FAST IMPLEMENTATION OF DIGITAL WATERMARKING SCHEMES BASED ON ARNOLD AND DISCRETE WAVELET TRANSFORMS
Keywords: Digital Watermarking, Arnold Transform, Discrete Wavelet Transform, Lookup Table
Abstract. In recent years, digital watermarking of photo and video materials has become more and more important in connection with the transmission of multimedia data over unsecured communication channels. Digital watermarking allows to reduce the amount of transmitted information and to protect embedded metadata. Improving robustness and security of embedded data increases computational costs, which obstruct usage of digital watermarks in mobile devices. In this research, we propose a number of improvements to the digital watermarking process based on Arnold and discrete wavelet transforms to reduce the computational cost. Considering the watermark as a linear sequence of pixels allows us to speed up its processing. The two-dimensional lookup table allows performing an Arnold transform in constant time regardless of the number of iterations. Number of iteration for each block of watermark is determined using hash function applied to the secret key. Also, the structure of the lookup table is proposed to accelerate the embedding of watermark. This table allows to determine the frequency coefficients for embedding based on the key hash code. Proposed improvements allow to speed up the watermark preparation by an average 14 times and the overall embedding process by 1.22 times for 1920×1080 images.