Securing Medical Images by Image Encryption Using Chaotic Key Sequence and Substitution Cipher

Abstract

Millions of images are transferred everyday across the network. Some of these images are confidential and transferred securely. Cryptography plays a significant role in transferring images securely. This paper presents two methods for encryption and decryption of medical images. In the first method the original image is encrypted by using chaotic key sequence generated by sequence of Logistic map and applied XOR operation. In the second method, to perform the encryption with some variation in substitution cipher algorithm on split sub matrices with different keys instead of sequence block of pixels. This method also uses XOR operation. Both the methods use a binary image of the same size as key for encrypting the original image. Then the reverse whole process to get original image. These processes are implemented in MATLAB environment and tested on various medical images which have shown good results. By applying this methodology, it increases the security a lot for the information and can be easily transmitted in the network.