Robust attack-aware spread spectrum watermarking in real scenes

Abstract

Digital image watermarking hides copyright information in digital images and allows for its extraction when necessary to confirm ownership. Imperceptibility and robustness, the key indices of watermarking performance, constrain each other and are affected by the embedding location and weight. Existing techniques resolve this constraint by prioritizing imperceptibility while endeavoring to maximize robustness, which still entails a risk of missing higher visual quality or a failure in watermark extraction in real scenes. When the spread spectrum scheme is applied to embed watermarks in the discrete cosine transform domain, the embedding location and weight are not well calibrated. The embedding location is heuristically selected from among the divisions of the frequency domain, and the determination of the embedding weight relies on the predetermined imperceptibility. We address the issue between imperceptibility and robustness with the opposite strategy, prioritizing robustness while maximizing imperceptibility, and propose the attack-aware spread spectrum watermarking (ASSW) algorithm. ASSW takes prior attacks into consideration when determining the embedding location and weight with three goals: ensuring the stability, small modulus and small weight of the feature vector of the embedding location. Our experiments indicate that, with a carefully calibrated embedding location and weight, ASSW achieves greater imperceptibility and robustness than the state-of-the-art methods both on average and individual images.