R i g h t s M a n a g e m e n t

RIGHTS MANAGEMENT DIGITAL WATERMARKING AS A FORM OF COPYRIGHT PROTECTION

Thomas Page

This article assesses the advance of digital water-marking as a form of rights management in the protection and authentication of digital images, audio and video files.

WHAT IS DIGITAL WATERMARKING?

Watermarking of paper has been used as a torm of identifying and validating documents for hundreds of years. The most obvious example is banknotes where watermarks are used as an extra layer of protect ion from counterfeiting.

Recent technology has allowed the principle of water- marking to be extended to digital images, audio and video files. As with the paper version, digital watermarking adds intbrmation which is normally" invisible or barely visible to the naked eye, but which can be detected in order to identil): the authenticity or copyright owner of the image, video or sound. For some purposes, however, a visible mark may actu- ally be a better deterrent than an invisible mark and these are often used, for example, by cable and satellite television chan- nels, where the station logo is often permanently placed in one corner of the screen.

WHY IS WATERMARKING USEFUL?

This decade has witnessed an explosion in the distribution of electronic digital publishing via media such as compact discs, CD-ROMs and the Internet as well as the latest technologies of digital video discs (DVDs) and digital television. This mass of digital technology has made copying and distributing illegal copies of copyright-protected material fast, easy and cheap.

In order to combat the potentially disastrous losses to their revenue streams, the major owners and distributors of copyright material, such as image libraries, music and film companies and online publishers, have sought ways to detect and prevent copyright infringement. Watermarking enables these owners or distributors to label material in order to make detection and proof of infringement easier as can be seen from the case study below.

It is already possible to use a 'spider' or 'Web crawler' to trawl the Internet searching lbr images which contain a par- ticular embedded copyright notice.~ These spiders use soft- ware similar to those used by Internet search engines, in that they will search sites and tbllow links from that site to others. The purpose is to cover as many sites as possible checking the images used on each page lbr watermarks.

IBM and NEC have recently agreed a standard for water- marking DVDs which they claim will enable them to prevent

illegal copying.They propose to insert chips into DVD video players and DVD drives which would detect watermarks in copyright material and prevent the content being copied, as well as preventing the play-back of illegal copies of the con- tent. However, in order to promote the use of recordable dri- ves, users would still be able to make a single copy for back-up purposes or for later viewing of a television broad- cast, as is currently allowed for standard video recorders.

In some cases watermarking can also be used to identify the source of the infringing material. A company which licenses images online and enables customers to download licensed images, can insert a separate watermark {or each download with infbrmation identifying the licensee. If an unauthorized use of an image is discovered, then the water- mark can be checked to determine from which licensee it came. it may be that the pirate copy was copied from a legiti- mate publication, but it helps a rightholder prevent unautho- rized dissemination.

Watermarking may also be useful as a l'orm of validation or authentication, for example in identity cards to prevent lbrgery. The producer of the identity, cards could place a watermark in the 'mugshot ' .When authentication of a card is required, the photograph can be scanned R)r a watermark and any image lacking such a mark would be identified as a R)rgery.

WATERMARKING VERSUS ENCRYPTION

The only way to prevent copying and unauthorized use of digital inlbrmation altogether is to encrypt it. Encryption scrambles the data into an illegible tbrm which can only be decrypted by the intended recipient with the proper 'key'. This means that the material is secure in transmission by rea- son of its illegibility. However, weaker lorms of encryption can be cracked by someone with sufficient time and process- ing power and in some countries there are legal restrictions on the use of stronger, supposedly unbreakable tbrms of encrypt ion.The US Government, for example, classes strong encryption as a weapon and prohibits the export of any strong encrypt ion software. 2

Encryption, however, has little use in the digital publish- ing industry where images are meant to be displayed in a vis- ible format, whe ther on a Web page, in a computer game or

390 Computer Law & Security Report Vol. 14 no. 6 1998 ISSN 0267 3649/98/$19.00 © 1998 Elsevier Science Ltd. All rights reserved

Rights M a n a g e m e n t

on a CI)-ROM. Watermarking leaves the original image unchanged to the naked eye. It is also a permanent method of protecting the image - - once material has been decrypted it is free of all protect ion and can be reproduced without hin- drance or indication of the source. Watermarked images can always be traced and detected. -*

As a result of the restrictions on the use of strong encryp- tion, watermarking technology could in fact replace encryp- tion in some circumstances.Anyone who wants to exchange secrets could use watermarking software to place a hidden message inside an innocuous image, video or audio file. A group of exper ts at the Universit ies of Dresden and Hildesheim have recently demonstrated a system lor transmit- ting hidden data alongside speech over an ISDN line. The advantage of this system over encryption is that no one would know that tile hidden message is there and it makes all tile restrictions on strong encryption irrelevant.

