The book is an introductory course in cryptology, based on the author's lectures at the Munich Institute of Technology and the materials of a seminar on cryptanalysis methods. The first part is devoted to the classical field of cryptography. Replacement ciphers and permutation ciphers are described in detail - the main bricks of symmetric cryptosystems. The analysis of this class of ciphers has been brought to modern implementations (DES and IDEA ciphers). With a smaller level of detail, public key encryption is considered. In the second part, on the classic examples of disclosing known ciphers, the main techniques of cryptataks are described - this is the first systematic presentation of cryptanalysis in Russian. The presentation is accompanied by numerous examples. Historical excursions included by the author make reading a book fascinating. The book has no analogues in Russian. It will be of interest to specialists and can be recommended to lovers of mathematics, cryptography and history, students, teachers and high school students.