Image Encryption Using Self-Invertible Key Matrix of Hill Cipher Algorithm

Abstract

The Hill cipher algorithm is one of the symmetric key algorithms that have several advantages in data encryption. But, the inverse of the key matrix used for encrypting the plaintext does not always exist. Then if the key matrix is not invertible, then encrypted text cannot be decrypted. In the Self-invertible matrix generation method the key matrix used for the encryption is selfinvertible. So, at the time of decryption we need not to find the inverse of the key matrix. This paper presents image encryption technique using the Hill cipher. Here we presented a proposed method of generating self-invertible matrix for Hill Cipher algorithm. Moreover this method eliminates the computational complexity involved in finding inverse of the matrix while decryption. However, a main drawback of this algorithm is that it encrypts identical plaintext blocks to identical ciphertext blocks and cannot encrypt images that contain large areas of a single color. Thus, it does not hide all features of the image which reveals patterns in the plaintext. But it works well for all other types of gray scale images as well as colour images.