Abstract: The present invention relates to a method for embedding and detecting watermark wherein forgery/alternation of image can be identified and the location of forgery/alternation can be verified by embedding and detecting watermark into a digital image which is shot in real time. Watermark is generated by using a quantized coefficient after frequency transform used in the compression process. By embedding this into an image, image can be compressed simultaneously with embedding watermark. The present invention discloses a method for embedding robust watermark which embeds a random sequence circular shifted from an original pseudo random sequence by the distance d as watermark into an image. The present invention discloses a technology for generating and embedding watermark by using a DCT coefficient quantized during the process for MPEG compressing the image, wherein said watermark can be generated and embedded in a unit of macro blocks or slices.