Pei-Ju Chiang

Printer identification based on graylevel co-occurrence features for security and forensic applications

In todays digital world securing different forms of content is very important in terms of protecting copyright and verifying authenticity. Many techniques have been developed to protect audio, video, digital documents, images, and programs (executable code). One example is watermarking of digital audio and images. We believe that a similar type of protection for printed documents is very important. The goals of our work are to securely print and trace documents on low cost consumer printers such as inkjet and electrophotographic (laser) printers. We will accomplish this through the use of intrinsic and extrinsic features obtained from modelling the printing process. In this paper we describe the use of image texture analysis to identify the printer used to print a document. In particular we will describe a set of features that can be used to provide forensic information about a document. We will demonstrate our methods using 10 EP printers.

Printer and scanner forensics

Contrary to popular opinion, the use of paper in our society will not disappear during the foreseeable future. In fact, paper use continues to grow rather than decline. It is certainly true that as individuals, we may be printing less than we used to. And the role of paper has been transformed from the archival record of a document to a convenient and aesthetically appealing graphical user interface. The use of paper is now intimately linked to the electronic systems that capture, process, transmit, generate, and reproduce textual and graphic content. Paper can be thought of as an interface between humans and the digital world. If this interface is not secure, the entire system becomes vulnerable to attack and abuse. Although paper is read by humans in the same way that it has been for millennia and has had the same fundamental form and composition for almost that long, the technologies for printing and scanning documents and capturing their content have evolved tremendously, especially during the last 20 years. This has moved the capability to generate printed documents from the hands of a select few to anyone with access to low-cost scanners, printers, and personal computers. It has greatly broadened the opportunities for abuse of trust through the generation of fallacious documents and the tampering with existing documents, including the embedding of messages in these documents.

Information embedding and extraction for electrophotographic printing processes

In todays digital world securing different forms of content is very important in terms of protecting copyright and verifying authenticity. One example is watermarking of digital audio and images. We believe that a marking scheme analogous to digital watermarking but for documents is very important. In this paper we describe the use of laser amplitude modulation in electrophotographic printers to embed information in a text document. In particular we describe an embedding and detection process which allows the embedding of 1 bit in a single line of text. For a typical 12 point document, 33 bits can be embedded per page.

Printer and Scanner Forensics: Models and Methods

Contrary to popular opinion, the use of paper in our society will not disappear any time during the foreseeable future. In fact, the use of paper continues to grow rather than decline. It is certainly true that as individuals, we may be printing less than we used to. And the role of paper has been transformed from the archival record of a document to a convenient and aesthetically appealing graphical user interface. The use of paper is now intimately linked to the electronic systems that capture, process, transmit, generate, and reproduce textual and graphical content. Paper can be thought of as an interface between humans and the digital world. If this interface is not secure, the entire system becomes vulnerable to attack and abuse. Although paper is read by humans in the same way that it has been for millennia, and has had the same fundamental form and composition for almost that long as well, the technologies for printing and scanning documents and capturing their content have evolved tremendously, especially during the last twenty years. This has moved the capability to generate printed documents from the hands of a select few to anyone with access to lowcost scanners, printers, and personal computers. It has greatly broadened the opportunities for abuse of trust through the generation of fallacious documents and tampering with existing documents, including the embedding of messages in these documents.

Channel model and operational capacity analysis of printed text documents

In todays digital world securing different forms of content is very important in terms of protecting copyright and verifying authenticity. One example is watermarking of digital audio and images. We believe that a marking scheme analogous to digital watermarking but for documents is very important. In this paper we describe the use of laser amplitude modulation in electrophotographic printers to embed information in a text document. In particular we describe an embedding and detection process which allows the embedding of between 2 and 8 bits in a single line of text. For a typical 12 point document this translates to between 100 and 400 bits per page. We also perform an operational analysis to compare two decoding methods using different embedding densities.

Extrinsic Signature Embedding and Detection in Electrophotographic Halftoned Images Through Exposure Modulation

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 decoding accuracy. One of the key issues with embedding extrinsic signatures is that the embedding should not degrade the image quality, but needs to be detectable by a detection algorithm. In this paper, we will demonstrate the feasibility of embedding code sequences in electrophotographic halftone images by modulating dot size through laser intensity modulation. We have developed corresponding embedding and detection algorithms to embed and extract information. Experimental results indicate that using a 600 dpi native resolution printers default halftone algorithm, we can encode 5 bits of information in every 310 printer scan-lines or approximately every 0.5 inches.

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

INFORMATION EMBEDDING AND EXTRACTION THROUGH EXPOSURE MODULATION FOR ELECTROPHOTOGRAPHIC TEXT DOCUMENTS

Abstract 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 signature (extrinsic signatures) will further extend the encoding capacity. In this paper we describe the use of laser modulation in electrophotographic printers to embed information in a text document. In particular we describe an embedding and detection process which allows the embedding of 1 bit in a single line of text. For a typical 12 point document with 50 lines of text, 33 bits can be embedded per page.