Printer Mechanism-Level Data Hiding for Halftone Documents

∗ Research partially supported by the National Science Foundation under Grant No. 0524540-CNS Abstract Techniques to embed information in printed documents have lately attracted considerable attention due to their various applications such as copyright protection and forensic document examination. One method is to embed data in the halftone portions of a document during the printing process. The printed hardcopy might then contain information about the printer that includes manufacturer, model name, and serial number, or information about the document, such as copyright, confidentiality, and date printed. However, previous approaches have mainly focused on methods that modify only the halftoning algorithm itself without considering the printer mechanism. Embedding data at the printer mechanism-level is desirable, since it is more robust and flexible. In this paper, we describe a printer mechanism-level information embedding and detection scheme for halftone documents that is suitable for electrophotographic laser printers. After we embed the information, the printed document is scanned for image analysis and data extraction. These processes include specific means to account for the inherent instability of the EP process and resulting noise in the scanned images. Preliminary experimental results suggest that our proposed scheme is feasible although much work remains to be done to fully prove out the concept.