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Lawful Interception: Identity Detection
Polčák, Libor ; Baggili, Ibrahim (oponent) ; Hudec,, Ladislav (oponent) ; James, Joshua I. (oponent) ; Švéda, Miroslav (vedoucí práce)
{Internet has became a regular communication channel between law offenders performing malicious activities. Courts or prosecutors authorise lawful interception that targets individual suspects. Lawful interception systems have to identify traffic of the suspects. However, the identifiers that appear in each network packet are short-lived, dynamically assigned, and a single communication session may be split into multiple flows identified by different identifiers. A lawful interception system has to immediately detect that a new identifier covered by an intercept appeared or disappeared. This thesis describes identification in modern computer networks compatible with lawful interception. The focus is on two partial identity detectors: IPv6 address assignment tracking based on monitoring of neighbor discovery and clock-skew-based remote computer identification. Additionally, this thesis proposes identity graphs that link partial identities according to optional constraints that reflect the wording of a warrant. Results of partial identity linking can be utilised by lawful interception systems. The results of this thesis are also applicable in network forensic, and in networks controlled according to user roles.
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Digital Forensics: The Acceleration of Password Cracking
Hranický, Radek ; Hudec,, Ladislav (oponent) ; Rowe, Neil (oponent) ; Šafařík, Jiří (oponent) ; Ryšavý, Ondřej (vedoucí práce)
Cryptographic protection of sensitive data is one of the biggest challenges in digital forensics. A password is both a traditional way of authentication and a pivotal input for creating encryption keys. Therefore, they frequently protect devices, systems, documents, and disks. Forensic experts know that a single password may notably complicate the entire investigation. With suspects unwilling to comply, the only way the investigators can break the protection is password cracking. While its basic principle is relatively simple, the complexity of a single cracking session may be enormous. Serious tasks require to verify billions of candidate passwords and may take days and months to solve. The purpose of the thesis is thereby to explore how to accelerate the cracking process. I studied methods of distributing the workload across multiple nodes. This way, if done correctly, one can achieve higher cracking performance and shorten the time necessary to resolve a task. To answer what "correctly" means, I analyzed the aspects that influence the actual acceleration of cracking sessions. My research revealed that a distributed attack's efficiency relies upon the attack mode - i.e., how we guess the passwords, cryptographic algorithms involved, concrete technology, and distribution strategy. Therefore, the thesis compares available frameworks for distributed processing and possible schemes of assigning work. For different attack modes, it discusses potential distribution strategies and suggests the most convenient one. I demonstrate the proposed techniques on a proof-of-concept password cracking system, the Fitcrack - built upon the BOINC framework, and using the hashcat tool as a "cracking engine." A series of experiments aim to study the time, performance, and efficiency properties of distributed attacks with Fitcrack. Moreover, they compare the solution with an existing hashcat-based distributed tool - the Hashtopolis. Another way to accelerate the cracking process is by reducing the number of candidate passwords. Since users prefer strings that are easy to remember, they unwittingly follow a series of common password-creation patterns. Automated processing of leaked user credentials can create a mathematical model of these patterns. Forensic investigators may use such a model to guess passwords more precisely and limit tested candidates' set to the most probable ones. Cracking with probabilistic context-free grammars represents a smart alternative to traditional brute-force and dictionary password guessing. The thesis contributes with a series of enhancements to grammar-based cracking, including the proposal of a novelty parallel and distributed solution. The idea is to distribute sentential forms of partially-generated passwords, which reduces the amount of data necessary to transfer through the network. Solving tasks is thus more efficient and takes less amount of time. A proof-of-concept implementation and a series of practical experiments demonstrate the usability of the proposed techniques.
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Privacy Protection on Mobile Devives
Aron, Lukáš ; Hudec,, Ladislav (oponent) ; Drahanský, Martin (oponent) ; Hanáček, Petr (vedoucí práce)
This thesis analyses privacy protection on mobile devices and presents the method for protecting these data against information leakage. The security is focused on using the mobile device for personal purposes and also for the working environment. The concept of the design solution is implemented in the form of prototype. Model of implementation is verified with the model of required behavior. The thesis also consists of experiments with prototype and verification experiments on defined models.
