Object - the formation process of security characteristics for symmetric block cipher (SBC) to linear and differential cryptanalysis. Purpose - a development of a new methodology for the security assessment of SBC to differential and linear cryptanalysis based on the application of scaled models of SBC and simulation of encryption transformations by random permutations for fast obtaining of provable SBC security indicators. Methods include probability theory, mathematical statistics for researching the randomness of permutations and permutation transformations (scaled models of ciphers) and for processing the results of statistical experiments; combinatorics and system analysis for substantiations of proposed cryptanalysis method based on the research and comparative evaluation of security characteristics and reduced models during the research of substitution structures combinatorial properties, methods of statistical tests - during the initial research for evaluation of efficiency substitution designs and different types of reduced models of a number of modern ciphers; Boolean algebra to assess the performance of cryptographic S-blocks of some modern ciphers and S-blocks generated by the new method of selection of random permutations. Equipment - the personal computer. Theoretical and practical results: it is developed a new methodology for fast cryptanalysis, which is based on the one hand, by assessing the characteristics and parameters of model prototypes, on the other, on the proven capabilities of mathematical modeling ciphers and random permutations can solve the contradiction between the impossibility of direct measurement of security characteristics of SBC to linear attacks and differential cryptanalysis and the need to obtain estimates of relevant parameters with a high level of confidence in acceptable time limits. The methodology is of great practical value for improving the technology of block symmetric encryption. Scientific novelty: first proposed and verified methodology for assessing the security of SBC to linear attacks and differential cryptanalysis, which involves the use of combination of six methods for forming opinions on the level of evidence of secure ciphers, thereby greatly accelerate the process of research and comparison of solutions in the building block algorithms for symmetric encryption, first proposed method for assessing the security of SBC to linear attacks and differential cryptanalysis, which involves the application to form opinions on the level of evidence of secure ciphers indicators of reduced models that allowed for the analysis of model performance indicators to determine the security of large prototypes, first proposed method for assessing the performance of evidence-based security SBC to differential attacks and linear cryptanalysis, which is based on random permutations of indices corresponding degree, which is not related to performance of nonlinear transformations (S-block) codes that greatly simplify the process of finding the parameters of evidence security modern SBC to linear and differential attacks crypto analysis first established the principle of formation of maxima of complete differentials and linear hulls symmetric block cipher based on the purchase of a random permutation cipher properties with increasing number of cycles, which makes it possible to determine the parameters of evidence-based security through the use of random parameters substitutions, the first time the method rapid estimation of linear and differential parameters of modern symmetric block ciphers, which involves the use of simplified relations for calculating the maximum values of the differential and linear probabilities of a random permutation corresponding degree, which can increase the speed of obtaining evidence of safety indicators symmetric block cipher to differential attacks and linear crypto analysis, first proposed two methods for evaluating the stability of symmetric block cipher to differential attacks and linear cryptanalysis AMDP and AMLHP, involving calculations of the average maximum differential probability and the average maximum likelihood linear body, allowing more adequately reflect the performance of evidence-based resistance codes, first proposed method of assessing the quality of cryptographic transformations on the basis of determining the number of cycles required for the acquisition of properties SBC random permutation, which makes it possible to compare SBC during the examination and verification of individual solutions, has acquired the further development of mathematical model of a random permutation in terms of bringing a number of theorems concerning the expression for the law displacement distribution tables of linear approximations, in contrast to existing approaches, allowed calculation obtain the maximum linear buildings codes and thus significantly speed up the determination of their evidence-based security to attack crypto linear analysis came the further development of mathematical model in a random permutation of the set relations between neighboring values of distribution laws XOR conversion tables and linear approximations of displacements tables of random permutations, which are presented in the form of simple ratios, allowing to obtain more suitable for calculating representation of the distribution XOR conversion tables, and set much more difficult level of linear cryptanalysis attacks differential attacks against crypto analysis gained further development of mathematical model in a random permutation of the establishment of additional criteria for selecting substitutions that unlike existing approaches using empirical comparison of distribution laws differential conversion tables and linear approximations of displacements table lookup with the theoretical, making it possible to strengthen the requirements for verification of cryptographic transformations to match the properties of random permutations. The results are implemented in the cryptographic protection of information in the course of several research and development activity in JSC "Institute of Information Technologies" (the act of implementation of 24.10.2011), and also used in the learning process of the information technologies security Department at National University of Radio Electronics (the act of implementation of 10/07/2011 City) and the formation and implementation of new curriculum department of information security Zaporizhzhya National Technical University (act introduction of 12.10.2011). Scientific and practical results of the thesis can be used: in organizations that are engaged in designing and constructing information security for the performance specification encryption algorithms that are already operating, as well as designing and developing new designs SBC, in organizations that are engaged in examination and evaluation of project and design solutions for building modern SBC, including commissions during the competitions for the selection of perspective solutions.
