Cryptography Techniques for Image Security and Authentication using Cellular Automata Algorithms

This Security and authentication are the two important criteria for any industrial product controlled through electronics. Microcontrollers interfacing along with electronic circuits, Controls various aspects of industry equipment. One among them is the communication and transfer of data between the equipment. In certain situations a need arises to secure the data and a proper authentication is required. From a small encoding and decoding methods to a high level Encryption and decryption algorithms are in use to secure data. Presently many smart devices are available in the areas of Communications, image processing, Mechatronics etc. One of the security authentication methods used for smart devices is I-Button technology. Many authentication techniques are used to secure data. Visual cryptography is one method which creates signatures by applying nonlinearity into the data. The signatures consist of cipher and the key. At the receiving end if the key and the cipher match then the authentication is done. Through this visual cryptography technique the users hide information securely based on key authentication. This paper presents a novel approach in visual cryptography using pextral coding algorithm in the framework of cellular automata. In this method a 3 x 3 matrix pextral icon is considered. A two dimensional pextral icon is a convex polygon formed of pixels in a nine neighborhood enclosing the central pixel. This central pixel is similar to a pixel considered for an image in visual cryptography where each pixel is expanded nonlinearly into four sub pixels. Now in cellular automaton dropping one, two or three pixels in the given matrix forms 16 convex polygons. Out of these 16 polygons, few will have mirror symmetry. Two such mirror symmetry polygons were considered and the central pixel of these polygons will form the image pixel. An algorithm is developed to generate two signatures on an image/jpeg image. Combining the two signatures will reconstruct the original image. Results show that no loss of information and improved security.