An image encryption scheme based on a modified AES algorithm by using a variable S-box

• Published in: Journal of optics (New Delhi) Vol. 53; no. 2; pp. 1170 - 1185
• Main Authors: Hadj Brahim, A., Ali Pacha, A., Hadj Said, N.
• Format: Journal Article
• Language: English
• Published: New Delhi Springer India 01.04.2024; Springer Nature B.V
• Subjects: Algorithms; Boxes; Encryption; Lasers; Optical Devices; Optics; Photonics; Physics; Physics and Astronomy; Research Article; Image encryption; Hyperchaotic system; AES; Substitution-box
• ISSN: 0972-8821; 0974-6900
• DOI: 10.1007/s12596-023-01232-8

This paper proposes a new image encryption scheme based on AES by using a variable S-box. The plain image is divided into blocks of the same size (128 bits), and then each block is encrypted by using AES, where the S-box needed is generated each time by the hyperchaotic system, which means each block is encrypted by a different S-box for the AES. This technique secures the image better than classical AES because, instead of using only one public S-box as in classical AES, the proposed method uses a hyperchaotic system to construct several secret S-boxes. To construct the S-box, the hyperchaotic system creates a sequence. The sequence values are then stored in ascending order to produce a sequence known as the AES algorithm's S-box. The last value of the previous sequence is used to construct the S-box of the next block and it is considered as the initial condition of the hyperchaotic system. Changing the S-boxes makes it possible to obtain different encrypted blocks even if the original blocks are the same. The cipher image is obtained after encrypting all of the plain image's blocks. Experimental and analytical results show that the proposed algorithm performs effectively in terms of security, key space expansion, and resistance to several attacks.