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Design of hardware cipher module
Bayer, Tomáš ; Stančík, Peter (referee) ; Sobotka, Jiří (advisor)
This diploma’s thesis discourses the cryptographic systems and ciphers, whose function, usage and practical implementation are analysed. In the first chapter basic cryptographic terms, symmetric and asymetric cryptographic algorithms and are mentioned. Also usage and reliability are analysed. Following chapters mention substitution, transposition, block and stream ciphers, which are elementary for most cryptographic algorithms. There are also mentioned the modes, which the ciphers work in. In the fourth chapter are described the principles of some chosen cryptographic algorithms. The objective is to make clear the essence of the algorithms’ behavior. When describing some more difficult algorithms the block scheme is added. At the end of each algorithm’s description the example of practical usage is written. The chapter no. five discusses the hardware implementation. Hardware and software implementation is compared from the practical point of view. Several design instruments are described and different hardware design programming languages with their progress, advantages and disadvantages are mentioned. Chapter six discourses the hardware implementation design of chosen ciphers. Concretely the design of stream cipher with pseudo-random sequence generator is designed in VHDL and also in Matlab. As the second design was chosen the block cipher GOST, which was designed in VHDL too. Both designs were tested and verified and then the results were summarized.
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Web application for file encryption
Tatar, Martin ; Blažek, Petr (referee) ; Zeman, Václav (advisor)
The bachelor thesis is focused on developing a web application for file encryption. In the theoretical part symmetric encryption algorithms are divided into block ciphers and stream ciphers. Selected ciphers are described and their properties are compared. Then the modes of operation for block ciphers are described. The developed application encrypts both files and text inputs by the selected algorithm and can operate in various modes of operation. In addition to this functionality the application is supplemented with descriptions of available ciphers and modes of operation.
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Key reconstruction from the inner state of RC4
Sladký, Lukáš ; Boháček, Milan (advisor) ; Drápal, Aleš (referee)
In the present work we analyse the key scheduling algorithm of the RC4 stream cipher. The internal permutation generated by the algorithm is biased towards the secret key which can be utilized in the key recovery attempts. Multiple sources were combined to provide proven formulae for these biases. We have completed missing proofs, experimentally verified resulting probabilities and created examples to illustrate usage of the biases in key recovery attempts. This together with methods for extracting information about the secret key gives analysis of the key scheduling algorithm. We have also selected an efficient key retrieval algorithm and implemented an improved version which results in better success probabilities of the key recovery. We have also provided a tool for extracting the key from a permutation obtained by the key scheduling algorithm. Powered by TCPDF (www.tcpdf.org)
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Web application for file encryption
Tatar, Martin ; Blažek, Petr (referee) ; Zeman, Václav (advisor)
The bachelor thesis is focused on developing a web application for file encryption. In the theoretical part symmetric encryption algorithms are divided into block ciphers and stream ciphers. Selected ciphers are described and their properties are compared. Then the modes of operation for block ciphers are described. The developed application encrypts both files and text inputs by the selected algorithm and can operate in various modes of operation. In addition to this functionality the application is supplemented with descriptions of available ciphers and modes of operation.
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Correlation attacks
Mařák, David ; Hojsík, Michal (advisor) ; Holub, Štěpán (referee)
This bachelor thesis decribes Correlation attacks on combination generator type stream ciphers. The reader is briefly acquainted with the basic definitions of cryptographic theory which is necessary to understand the text. Afterwards, the thesis describes the original article that presented this type of attack, and which was the inspiration for further improvements and modifications. These improvements are then described in more details, namely the group called "Fast correlation attacks" which are more efficient and fully replaced the original attack. Finally, the thesis describes some modifications of Fast correlation attacks. 1
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Key reconstruction from the inner state of RC4
Sladký, Lukáš ; Boháček, Milan (advisor) ; Drápal, Aleš (referee)
In the present work we analyse the key scheduling algorithm of the RC4 stream cipher. The internal permutation generated by the algorithm is biased towards the secret key which can be utilized in the key recovery attempts. Multiple sources were combined to provide proven formulae for these biases. We have completed missing proofs, experimentally verified resulting probabilities and created examples to illustrate usage of the biases in key recovery attempts. This together with methods for extracting information about the secret key gives analysis of the key scheduling algorithm. We have also selected an efficient key retrieval algorithm and implemented an improved version which results in better success probabilities of the key recovery. We have also provided a tool for extracting the key from a permutation obtained by the key scheduling algorithm. Powered by TCPDF (www.tcpdf.org)
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A stream cipher based on continued fractions
Krasnayová, Dáša ; Drápal, Aleš (advisor) ; Holub, Štěpán (referee)
This bachelor thesis deals with the theory of continued fractions which is design of a stream cipher in article On the use of continued fractions for stream ciphers based on. Since results about probability for a positive integer number to be a partial quotient of a generalised continued fraction which are necessary for proving the cipher secure, has not been proved yet, there are summarized previous results which could lead to proving them. In particular, basic properties of classical and generalised continued fractions and proof of Kuzmin theorem are presented here. Distribution of probability for a positive integer number to be a partial quotient of a classical continued fraction follows from Kuzmin theorem. The design of the stream cipher from the article is briefly introduced at the end of the thesis. Powered by TCPDF (www.tcpdf.org)
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Correlation attacks
Mařák, David ; Hojsík, Michal (advisor) ; Holub, Štěpán (referee)
This bachelor thesis decribes Correlation attacks on stream ciphers combination generator type. The reader is briefly acquainted with the basic definitions of cryptographic theory which is necessary to understand the text. Afterwards, the thesis describes the original article that presented this type of attack, and which was the inspiration for further improvements and modifications. These improvements are then described in more details, namely the group called "Fast correlation attacks" which are more efficient and fully replaced the original attack. Finally, there are described some modifications of Fast correlation attacks. Powered by TCPDF (www.tcpdf.org)
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Design of hardware cipher module
Bayer, Tomáš ; Stančík, Peter (referee) ; Sobotka, Jiří (advisor)
This diploma’s thesis discourses the cryptographic systems and ciphers, whose function, usage and practical implementation are analysed. In the first chapter basic cryptographic terms, symmetric and asymetric cryptographic algorithms and are mentioned. Also usage and reliability are analysed. Following chapters mention substitution, transposition, block and stream ciphers, which are elementary for most cryptographic algorithms. There are also mentioned the modes, which the ciphers work in. In the fourth chapter are described the principles of some chosen cryptographic algorithms. The objective is to make clear the essence of the algorithms’ behavior. When describing some more difficult algorithms the block scheme is added. At the end of each algorithm’s description the example of practical usage is written. The chapter no. five discusses the hardware implementation. Hardware and software implementation is compared from the practical point of view. Several design instruments are described and different hardware design programming languages with their progress, advantages and disadvantages are mentioned. Chapter six discourses the hardware implementation design of chosen ciphers. Concretely the design of stream cipher with pseudo-random sequence generator is designed in VHDL and also in Matlab. As the second design was chosen the block cipher GOST, which was designed in VHDL too. Both designs were tested and verified and then the results were summarized.
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