Entropy and information theory. The complexity of algorithms and complexity classes. Classic encryption systems. Modern encryption systems. Symmetric and asymmetric encryption systems. One-way functions. Hash functions. The problem of number factorization. Discrete logarithm problem. Cryptanalysis of classical encryption systems. Cryptanalysis of sequential encryption algorithms. Correlation techniques. Techniques of recognition. Techniques related to a compromise between time and memory. Linear cryptanalysis. Differential cryptanalysis.