Nadiia Kazakova

This paper addresses the problem of improving the robustness of image steganographic methods under lossy compression while preserving high perceptual quality and low computational complexity. The paper proposes an adaptive code-controlled steganographic method that enables spectrally selective embedding in the spatial domain through structured codewords. The proposed approach introduces block-level adaptivity in which the energy of the embedding codeword is dynamically selected according to the robustness characteristics of each image block. Instead of applying uniform embedding strength, the method determines the minimal codeword energy required to guarantee reliable message extraction under a predefined worst-case JPEG compression level. Experimental evaluation demonstrates that the proposed adaptive strategy significantly improves robustness to compression attacks while preserving high perceptual reliability and strong resistance to statistical steganalysis techniques. In particular, for JPEG quality factor (QF) = 50, the bit error rate is reduced to 1.25% while a high perceptual quality of 52.07 dB peak signal-to-noise ratio (PSNR) is achieved. For stronger attack conditions, QF = 20, the method achieves 6.6% bit errors with a PSNR of 47.7 dB. Overall, the proposed adaptive energy selection provides up to 22.68% fewer errors or up to 6.05 dB higher PSNR compared to the classical code-controlled steganographic method, confirming its effectiveness for practical steganographic applications.

The S-box is a key component of modern ciphers, determining the quality and performance of the cryptographic algorithms in which it is applied. Many constructions for synthesizing high-quality S-boxes have been established, and those based on Galois fields theory—for example, the Nyberg construction applied in the AES cryptographic algorithm—are particularly important. An integral component of the Nyberg construction is the affine transformation, which is used to improve the avalanche and correlation properties of the S-box. In this paper, a new approach is adopted for synthesizing affine transformations for S-boxes based on the quaternary matrices over the Galois field GF(4). We describe four basic structures that serve as the foundation for synthesizing a complete class of 648 affine transformation matrices of order n = 3 and a class of 7776 matrices of order n = 4 and introduce a recurrent structure to facilitate the synthesis of matrices for higher orders. Using these matrices in combination with the Nyberg construction, it is possible to construct bijective S-boxes that outperform the original Nyberg construction and many other known S-boxes in terms of strict avalanche criterion (SAC) and bit independence criterion strict avalanche criterion (BIC SAC) values, while maintaining a maximal level of nonlinearity and good cryptographic properties. We also propose modified GF(4) affine transformations that can be applied to specialized S-boxes which already satisfy the SAC for both component Boolean and 4-functions, as well as the criterion of minimal correlation between input and output, allowing us to enhance their nonlinearity to the value of N_f = 96. We integrate the synthesized S-boxes into the AES algorithm and evaluate their practical performance. The encryption outputs successfully pass the NIST statistical test suite in 96 out of 100 cases, outperforming both the original AES S-box and other reference constructions, confirming the practical strength of the proposed method.

Modern computer modeling is an important stage in the design of control systems for the distribution of information flows in computer networks and in modern control systems for complex technological processes. The core of any computer model is a source of randomness, which should generate a uniformly distributed stream of random integers or real numbers. In addition to the uniformity of distribution, such a source must meet the requirements of economic use of computing system resources. An analysis of simple arithmetic generators is given and, based on it, it is shown that generators such as the Fibonacci sequence generator with a delay and the Xorshift generator proposed by J. Marsaglia are suitable as a generator for the needs of modeling stochastic processes, which are an alternative to the random number generators built into existing programming environment. On the basis of the conducted research, it was concluded that any unevenness of the numbers at the output of the generator chosen as a source of randomness significantly affects the quality of the process to be modeled, and because of this, the numerical flows from such generators should be additionally processed by methods extraction of that part of them that provides maximum randomness. The method of performing such extraction by "slicing" the input stream, the criteria used in this, and the results of its experimental research for the Xorshift128 generator are presented. A conclusion is made about the advantages of using simple and economical generators in a heap with post-processing procedures performed at the level of integers or real numbers. The results of the evaluation of the Xorshift generator, taking into account the methods described in the work, are given, and a conclusion is made about the feasibility of its use for the needs of modeling stochastic processes.

