Enhanced least significant qubit watermarking scheme for quantum images

Abstract

Quantum watermarking aims to protect the copyright of an image and authenticate its ownership by using visible or invisible signals embedded into the carrier image. An enhanced quantum watermarking scheme is proposed on the basis of the improved novel enhanced quantum representation of digital images. In contrast to previous quantum watermarking techniques where all the pixels of a carrier image are considered, the proposed scheme utilizes the edge pixels of a carrier image, which cannot be noticed visually as the embedding region. This was accomplished by embedding the scaled watermark image into the two least significant qubits of the selected pixels on the basis of a careful analysis of the size of the edge pixels of the carrier image and the watermark image. Then, the corresponding quantum realization circuits were obtained using some basic quantum operations. Theoretical analysis and simulation-based experimental results proved both the feasibility and the capabilities of the proposed watermarking scheme, which is keyless and blind, with higher visual quality and better robustness.