Darbe apžvelgiami esami duomenų šifravimo metodai, jų klasifikacija. Taip pat detaliai aprašomi keletas šifravimo algoritmų. Pagal AES šifravimo algoritmą sukuriama informacijos kodavimo programa Visual Basic kalba ir pademonstruojama keletas palyginamųjų rezultatų su jau egzistuojančiomis, analogiškomis programomis. / Data protection problem is relevant in now days living. This paper takes a review of the existing methods and programs in digital data cryptography. Also it explains AES (advanced encryption standard) method, the most trustful one and overviews software tool, that was coded and used in experiments analysing this algorithm. The new AES class, that was created in this project, is compared using few parameters with the older one, created by Microsoft. Despite the only purpose, to create a better program, the older implemented AES cipher class and it’s methods beats the new one.

The aim of the final Master degree work is to create a method, algorithms and program for cryptographic security of text files. The algorithms of cryptographic security and algorithms aspects are analyzed in the work. Construct program is used for coding / decoding text files using Pseudo – Random Number Generator and it is applied to use in Windows operating system. The program and instructions for its user are formed. The experimental adaption of method and program is done. The program synthesis of coding / decoding text files is described.