Quantum Watermark Algorithm Based on Maximum Pixel Difference and Tent Map

A new quantum watermark algorithm is presented by combining maximum pixel difference partitioning with the least significant bit substitution strategy. A quantum cover image with the novel enhanced quantum image representation is divided into non-overlapping blocks. And the difference between the maximal and the minimal pixel values in a block is calculated and compared with the predefined threshold. Then the current block is defined as an edge block or a smooth block according to the comparison result. Subsequently, an edge block could be embedded into more secret information than a smooth block due to the visual characteristic of human eyes. To enhance the security of the quantum watermark algorithm, the chaos matrix obtained by tent map is utilized in the scrambling and embedding process. The scrambled quantum watermark image is embedded into a quantum carrier image with the least significant bit substitution strategy. Quantum circuit analyses demonstrate that the complexity of embedding process is O ( n 2 ). Compared with other quantum watermark schemes, the proposed quantum watermark algorithm based on maximum pixel difference and tent map could achieve a better visual quality and a higher embedding capacity.