Bit-Plane Image Encryption Using Parallel Chaos Mapping

To improve the cryptographic robustness and dynamical behavior of traditional one-dimensional chaotic maps, this study introduces a novel image encryption scheme that integrates a parallel chaotic framework with bit-plane level processing. The proposed system incorporates a delayed feedback unit into a multi-map parallel structure, thereby enhancing the nonlinearity and coverage of the state space while reducing the risk of short cycles and degradation. The input image is separated into high and low-order bit planes, which are processed through mutually coupled diffusion and inter-group permutation mechanisms. This structure not only strengthens the encryption capability but also increases resistance against statistical analysis and differential cryptanalysis. Experimental validations confirm that the method offers strong performance in both encryption and decryption. The histogram of the encrypted image approximates uniform distribution, the pixel correlation is significantly reduced, the NPCR reaches $\mathbf{9 9. 6 2 \%}$, and the key space exceeds $2^{100}$, meeting the requirements of information security applications.