A Robust Image Encryption Scheme Based on Quantum Walks and Dynamic DNA for Secure Cloud Applications

With the rapid development of cloud-based services, ensuring the confidentiality of image data in cloud environments has become increasingly critical. Furthermore, advances in quantum computing pose a significant threat to traditional cryptosystems, including those used in cloud systems, as they may become vulnerable to quantum-based attacks. This paper presents a robust image encryption approach based on integrating quantum walks, a 4-D hyperchaotic system, and dynamic DNA operations to ensure high security. To enhance sensitivity to the plain image, our encryption algorithm initializes the hyperchaotic system with key parameters, generating chaotic sequences that are used to substitute the plain image. It then extracts information from the initially substituted image to update the binary message that controls the operation of quantum walks while simultaneously updating the initial parameters of the hyperchaotic system. These updated parameters operate both the quantum walks and the hyperchaotic system. The probability distribution generated by the quantum walks is integrated with the chaotic sequences of the hyperchaotic system to permutate the DNA-encoded image sequence, perform dynamic DNA operations, and execute dynamic DNA decoding, thereby increasing complexity and enhancing security. Finally, after decoding, the pixel permutation and substitution processes are applied to produce the final cipher image. Experimental analysis demonstrates that the proposed approach achieves high encryption quality and robust resistance to cryptographic attacks, which makes it suitable for secure cloud-based services. The results show an average correlation coefficient of -0.00007, a Chi-square of 254.26013, NPCR of 99.61238%, UACI of 33.45688%, global entropy of 7.99954, local entropy of 7.90219, PSNR of 7.8537, key space of 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">240</sup>, and an encryption speed of 0.1426 megabits per second.