MATLAB-Based Software Tool for Implementation of Bifid Ciphers

The paper presents one of the classical ciphers in cryptography, the bifid cipher, a type of cipher that was used historically but now has fallen into disuse. Most classical ciphers can be practically computed and solved by hand. They are also usually very simple to break with modern technologies. In classical cryptography, the bifid cipher is a cipher which combines the Polybius square with transposition, and uses fractionation to achieve diffusion. It was invented around 1901 by Felix Delastelle. The paper presents MATLAB-based software tool implementing encryption and decryption of English texts using the bifid cipher and 3 options for creating the Polybius square: 5x5, 6x6 and 8x8. The tool will be used in the course "Telecommunication Security" by students of the specialty "Telecommunication Systems" for the Bachelor degree at the University of Ruse.