Sirenko О. Algebraic methods for stability analysis of block symmetric encryption algorithms

The Thesis contains new theoretical research in building reliable informational systems and a new approach to analysis of stability of the block symmetric encryption algorithms and modern methods of cryptanalysis, based on the method of homomorphism and truncated differential cryptanalysis . Symmetrical block cryptoalgorithms take an important place in modern information security. One of their main advantages is relatively fast software implementation, and that's why studying their resistance to various modern attacks, particularly the group and differential cryptanalysis, is an important and urgent issue. Normally, their resistance to the homomorphism methods is defined by the algebraic properties of different groups of substitutions that in turn are related to the system of round encrypting transformations of a given cipher. This work is dedicated to the study of algebraic properties of permutations that are generated by round functions, particularly "mixing" properties of the group operations, which are defined on a set of plain text data.