Cryptanalysis of an Extension of the Hill Cipher

Abstract

B. Thilaka and K. Rajalakshmi [2] propose extensions of Hill Cipher using affine transformation and polynomial transformation to make it more secure. In this article, we show that these extensions of Hill Cipher are prone to cryptanalytic attacks. We have proposed known plaintext attack for cryptanalizing ciphers based on the modified Hill Cipher system. We illustrate the method with the help of examples and show that the suggested modifications in Hill Cipher do not make it significantly stronger.