Sulak, Fatih
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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
21
Articles
16
Citation Count
67
Supervised Theses
2
20 results
Scholarly Output Search Results
Now showing 1 - 10 of 20
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.Conference Object Citation Count: 0Statistical Randomness Tests of Long Sequences by Dynamic Partitioning(Ieee, 2020) Sulak, Fatih; Asian, Melis; Karabayir, Ozgur; Doganaksoy, Ali; Uguz, Muhiddin; Sulak, Fatih; 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 lixed 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.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.Article Citation Count: 13New Statistical Randomness Tests Based on Length of Runs(Hindawi Ltd, 2015) Sulak, Fatih; Sulak, Fatih; Uguz, Muhiddin; Seker, Okan; Akcengiz, Ziya; MathematicsRandom sequences and random numbers constitute a necessary part of cryptography. Many cryptographic protocols depend on random values. Randomness is measured by statistical tests and hence security evaluation of a cryptographic algorithm deeply depends on statistical randomness tests. In this work we focus on statistical distributions of runs of lengths one, two, and three. Using these distributions we state three new statistical randomness tests. New tests use chi(2) distribution and, therefore, exact values of probabilities are needed. Probabilities associated runs of lengths one, two, and three are stated. Corresponding probabilities are divided into five subintervals of equal probabilities. Accordingly, three new statistical tests are defined and pseudocodes for these new statistical tests are given. New statistical tests are designed to detect the deviations in the number of runs of various lengths from a random sequence. Together with some other statistical tests, we analyse our tests' results on outputs of well-known encryption algorithms and on binary expansions of e, pi, and root 2. Experimental results show the performance and sensitivity of our tests.Article Citation Count: 1A SECOND PRE-IMAGE ATTACK AND A COLLISION ATTACK TO CRYPTOGRAPHIC HASH FUNCTION LUX(Ankara Univ, Fac Sci, 2017) Sulak, Fatih; Kocak, Onur; Saygi, Elif; Ogunc, Merve; Bozdemir, Beyza; MathematicsCryptography is a science that provides the security of information in communication. One of the most important sub-branches of cryptography is the hash functions. Hash functions are known as the digital fingerprints. Following the recent attacks on the widely used hash functions MD5 and SHA-1 and the increase in computational power, the need for a new hash function standard has arisen. For this purpose, US National Institute of Standards and Technology (NIST) had announced a competition to select a standard hash function algorithm which would eventually become the Third Secure Hash Algorithm, SHA-3. Initially 64 algorithms were submitted to NIST and 51 of them were announced as the First Round Candidates. After an analysis period, 14 of these algorithms were announced as the Second Round Candidates, and 5 algorithms were announced as Finalists. The winner of the competition, Keccak, was announced in 2012. LUX is one of the 64 algorithms submitted to the SHA-3 competition by Nikolic et al. It is designed as a byte oriented stream cipher based hash function. For LUX-256, Schmidt-Nielsen gave a distinguisher and later Wu et al. presented collision attacks, both of which for reduced rounds of LUX. As a result of these attacks, LUX is eliminated in the first round. In this work, we first give a procedure for the second preimage attack. Then we extend this to the collision and second preimage attacks for the reduced rounds of LUX hash family. Moreover, we implement the attacks and give the specific examples by taking the padding into consideration.Article Citation Count: 0Ls-14 Test Suite for Long Sequences(Hacettepe Univ, Fac Sci, 2024) Akcengiz, Ziya; 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 İkinci Tur Aday Algoritmaların İstatistiksel Rastgelelik Testleri(2016) Özdemir, Betül Aşkın; 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: 0On the Success Probabilities of Differential Attacks On Present(2016) Sulak, Fatih; 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 attacksArticle Citation Count: 0Mutual Correlation of Nist Statistical Randomness Tests and Comparison of Theirsensitivities on Transformed Sequences(2017) Doğanaksoy, Ali; 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: 1Modifications of Knuth Randomness Tests for Integer and Binary Sequences(Ankara Univ, Fac Sci, 2018) Kocak, Onur; 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.
