A plaintext-related image protection scheme based on dynamic Josephus ring and simultaneous permutation-diffusion operations

Currently, various encryption methods have been suggested to address the in-creasing worries about image data security. Weaknesses have been identified in current image cryptosystems. One issue is that these cryptosystems do not link the encryption key to the plaintext image. Another problem is that they use permutation and diffusion operations separately, leading to a time-consuming encryption process and independent operations, which can make separate attacks feasible. We propose a plaintext-related image cryptosystem to address these vulnerabilities using simultaneous permutation-diffusion operations. Initially, the key generation of a two-dimensional Ikeda map is per-formed based on the input key and statistical plaintext image. Then, the plaintext image is divided into eight blocks. After that, we scramble the blocks using an improved Josephus ring to decrease the correlation between the adjacent regions. The scrambled blocks are then reorganized into one matrix. Finally, the simultaneous encryption architecture is applied to change the value and position of the pixels simultaneously to avoid separate attacks and decrease the encryption time. The proposed cryptosystem has been rigorously evaluated using a set of new and fair tests, demonstrating its robustness, efficiency, and strong resistance to various attacks. Compared to recent cryptosystems, it outperforms in several key metrics, including an impressive average Chi-square value of 260.586, a high local entropy of 7.908, and a CDR measure of 99.602%. Additionally, the cryptosystem achieves an efficient encryption time of 0.094 seconds, a high encryption throughput of 8.0559 MB/s, and an optimized number of cycles per byte at 321, highlighting its superior performance in security and speed. Therefore, the proposed system is appropriate for current image encryption applications.