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.