Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis A Genetic Algorithmic Approach To the Differential and Linear Cryptanalysis(Izmir Institute of Technology, 1999) Eminağaoğlu, Mete; Koltuksuz, Ahmet HasanThe two most well known and recently developed methods in cryptanalysis of DES and DES-like symmetric block ciphers are difTerential and linear cryptanalysis. But these cryptanalytic attacks need to be improved due to the computational performance and storage capacity problems On the other hand, genetic algorithms can be a good solution in cases where the optimum value or near-optimum solutions are sought in complex systems or for non-linear problems. This is a valid situation for the cryptanalysis case where DES and DES-like ciphers are non-linear in structure making dilTerential and linear cryptanalysis a complex system with a very large search landscape and extreme amount of conditional and probabilistic candidates for the key being sought. In this study, a new and promising method wit h bet ter performance is to be developed for differential/linear cryptanalysis of DES and similar symmetric cryptosystems exploiting genetic algorithms' broadened search and optimum finding capacity.Master Thesis Modelling of Turkey Turkish Words by Discrete Markov Processes(Izmir Institute of Technology, 1998) Güventürk, Jale; Koltuksuz, Ahmet HasanThis study based on the previous works of Assistant Prof. Dr. Ahmet Hasan KOLTUKSUZ, is about obtaining cryptanalytical measures of Turkey Turkish words based on Markov processes approach.Master Thesis Basic Key Exchange Protocols for Secret Key Cryptosystems Under Crympix Library(Izmir Institute of Technology, 2007) Uslu, Sevgi; Koltuksuz, Ahmet HasanKey exchange protocols are developed in order to overcome the key distribution problem of symmetrical cryptosystems. These protocols which are based on various algebraic domains are different implementations of public-key cryptography. In this thesis, the basic key exchange protocols are reviewed and CRYMPIX implementations of them are provided. CRYMPIX has a portable structure that provides platform independence for generated code. Hence, the implemented key exchange mechanisms are suitable to be used on different hardware and software platforms.Master Thesis The Comparative Performance Analysis of Lattice Based Ntru Cryptosystem With Other Asymmetrical Cryptosystems(Izmir Institute of Technology, 2007) Mersin, Ali; Koltuksuz, Ahmet HasanCurrent popular asymmetrical cryptosystems are based on hardness of number theoretic problems. In the future, these problems may become practically solvable with the improvements of processing power, the development of quantum computation and distributed computation. So the need for new cryptosystems which are not based on these problems has risen. Researches on hardness of lattice problems have brought a new candidate for asymmetrical cryptography: Lattice Based Cryptography. NTRU is one of these cryptosystems. For practical use, the actual performance results of NTRU with respect to current asymmetrical cryptosystems should be known. This thesis is developed based on this purpose.Master Thesis Reduction Algorithms for the Cryptanalysis of Lattice Based Asymmetrical Cryptosystems(Izmir Institute of Technology, 2008) Beyazıt, Mutlu; Koltuksuz, Ahmet HasanThe theory of lattices has attracted a great deal of attention in cryptology in recent years. Several cryptosystems are constructed based on the hardness of the lattice problems such as the shortest vector problem and the closest vector problem. The aim of this thesis is to study the most commonly used lattice basis reduction algorithms, namely Lenstra Lenstra Lovasz (LLL) and Block Kolmogorov Zolotarev (BKZ) algorithms, which are utilized to approximately solve the mentioned lattice based problems.Furthermore, the most popular variants of these algorithms in practice are evaluated experimentally by varying the common reduction parameter delta in order to propose some practical assessments about the effect of this parameter on the process of basis reduction.These kind of practical assessments are believed to have non-negligible impact on the theory of lattice reduction, and so the cryptanalysis of lattice cryptosystems, due to thefact that the contemporary nature of the reduction process is mainly controlled by theheuristics.Master Thesis A Distributed Multiprecision Cryptographic Library Design(Izmir Institute of Technology, 2005) Hışıl, Hüseyin; Koltuksuz, Ahmet HasanCryptographic schemes require specialized software libraries to work with large numbers on fixed-precision processors. The concept is known as multiple-precision computation. In this thesis, we aim to review the multiple-precision algorithms with the contemporary modifications. With this motivation, we develop a new multiprecision library named CRYMPIX and we carefully benchmark CRYMPIX in comparison with the fastest alternatives. We also develop a distributed wrapper for computationally expensive functions. Hence, we provide an abstraction method for the higher level cryptographic implementations by allowing them run in a distributed environment without containing any specialized code for distribution.