Multiple-image encryption based on cascaded gyrator transforms and high-dimensional chaotic system

Abstract

In order to increase encryption capacity and improve transmission efficiency, this paper investigates an encryption scheme for multiple-image based on cascaded gyrator transforms and high-dimensional chaos. Firstly, each plainimage is converted into a real matrix through modulation, quaternion gyrator transform and sharing. The real matrices are connected in turn by plural coding and gyrator transforms. During the process of cascade, phase truncation and preservation operations are performed. The phase of the preceding transformation is modulated by that of the latter complex matrix to enhance security. Followed by splicing and scrambling, a real-valued ciphertext can be obtained. At the receiver end, all the plaintext images can be restituted by the reverse operation of the encryption process using the authorized keys. The adoption of high-dimensioanl chaos and Kronecker product further guarantees the security of the cryptosystem. The numerical results performed on 300 color images have demonstrated that the average PSNR of correctly decrypted images is up to 303.9939 dB, the NMSE is as low as 2.8024 × 10−28 and SSIM is equal to 1.0000. The analysis of sensitivity, statistical characteristic and robustness proves the feasibility and relibility of the proposed encryption scheme.