Cryptography of a Gray Level Image using a Novel Block Cipher Involving Feistel Structure and Modular Arithmetic

Abstract

In this paper, we have made use of a novel block cipher involving Feistel structure and modular arithmetic for encrypting a Gray level
image. The image is represented in the form of a matrix of size 256 x 256, and this is divided into 32 parts, wherein each part is of size 32 x 64.
A key of size 8 x 8 is taken and it is transformed into a key of size 32 x 32. This key is utilised in carrying out the computations required for
encryption and decryption. As the cipher is a strong one, we find that no one can identify the original image by any means.

Keywords: Block Cipher, Gray level image, Feistel structure, Modular arithmetic, Encryption, Decryption and Encrypted image.