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Safe Cryptography Algorithms
Zbránek, Lukáš ; Schäfer, Jiří (referee) ; Chmelař, Petr (advisor)
In this thesis there is description of cryptographic algorithms. Their properties are being compared, weak and strong points and right usage of particular algorithms. The main topics are safeness of algorithms, their bugs and improvements and difficulty of breaching. As a complement to ciphers there are also hash functions taken in consideration. There are also showed the most common methods of cryptanalysis. As a practical application of described algorithms I analyze systems for secure data transfer SSH and SSL/TLS and demonstrate an attack on SSL connection. In conclusion there is recommendation of safe algorithms for further usage and safe parameters of SSH and SSL/TLS connections.
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Security of data stored on the hard disk
Polášková, Markéta ; Hajný, Jan (referee) ; Martinásek, Zdeněk (advisor)
This work is dedicated to the security of data stored on the hard drive of your computer and using encryption. The first part explains the basic concepts of cryptography and describes her in history. In other chapters, this work is dedicated to a description of the side channels and attacks on these channels. How can the attacker obtain information from a cryptographic module. The following section describes the types of encryption they use nowadays and what are their weaknesses. Bachelor thesis continues with examples of individual encryption programs and device ICZ Protect Boot. The last part deals with resistance testing on equipment ICZ Protect Boot. Testing of resistance to flow analysis using a side channel. Finally, bachelor thesis deals with the analysis of communication between the computer and ICZ Protect Boot.
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Side-channel analysis
Novosadová, Tatiana ; Lieskovan, Tomáš (referee) ; Gerlich, Tomáš (advisor)
This thesis deals with an issue of side channels, elliptic curves and their implementation in algorithms. Theoretical part is aimed at describing the basic concepts and various possibilities of side-channel attacks, with a more detailed focus on power analysis. The second theoretical part is focused on describing methods of elliptic curves and different elliptic curves-based protocols. The practical part deals with implementation of such cryptosystem on smart card, using the experimental environment to measure power consumption and analysis of this consumption.
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Web-based application for cryptographic protocols visualization
Ryšavá, Pavla ; Dzurenda, Petr (referee) ; Ricci, Sara (advisor)
Práce se zabývá vytvořením interaktivní webové aplikace pro substituční šifry a jejich interaktivní kryptoanalýzu. V práci je implementováno šest šifer a zástupci monoalfabetických šifer jsou Caesarova šifra, Atbaš a substituce s klíčovým slovem. Dále zástupci polyalfabetických šifer jsou Vigenrova šifra, Kryptos a Vernamova šifra. Pro interaktivní analýzu je použita frekvenční analýza, index koincidence a n-gramová statistika jako fitness funkce. Výsledek byl dosažen za pomoci HTML5, CSS a skriptovacího jazyka ReactJS což je JavaScriptová knihovna s možností typové kontroly proměnných.
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Side channels - preparation of lab task
Holemář, Jan ; Malina, Lukáš (referee) ; Martinásek, Zdeněk (advisor)
This thesis deals with side-channel cryptoanalysis. It is focused on power side-channel attack on cryptographic device. The smart card Gemalto .NET is used as the cryptographic device. This smart card performs encryption through algorithm RSA, DES, AES. The power consumption of the smart card was scanned by a Tektronix CT-6 current probe. Data obtained by measuring were processed on the computer with relevant software and provided important information about the encryption key that was used.
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Demonstration of Cryptographic Problems through an Interactive Educational Game
Fišarová, Anežka ; Mezina, Anzhelika (referee) ; Mikulec, Marek (advisor)
The bachelor thesis is focused on the design and implementation of a cryptographic interactive educational game. It focuses on various cryptographic ciphers specifically selected so that people outside the field can be introduced to the subject in a demonstrative and entertaining way. Java and JavaFX were used as the programming language. The thesis consists of four parts, the first two are oriented towards the theoretical part of cryptography and the second two are more focused on the practical application and code development. As motivation for the players, a score for correctly cracked ciphers was used. Furthermore, the work includes a choice of difficulty, which influences which ciphers will be presented to the players. At the end of the thesis, the author reflects on the results and explores ways to further improve the methods presented.
