Special Feature

Content Copyright Protection Technology Needed for
Cooperative Broadcasting/Communication Services
Shinji Ishii†, Sadakatsu Muto, Masahito Kawamori, andKatsuhiko Kawazoe
Abstract
Content distribution involving cooperation between broadcasting and communication services
requires permission for the use of copyrighted digital content for both services. Moreover, these permissions must be handled securely by the receiving terminals. This article introduces copyright protection technology that can be applied to server-type broadcasting services for which operating standards
are currently being formulated.

1. Copyright protection technology for digitalcontent
The digital content distribution in current use isbroadly divided between viewing digital broadcasting using a set-top box (STB) or TV set with a builtin digital tuner and viewing digital content on theInternet using a personal computer. From the perspective of the content user, there is no need to distinguish between digital broadcasting services anddigital content distribution over the Internet. However, there are differences in the establishment of services based on TV broadcasting, which began under
the guidance of a national policy, and the Internet,
which arose through free thinking. Consequentially,
there are also technological differences.
2. Copyright protection technology
One of the main differences between digital andanalog recording is that digital recording does notdegrade the quality and further copies can easily bemade from any copy. While these features are majoradvantages for the user, they make it possible for people to freely copy copyright-protected content for
purposes other than personal use, which is not desir† NTT Cyber Solutions Laboratories
Yokosuka-shi, 239-0847 Japan
E-mail: ishii.shinji@lab.ntt.co.jp52

able from the viewpoint of a healthy content distribution market. Copyright protection technology is atechnological solution for mediating between thesetwo conflicting aspects.
Our aim is to utilize the advantages of both broadcasting and communication to develop an optimal
hybrid system.
Examples of broadcasting and communication services are listed in Table 1, along with comparisons ofencryption and copyright protection technology. The
copyright protection technologies for digital broadcasting and Internet streaming that are currently thesubject of standardization activities are compared inFig. 1.
The copyright protection technology for current
digital broadcasting can be broadly classified into
conditional access systems (CASs), which restrict
reception, and rights management and protection(RMP) technology, for which operation specifications are now being formulated. Reception restriction
technology is the standard [1] used since the beginning of CS (communication satellite) digital broadcasting (subscription-based services) in 1996, but thescrambling of free-of-charge broadcasting services
began in April of this year, with additional standards
for BS (broadcast satellite) digital broadcasting [2].
The same kinds of systems are used for digital broadcasting, including terrestrial broadcasting, satellite
broadcasting, and cable broadcasting (simultaneousretransmission of CATV (cable TV)), both in JapanNTT Technical Review

Special Feature

Table 1. Examples of broadcasting and communication services and comparison of encoding processing and copyrightprotection technology.
TypeService examples

NoStreaming

Fixed reception technology
Terrestrial, BS, and(with scrambling)
CS are in service
performed by CAS

Yes

Downloaded
fileServer-type
broadcasting
operation use
being decided

No

Streaming

VOD

Yes

Downloaded
file

Download fromserver and store

Broadcasting

Communication

Encoding processing technology

Transmission
systemStorage*1CAS

Copyright protection technology

DRM

RMPDRM

CCI function(part of the CAS function)
can be used——

Limited playback
technology (encryption)using ACI

Using RMPI
(capable of more detailed
description than is CCI)

Implemented by same
method as limited
playback

Using RMPIDRM (capable of more detailed DRM
description than is CCI)

*1 Indicates whether or not the service providers assume local storage (excluding recording for private use)

BS: broadcast satellite
ACI: accounting control information
CCI: copy control information

BroadcasterOne-way

Concept of CAS and RMP
CAS: Image scrambling and descrambling
RMP: Implementation of viewing based onprotection of rights

Digital broadcasting
interactive TV

Broadcasting network
Two-way

CAS: Transfer of charging information
Full use of the communication network(pay per view, interactive programs, etc.)

Communicationenterprise, etc.

CAS card

DRM concept
Comprehensive implementation of video
scrambling and rights protection

Communication network
Two-way

Personal computer with
DRM installedFig. 1. Comparison of rights protection system concepts for content distribution.

and worldwide. On the other hand, digital rights management (DRM) has come to be widely used as copyright protection technology for streaming content on
the Internet. Both of those approaches ensure secureviewing of copyrighted content within the range ofauthorized use, so they both have the same functions.
For subscription-based TV broadcasting, it is necessary to enable anyone installing a TV receiver toimmediately receive the programs of any of thebroadcast channels, as long as the viewing contract orother such preparation has been completed in the caseof pay channels. For that purpose, TV receivers,Vol. 2 No. 8 Aug. 2004

including those for digital broadcasting, must bebased on specifications for broadcasting systems thatare standard, even among different broadcasters [3],[4].
For Internet distribution of content using personalcomputers, on the other hand, the user terminals (i.e.,personal computers) vary in their performance, memory and storage capacities and operating system types
and versions, and the user must install the application
software required for each Internet service provider.
Considering this situation, we believe that using standard specifications that extend communication func53

