Sulak, Fatih
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Name Variants
Sulak, Fatih
F., Sulak
S.,Fatih
Sulak, F
F.,Sulak
Fatih, Sulak
Sulak,F.
S., Fatih
F., Sulak
S.,Fatih
Sulak, F
F.,Sulak
Fatih, Sulak
Sulak,F.
S., Fatih
Job Title
Doçent Doktor
Email Address
fatih.sulak@atilim.edu.tr
ORCID ID
Scopus Author ID
Turkish CoHE Profile ID
Google Scholar ID
WoS Researcher ID
Scholarly Output
15
Articles
11
Citation Count
67
Supervised Theses
2
15 results
Scholarly Output Search Results
Now showing 1 - 10 of 15
Article Citation Count: 0LS-14 test suite for long sequences(Hacettepe Univ, Fac Sci, 2024) Sulak, Fatih; Aslan, Melis; Doganaksoy, Ali; Sulak, Fatih; Uguz, Muhiddin; MathematicsRandom number sequences are used in many branches of science. Because of many technical reasons and their practicality, pseudo random sequences are usually employed in place of true number sequences. Whether a sequence generated through a deterministic process is a pseudo random, in other words, random-looking sequence or it contains certain patterns, can be determined with the help of statistics and mathematics. Although, in the literature there are many statistical randomness tests for this purpose, there is no much work on test suites specialized for long sequences, that is sequences of length 1,000,000 bits or more. Most of the randomness tests for long sequences use some mathematical approximations to compute expected values of the random variables and hence their results contain some errors. Another approach to evaluate randomness criteria of long sequences is to partition the long sequence into a collection short sequences and evaluate the collection for the ran- domness using statistical goodness of fit tests. The main advantage of this approach is, as the individual sequences are short, there is no need to use mathematical approximations. On the other hand when the second approach is preferred, partition the long sequence into a collection of fixed length subsequences and this approach causes a loss of information in some cases. Hence the idea of dynamic partition should be included to perform a more reliable test suite. In this paper, we propose three new tests, namely the entire R2 run, dynamic saturation point, and dynamic run tests. Moreover, we intro duce a new test suite, called LS-14, consisting of 14 tests to evaluate randomness of long sequences. As LS-14 employs all three approaches: testing the entire long sequence, testing the collection of fixed length partitions of it, and finally, testing the collection obtained by the dynamic partitions of it, the proposed LS-14 test suit differs from all existing suites. Mutual comparisons of all 14 tests in the LS-14 suite, with each other are computed. Moreover, results obtained from the proposed test suite and NIST SP800-22 suite are compared. Examples of sequences with certain patterns which are not observed by NIST SP800-22 suite but detected by the proposed test suite are given.Master Thesis Caesar yarışmasına katılan ikinci tur aday algoritmaların istatistiksel rastgelelik testleri(2016) Sulak, Fatih; Sulak, Fatih; MathematicsSimetrik anahtarlı şifreleme çalışmalarını geliştirmek için NIST ve IACR tarafından birçok yarışma düzenlenmiştir. Son zamanlarda kimlik denetimini sağlayan şifrelemenin önemi hızlı bir şekilde artmaktadır çünkü bütünlüğün, gizliliğin ve kimlik denetiminin aynı anda sağlanmasına ihtiyaç vardır. Bu tür güvenliğe ihtiyaç duyulmasından dolayı, Ocak 2013'te Erken Simetrik Kripto Çalıştayında CAESAR Yarışması duyurulmuştur. Bu yarışma IACR tarafından yürütülmektedir ve final algoritmalarını bu araştırma grubu seçecektir. Yarışma boyunca her turun sonunda birtakım algoritmalar elenecektir. Sonuç olarak, algoritmaların analizi CAESAR Yarışması için çok önemlidir. Bu amaçla, biz yarışma devam ettiği sürece AEGIS, Ascon, Joltik, MORUS, Pi-Cipher and Tiaoxin adlı algoritmalara istatistiksel rastgelelik testlerini uyguluyoruz. Bu tezde, biz istatistiksel rastgelelik testlerini kullanarak CAESAR Yarışması algoritmalarının analizine odaklandık ve algoritmaların istatistiksel rastgelelik testlerine göre hangi tur sayısına kadar rastgele davrandıklarını gözlemledik.Article Citation Count: 8Periodic template tests: A family of statistical randomness tests for a collection of binary