Ciphers based on special graphs

Applications of Graph theory in Cryptography have recently gained momentum. In the last two decades new methods of encryption and decryption using extremal graph theory and expander graphs have been proposed. In this work, new algorithms for binary encoding and decoding are designed. These algorithms use Hadamard encoding by generating random Hadamard matrices of order 16 × 16 from strongly regular graphs that have a specific property. Choice of keys from 16! number of random permutations makes the algorithms stronger against attacks. The performance of these algorithms is demonstrated on different images and text messages.