Special Featuretions to current digital broadcasting is a realistic
approach to cooperative broadcasting and communication services during the market establishment
phase. From these viewpoints, server-type broadcasting, for which operation specifications are currently
being formulated, is being studied on the basis of digital broadcasting standards [5].

to protect the user, public key encryption isused for mutual authentication to ensure thatthe receiver is connected to a reliable distribution center.
(4) On the basis of the user’s request, the pay
request management function makes a request
for license issuing processing.
(5) The user’s contract is retrieved by the databasemanagement system to check for permission toview the content before proceeding to the actual licensing procedure.
(6) The RMPI for the content that is relevant to theuser’s request is obtained from the RMPI management function, and a license that reflects theconditions set in that information is generated.
(7) The license is generated. At the same time, if
the content has an associated charge, charging
processing is executed. The receiver can thenoperate within the bounds of the issued license.
For example, if the number of times the content
may be played is specified, the TV set will present the content that many times, but no more
unless the license is renewed. To increase thesecurity level, the TV set can report the numberof remaining plays to the content distribution
center for checking just before each replay
when a multi-play license has been issued, as ameasure against unauthorized modification ofthe receiver.
Steps such as those described above ensure honest
operation of the receiver according to the RMPI specified by the broadcaster. Typical RMPI items that are
specifically needed for server-type broadcasting ser-An overview of viewing licensing based on rights
management and protection information (RMPI) isshown in Fig. 2. The order of operations is indicatedby the numbers in the figure.
Preparation for registration of content in thedistribution center(1) RMPI is obtained from the broadcasting company or other content owner.
(2) If it is necessary to append RMPI that provides
details within the range permitted by the RMPIof (1) according to the specific environment of
the distribution network management function,then supplementary RMPI is defined andreserved. Of course, this supplementary RMPI
may not contradict the permissions received in
the RMPI of (1).
Operational steps for when the user wants toplaying the content(3) The user makes a request to play the content.
The playing request management function first
confirms that the receiver is of the proper type
for the content on the basis of the RMPI. Then,

RMPI specified by
the broadcaster, etc.

RMPI specified by
the broadcaster, etc.

Viewer databasemanagement function

Viewer request
reception andmanagement function

(2)

(5)

(4)

(1) RMPIRMPI managementfunction(6)

License issuing function(3) Viewer
requestDistribution network

3. Rights management and protection
informationViewer(7) License
Distribution center

Fig. 2. Issuing of a license that permits viewing on the basis of rights management and protection information (RMPI).

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Special Feature

vices or are assumed are shown in Table 2 and an
example of the XML (extensible markup language)
description for those items is shown in Fig. 3.
4. Future copyright protection systems
We have developed a rights protection system thatmeets the needs of a content distribution system
based on cooperation between broadcasting and communication services. With recent technicaladvances—optical fiber, which can deliver the highquality digital content of an HDTV (high-definitionTV) program library via both broadcasting andbroadband networks, large hard disk drives that canrecord and replay digital HDTV programs, and Bluray*1 discs for high-density digital recording—it has
become technically feasible to draw up a true busi-*1 Blu-ray: A next-generation optical disc format jointly developedby thirteen leading consumer electronics and PC companies inJapan and other countries. It uses a blue-violet (wavelength: 405nm) laser and can store 27 GB of data on one side of a 12-cm disc,which is sufficient for recording HDTV broadcasting directly indigital form. http://www.blu-ray.com/info/

ness model for broadcasting/telecommunicationcooperative services.
In this article, we focused on how copyright protection information for digital content can be used in abusiness-to-consumer (B2C) environment, where
digital content moves from the communication company to the user’s receiver. However, since the business-to-business (B2B) distribution of digital content
among broadcasters and telecommunications companies must also be accompanied by copyright management information, the distribution of copyright permission management and digital content should beintegrated. We believe that, in the future, mobile services involving AV (audio/visual) equipment, personal computers, and hand-held recording devices (cellular phones, PDAs, etc.) centered around a homeserver within the household will further enrich ourlives. It goes without saying that copyright management of digital content use within the permitted range
is necessary in this case too. We will continue
research and development of the copyright protection
technology and copyright management methods
needed to support such a digital content distribution
market.

Table 2. Examples of rights manegement and protection information.
Content charge control

Charges are presented for each form of content purchase.

Control of copy generations

The number of permitted copy generations (i.e., a copy made from a copy) is controlled.
In current digital broadcasting, three types of control are being used: unlimited copying,
one generation of copying, and no copying.

Control of number of copies

The number of copies that can be made in one generation from the purchased content iscontrolled.

Control of the copying destination

This specifies authorized devices when the content is to be written to an external storage
device.

Control of the number of playbacks

Playback is permitted only a certain number of times.

Time control of the playback function

Content stored in the receiver can be played back only during a limited period.

Control of whether local storage is permitted.

