Quantum Image Watermarking Based on Quantum State Modification Using Rotation Gate

Information and Communication Technology (ICT) has significantly developed nowadays, making things easier for users. However, alongside the ease of communication, several concerns arise, particularly regarding data authenticity. Security, which affects the authenticity of data, is a major concern. Quantum watermarking offers a much better solution for this problem in the next generation of technology, as it provides superior security compared to classical watermarking. In this paper, we propose a quantum watermarking method using Taylor sequence modification and rotation gates for watermark embedding. Before the embedding process, we convert the images into the quantum domain using the Flexible Representation of Quantum Images (FRQI). We then calculate the phase representation of the host and watermark pixels. Using a Taylor sequence, we modify the watermarked phase and calculate the difference between the host and watermarked phases. Several rotation gates are used to modify the host phase on the quantum circuit. At the end of the embedding process, we reconstruct the watermarked quantum images into a classical images. The experimental results demonstrated watermarking imperceptibility, represented by Peak Signal to Noise Ratio-H (PSNR-H) and watermark robustness, represented by Peak Signal to Noise Ratio-W (PSNR-W). The PSNR-H values ranged between 10–80 dB, while the PSNR-W values reached up to 20 dB. This proposed method has a unique outcome even when the PSNR-H value is infinite, the watermark can still be detected and is subjectively visible to the human eye.