Electronic marking and identification techniques to discourage document copying

Abstract

Abstract-Modern computer networks make it possible to distribute documents quickly and economically by electronic means rather than by conventional paper means. However, the widespread adoption of electronic distribution of copyrighted material is currently impeded by the ease of unauthorized copying and dissemination. In this paper we propose techniques that discourage unauthorized distribution by embedding each document with a unique codeword. Our encoding techniques are indiscernible by readers, yet enable us to identify the sanctioned recipient of a document by examination of a recovered document. We propose three coding methods, describe one in detail, and present experimental results showing that our identification techniques are highly reliable, even after documents have been photocopied.

Text Steganographic Approaches: A Comparison

“…For example, point in letters i and j can be displaced, length of strike in letters f and t can be changed, or by extending or shortening height of letters b, d, h, etc. [6,14]. A flaw of this method is that if an OCR program is used or if re-typing is done, the hidden content would get destroyed.…”

Multimedia Data-Embedding and Watermarking Technologies Manuscript received July 15, 1997; revised January 15, 1998. The Guest Editor coordinating the review of this paper and approving it for publication was A. M. Tekalp. This work was supported in part by the Air Force Office of Scientific Research under Grant AF/F49620-94-1-0461 and in part by the Advanced Research Project Agency under Grant AF/F49620-93-1-0558.Publisher Item Identifier S 0018-9219(98)03519-1.

“…Embedding of messages by lowering specified letters and varying spacing between words appears time and again throughout history. Recently, the technique has been revisited in a digital context by scientists who are investigating digital watermarking of text files [6], [49], [56], [93], [98]. Examples of nontextual semagrams are equally replete.…”

“…In a second scheme, which uses ordered dithering, an image is divided into 4-by-4 pixel blocks and brightness thresholds ; for each of the 16 pixels in the block are assigned from top to bottom, left to right. Next, define sets (6) Let be a pair of output signals that pass through . Then is either , , , or , where 0 indicates that the pixel will be turned "off" and 1 indicates "on."…”

“…North Carolina State University's SHANG Group has developed software called "Secure MPEG," which is available for free over the Internet. 6 Sanford et al are currently investigating extensions of their data-embedding method for still images to video data [80].…”

DHWM: A scheme for managing watermarking keys in the Aquarelle multimedia distributed system

“…-The algorithm introduced in [15] is envisaged to have application in image tagging, copyright enforcement, counterfeit access and controlled access, although the authors do not explain how to use their algorithm to perform these functionalities. -In [1], electronic marking is applied to textual document, by word or line…”