated methods digital data watermarking in MATLAB program. For reason of a quite large scale of different watermarking methods are chosen at this time only two of take were choosen. First of the methods is Watermark injection in the spatial domain and the second in the freuquency domain. Both methods are set up in a special way and finish goals of the process. Expected result are, that digital picture user doesn't know about the watermarking technique was aplied on this picture and the watermarking data are the most resistant as possible as can be. These attacks were simulated in Checkmark program.
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