A Quantum Color Image Watermarking Protocol Based on Least Significant Bit

Quantum watermarking uses quantum images as carriers to achieve secure transmission of secret information. In this paper, a quantum color image watermarking protocol based on LSB (Least Significant Bit, LSB) is proposed. Firstly, the protocol divides an image into several 2×2 non-overlapping blocks. Next, watermarking image calculates the absolute differences with R channels of carrier image, and embeds it into the minimum difference position. Then, taking watermarking image clockwise is embedded into the carrier image counterclockwise. Embedding all blocks generates a $2^{n}\times2^{n}$ watermarked image finally. The extraction is the reverse process of embedding. This protocol also gives quantum circuit diagrams for embedding and extraction. Simulation results show that the protocol has a high embedding capacity up to 8 bits/pixel, PSNR (Peak Signal-to-Noise Ratio, PSNR) over 40 dB, SSIM (Structural Similarity Index Metric, SSIM) around 0.98, and the complexity lower than $o(2^{2n2})$.