Further development and improvement of the efficiency of ciphers largely depend on the success of solving the problem of synthesizing cryptographic primitives that correspond to the quality criteria both when they are represented by Boolean functions and many- valued logic functions. Among these most significant cryptographic quality criteria are algebraic nonlinearity, distance nonlinearity, error propagation criterion, and correlation immunity criterion. To solve the problem of synthesizing high-quality cryptographic structures, it is important to research the relationship between the level of cryptographic quality of the resulting functions of many-valued logic and their component Boolean functions. In this paper, we represent the results of the research on the algebraic nonlinearity of 4-functions of two variables when they are constructed based on two Boolean functions with given cryptographic quality parameters. The results obtained can be considered as a theoretical basis for improving existing and developing new methods for synthesizing cryptographic primitives, which are characterized by the high cryptographic quality of both component Boolean functions and component many-valued logic functions.

Tr en The evolution of computer-integrated technologies as a global trend in developing the safety to navigation of the innovative society is presented. Computer integrated technologies contributed to the development of computer intelligence determined by the paradigm of information technology, which contributed to the formation of computer integrated navigation systems. It is revealed that a global phenomenon that is communicative in its scope organized according to the principle of an integration system, giving rise to the phenomenon of a control system. The emergence of a new global solution to navigation safety was facilitated by the emergence of a new form of a navigation system is a computer integrated navigation system. It is concluded that the new navigation system, which is led by integration today, is the key to safe navigation driven by computer-integrated technologies. Computer-integrated technologies are the source of reliability, security, and manageability in the age of innovation. The evolution of computer-integrated technologies as a global trend in developing the safety to navigation of the innovative society is presented. Computer integrated technologies contributed to the development of computer intelligence determined by the paradigm of information technology, which contributed to the formation of computer integrated navigation systems. It is revealed that a global phenomenon that is communicative in its scope organized according to the principle of an integration system, giving rise to the phenomenon of a control system. The emergence of a new global solution to navigation safety was facilitated by the emergence of a new form of a navigation system is a computer integrated navigation system. It is concluded that the new navigation system, which is led by integration today, is the key to safe navigation driven by computer-integrated technologies. Computer-integrated technologies are the source of reliability, security, and manageability in the age of innovation.

This paper proposes an approach to the geospatial assessment of a territorial road network based on the fractals theory. This approach allows us to obtain quantitative values of spatial complexity for any transport network and, in contrast to the classical indicators of the transport provisions of a territory (Botcher, Henkel, Engel, Goltz, Uspensky, etc.), consider only the complexity level of the network itself, regardless of the area of the territory. The degree of complexity is measured by a fractal dimension. A method for calculating the fractal dimension based on a combination of box counting and GIS analysis is proposed. We created a geoprocessing script tool for the GIS software system ESRI ArcGIS 10.7, and a study of the spatial pattern of the transport network of the Ukraine territory, and other countries of the world, was made. The results of the study will help to better understand the different aspects of the development of transport networks, their changes over time and the impact on the socioeconomic indicators of urban development.

The ways of enhancement of productivity of generation of random sequences, derived from physical sources for information protection systems were substantiated. This is necessary because today there is a rapid growth of technological capabilities and of rate indicators of implementation of various information services and applications, required by community. One of the main issues of the safe use of these services is to ensure information security, which requires the use of effective high­rate information protection systems and high­performance generation of random data sequences. In the course of conducting research with the aim of enhancing productivity, the features of conversion of actual noise processes, taking into consideration their non­stationarity and deviations from the probability distribution were analyzed. We proposed the ways to improve the methods of analog­to­digital conversion with the optimization of the scale dynamic range quantization and the pitch of discretization of a noise process over time. With a view to aligning statistical characteristics, the possibility of using the processing methods that enhance its statistical quality with economy of high­rate losses was explored. These are the method of sampling equally probable combinations (von Neumann – Elias –Ryabko – Matchikina) and the method of code processing (Santha – Vazirani) that provide an increased effectiveness due to code extension and involve conversion of the sequence: in the first method, with the use of equally probable combinations with rejection of unnecessary data; in the second method, without their rejection with the possibility of linear conversion. In order to optimize the conversion parameters at both stages of generation and to adapt these parameters to the peculiarities and changeability of characteristics of converted random processes, it was proposed to use feedbacks of converters’ outputs with previous conversion elements. The adjustment of the specified parameters can be made during the generation based on the results of statistical analysis of the outputs of conversion stages. The obtained results are quite important, since their implementation in modern information protection systems will enable guaranteeing information security and safe usage of applications of the modern information service and the introduction of new applications.