1. A blind wavelet-based watermarking method for extracting at least one hidden watermark from a watermarked image, the method comprising: performing a wavelet transform to decomposed the watermarked image into a first data set in a subband LL 1 , a second data set in a subband LH 1 , a third data set in a subband HL 1 and a fourth data set in a subband HH 1 ; converting the first data set in the subband LL 1 into a first predicted data set in the subband LH 1 , into a second predicted data set in the subband HL 1 , and into a third predicted data set in the subband HH 1 via three LMS (least-mean-square) filters; and extracting the at least one hidden watermark by comparing the first predicted data set with the second data set, comparing the second predicted data set with the third data set, or comparing the third predicted data set with the fourth data set.