Gabor Filter Based Attack on Printed Documents Protection Methods via Digital Watermarks

In this paper an attack on information hiding algorithms used for protection of printed documents or covert communication through them is proposed. This universal attack is applicable to a broad class of algorithms, in which information embedding is carried out by visually imperceptible distortion of background texture of documents. This attack, based on spectral analysis of electronic copies of printed documents and used Gabor filtering, makes it possible to extract the embedded information, and in some cases to determine the key of the attacked watermarking or steganography system. This key can then be used for insertion of own information in any appropriate container. Examples of successful data extraction using the proposed technique are shown.