Browsing by Author "Şeker, Okan"
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Article Citation Count: 0Mutual correlation of NIST statistical randomness tests and comparison of theirsensitivities on transformed sequences(2017) Sulak, Fatih; Sulak, Fatih; Uğuz, Muhiddin; Şeker, Okan; Akcengiz, Ziya; MathematicsRandom sequences are widely used in many cryptographic applications and hence their generation is oneof the main research areas in cryptography. Statistical randomness tests are introduced to detect the weaknesses ornonrandom characteristics that a sequence under consideration may have. In the literature, there exist various statisticalrandomness tests and test suites, de ned as a collection of tests. An efficient test suite should consist of a number ofuncorrelated statistical tests each of which measures randomness from another point of view. `Being uncorrelated\\' is nota well-de ned or well-understood concept in the literature. In this work, we apply Pearson\\'s correlation test to measurethe correlation between the tests.In addition, we de ne ve new methods for transforming a sequence. Our motivation is to detect those testswhose results are invariant under a certain transformation. To observe the correlation, we use two methods. One is thedirect correlation between the tests and the other is the correlation between the results of a test on the sequence andits transformed form. In light of the observations, we conclude that some of the tests are correlated with each other.Furthermore, we conclude that in designing a reliable and efficient suite we can avoid overpopulating the list of testfunctions by employing transformations together with a reasonable number of statistical test functions.Article Citation Count: 0ON THE SUCCESS PROBABILITIES OF DIFFERENTIAL ATTACKS ON PRESENT(2016) Sulak, Fatih; Şeker, Okan; MathematicsAdvanced growth in ubiquitous devices leads to increasing popularity of lightweight cryptography and as a result, various block ciphers are designed. The analysis of these algorithms has become popular and as a result, underlying theory of analysis tools including success probabilities has widely been studied recently. In this work, we focus on Present, a lightweight block cipher introduced by Bogdanov et al. and the analysis of this algorithm. We give a detailed information of differential cryptanalysis and multiple differential cryptanalysis on Present. Also, the underlying theory of statistical cryptanalysis are presented. As an important part of cryptanalysis, success probability is examined and expressed by the formulas given by Selçuk and Blondeau et al. The main aim of this work is to contribute to the theory of statistical cryptanalysis. Therefore, we give a general framework of statistical cryptanalysis and success probabilities. The details of success probabilities are given with experimental results. Also, we apply the sieving phase to decrease the cost of the attacks