Visually Meaningful Quantum Color Image Encryption Scheme Based on Measured Alternate Quantum Walks and Quantum Logistic Mixed Linear-Nonlinear Coupled Mapping Lattices

The probability distribution generated by quantum walk may appear zero-probability at multiple positions. To avoid this limitation, the measured alternate quantum walks (MAQWs) are presented. A quantum color image encryption algorithm is presented based on the MAQWs and the quantum logistic mixed linear-nonlinear coupled mapping lattices (QLMLNCML). The plaintext image is transformed into a quantum form with quantum representation for color digital images (NCQI). Subsequently, the quantum image is divided into two sub-blocks, on which permutation and diffusion operations are respectively implemented with the probability distribution generated by the MAQWs. To achieve high randomness and high complexity, the QLMLNCML is obtained by combining the quantum logistic map with the mixed linear-nonlinear coupled mapping lattices. The two encryption sub-blocks are combined and then XORed with the quantum key images originated from the QLMLNCML to acquire the secret image. The whole encryption scheme employs the basic quantum gates, including C-NOT gate, swap gate and Toffoli gate. To further enhance the security of the cryptosystem, a novel visually meaningful image encryption algorithm is designed, and the generated visually meaningful ciphertext image is more imperceptible than the secret image. The proposed quantum color image encryption algorithm is superior to its classical counterparts in terms of security, robustness and computational complexity.