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Implementation and testing of MD5 hash algorithm
Legéň, Michal ; Kacálek, Jan (referee) ; Malý, Jan (advisor)
Hash functions are one of basic structural components of modern cryptography. Their task is to create unique bit order for entry information called message digests. This way the inevitable integrity of information is secured because data transferring via different transfer media may be altered during the transfer. They provide a possibility of fast and effective encryption of passwords because of one-way as well. The aim of this bachelor’s thesis is to analyse one of the most well-known hash functions MD5, to implement it in programming language, to analyse its security risks and to try to use practical exhibitions to the benefit of an attacker. The bachelor’s thesis is presenting theoretical and practical part on Implementation and testing of MD5 hash algorithm. The introduction of the work is devoted to the basics of cryptography, to explanation of the concept of hash function and its basic attributes. The chapter 3 is focussed on the analysis of algorithm MD5 itself. The following part describes its implementation in programming language C++. The last two parts are about problems of security and weak sides of hash algorithm MD5. On the basic of existance of first order collisions, there is in practical demonstration presented creating two different programmes with the same message digest. The final part belongs to description of implementations of attacks on one-way algorithm MD5 and comparisons of their time possibilities during getting original information on the basis of their message digests.
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Invisible watermarking method for images
Trbušek, Pavel ; Říha, Kamil (referee) ; Malý, Jan (advisor)
Bachelor´s thesis deals with embedding of invisible watermark into image. The methods used for reach the main objective of this thesis are given in the first part. I mention three methods: Discrete Cosine Transform method, Discrete Wavelet Transform method and Set Partitioning in Hierarchical Trees method. In the second part I describe implementation of Discrete Wavelet Transform method and Set Partitioning in Hierarchical Trees method in MATLAB setting. The last part deals with the test of the watermark endurance to geometrical attacks. I summarize the results of the watermark endurance test are very satisfactory even by the disruption of the image quality.
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Decentralized communication tool with anonymity guarantee
Legéň, Michal ; Burget, Radim (referee) ; Malý, Jan (advisor)
Anonymity on the internet is becoming a actuall issue nowadays. There are several tools, that can be used to monitor user's activity and it can lead to lose privacy of users. The aim of this master's thesis is to describe different ways of working anonymous systems, especially the method called Onion Routing. The introduction of this work is devoted to the description of this method together with asymmetric cryptosystem RSA. The second part belongs to basics of socket programming and to the implementation of anonymous system in programming language C++. The final part is focussed on analysis of system in terms of security and time complexity. The conditions of anonymity and decentralization are accomplished. There is no presence of central server in the system and the management is handled by signalling messages.
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Implemetation of algorithms for blind source separation in C/C++ language
Funderák, Marcel ; Malý, Jan (referee) ; Míča, Ivan (advisor)
This thesis is describing one of the methods of Blind Source Separation (BSS) which is Independent Component Analysis. There is shown some brief introduction to the theory behind in which there are explained some basic findings. These findings are important for understanding the theory behind algorithms of ICA. These theoretical findings include primarily explanations of basic knowledge of statistics science. In next part there are described methods which are advisable for preprocessing of input signals – mainly Principal Component Analysis (PCA) and whitening of signals. Mainly whitening is very important part of solution of ICA algorithms. Then there are described different ICA algorithm solutions and especially introduction in this problematic. FastICA algorithm description is mainly depicted because it is very good for computer processing since it is strong and it is less computer demanding than other algorithms. After that follows implementation of one of the ICA algorithm in C++ programming language. FastICA algorithm for complex valued signal was chosen.
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Modern computer viruses
Malina, Lukáš ; Malý, Jan (referee) ; Pust, Radim (advisor)
Bachelor’s thesis “Modern computer’s viruses” is composed from two mainly object (analysis computer’s viruses and suggestion of security middle computer network), separated for three parts: Analysis computer’s viruses, Personal suggestion of security personal computer end-user (computer terminal) and Personal suggestion of security middle computer network. Methods of transmission and infection, specific properties of viruses and impact upon personal computers are examined in the first part. Resolution of personal suggestion of security personal computer with help of antivirus software, personal firewall and antispam software is inducted in the second part. Futher, results of testing some free AV software and other security software are summarized with possible progress of configuration and recommendation for correct running this software. Complex suggestion of security middle computer network is adduced in the third part, where is inducted structure of security network. Configuration progression and recommendation for maximum security is indicated on particular used components. Structure is adapted for active network Cisco components, which are most used around these days. Completely suggestion of security network is directed on hardware firewall Cisco PIX, where is unfolded potential possibility of options. Futher, the third part contain some important tips and recommendation for completely working network, including setting security preference, security passwords and data encryption. Also, there is described various techniques monitoring and supervision working security network using complex monitoring software MARS (Cisco security monitoring, analyzing and response system) from Cisco company.
