Rudnytska Y. The information technology for modeling symmetric operations of cryptographic encoding for protected information systems of critical infrastructure

The thesis is devoted to increasing the scientific research productivity of the security improving processes in the information systems of critical infrastructure by creating new methods of symmetric cryptographic coding operations' modeling and analysis. In the first section, it is determined that one of the promising directions of information systems and technologies development is their improvement to ensure the possibility of automating the scientific research conduction aimed at increasing the security of information systems of critical infrastructure. An analytical review of protected information systems of critical infrastructure was conducted, which showed the need for its constant improvement. As a result of analysizing the models and methods of information protection in information systems of critical infrastructure it was found that they are generally similar to the information protection methods in information and telecommunication systems, and do not take into account the peculiarities of practical application. The results of the current state of scientific research related to the synthesis and analysis of cryptographic coding operations are presented. The results have shown the possibility of information protection systems adaptation to the features of information representation, which is used in information systems of critical infrastructure objects management. It has been established that symmetric two-operand operations are used in the construction of almost all cryptographic algorithms, but not enough attention was paid to the automating processes of their modeling and research. The aim and objectives of the study are formulated. The second section is devoted to constructing a method for synthesizing the models of symmetric two-operand operations of cryptographic encoding based on tuples of symmetric one-operand operations. For this purpose, the possibility of synthesizing the models of symmetric two-operand operations of cryptographic encoding based on modulo union of symmetric one-operand operations models was investigated. The possibility of synthesizing symmetric two-operand operations of cryptographic encoding based on modulo duplication and modulo union of symmetric one-operand operations models has been studied. The possibility of synthesizing the models of symmetric two-bit two-operand operations of cryptographic encoding based on the tuples of symmetric one-operand operations of information transformation has been investigated. At the research, the qualitative and quantitative characteristics of various approaches to synthyzing symmetric two-operand operations were established. Basing on the obtained results, a method for synthesizing the models of symmetric two-operand operations of cryptographic encoding through the tuples of symmetric one-operand operations was proposed and an algorithm for its implementation was developed. The third section is devoted to developing a method of synthesizing the models' groups of symmetric two-operand operations of cryptographic encoding for block cypher based on a given symmetric two-operand operation. For this purpose, based on the generalization of the known methods of analyzing the results of the groups of symmetric modified operations synthesis, it was proposed a concept of synthesis, which allows combining the methods of synthesizing the groups of symmetric two-bit two-operand operations that were studied. Based on the proposed concept, two new groups of symmetric two-operand operations are synthesized. The constructed groups of operations confirmed the correctness of the proposed concept of modified two-operand operations synthesis. On the basis of the proposed concept of the synthesized groups of symmetric two-operand operations synthesis and analysis, a method of synthesizing models of symmetric two-operand operations of cryptographic encoding was constructed and an algorithm for its implementation has been developed. The fourth section is devoted to the improvement of the methods for building information systems and information technologies of cryptographic encoding operations modeling and research. For this purpose, the implementation features of the method for synthesizing the models of symmetric two-operand operations of cryptographic encoding based on tuples of symmetric one-operand operations for the block cipher systems were investigated. Based on the obtained practical results, a search algorithm of symmetric commutative two-operand operations is proposed. The implementation peculiarities of the method for synthesizing the groups of symmetric two-operand operations of cryptographic encoding on the basis of the selected symmetric commutative operation are studied. Basing on the obtained results, the methods for building information systems and information technologies of cryptographic encoding operations modeling and research have been improved. It has been developed the structure of the information system, which ensures the impl