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Aplikace teorie formálních jazyků v oblasti počítačové bezpečnosti
Regéciová, Dominika ; Kolář, Dušan (oponent) ; Meduna, Alexandr (vedoucí práce)
Počítačová bezpečnost je a vždy bude kritickou oblastí, která ovlivňuje každého z nás. Přes veškeré úsilí vynaložené na tvorbu bezpečnějších systémů a jejich testování se však stále objevují nové chyby a zranitelnosti budící dojem boje s větrnými mlýny. Částečné odůvodnění současného stavu, ale i možná řešení, přináší v mnoha ohledech výjimečný pohled na bezpečnost skrze teorií formálních jazyků. Důraz by podle něj měl být kladen především na odpovědnější přístup k rozpoznávání a zpracování vstupů, které jsou často vstupní branou mnoha útokům. V této práci se blíže seznámíme s tímto směrem a jeho doporučeními pro vývoj a následně si představíme novou metodu detekce SQL injection útoků postavené na jeho základech.
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New Parallel and Regulated Automata and Grammars
Kučera, Jiří ; Průša, Daniel (oponent) ; Sawa, Zdeněk (oponent) ; Meduna, Alexandr (vedoucí práce)
This thesis introduces and studies four new language models with focus on regulation and parallelism in automata and grammars. First, state-synchronized automata systems , present systems consisting of a finite number of pushdown automata controlled by words of a control language over a set of states. Second, unlimited deep pushdown automata , are a modification of deep pushdown automata with no restrictions imposed on the depth of expansion on the pushdown. Third, jumping pure grammars , introduces jumping grammars with no nonterminal symbols. The last one, k#$-rewriting systems , extends #-rewriting systems with additional pushdown memory. The contents of this thesis are divided into three parts. The first part outlines the motivation for introduction of the studied language models and puts them into the context of related formal language theory areas. Furthermore, it gives an overview of the structure of the thesis, reviews fundamental notions of formal language theory and gives a survey of current knowledge related to the subject of research. The second part presents the core of this thesis. Here, formal definitions of all newly introduced language models are given and their expressive power is studied. Finally, this thesis is concluded with a summary of achieved theoretical results as well as related open problem areas, and an outline of the possibilities for further research along with a sketch of possible applications.
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One-Sided Random Context Grammars
Zemek, Petr ; Černá, Ivana (oponent) ; Doc. In.g Petr Sosík, Dr. (oponent) ; Meduna, Alexandr (vedoucí práce)
This thesis introduces the notion of a one-sided random context grammar as a context-free-based regulated grammar, in which a set of permitting symbols and a set of forbidding symbols are attached to every rule, and its set of rules is divided into the set of left random context rules and the set of right random context rules . A left random context rule can rewrite a nonterminal if each of its permitting symbols occurs to the left of the rewritten symbol in the current sentential form while each of its forbidding symbols does not occur there. A right random context rule is applied analogically except that the symbols are examined to the right of the rewritten symbol. The thesis is divided into three parts. The first part gives a motivation behind introducing one-sided random context grammars and places all the covered material into the scientific context. Then, it gives an overview of formal language theory and some of its lesser-known areas that are needed to fully grasp some of the upcoming topics. The second part forms the heart of the thesis. It formally defines one-sided random context grammars and studies them from many points of view. Generative power, relations to other types of grammars, reduction, normal forms, leftmost derivations, generalized and parsing-related versions all belong between the studied topics. The final part of this thesis closes its discussion by adding remarks regarding its coverage. More specifically, these remarks concern application perspectives, bibliography, and open problem areas.
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New Parallel and Regulated Automata and Grammars
Kučera, Jiří ; Průša, Daniel (oponent) ; Sawa, Zdeněk (oponent) ; Meduna, Alexandr (vedoucí práce)
This thesis introduces and studies four new language models with focus on regulation and parallelism in automata and grammars. First, state-synchronized automata systems , present systems consisting of a finite number of pushdown automata controlled by words of a control language over a set of states. Second, unlimited deep pushdown automata , are a modification of deep pushdown automata with no restrictions imposed on the depth of expansion on the pushdown. Third, jumping pure grammars , introduces jumping grammars with no nonterminal symbols. The last one, k#$-rewriting systems , extends #-rewriting systems with additional pushdown memory. The contents of this thesis are divided into three parts. The first part outlines the motivation for introduction of the studied language models and puts them into the context of related formal language theory areas. Furthermore, it gives an overview of the structure of the thesis, reviews fundamental notions of formal language theory and gives a survey of current knowledge related to the subject of research. The second part presents the core of this thesis. Here, formal definitions of all newly introduced language models are given and their expressive power is studied. Finally, this thesis is concluded with a summary of achieved theoretical results as well as related open problem areas, and an outline of the possibilities for further research along with a sketch of possible applications.
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Aplikace teorie formálních jazyků v oblasti počítačové bezpečnosti
Regéciová, Dominika ; Kolář, Dušan (oponent) ; Meduna, Alexandr (vedoucí práce)
Počítačová bezpečnost je a vždy bude kritickou oblastí, která ovlivňuje každého z nás. Přes veškeré úsilí vynaložené na tvorbu bezpečnějších systémů a jejich testování se však stále objevují nové chyby a zranitelnosti budící dojem boje s větrnými mlýny. Částečné odůvodnění současného stavu, ale i možná řešení, přináší v mnoha ohledech výjimečný pohled na bezpečnost skrze teorií formálních jazyků. Důraz by podle něj měl být kladen především na odpovědnější přístup k rozpoznávání a zpracování vstupů, které jsou často vstupní branou mnoha útokům. V této práci se blíže seznámíme s tímto směrem a jeho doporučeními pro vývoj a následně si představíme novou metodu detekce SQL injection útoků postavené na jeho základech.
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One-Sided Random Context Grammars
Zemek, Petr ; Černá, Ivana (oponent) ; Doc. In.g Petr Sosík, Dr. (oponent) ; Meduna, Alexandr (vedoucí práce)
This thesis introduces the notion of a one-sided random context grammar as a context-free-based regulated grammar, in which a set of permitting symbols and a set of forbidding symbols are attached to every rule, and its set of rules is divided into the set of left random context rules and the set of right random context rules . A left random context rule can rewrite a nonterminal if each of its permitting symbols occurs to the left of the rewritten symbol in the current sentential form while each of its forbidding symbols does not occur there. A right random context rule is applied analogically except that the symbols are examined to the right of the rewritten symbol. The thesis is divided into three parts. The first part gives a motivation behind introducing one-sided random context grammars and places all the covered material into the scientific context. Then, it gives an overview of formal language theory and some of its lesser-known areas that are needed to fully grasp some of the upcoming topics. The second part forms the heart of the thesis. It formally defines one-sided random context grammars and studies them from many points of view. Generative power, relations to other types of grammars, reduction, normal forms, leftmost derivations, generalized and parsing-related versions all belong between the studied topics. The final part of this thesis closes its discussion by adding remarks regarding its coverage. More specifically, these remarks concern application perspectives, bibliography, and open problem areas.
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