sequences(Elsevier, 2019) Sulak, Fatih; Doganaksoy, Ali; Uguz, Muhiddin; Kocak, Onur; MathematicsIn this work, we classify all templates according to their periods and for each template we evaluate the exact probabilities using generating functions. Afterwards, we propose a new family of statistical randomness tests, that is periodic template tests, for a collection of binary sequences. We apply these tests to the outputs of AES, SHA-3, SHA-2 family, SHA-1 and MD5 and the binary expansion of pi and root 2 and biased non-random data to test the power of new tests. Moreover, we give the probabilities for all templates for the overlapping template matching test in the NIST test suite. Afterwards, we analyse the power of templates and compare the periodic template tests with NIST overlapping template test. (C) 2019 Elsevier B.V. All rights reserved.Article Citation Count: 2New statistical randomness tests: 4-bit template matching tests(Tubitak Scientific & Technological Research Council Turkey, 2017) Sulak, Fatih; MathematicsFor cryptographic algorithms, secret keys should be generated randomly as the security of the system depends on the key and therefore generation of random sequences is vital. Randomness testing is done by means of statistical randomness tests. In this work, we show that the probabilities for the overlapping template matching test in the NIST test suite are only valid for a specific template and need to be recalculated for the other templates. We calculate the exact distribution for all 4-bit templates and propose new randomness tests, namely template matching tests. The new tests can be applied to any sequence of minimum length 5504 whereas the overlapping template matching test in the NIST test suite can only be applied to sequences of minimum length 10(6). Moreover, we apply the proposed tests to biased nonrandom data and observe that the new tests detect the nonrandom behavior of the generator even for a bias of 0.001, whereas the template matching tests in NIST cannot detect that bias.Article KRİPTOLOJİ(Bilim ve Teknoloji, 2015) Sulak, Fatih; Turan, Mehmet; MathematicsKriptografi, Yunancada “kriptos (gizli)” ve “graphi (yazı)” kelimelerinin birleşmesinden oluşur. Kriptoloji ise şifre bilimi olarak bilinir. Daha detaylı bir tanım yapmak istersek; kriptoloji belirli bir sisteme göre bir metnin şifrelenmesi, alıcıya güvenli bir şekilde iletilmesi ve alıcı tarafından şifreli metnin şifresinin çözülmesidir. İletişimin ve teknolojinin günümüzdeki kadar gelişmiş ve hızlı olmadığı zamanlarda, en çok kullanılan iletişim yöntemi mektuplaşmaydı. Mektup yazan kişi, mektubu yazdıktan sonra bir zarfa koyar, daha sonra alıcıya gönderirdi. Bunun amacı ise, yazılan mektubun başkaları tarafından okunmasını engellemekti. Bu örneği bir şifreleme sistemi gibi düşünürsek, şifrelemenin güvenli olması yani yabancı bir kişinin şifreli metni çözememesi önemli bir yere sahiptir.Master Thesis Blockchaın tabanlı e-oylama sistemlerinin katılım mahremiyeti analizi(2022) Sulak, Fatih; Özdemir, Buse Yeşim; Sulak, Fatih; MathematicsTeknoloji neredeyse her gün ilerlemektedir ve bu ilerleme, hayatımızdaki dengeyi değiştirmektedir. Bu değişikliklerden biri de oylama sistemlerinin artık uzaktan yapmanın elverişli olmasıdır. Uzaktan oylama sistemleri, genel olarak, seçtikleri adaya oy vermek için kimsenin fiziksel olarak belirli bir yerde bulunması gerekmediği anlamına gelen sistemlere verilen addır. Uzaktan oylama sistemlerine eklenen yeni teknolojilerden biri de blokzincir teknolojisidir. Bir e-oylama sistemi oluşturmak çok önemli bir konudur ve blokzincir teknolojisinin e-oylama sistemlerine entegrasyonu ile merkezi olmayan, değiştirilemez ve şeffaf hale gelebilirler. Bu geliştirmeler sayesinde e-oylama sistemi üyeleri (seçmenler, yetkililer vb.) birbirlerine daha çok güvenmekte ve böylece sistemin başarısı artmaktadır. Ek olarak, blok zinciri tabanlı e-oylama sistemleri diğer uzaktan oylama sistemlerinin sağlaması beklenen bütünlük, sağlamlık, anonimlik, yeniden oy kullanılamamazlık, adillik, uygunluk ve doğrulanabilirlik gibi temel isterleri sağlamasının yanı sıra katılım mahremiyeti isterini de sağlaması ö-nemlidir. Bu tezde; Zhang, Gajek, Lewandowsky, Zhou ve Krillov tarafından yayınla-nan blok zinciri tabanlı oylama sistemleri derinlemesine açıklanmış ve