Artuğer, Fırat; Özkaynak, Fatih

In recent years, the need for secure cryptographic keys for various purposes has been constantly increasing. One of these areas is undoubtedly image encryption. In this study, a new key generation algorithm has been developed for use in image encryption algorithms. The proposed generator has a hybrid structure based on the chaotic sine map and the SHA-3 algorithm. It is aimed to produce strong keys by using the benefits of these two structures. To do this, first, bit sequences of the desired length are generated using the basic parameters of the sine map. Then, bit sequences of the same length are obtained using the SHA-3 algorithm. These two bit sequences are then subjected to an XOR operation to generate key values ​​of the desired length. With this structure, 3 different bit sequences of 1 million length were produced. All of these bit sequences successfully passed NIST SP 800 − 22 tests. This key value obtained in this study has been successfully applied to a new image encryption algorithm. The results of the study demonstrate that the proposed algorithm meets important cryptographic criteria such as information entropy, correlation-histogram analysis, NPCR, and UACI values. In addition, the simple and fast structure of the algorithm in key generation was the most important difference from other studies.

AtıfScopus3·OpenAlex2

İncele

Artuğer, Fırat

The most used approach for data encryption is block cipher. One of the most important structures for block cipher algorithms is undoubtedly s-boxes. The s-box structure used in the AES algorithm contains 256 values. Therefore, obtaining powerful s-boxes is a rather difficult search problem. Because the search space is very large (256!). In this study, a new method based on squirrel search algorithm (SSA) is proposed to overcome this problem. The proposed method is displacement-based. In an s-box taken at the entrance, stronger s-box structures are sought by changing the location of the elements. The most important innovation in this study is that the elements to be displaced in the s-box were selected with the positioning states of the SSA. The chaotic Gompertz map was used for the initial population. Four different s-boxes were produced with the method developed thanks to the effective positioning states of SSA. As the fitness function, the nonlinearity value, which is the most important evaluation criterion of an s-box structure, was used. The proposed four s-box structures increased up to 110 nonlinearity values after only 4500 iterations. Here, it has been shown that the algorithm can be effective in all s-boxes by generating four different s-boxes. Considering these results, it has been determined that the proposed method gives more effective results than most methods in the literature.

AtıfScopus1·WoS1·OpenAlex2

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Artuğer, Fırat

With today's developing technologies, the need for new image encryption algorithms to encrypt images is inevitable. In this study, an innovative image encryption algorithm is proposed. The proposed algorithm first XORs each layer of the image with a unique and strong new key. Each layer is then subjected to a random permutation process. Each of the encrypted layers obtained here is finally passed through a new s-box structure with a high nonlinearity value. After these processes, all layers are combined to obtain an encrypted image. Thus, XOR and s-box confusion meet the criteria, while random permutation meets the diffusion criteria. In this study, both key and s-box structures were originally obtained with a chaotic Gaussian map. The outputs of the chaotic map were converted into bit sequences and five different sequences with a length of 1 million were obtained. All these arrays have successfully passed all NIST SP 800-22 tests. On the other hand, the proposed s-box structures surpassed many studies with nonlinearity values of 108, 108.5, and 108.75. The images were successfully encrypted with the proposed algorithm, and the encrypted images successfully completed tests such as NPCR-UACI, information entropy, histogram analysis, and correlation analysis. It is thought that this study will make many contributions to the fields of s-box development, random number generation, and image encryption.

AtıfScopus3·OpenAlex3

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Artuger, Firat; Karakuş, Songül