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Digital Forensics: The Acceleration of Password Cracking
Hranický, Radek ; Hudec,, Ladislav (oponent) ; Rowe, Neil (oponent) ; Šafařík, Jiří (oponent) ; Ryšavý, Ondřej (vedoucí práce)
Cryptographic protection of sensitive data is one of the biggest challenges in digital forensics. A password is both a traditional way of authentication and a pivotal input for creating encryption keys. Therefore, they frequently protect devices, systems, documents, and disks. Forensic experts know that a single password may notably complicate the entire investigation. With suspects unwilling to comply, the only way the investigators can break the protection is password cracking. While its basic principle is relatively simple, the complexity of a single cracking session may be enormous. Serious tasks require to verify billions of candidate passwords and may take days and months to solve. The purpose of the thesis is thereby to explore how to accelerate the cracking process. I studied methods of distributing the workload across multiple nodes. This way, if done correctly, one can achieve higher cracking performance and shorten the time necessary to resolve a task. To answer what "correctly" means, I analyzed the aspects that influence the actual acceleration of cracking sessions. My research revealed that a distributed attack's efficiency relies upon the attack mode - i.e., how we guess the passwords, cryptographic algorithms involved, concrete technology, and distribution strategy. Therefore, the thesis compares available frameworks for distributed processing and possible schemes of assigning work. For different attack modes, it discusses potential distribution strategies and suggests the most convenient one. I demonstrate the proposed techniques on a proof-of-concept password cracking system, the Fitcrack - built upon the BOINC framework, and using the hashcat tool as a "cracking engine." A series of experiments aim to study the time, performance, and efficiency properties of distributed attacks with Fitcrack. Moreover, they compare the solution with an existing hashcat-based distributed tool - the Hashtopolis. Another way to accelerate the cracking process is by reducing the number of candidate passwords. Since users prefer strings that are easy to remember, they unwittingly follow a series of common password-creation patterns. Automated processing of leaked user credentials can create a mathematical model of these patterns. Forensic investigators may use such a model to guess passwords more precisely and limit tested candidates' set to the most probable ones. Cracking with probabilistic context-free grammars represents a smart alternative to traditional brute-force and dictionary password guessing. The thesis contributes with a series of enhancements to grammar-based cracking, including the proposal of a novelty parallel and distributed solution. The idea is to distribute sentential forms of partially-generated passwords, which reduces the amount of data necessary to transfer through the network. Solving tasks is thus more efficient and takes less amount of time. A proof-of-concept implementation and a series of practical experiments demonstrate the usability of the proposed techniques.
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Kazatelská činnost u Origena a Jana Zlatoústého
Hudec, Jonatan ; Filipi, Pavel (vedoucí práce) ; Beneš, Ladislav (oponent)
Tato práce chce poukázat na kazatelskou činnost Origena a Jana Zlatoústého. Nejprve se zabývá křesťanským kázáním v prvních stoletích obecně. Zpracovává jednotlivé termíny, užívané v této době pro slovo kázání, pokouší se o rozdělení kázání podle různých kategorií a zmiňuje i způsob uchovávání kázání s tím, že se také dotýká otázky autorství. Rozebírá problematiku kazatelské činnosti otců. Dále uvádí statě o původu kázání a o okolnostech, za kterých kázání vznikala nebo byla pronášena. Ústředním tématem práce je dílo autorů Origena a Zlatoústého a kontext jejich kazatelské činnosti. Postupně se věnuje Origenovi a překladu jeho dvanáctého kázání na Jeremiáše s rozborem tohoto kázání a Zlatoústému a jeho činnosti kazatele, rovněž s překladem jednoho z jeho kázání. Jde o šesté kázání na knihu Genesis s jeho následným rozborem. Powered by TCPDF (www.tcpdf.org)
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Privacy Protection on Mobile Devives
Aron, Lukáš ; Hudec,, Ladislav (oponent) ; Drahanský, Martin (oponent) ; Hanáček, Petr (vedoucí práce)
This thesis analyses privacy protection on mobile devices and presents the method for protecting these data against information leakage. The security is focused on using the mobile device for personal purposes and also for the working environment. The concept of the design solution is implemented in the form of prototype. Model of implementation is verified with the model of required behavior. The thesis also consists of experiments with prototype and verification experiments on defined models.
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Lawful Interception: Identity Detection
Polčák, Libor ; Baggili, Ibrahim (oponent) ; Hudec,, Ladislav (oponent) ; James, Joshua I. (oponent) ; Švéda, Miroslav (vedoucí práce)
{Internet has became a regular communication channel between law offenders performing malicious activities. Courts or prosecutors authorise lawful interception that targets individual suspects. Lawful interception systems have to identify traffic of the suspects. However, the identifiers that appear in each network packet are short-lived, dynamically assigned, and a single communication session may be split into multiple flows identified by different identifiers. A lawful interception system has to immediately detect that a new identifier covered by an intercept appeared or disappeared. This thesis describes identification in modern computer networks compatible with lawful interception. The focus is on two partial identity detectors: IPv6 address assignment tracking based on monitoring of neighbor discovery and clock-skew-based remote computer identification. Additionally, this thesis proposes identity graphs that link partial identities according to optional constraints that reflect the wording of a warrant. Results of partial identity linking can be utilised by lawful interception systems. The results of this thesis are also applicable in network forensic, and in networks controlled according to user roles.
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Kazatelská činnost u Origena a Jana Zlatoústého
Hudec, Jonatan ; Filipi, Pavel (vedoucí práce) ; Beneš, Ladislav (oponent)
Tato práce chce poukázat na kazatelskou činnost Origena a Jana Zlatoústého. Nejprve se zabývá křesťanským kázáním v prvních stoletích obecně. Zpracovává jednotlivé termíny, užívané v této době pro slovo kázání, pokouší se o rozdělení kázání podle různých kategorií a zmiňuje i způsob uchovávání kázání s tím, že se také dotýká otázky autorství. Rozebírá problematiku kazatelské činnosti otců. Dále uvádí statě o původu kázání a o okolnostech, za kterých kázání vznikala nebo byla pronášena. Ústředním tématem práce je dílo autorů Origena a Zlatoústého a kontext jejich kazatelské činnosti. Postupně se věnuje Origenovi a překladu jeho dvanáctého kázání na Jeremiáše s rozborem tohoto kázání a Zlatoústému a jeho činnosti kazatele, rovněž s překladem jednoho z jeho kázání. Jde o šesté kázání na knihu Genesis s jeho následným rozborem. Powered by TCPDF (www.tcpdf.org)
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