Combinatorics-algebraic models in cryptography

These lectures are devoted to the characterization of descriptive, algorithmic and metric applied aspects of combinatorics-algebraic models for investigation of modern cryptography problems. Some basic ways for application of chaotic dynamics models and methods are presented. Linear and non-linear automata described by systems of equations over the ring $\mathbf Z_{p^k}$ are characterized. Some subsets of invertible automata for design of symmetric stream ciphers are considered.