Extrinsic signatures embedding and detection for information hiding and secure printing in electrophotography

Printer identification based on printed documents can provide forensic information to protect copyright and verify authenticity. In addition to intrinsic features (intrinsic signatures) of the printer, modulating the printing process to embed specific features (extrinsic signatures) will further extend the encoding capacity and accuracy. One of the key issues with embedding extrinsic signature is the information should not be detectable by the human observer, but needs to be detectable by a suitable detection algorithm. In this paper, we discuss the methods used to develop the amplitude threshold and frequency constraints for embedding extrinsic signature in electrophotography by modulating laser intensity