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Systems for checing electronic texts
Zouhar, Petr ; Malý, Jan (referee) ; Pfeifer, Václav (advisor)
The work deals with the possibility of control of electronic texts. Whether it is a source codes or standard text documents. The first chapter is devoted to a brief explanation of the term plagiarism and its characters. Sequentially we describe the methods and metrics used to detect plagiarist. Then we pay attention to detect plagiarism in the free text and source codes. We describe the way of preprocessing of a file and choice of basic units, which represent the document in the comparing. Source codes have a exact syntax. Therefore we attend to the syntax and semantic analysis in the chapter, which describes the check of source codes. The second half of the work is focused on the practical part, particularly on programs intended to control the source codes. The programs are divided to the freely available and the commercial. This is followed by their brief description and if it is a free trial possible we mention the results from this comparing. So we created a corpus of source codes. At the end of the work we focus on design of a program, which compares two source codes on the basis of statistical similarities.
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Advanced objective measurement criteria applied to image compression
Šimek, Josef ; Průša, Zdeněk (referee) ; Malý, Jan (advisor)
This diploma thesis deals with the problem of using an objective quality assessment methods in image data compression. Lossy compression always introduces some kind of distortion into the processed data causing degradation in the quality of the image. The intensity of this distortion can be measured using subjective or objective methods. To be able to optimize compression algorithms the objective criteria are used. In this work the SSIM index as a useful tool for describing the quality of compressed images has been presented. Lossy compression scheme is realized using the wavelet transform and SPIHT algorithm. The modification of this algorithm using partitioning of the wavelet coefficients into the separate tree-preserving blocks followed by independent coding, which is especially suitable for parallel processing, was implemented. For the given compression ratio the traditional problem is being solved – how to allocate available bits among the spatial blocks to achieve the highest possible image quality. The possible approaches to achieve this solution were discussed. As a result, some methods for bit allocation based on MSSIM index were proposed. To test the effectivity of these methods the MATLAB environment was used.
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Web applications with respect to accessibility
Kříž, Tomáš ; Malý, Jan (referee) ; Morávek, Patrik (advisor)
This master’s thesis deals with problems of the web applications with respect to accessibility. At first it describes accessibility of the web pages. There are mentioned main reasons and initiatives for making accessible web pages. The first chapter is also aims to handicapped users. The handicapped users are separated to groups according to their handicap and impacts on accessibility of the web pages. The second chapter presents methodics of the accessible website, Czech and foreign rules and lawful orders. The foreign (WCAG, Section 508) and the Czech (Blind Friendly Web and Pravidla pro tvorbu přístupného webu) representatives of the rules are introduced in the next part of this chapter. The idea of the accessible web application – electronic shop - is presented in the third chapter. There are subscribed the conception of electronic shop, advantages and disadvantages and main functions. In the next part of this chapter there are mentioned the primary rules of the writing the source code of the web pages which are used during the creating of the accessible web application of the electronic shop. Closely there are introduced scripting language PHP, database system MySQL and Cascading Styles Sheets (CSS). The part of the master’s thesis is a mentioned accessible web application of the electronic shop. The presentation is placed on http://www.xandy.cz/tmp/ and presents the accessible web system with the respect to accessibility. Creation and description of this web application is mentioned in the last fourth chapter.
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Design of exercises for data mining - Classification and prediction
Martiník, Jan ; Malý, Jan (referee) ; Burget, Radim (advisor)
My master's thesis on the topic of "Design of exercises for data mining - Classification and prediction" deals with the most frequently used methods classification and prediction. There are association rules, Bayesian classification, genetic algorithms, the nearest method neighbor, neural network and decision trees on the classification. There are linear and non-linear prediction on the prediction. This work also contains a summary of detail the issue of decision trees and a detailed algorithm for creating the decision tree, including development of individual diagrams. The proposed algorithm for creating the decision tree is tested through two tests of data dowloaded from Internet. The results are mutually compared and described differences between the two implementations. The work is written in a way that would provide the reader with a notion of the individual methods and techniques for data mining, their advantages, disadvantages and some of the issues that directly relate to this topic.
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