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Side-channel cryptanalysis using deep learning methods
Matuška, Jakub ; Martinásek, Zdeněk (referee) ; Sikora, Pavel (advisor)
Cryptographic systems are getting unbreakable on paper. Therefore attacks on the implementations using side-channels are getting in front of others. Especially when neural networks (NN) got involved in this field. With deep learning, these attacks can recover secret keys even on implementations with countermeasures. Deep learning assisted sidechannel analysis (DL-SCA) dominated this field over the statistical methods. That is why it is important to understand its concepts. This thesis will showcase these methods and introduce some new tools regarding correlation power analysis (CPA) and the training of NNs. An attack on ASCAD dataset will take place and the proposed NN to conduct this attack will be evaluated against other models using proper metrics. Lastly, improvements to SITM (See-In-The-Middle) attack using deep learning are proposed and implemented in the console application.
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Triangulation algorithm for non-linear equation systems
Väter, Ondřej ; Hojsík, Michal (advisor) ; Šaroch, Jan (referee)
The topic of this thesis is a triangulation algorithm and its use in cryptanalysis. First of all we will define a non-linear equation system on which we can apply triangulation algorithm and we will explain what its output is. Then we will demonstrate its application in cryptanalysis, more specificaly during the attack on the Rinjdael cifer. We will illustrate this attack by a search of collision for our hash function, created for this purpose in Davies-Mayer mode using Rijndael cipher This thesis also contains a practical part in which we will demonstrate the search of collision for our hash function mention before.
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Applications of Gröbner bases in cryptography
Fuchs, Aleš ; Šťovíček, Jan (advisor) ; Žemlička, Jan (referee)
Title: Applications of Gröbner bases in cryptography Author: Aleš Fuchs Department: Department of Algebra Supervisor: Mgr. Jan Št'ovíček Ph.D., Department of Algebra Abstract: In the present paper we study admissible orders and techniques of multivariate polynomial division in the setting of polynomial rings over finite fields. The Gröbner bases of some ideal play a key role here, as they allow to solve the ideal membership problem thanks to their properties. We also explore features of so called reduced Gröbner bases, which are unique for a particular ideal and in some way also minimal. Further we will discuss the main facts about Gröbner bases also in the setting of free algebras over finite fields, where the variables are non-commuting. Contrary to the first case, Gröbner bases can be infinite here, even for some finitely generated two- sided ideals. In the last chapter we introduce an asymmetric cryptosystem Polly Cracker, based on the ideal membership problem in both commutative and noncommutative theory. We analyze some known cryptanalytic methods applied to these systems and in several cases also precautions dealing with them. Finally we summarize these precautions and introduce a blueprint of Polly Cracker reliable construction. Keywords: noncommutative Gröbner bases, Polly Cracker, security,...
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Time-memory tradeoff útoky
Seidlová, Monika ; Hojsík, Michal (advisor) ; Holub, Štěpán (referee)
Martin Hellman proposed the first time-memory tradeoff attack on block ciphers. It is a chosen plaintext attack, in which the attacker precomputes a large amount of data for some block cipher and can then use it repeatedly in attacks on that block cipher. An improvement suggested by Ron Rivest speeds up the attack by reducing the number of memory accesses. Another modification of the original attack called rainbow tables speeds up the attack even more and brings other advantages. Time-memory tradeoff attacks can also be applied to stream ciphers as known plaintext attacks. This bachelor thesis describes in detail the original attack, its improvements and a modification to stream ciphers. As an example, we summarize an attack on A5/1, a stream cipher used in mobile phones. We also propose a new time-memory tradeoff attack on block ciphers called r-coloured rainbows. The new attack is a modification of Hellman's attack and shares similarities with the rainbow table attack. We give a comparison of the properties of the three attacks and conclude that, for certain block ciphers, our attack may be the most effective of the three.
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