Blum Blum Shub (BBS) algoritması bilinen güçlü sözde rastgele sayı üreteçlerinden bir tanesidir. Bu algoritma anahtar üretiminde kullanılabilir. BBS temelde iki büyük asal sayının çarpımına ve bir tohum değerine dayanmaktadır. Bu değerlerin seçilmesi oldukça kritik bir konudur. Bu çalışmada bu problemin üstesinden gelmek için yeni bir yaklaşım önerilmiştir. Önerilen yaklaşımda öncelikle asal sayı havuzu oluşturulmaktadır. Bu noktada kullanıcı bir başlangıç ve bitiş değeri belirlemektedir. Belirlenen bu aralıktaki asal sayılar üretilerek bir diziye kaydedilir. Daha sonra bu asal sayı havuzundan kaotik haritalar ile rastgele iki asal sayı seçilir. Seçilen bu asal sayıların dizideki konumları kaydedilir. Tohum değeri ise bu iki asal sayının konumları toplamı olarak ele alınmıştır. Yani seçilecek olan parametreler o an kullanıcının gireceği aralıklarda rastgele bir şekilde seçilecektir. Bu çalışmada bu şekilde rastgele iki bit dizisi elde edilmiştir. Bu diziler 1 milyon bit uzunluğundadır. Elde edilen bu dizilere NIST SP 800-22 testleri uygulanmış olup diziler tüm testleri başarı ile tamamlamıştır.

AtıfOpenAlex2

İncele

Artuger, Firat

Şifreleme algoritmalarında en önemli gereksinimlerden bir tanesi karıştırma olarak adlandırılmaktadır. Bu nedenle şifrelenecek verinin etkin bir şekilde karıştırılması gerekmektedir. İkame kutusu (s-box), bu gereksinimi sağlayan en önemli yapılardan bir tanesidir. Bu yapının en önemli özelliklerinden biri olan lineer olmama değeri ne kadar yüksek olursa karıştırmayı o kadar sağlıklı bir şekilde yerine getirecektir. İkame kutularının elde edilmesinde birçok teknik kullanılmaktadır. Bu tekniklerden en çok kullanılan, optimizasyon tekniğidir. Bu teknikte, başlangıçta genellikle kaos yardımıyla bir s-box elde edilir. Daha sonra bir optimizasyon tekniği kullanılarak elemanların konumları değiştirilir. Uygunluk değeri olarak lineer olmama kriteri kullanılır. Yeni konumlandırmalardan sonra lineer olmama değeri arttığında s-box yapısı güncellenmektedir. Bu çalışmada öncelikle s-box yapılarında lineer olmama değerinin nasıl optimize edildiği açıklanmıştır. Daha sonra sinüs kosinüs algoritması kullanılarak bir s-box optimize edilmiştir. Elde edilen s-box yapısının, 500 iterasyon sonunda lineer olmama değeri 108 olarak gözlemlenmiştir. Ayrıca bir s-box yapısının diğer performans kriterleri de açıklanmıştır.

AtıfOpenAlex1·TR Dizin1

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Artuğer, Fırat; Özkaynak, Fatih

One of the successful practical applications of chaos theory and nonlinear dynamics is chaos-based cryptology studies. In this study, a new chaotic system is proposed. The proposed chaotic system generator model has a simple algorithmic structure. In addition to, generated chaotic systems have rich dynamics. It has been examined whether this system has potential advantages, especially for information security applications. As a result of the analysis and experimental studies, it is seen that the study makes many contributions to the literature. The simple mathematical generator structure has the potential to reduce computational complexity, which is an important problem for cryptology applications. One of the most comprehensive studies has been realized for chaos-based substitution box designs. 70,000 different substitution box structures have been generated. It has been known that the highest nonlinearity value that can be achieved for designs that transform chaotic system outputs into substitution box structures is 106.75 today. It has been shown that this value may be higher. The new highest nonlinearity value is calculated as 107. Side channel analysis has been examined for substitution box structures with the highest nonlinearity value among the substitution boxes generated in the study. Analysis results show that the proposed new substitution box structures may have an advantage for application-oriented attacks. Among the generated substitution box structures, 289 substitution box structures with a nonlinearity value of 106 and above are presented as a public dataset for researchers to use. In addition, 3 different random sequences with a length of 1 million-bit were produced with the proposed map, and the NIST SP 800–22 test was applied. Test results for all datasets were successful. In this way, the proposed map can also be used as a random number generator.

