Digital Watermarking System for Hard Cover Objects Against Cloning Attacks

Abstract

We consider an application of digital watermark system technique for hard carriers (paper or plastic cover objects in addition). Algorithms of watermark embedding and extraction are proposed and the corresponding error probabilities of the extracted bits both for informed and blind decoders are presented. The spread spectrum signals used for embedding of watermark are optimized on their parameters. Similar experimental results are presented for data matrices carriers depending on paper sizes of data matrix copies. A protection against so-called “cloning” attack is elaborated where certificates are copied by attack scanner or photo camera and next printed and fixed as forges. The formulas for a missing the cloning attack and false alarm probabilities are proved. A full-scale experiment with a real scanner and printer confirms that the reliability of cloning attack detection can be provided under appropriate selection of watermark system parameters.