EMBEDDING OF DIGITAL WATERMARKS

Digital watermarking works by subtly altering parts of the intbrmation which tbrms the digital description of the image. A computer is able to encode a standard copyright notice and add it to, for example, the inlbrmation which describes the cohmr balance of the image.The addition of this inlbrmation will subtly change the colour of the image whenever it is dis- played or printed, but the changes will be so slight that they are tmdetectable to tile human eye. However, a computer equipped with tile relevant software 'reader' will easily be able to identify the changes and decode tile in/brmation to identify tile copyright notice.

One of the main problems laced by the developers of watermarking software is that of image processing. Digital images, by their nature, are easy to process in a number of wavs, whether by compression methods (especially so-called 'loss}' compression methods such as JPEG) to make transmis- sion quicker or by manipulation of the image, such as blur- ring, filtering, or cropping.Any such form of processing may damage or even remove that part of the image in which the

Case Study - - Contact Images Limited Contact is a publishing company which produces source books, CD-R()Ms and a Web site containing intbrmation about photographers, illustrators and designers along with copies of their portfolios as well as libraries of images avail- able R)r licensing. These hooks and ('D-ROMs are distrib- uted free to image users such as magazine and newspaper publishers who can then arrange to license images ff)r pub- lication as anti when they need them.

In order to prevent exploitation of the images, Contact uses the SureSign software from Signum Technologies to digitally watermark their images.These watermarks are still detectable when printed onto paper and then scanned back into a compute r meaning that Contact is able to detect and tn~ce unauthorized copies of their images, whether they have been copied fi-om the CI)-ROM or scanned in from the book and whether they are published on the Net or in a magazine.

Cotttact Images L im i t ed on: u ,u ,u:contac t -uk .co .uk

copyright information is encoded. In order fi]r the watermark to survive simple processing, it is necessary to include the copyright notice in all parts of the image in information which is unlikely to be materially altered. For this reason, tile watermarks are usually embedded in the frequency rather than spatial domains of an image, or in the colour or lumi- nance bands which contain the most significant information of an image. 4

There are various watermarking software products on the market s and these use different methods to encode the copy- right information. Each different method has its advantages depending on the precise form of protection required. At the moment it appears that no watermarking products are com- pletely immune from the processing of images. But if water- marks can only be removed by such heavy processing, so that the image is substantially different from the original, then it will remain an effective deterrent to copyright infringement. There are also at least two software products ~' which claim to be able to delete watermarks which have been embedded by any of the main watermarking products on the market.These are being distributed as testing tools to determine how secure each system is, but inevitably will also be used by copyright pirates to remove notices and avoid detection. In using these products, there may well be deterioration of image quality and this may be sufficient to deter their use for unauthorized copying of high-quality images.

EUROPEAN LEGISLATION

In December 1997' a proposal for a European Parliament and Council Directive was published on the harmonization of certain aspects of copyright and related rights in the Information Society- ( the 'Proposed Direct ive ' ) . The Proposed Directive seeks to harmonize intellectual property protect ion throughout the EU and takes account of the pro- visions of the WIPO Treaties. s One of tile provisions of the WIPO Treaties is to prohibit the removal or altering of cer- tain electronic rights management information which is attached to a copyright work. 9

For the purposes of the Proposed Directive, Article 7(2) defines "rights management intbrmation" to include any "intbrmation provided by rightholders which identifies the work .... the author or any other rightholder, or information about the terms and conditions of use of tile work ... and any codes that represent such information". This definition is wide enough to cover the copyright information inserted as a watermark into an image, video or audio file.

The European Commission recognizes that technical developments such as watermarking facilitate the distribu- tion of copyright material m as owners become more confi- dent that the}, have sufficient safeguards against widespread piracy of their works.At the moment, owners may be reh,c- tant to distribute their copyright works outside the UK when they are uncertain as to the legal protection they will receive in other countries. To aid this process of wider distribution, the Commission suggests in Article 7(1) of the Proposed Directive to follow tile WIPO Treaties in prohibiting the removal or alteration of electronic rights-management intbr- mation, and the distribution, broadcasting communicat ion or publishing of an}, copyright material from which such inff)r- marion has been removed or altered.

