The paper deals with various types of cryptographic systems. These are: symmetric key systems, for example, DES algorithm accepted in USA as the official cryptographic standard for protecting unclassified information, public key cryptosystems (RSA, DSS and SHS projects). The systems developed in Russia are mentioned, for example, the 'TERKOM-Kript' program system, which is a set of programs using the C language of the ANSI standard. Special versions of this system optimized for IBM AT 286, 386, and 486 are available.