Hybrid approach for dual image encryption using nibble exchange and Hill-cipher

Information security is a very important and high priority topic in the fast growing internet technology. Encryption is one of the ways to secure information. This paper presents an approach to improve the entropy of an encrypted image using Hill-cipher technique. Dual image encryption process involves three stages including Hill-cipher technique. In first stage each pixels of both the images are bitwise rotated and reversed to manipulate the pixel value. In second stage, lower nibbles in each pixel of two resultant images are exchanged. Hill-cipher is applied in stage three to obtain the final encrypted images. The resultant encrypted images are found to be more distorted and having higher entropy. This hybrid approachis implemented using LabVIEW. Decryption operation follows the reverse process of encryption, which results in undistorted images.