This paper contains a brief description of cryptographic systems that are processed in the course of Cryptology at the Faculty of Humanities and Social Sciences in Zagreb and as such should serve only as a reminder to help in teaching. In addition to the description of the substitute cryptographic system, the transposition cryptographic systems and the complex cryptographic system, the Vigenere code and DES, an asymmetric system called RSA is also described. In addition to this paper, there is an accompanying console application written using the C# programming language. After each description of the cryptographic system, instructions for using the program and the problems that arose during its creation were written. Of all the symmetric cryptographic systems processed, only DES is directly embedded in C # in the System.Security.Cryptography namespace. This built-in implementation was used in the accompanying application, because for the needs of the course a description of the concealment and disclosure procedure is sufficient, and in this way the use of the DES system is easily enabled. Of course, the accompanying console application can also be used for leisure or as additional security on untrusted Internet systems, making it the simplest way to use old cryptographic systems in modern technology.