Training module with graphical user interface for encryption and decryption using affine ciphers applied in cryptosystems

The paper describes the algorithm and the developed training module with graphical user interface for encryption and decryption of texts using affine ciphers, which will be used in the course “Telecommunications Security” included as compulsory in the curriculum of the specialty “Telecommunication Systems” for “Bachelor” educational qualification degree at the University of Ruse. The training module is implemented using MATLAB and Graphical User Interface Development Environment GUIDE. The application allows selecting the language through radio-buttons and the parameters of the encryption/decryption key from a drop-down menu. It illustrates step by step the process of encryption/decryption of the plain-text/cipher-text entered in the text field by the user, using affine ciphers. The novelty is that the algorithm for encryption/decryption of texts in English using affine ciphers is modified to be used for texts in Bulgarian, Russian or Romanian and it could be implemented in other languages (depending on the number of letters in the alphabet). The module has a possibility to display information on affine ciphers and to illustrate the principle of its operation in a separate graphical window, if desired by the user.