Computer Law & Security Report Vol. 14 no. 6 1998 391 ISSN 0267 3649/98/$19.00 © 1998 Elsevier Science Ltd. All rights reserved

Rights M a n a g e m e n t

The WIPO Treaties and the Proposed Directive also deal with the use of"effective technical measures designed to pro- tect copyright". 1~ These 'technical measures' include only restricted access measures such as encrypt ion or scrambling of broadcast signals and do not include watermarking. The Proposed Directive goes one stage further with these techni- cal measures and Article 6(1) requires member states to implement legal protection against the manufacture or distri- bution of devices or the provision of services which have no commercial use other than the circumvention of such techni- cal measures. There are no similar provisions in respect of devices or services to remove watermarks. However, it has been questioned as to whether the prohibition of de-scram- biers, decrypters and watermark removers is actually in the public interest.Writers of such software argue that their soft- ware plays an important role in aiding the development of ever more secure systems - - they liken themselves to 'ethical hackers' employed by large companies such as BT to test the robustness of their IT networks. By proving that encryption can be cracked or watermarks removed, the writers of such software prevent the suppliers of encrypt ion and watermark- ing software from becoming complacent in their claims of security and robustness.

DATA PROTECTION

In the Proposed Directive, the Commission also acknowledges that teclmology incorpor-ating rights management intbrmation may be used to process personal data about the use of the copy- right work by individuals and to trace online behaviour)-' They note that any such teclmology must incorporate privacy sali> guards in order to comply with the Data Protection Directive. 1~

"l]ais Directive is in the process of being implemented into UK law.The Data Protection Act 1998 received Royal Assent on 16 July 1998 but is unlikely to complete the Directive's imple- mentation deadline of 24 October 1998 until the new Act is brought fully into effect in early 1999 by Orders in Council. However, the technology of tracing online behaviour goes beyond that of current watermarking software and discussion of the Data Protection Act is an entirely separate article in itself.

CONCLUSION

Digital watermarking is likely to become standard technology in the image and audio distribution industries and the tech- nology will be incorporated into industry-standard image manipulation software such as Adobe Photoshop.

In conjunction, member states of the EU are likely to have to implement legislation to protect the watermarks from removal or alteration. Similar provisions are also being con- sidered in the US as a result of the WIPO Treaties.

Together, these developments will enable rightholders to enforce their intellectual property rights by seeking out and prosecuting copyright pirates. As with much Internet law, there are jurisdictional problems, with infringement being rile in countries with the least protection, but the proposed harmonization provisions will at least ensure that righthold- ers are able to exploit fully their works commercially in a large part of the world markets.

Thomas Page Camcron McKenna Information Technology Group E-mail: tip@crock.corn

FOOTNOTES

IMarcSpiderrM from Digimarc Corporation - - ~br more infor- mation see www.digimarc.com/prod_fam.html. 2Research has shown that 40-bit encryption, the strongest form allowable lbr export from the [IS, can be cracked by a so called 'hardware brute force attack' in 0.002 seconds on average by an organization with a computer system costing $100mill ion (e.g. a government) . (Source: Applied Cwpt~rapby) . ~But note watermark removal software discussed below (note 6). iFor more intbrmation on the technical methods of embed- ding watermarks see "Watermarhing Digital hnages fi)r Copyright Protection" by J.J.K. o Ruanaidh, EM.Boland and O.Sinnen at cu iwww.unigc .ch/~oruanaid /eva_pap.h tml ; "Digital Watermarking" by Hal Berghel and Lawrence O 'Gorman at www.acm.org/ -h lb /publ ica t ions / dig wtr/ dig watr.html; and "Digital watermarking is the best way to protect intellectual proper ty from illicit copying" by Jian Zhao in Byte magazine at www.byte. com/art/9701/sec 18/art l .htm.

SFor example, JK_PGS from Swiss Federal Institute of Technology, Lausanne, Switzerland, (EPFL); Digimarc from Digimarc Corporation; and SureSign Dom Signum Technologies. <'(1) StirMark from Markus G. Kuhn; and (2) l_JnZign (no author credited - - see www.altern.org/watermark/). =See COM(97) 628 final. UThe WIPO Treaties consist of the WIPO Copyright Treaty (WCT) and the WIPO Performances and Phonograms Treaty (WPPT) which were adopted by the Diplomatic Conli:rence on Certain Copyright and Neighbouring Rights Questions on the 20 December 1996.The Conference was convened by the World Intellectual Property Organization (WIPO) in Geneva. 9See Article l 1 WCT and Article 18 WPPT. ")See Proposal lbr a Copyright Directive (COM(97) 628 final), recital 33. I llbid, Article 6(2). l'-lbid, paragraph III.A.1 of Chapter 3 of the Explanatory Memorandum. I-~European Parliament and Council Directive 95/46/EEC.

392 Computer Law & Security Report Vol. 14 no. 6 1998 ISSN 0267 3649/98/$19.00 © 1998 Elsevier Science Ltd. All rights reserved