Some existing image encryption schemes use simple low-dimensional chaotic systems, which makes the algorithms insecure and vulnerable to brute force attacks and cracking. Some algorithms have issues such as weak correlation with plaintext images, poor image reconstruction quality, and low efficiency in transmission and storage. To solve these issues, this paper proposes an optical image encryption algorithm based on a new four-dimensional memristive hyperchaotic system (4-D MHS) and compressed sensing (CS). Firstly, this paper proposes a new 4-D MHS, which has larger key space, richer dynamic behavior and more complex hyperchaotic characteristics. The introduction of CS can reduce the image size and the transmission burden of hardware devices. The introduction of double random phase encoding (DRPE) enables this algorithm has the ability of parallel data processing and multi-dimensional coding space, and the hyperchaotic characteristics of 4-D MHS make up for the nonlinear deficiency of DRPE. Secondly, a construction method of the deterministic chaotic measurement matrix (DCMM) is proposed. Using DCMM can not only save a lot of transmission bandwidth and storage space, but also ensure good quality of reconstructed images. Thirdly, the confusion method and diffusion method proposed are related to plaintext images, which require both four hyperchaotic sequences of 4-D MHS and row and column keys based on plaintext images. The generation process of hyperchaotic sequences is closely related to the hash value of plaintext images. Therefore, this algorithm has high sensitivity to plaintext images. The experimental testing and comparative analysis results show that proposed algorithm has good security and effectiveness.
Traditional visually meaningful image encryption (VMIE) works by embedding a secret image (SI) into a visually meaningful carrier image (CAI), thus achieving the dual protection of both data information and appearance features. However, the current VMIE algorithm still suffers from problems of reconstruction quality and transmission efficiency. To address these issues, this paper proposes an innovative VMIE algorithm that utilizes a newly designed two-dimensional hyperchaotic map, multi-parameter fractal matrix (MPFM) theory and compressive sensing. The proposed algorithm achieves dual protection of both the semantic information and appearance image data. First, a newly designed 2D infinite triangle folding map (2D-ITFM) is presented to generate a binary key-controlled measurement matrix to measure and compress a plain image (PI) to generate measured image (MI) and decrease the amount of transmission information. Next, based on the hyperchaotic map 2D-ITFM and MPFM, we present the inter-block scrambling (IBS) algorithm and intra-block synchronous sorting diffusion (IBSSD) algorithm, which are used to process the MI and generate SI. Then, the matrix encoding embedding (MEE) technique is utilized to hide the SI into the CAI to produce a visually secure cipher image (CII). Finally, the experimental results demonstrate that our scheme is effective in improving the anti-attack ability while guaranteeing good imperceptibility and reconstruction performance. This scheme can be employed in the field of information security communication.
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