A plain-image dependent image encryption scheme with half-pixel-level swapping permutation strategy is proposed. In the new permutation operation, a pixel-swapping operation between four higher bit-planes and four lower bit-planes is employed to replace the traditional confusion operation, which not only improves the conventional permutation efficiency within the plain-image, but also changes all the pixel gray values. The control parameters of generalized Arnold map applied for the permutation operation are related to the plain-image content and consequently can resist chosen-plaintext and known-plaintext attacks effectively. To enhance the security of the proposed image encryption, one multimodal skew tent map is applied to generate pseudo-random gray value sequence for diffusion operation. Simulations have been carried out thoroughly to demonstrate that the proposed image encryption scheme is highly secure thanks to its large key space and efficient permutation-diffusion operations.
Thanks to the exceptionally good properties in chaotic systems, such as sensitivity to initial conditions and control
parameters, pseudo-randomness and ergodicity, chaos-based image encryption algorithms have been widely studied and
developed in recent years. A novel digital image encryption scheme based on the chaotic ergodicity of Baker map is
proposed in this paper. Different from traditional encryption schemes based on Baker map, we permute the pixel
positions by their corresponding order numbers deriving from the approximating points in one chaotic orbit. To enhance
the resistance to statistical and differential attacks, a diffusion process is suggested as well in the proposed scheme. The
proposed scheme enlarges the key space significantly to resist brute-force attack. Additionally, the distribution of gray
values in the cipher-image has a random-like behavior to resist statistical analysis. The proposed scheme is robust against
cropping, tampering and noising attacks as well. It therefore suggests a high secure and efficient way for real-time image
encryption and transmission in practice.