önerilen sistemlerde katılım gizliliği ilkesinin sağlanmadığı gösterilmiştir.Article Citation Count: 2R-2 composition tests: a family of statistical randomness tests for a collection of binary sequences(Springer, 2019) Sulak, Fatih; Doganaksoy, Ali; Sulak, Fatih; Kocak, Onur; MathematicsIn this article a family of statistical randomness tests for binary strings are introduced, based on Golomb's pseudorandomness postulate R-2 on the number of runs. The basic idea is to construct recursive formulae with computationally tenable probability distribution functions. The technique is illustrated on testing strings of 2(7), 2(8), 2(10) and 2(12) bits. Furthermore, the expected value of the number of runs with a specific length is obtained. Finally the tests are applied to several collections of strings arising from different pseudorandom number generators.Article Citation Count: 1MODIFICATIONS OF KNUTH RANDOMNESS TESTS FOR INTEGER AND BINARY SEQUENCES(Ankara Univ, Fac Sci, 2018) Sulak, Fatih; Sulak, Fatih; Doganaksoy, Ali; Uguz, Muhiddin; MathematicsGenerating random numbers and random sequences that are indistinguishable from truly random sequences is an important task for cryptography. To measure the randomness, statistical randomness tests are applied to the generated numbers and sequences. Knuth test suite is the one of the first statistical randomness suites. This suite, however, is mostly for real number sequences and the parameters of the tests are not given explicitly. In this work, we review the tests in Knuth Test Suite. We give test parameters in order for the tests to be applicable to integer and binary sequences and make suggestions on the choice of these parameters. We clarify how the probabilities used in the tests are calculated according to the parameters and provide formulas to calculate the probabilities. Also, some tests, like Permutation Test and Max-of-t-test, are modified so that the test can be used to test integer sequences. Finally, we apply the suite on some widely used cryptographic random number sources and present the results.Article Citation Count: 0Improvement on Bit Diffusion Analysis of π-Cipher(De Gruyter Open Ltd, 2017) Sulak, Fatih; Bozdemir,B.; Özdemir,B.A.; Koçak,N.; Koçak,O.; Mathematicsπ-Cipher, designed by Gligoroski et al., is a second round candidate of the CAESAR competition. The designers analyzed the bit diffusion of the cipher by examining the ∗ operation and 1 round π-function. We improve this analysis by applying Strict Avalanche Criterion (SAC) test to ∗ operation and reduced round versions of π-function for π 16-Cipher. We found out that ∗ operation fails SAC test whereas all versions of π-function for π 16-Cipher pass the test. © 2017 Mathematical Institute, Slovak Academy of Sciences.Conference Object Citation Count: 2Statistical Randomness Tests of Long Sequences by Dynamic Partitioning(Institute of Electrical and Electronics Engineers Inc., 2020) Sulak, Fatih; Aslan,M.; Karabayir,O.; Doganaksoy,A.; Uguz,M.; Sulak,F.; MathematicsRandom numbers have a wide usage in the area of cryptography. In practice, pseudo random number generators are used in place of true random number generators, as regeneration of them may be required. Therefore because of generation methods of pseudo random number sequences, statistical randomness tests have a vital importance. In this paper, a randomness test suite is specified for long binary sequences. In literature, there are many randomness tests and test suites. However, in most of them, to apply randomness test, long sequences are partitioned into a certain fixed length and the collection of short sequences obtained is evaluated instead. In this paper, instead of partitioning a long sequence into fixed length subsequences, a concept of dynamic partitioning is introduced in accordance with the random variable in consideration. Then statistical methods are applied. The suggested suite, containing four statistical tests: Collision Tests, Weight Test, Linear Complexity Test and Index Coincidence Test, all of them work with the idea of dynamic partitioning. Besides the adaptation of this approach to randomness tests, the index coincidence test is another contribution of this work. The distribution function and the application of all tests are given in the paper. © 2020 IEEE.
