In this paper a new quaternion-based lossless encryption technique for DICOM images is proposed. We have scrutinized and slightly modified the concept of the DICOM Network to point out the best location for the proposed encryption scheme, which significantly improves speed of DICOM images encryption in comparison to those originally embedded into DICOM AES and 3DES algorithms. The proposed algorithm decomposes a DICOM image into two 8-bit gray-tone images in order to perform encryption.
The algorithm implements Feistel network like the scheme proposed by Sastry and Kumar (2012). It uses special properties of quaternions to perform rotations of data sequences in 3D space for each of the cipher rounds. The images are written as Lipschitz quaternions and modular arithmetic was implemented for operations with the quaternions. A computer-based analysis has been carried out and obtained results are shown at the end of this paper.