A Quantum Image Encryption and Watermarking Algorithm Based on QDCT and Baker map

In many situations, the dual protection of image information transmission security and identity authentication is required. A quantum encryption and watermarking technique combining quantum Baker map (QBM) and quantum discrete cosine transform (QDCT) is presented to address this issue. Firstly, the watermark information used for identity authentication is scrambled by QBM, and the original image is decomposed by two-level quantum Haar wavelet transform (QHWT). To ensure the invisibility and robustness of the watermark, HL_1 obtained from LH is selected for further segmentation, and then QDCT is applied to HL_1 sub-block. The obtained matrix is used for watermark embedding. Special pre-processing is applied to the binary image before embedding the identity information, increasing embedding capacity while ensuring robustness and invisibility. Then the watermarked image is encrypted. In the encryption process, QBM is used for block scrambling. A quantum artificial image constructed with chaotic sequences manufactured from 3D Henon hyperchaotic system is utilized to diffuse pixel values. Quantum swap operation is used to achieve further bit-level scrambling, and the ciphertext image containing identity information is obtained. The encrypting security and the invisibility and robustness of watermarking are tested through numerical simulation.