关键词: 数字水印，分数阶微分，小波变换，微分阶次

Abstract: In this paper, a novel digital watermark algorithm, based on fractional calculus and wavelet transform, for still images is proposed. It makes fully use of the characteristic of the fractional order that is highly sensitive. The algorithm makes sinusoidal signal by fractional Cauchy formula with two differential orders. The sampled signals of the differential signals were superimposed as the pseudo-random sequence which is used to scramble the watermark. By exchanging the high-frequency coefficients of the carrier image, the scrambled watermark was embedded into the carrier image. Several experiments to verify the proposed method are given and the results show that this novel algorithm is robust to a number of regular geometric attacks and other image processing operations. The new method has a good performance on both robustness and invisibility.

Key words: digital watermarking，fractional calculus，wavelet transform，differential-order