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National Repository of Grey Literature 12 records found  previous11 - 12  jump to record: Search took 0.00 seconds. 
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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Secure communication in systems using restricted devices
 Michálek, Tomáš ; Martinásek, Zdeněk (referee) ; Malina, Lukáš (advisor)
This thesis presents the usability and analysis of cryptographic methods on devices with low computing power and low memory capacity. The thesis describes different methods and shows examples of their usability in practice. According to certain parameters of security methods, such as code size and memory size it is selected and compared symetric ciphers and authentication codes. There are also described some security protocols and possible attacks. The next part includes a comparison of ciphers and chosen candidates are tested on our microcontroller. In the end there are propose, implemented and analyzed security protocols.
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National Repository of Grey Literature : 12 records found   previous11 - 12  jump to record:
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