1. A method for embedding watermarks based on integer-to-integer wavelet transform, the method comprising the steps of: (A) dividing an original image (X×Y) to a plurality of image blocks (M×N); (B) selecting image blocks for embedding a location information that indicates image blocks to be watermarked; (C) embedding the location information into the image blocks selected in the step (B); (C-1) creating a matrix (P) whose elements indicate the number of bits that can be shifted in each image block; and (D) embedding watermark and side information into remaining image blocks which are not selected in the step (B), wherein the side information includes the matrix (P) and a set of original LSBs (Bo) replaced during the embedding of the location information.