Novel Modified Hill Cipher Algorithm

Abstract

The Hill cipher algorithm is one of the symmetric key algorithms that have several advantages in data encryption. However, a drawback of this algorithm is that the inverse of the matrix used for encrypting the plaintext does not always exist. So, if the matrix is not invertible, the encrypted text cannot be decrypted. This paper presents a variant of the Hill cipher that overcomes this disadvantage. The proposed technique adjusts the encryption key to form a different key for each block encryption. The proposed variant yields higher security compared to the original one. Also in this paper, a method of generating self-invertible matrix for Hill Cipher algorithm has been proposed. In the self-invertible matrix generation method, the matrix used for the encryption is itself self-invertible. So, at the time of decryption, we need not to find inverse of the matrix. Moreover, this method eliminates the computational complexity involved in finding inverse of the matrix while decryption.