On differential properties of a symmetric cryptoalgorithm based on pseudo-dynamic substitutions

A general structure of a block cryptoalgorithm “Collapser” based on pseudo-dynamic substitutions is proposed. Such approach allows to combine advantages of fixed substitutions (high speed implementation and efficient usage of computational resources) and dynamic substitutions (neutralization of statistical methods of cryptanalysis). The differential properties of reduced version of “Collapser” are compared with ones of random substitutions of similar order. It is shown that after 3 rounds “Collapser” looks as a random substitution.