AtıfScopus13

İncele

Artuğer, Fırat; Özkaynak, Fatih

Symmetric encryption approaches are generally used for data encryption. One of the basic requirements for symmetric encryption algorithms to provide security is strong s-box structures. Because s-box is a nonlinear unit in these encryption algorithms and provides the requirement called confusion. In this article, a new technique is developed to produce effective s-boxes like the 16*16 s-box structure used in the AES algorithm. In the proposed method, the sine cosine algorithm (SCA), one of the recently developed optimization algorithms, is used. SCA is a suitable option for generating strong s-boxes because of its strong randomness and ease of implementation. The proposed method first uses a logistic map to generate the initial population. Then, the nonlinearity value is optimized with the help of the sine cosine algorithm. The proposed method reaches the highest nonlinearity value (112) by relocating 126 values in the s-box structure produced initially. Looking at the results, it is seen that the proposed method gives better results than other optimization-based s-box creation methods. This new method has significant potential to improve the security of symmetric encryption algorithms and make data encryption processes stronger.

AtıfScopus19·WoS22·OpenAlex24

İncele

Artuğer, Fırat

S-boxes are very important structures for encryption algorithms. For S-boxes to be strong, they should not be as linear as possible. Obtaining an S-box with high nonlinearity is a difficult problem. For this reason, it has attracted the attention of researchers for many years. In this study, cellular automata logic was used to overcome this problem. A chaotic tent map was used for the initial population. Then, in this weak S-box, the elements were replaced with their neighbors, and the nonlinearity value was checked. When this value increased, the S-box was transferred to the next generation. With the proposed algorithm, an S-box structure with a nonlinearity value of 110.5 was obtained. This value surpasses most studies in the literature. In addition, it has been proven because of the analysis that the proposed S-box also provides other performance criteria.

AtıfScopus6·WoS8·OpenAlex7

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Artuğer, Fırat

Cryptography aims to design algorithms for the protection of important data transmitted over unsecured networks. These algorithms encrypt the data and render it incomprehensible even if it is captured by enemies. Today’s data encryption standard is the AES algorithm. The most important and nonlinear unit in the AES algorithm is the s-box structure. The S-box provides the mixing process in the algorithm, that is, the confusion. An s-box structure with a high nonlinearity value greatly increases the security against various attacks. Therefore, s-box is of vital importance in an encryption algorithm. When we look at the literature, chaos-based s-box structures are frequently used. However, the nonlinearity value of s-boxes produced with chaos is low. In this article, a new, fast, and very simple method is proposed to increase the nonlinearity value of chaos-based s-box structures. In the proposed method, the nonlinearity value is calculated by changing the places of the elements respectively. When the nonlinearity value increases, the s-box is updated, and the next element is passed. In this way, many iterations are not looked at in vain. This saves a lot of time. As a result of the analysis, it has been proven that the s-box structure obtained by the proposed method is cryptographically strong and has a high nonlinearity value. It is thought that the proposed method will provide many advantages for future cryptography applications.

AtıfScopus9·WoS7·OpenAlex8

İncele

Artuğer, Fırat

Substitution boxes are very important for cryptographic structures. But getting an 8-bit strong s-box is a difficult problem. To address this problem, a new approach is proposed in this study. DNA chains are used in the proposed approach. First of all, a weak s-box is obtained with the help of a chaotic map. Then, a DNA chain is formed with the same chaotic map. In this study, 2000-long DNA chains were produced. Then, two random values consisting of four components are determined from these DNA chains, and these values are addressed to the s-box structure. By changing the places of these values, the s-box structure is improved up to a certain iteration. In this study, 10,000 iterations were examined, and three different strong s-boxes were obtained by using three different DNA chains. The nonlinearity values of these s-box structures were observed as 110.25, 110.5, and 110.75, respectively. The proposed study has proven to work effectively with effective results in three different chains. In addition, it has been proven as a result of the analysis that the proposed s-box structures also have other cryptographic features. The proposed algorithm has surpassed many s-box generation philosophies in the literature. In addition, the proposed algorithm will provide serious gains to cryptographic structures that will be developed in the future.

AtıfScopus21·WoS22·OpenAlex24

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