A digital home network is a cluster of digital audio/visual (A/V) devices including set-top boxes, TVs, VCRs, DVD players, and general-purpose computing devices such as personal computers. Copyrighted digital multimedia content may be delivered to the consumers from a number of sources including the Internet, and satellite, terrestrial or cable broadcast systems. It may also be made available as prepackaged media (e.g., a digital tape or a digital video disc) at retail stores.

Before releasing their content for distribution, the content owners may require protection by specifying certain access conditions such as payment, identification or authorization. Once the content is accessed by the consumer, it moves across the home network until it reaches its destination where it is stored or displayed. Hence, a copy protection system is needed to prevent unauthorized use of bit streams in transmission from one A/V device to another or in storage on magnetic or optical media.

Although legal institutions exist for protecting intellectual property (trademarks and patents) owned by the content creators, complimentary technical measures are needed to sustain financial returns and to ensure incentives for new creations. Recently, two fundamental groups of technologies, encryption and watermarking, have been identified for protecting copyrighted digital multimedia content. Encryption-based technologies transform content into unintelligible form. This transformation, being reversible in nature, allows perfect recovery of content before consumption. Technologies based on watermarking serve several purposes. Some common uses are the identification of the origin of content, tracing illegal copies and disabling unauthorized access to content.

Three major industries have a vital interest in this problem: The motion picture industry, the consumer electronics (CE) industry, and the information technology (IT) industry. A major group of content owners is the motion picture studios represented by the Motion Picture Association of America (MPAA). Their content (movies) is consumed or recorded on audio/visual devices manufactured by consumer electronics companies. The information technology industry manufactures general purpose computing devices, such as personal computers, which are also used to consume or store content.

This tutorial is an overview of the work done for protecting content owners' investment in intellectual property. It highlights the important developments within several forums including the DVD Forum, SDMI, ATSC, DVB, and Open Cable.

Consumer Electronics Association (CEA), USA, 1998-Present. Co-Chair, R4.8 Working Group on Copy Protection. Investigated the impact of copy protection systems on the digital interfaces including the IEEE 1394 DTV and RF Remodulation interfaces. Wrote an extensive report summarizing the proposed systems.

Advanced Television Systems Committee (ATSC), USA, 1997-1999.
Member, T3/S8 Conditional Access Ad Hoc Working Group. Participated in determining the ATSC needs for a conditional access system for digital TV. Reviewed proposals concerning the essential components such as scrambling algorithms, EMM and ECM generation and distribution, host conditional access software, and copy protection.

Copy Protection Technical Working Group (CPTWG), California, 1997-1999.
Member, Data Hiding Subgroup. Participated in determining the requirements of a system for watermarking digital video content. Reviewed submitted proposals.

Copy Protection Technical Working Group (CPTWG), California, 1996-1998.
Member, Digital Transmission Discussion Group. Participated in determining the requirements of a system for the protection of digital audio/video data transmitted on the IEEE 1394 serial bus. Reviewed submitted proposals.

International Digital Video Disk Forum, California, 1996-Present.
Member, Copy Protection Technical Working Group. Evaluated proposals for protecting DVD Video and DVD Audio, and participated in the development of copy protection systems for DVD players, DVD recorders and DVD-ROM drives.

EIA-NCTA Joint Engineering Committee, USA, 1996-Present.
Member, NRSS Subcommittee. Revised and edited both Part A and Part B of the National Renewable Security Standard. Proposed a system for the protection of the common interface between the host device and the renewable security module.