Mathematical basics of cryptography, methods and means of cryptographic information protection, modern standards of encryption, basics of cryptanalysis are considered in the textbook. Stream ciphers and pseudorandom number generators, information encoding, symmetric and asymmetric encryption systems are described. Authentication methods, methods and means of electronic signature, algorithms and protocols for authentication and exchange of key information, cryptographic protocols are described. The issues of cryptographic protection of information in computer systems and data transmission networks are considered. The material of the educational publication is intended both for classroom classes and for individual and independent work of students. For students of institutions of secondary vocational education.