To ensure stringent security strategies for image information involving personal privacy during conveyance and storage, we propose an innovative multiface privacy protection scheme based on chaos theory. Compared to single-face encryption algorithms, the proposed scheme has broader potential applications in fields, such as smart cities and smart transportation. Specifically, a new spatiotemporal chaotic system named the sine-cosine coupled mapping lattice system (SCCML) is designed. It features a larger parameter domain, complexity, and profound unpredictability, yet maintains a simpler construction aimed at providing potential benefits and implementations in the field of information security. In the proposed multiface privacy protection scheme, multiple faces within an image are rapidly and accurately identified and then encrypted using the proposed SCCML-based digital separation loop encryption algorithm. The encryption algorithm exhibits a synchronous scrambling diffusion mechanism. Additionally, the introduction of mixed multibase cascade diffusion offers multiple layers of security for facial data, prevents diffusion singularity, and enhances diversity, making it significantly more challenging to crack. Experimental verification on a real multiface image dataset shows that the algorithm is superior, practical, safe, and efficient.

It is analyzed that the important part of the fingerprint image is concentrated in one part of the image, and the gray image is the part with useful information in the whole image. Therefore, this paper combines a new fingerprint image encryption algorithm proposed by combining two new one-dimensional chaotic systems, nonlinear functions , and rules with a dynamic "X" model. We propose two new one-dimensional chaotic systems, one is Sin-Cos chaotic system (SCCS) and the other is Cos-Cos chaotic system (CCCS). Firstly, the fingerprint image is binarized and the contour is extracted to get the area of the fingerprint in the image. Then, for the fingerprint area, a round of encryption is carried out by using nonlinear rules and 24 rules of the dynamic X model. Then the whole image is separated into several parts according to the fingerprint position, read into a sequence at one time, and the whole fingerprint image is scrambled and diffused synchronously by using nonlinear rules and functions. The entropy, NPCR, and UACI of the algorithm are very close to the ideal value, and the performance in time efficiency is passable. The algorithm is extremely secure in a large number of test performance analysis results.

This article proposes a new infinite parameter range spatiotemporal chaotic system named improved sinusoidal dynamic non-adjacent coupled mapping lattice (ISDNCML). The system performance test shows that ISDNCML has more random lattice interaction, better chaos and excellent cryptography. Based on the characteristics of ISDNCML, the globally coupled private image encryption algorithm is proposed. The algorithm first identifies the private area of an image and then couples the private and non-private areas for encryption. While coupling encryption, ill-conditioned dynamic diffusion is introduced into the private area, which avoids the repeated encryption of the private area on the premise of ensuring the security of private information. The security and practicability of this proposed cryptographic system are verified by the analysis of ISDNCML and various tests of encryption effect.

Although image encryption is developing rapidly, it lacks the pertinence of specific scenarios. This paper proposes a complementary embedding encryption strategy. The strategy firstly identifies the airport area, then replaces the optimal similar area and embeds the airport image into a random position through the complementary embedding algorithm. In the encryption stage, to generate a better key stream, we propose an improved sine cross coupled mapping lattice (ISCCML). Comprehensive performance analysis shows that ISCCML has a larger parameter space and better chaotic cryptographic properties. Furthermore, a fractal disordered matrix (FDM) with iterative and out-of-order properties is presented for the simultaneous scrambling diffusion of images. In particular, the encryption algorithm has generalization and is also suitable for ordinary image encryption. Our results indicate that the proposed scheme can avoid repeated encryption on the premise of ensuring the security of important information; at the same time, the security analysis shows that our algorithm has security, practicality and scalability.

For the security of multiple image regions of interest, this paper designs a multi-image visual encryption algorithm based on region of interest (ROI). Firstly, a new one-dimensional chaotic system (1-DLCP) is proposed. The performance analysis shows that the system has better dynamic behavior. Then, the salient parts of multiple images are extracted using multilayer cellular automata saliency detection. The measured matrix generated by the proposed chaotic system compresses the extracted plaintext images respectively. The compressed image and the extracted salient parts are recombined into one image, and a scrambling-diffusion synchronization operation is performed on the recombined image to obtain a secret image. The final embedding stage uses integer wavelet transform (IWT) to embed the secret image into a color carrier image. It is worth mentioning that this design scheme not only reconstructs the significant part without damage, but also reduces the storage space.

Since chaotic cryptography has a long-term problem of dynamic degradation, this paper presents proof that chaotic systems resist dynamic degradation through theoretical analysis. Based on this proof, a novel one-dimensional two-parameter with a wide-range system mixed coupled map lattice model (TWMCML) is given. The evaluation of TWMCML shows that the system has the characteristics of strong chaos, high sensitivity, broader parameter ranges and wider chaos range, which helps to enhance the security of chaotic sequences. Based on the excellent performance of TWMCML, it is applied to the newly proposed encryption algorithm. The algorithm realizes double protection of private images under the premise of ensuring efficiency and safety. First, the important information of the image is extracted by edge detection technology. Then the important area is scrambled by the three-dimensional bit-level coupled XOR method. Finally, the global image is more fully confused by the dynamic index diffusion formula. The simulation experiment verified the effectiveness of the algorithm for grayscale and color images. Security tests show that the application of TWMCML makes the encryption algorithm have a better ability to overcome conventional attacks.