Intrinsic and Extrinsic Signatures for Information Hiding and Secure Printing with Electrophotographic Devices

There are a number of applications in which it is desirable to be able to identify the technology, manufacturer, model, or even specific unit that was used to print a given document. Also, it may be desirable to embed additional information in the printed document, such as the date and time that it was printed. In previous work with laser electrophotographic printers, we developed strategies to reduce quasiperiodic banding artifacts that are characteristic of the specific print mechanism. The dominant process-direction spatial frequencies associated with these artifacts are determined by the parameters of the gear train in the print mechanism. Here we take a different view of these artifacts, treating them as a signature of the printer that can be identified by appropriate image analysis techniques. We refer to the characteristics of the native device as its intrinsic signature. By using the same strategies employed earlier to reduce the banding artifacts, we can amplify and modulate the banding to embed additional information, as discussed above. We refer to this as an extrinsic signature. In this paper, we describe our on-going research in this area. We present preliminary results from our effort to identify intrinsic printer signatures for a number of electrophotographic printers that are now on the market.