Specifies the conditions for storage in the receiver (for server-type broadcasting)Regional control

Specifying viewing permissions region by region

Gender-based control

Used to provide services specific for males or females

Control over special playback features

Controls playback features other than simple playback, such as skipping certain parts(e.g., commercials), pausing, fast forward, rewind, etc.

Viewer age control function

Controls viewing by comparing the age classification of the content with the age setting
on the receiver

Control of use by viewer attributes

When viewer attributes are used in two-way services, etc., viewer authentication isperformed to protect the viewer.

Encryption processing specification control

Specifies the encryption algorithm and use mode

Authentication processing specification control

Specifies the authentication method

Distribution media control

Applied when matching the content to the transmission capacity of the distribution
network, etc.

Control of number of distribution times

Limits the number of times the content can be distributed

Vol. 2 No. 8 Aug. 2004

55

Special Feature<licenseGroup
xmlns:nx="http://www.ntt.co.jp/schema/2003/8/rmpi"
xmlns:sx="http://www.xrml.org/schema/2001/11/xrml2sx"
C:\RMPI\RMPI0119\rmpi_v10_r2.xsd"><license licenseId="0"><title>TEST SAMPLE</title>
Displays the crid<!--grant1 PLAY_SAMPLE-->of the target<grant><!--principal-->content.
<!--right--><cx:play/><!--resource--><nx:digitalContent><nx:cri caBroadcasterGroupId="01" caContentId="0001"><nx:crid>crid://hoge</nx:crid><nx:imi>imi:hogehoge</nx:imi>
Camellia is used</nx:cri>for the encryption<nx:SecurityInformation><nx:EncryptionData>
processing.
<nx:EncryptionAlgorithm><nx:Camellia/></nx:EncryptionAlgorithm></nx:EncryptionData></nx:SecurityInformation></nx:digitalContent><!--condition-->Charge is 100 yen.
<allConditions><sx:fee><sx:paymentPerUse><sx:rate currency="JPY">100</sx:rate></sx:paymentPerUse></sx:fee>
Viewable one<sx:exerciseLimit><sx:stateReference>time only<sx:stateReferenceValuePattern><sx:count>1</sx:count>
Can be viewed</sx:stateReferenceValuePattern></sx:stateReference>
between Jan. 1 and</sx:exerciseLimit>
Dec. 31, 2004
<validityInterval><notBefore>2004-01-01T00:00:00+09:00</notBefore><notAfter>2004-12-31T00:00:00+09:00</notAfter></validityInterval><tvax:distributionMedium>Can be distributed<tvax:FTTH/>
by FTTH</tvax:distributionMedium></allConditions></grant>
When a different charge for the<!--grant2 COPY_SAMPLE-->same content is specified, the<grant></license>
details are described here.
</licenseGroup>

Fig. 3. Example of XML description of RMPI.

References
[1]
[2]

56

“CS digital broadcasting receivers,” Association of Radio Industries
and Businesses, Standard ARIB STD-B1, May 2001.
“Access restriction standards for digital broadcasting,” Association ofRadio Industries and Businesses, Standard ARIB STD-B25, Jun.
2003.

[3]
[4]
[5]

http://www.arib.or.jp/
http://www.catv.or.jp/jctea/“Coding, transmission and recording restriction methods for servertype broadcasting,” Association of Radio Industries and Businesses,
Standard ARIB STD-B38, Feb. 2003.

NTT Technical Review

Special Feature

Shinji Ishii

Masahito Kawamori

Senior Research Engineer, Promotion Project
1, NTT Cyber Solutions Laboratories.
He joined NTT in 1989. He is interested indevelopmental research on security systems for
multimedia communications. Recently, he has
been engaged in the development of copy protection systems for digital broadcasting and broadband communications.

Senior Research Engineer, NTT Cyber Solutions Laboratories.
He joined NTT Laboratories in 1989. He has
worked in research areas such as artificial intelligence, language processing, and interactive
agents using speech recognition. His current
research area is metadata and media delivery systems for broadcasting and broadband communications.

Sadakatsu Muto

Katsuhiko Kawazoe

Promotion Project 1, NTT Cyber Solutions
Laboratories.
He joined NTT in 1989 and engaged in thedevelopmental research on the database system
supporting web services. Recently, he has been
engaged in the development of copy protection
systems for digital broadcasting and broadband
communications.

Senior Research Engineer, NTT Cyber Solutions Laboratories.
He received the B.E. and M.E. degrees in engineerring from Waseda University, Tokyo in 1985
and 1987, respectively. Since joining NTT in
1987, he has mainly been engaged in R&D ofradio communication systems, satellite communication systems, and the personal handy-phonesystem (PHS). His specialty is forward error correction systems. He is currently a co-chairman of
the Association of Radio Industries and Businesses Working Group for Broadcasting Systems
based on a Home Server. He is a member of theInstitute of Electronics, Information and Communication Engineers (IEICE) and received theYoung Engineer Award from IEICE in 1995.

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