Patent ID: 7302078

Claim:
An apparatus for preventing illegitimate distribution of digital contents on Internet by employing a fingerprinting technique, comprising: a first wavelet image obtained by performing a wavelet transformation (WT) to an original image of the digital contents, wherein the first wavelet image has a user information embedding region; a second wavelet image obtained by performing a WT to the user information embedding region of the first wavelet image, wherein the second wavelet image is composed of a discrete cosine (DC) region and high-frequency regions; a high-frequency components removed image composed of the DC region and regions obtained by removing high-frequency components in the high-frequency regions of the second wavelet image, i.e., by setting high-frequency components other than the DC as “0”, and subjected to an inverse WT (IWT) to be outputted as an IWT image; and a user information embedding unit for embedding user information, which is provided from an operator, to the IWT image, thereby obtaining a user information embedded image with a new user information embedding region, comparing the user information embedding region of the first wavelet image with the new user information embedding region of the user information embedded image, and embedding the user information to positions where a difference value between the user information embedding region and the new user information embedding region is small while minimizing a size change of the user information embedding region in the first wavelet image, to thereby reset the user information embedding region in the first wavelet image as the user information.