Golovashych S. Design methods of high strength block ciphers and its modes of operations

Dissertation is devoted to the development construction methods and principles of modern symmetric block ciphers and schemes of their stream application. A building methods set of basic cryptographic transformations is developed: a building method of controlled elementary "almost perfect non-linear" bijective transformations with non-linearity indexes, which are independent of controlling signal (PS-boxes); a building method of f-functions with fixed indexes of non-linearity, "dispersion" and "expansion" of activation; a general principle of "involution" cipher building, which is based on Feistel- or IDEA- structures; a method of stream encryption (and authentication) schemes building, which do not have the found weaknesses, is proposed.