A method of encoding a watermark into a digital image is provided. The method includes partitioning an image into a plurality of blocks of a same size; accumulating the plurality of blocks of the same size into a single block image; performing a Fourier transformation on the single block image to obtain a two-dimensional Fourier spectrum defined by Fourier coefficients at different positions of a Fourier domain; inserting a watermark into a frequency domain of the two-dimensional Fourier spectrum by modifying the two-dimensional Fourier spectrum as a function of watermarking coefficients in the watermark, to obtain a modified Fourier spectrum; performing an inverse Fourier transformation on the modified Fourier spectrum to obtain a watermarked image; copying the watermarked image horizontally and vertically into a plurality of copied watermarked images; and splicing the plurality of copied watermarked images into a reconstituted watermark image.