OMA DRM
Kevin Liu
Advisor Prof. Hsing Mei
Web Computing Laboratory
Graduate Institute of Applied Science and Engineering,
Fu Jen Catholic University
March 15, 2008
Outline
• Introduction
• DRM System Overview
• Three DRM V1.0 methods
•
•
•
•
– Combined delivery
– Forward-Lock
– Separate delivery
Introduction of DRM V2.0
DRM Website
Conclusion
Reference
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OMA DRM
• OMA：Open Mobile Alliance
– 正式成立於2002年6月初，其前身為：Open
Mobile Architecture Initiative Supporters
和WAP Forum。後續有一些組織加入了OMA.
• DRM：Digital Rights Management
– Is the means to control the usage of the
media object once it has been
downloaded.
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Preface
• Without protection and management of digital
rights,
– Digital content can be easily copied, altered, and
distributed to a large number of recipients, which could
cause revenue loss to media companies.
• There is a need for content providers and
operators to control the usage of downloaded
media objects.
• To protect commercial digital intellectual property
and avoid digital piracy,
– we need a system that prevents unauthorized access to
digital content and manages content usage right.
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Introduction of DRM
• A content provider can grant a user the
rights to preview media objects for free
and charge the user only for the full usage
rights.
• The value lies in the rights and not in the
media object itself
• DRM makes it possible to sell the rights to
use the media object, rather than selling
the media object itself.
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Introduction of DRM
• A DRM system should offer a persistent
content protect against unauthorized access
to the digital content ,
– limiting access to only those with the proper
authorization.
• DRM enables content providers to define
rules (rights) for how the media object
should be used.
– the ability to preview DRM content
– to prevent downloaded DRM content from being
illegally forwarded (copied) to other users
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Introduction
• The rights can be delivered to the consuming
device by downloading them together with the
content or by sending the rights object separately
from content.
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DRM System Overview
License Server
Paying royalty fees
Usage rules
Content
Provider
Digital License
Requiring license
and paying
Paying distribution
Protected Content
Consumer
Protected content
Content Server
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Three DRM V1.0 Methods
• Forward-Lock
• Combined delivery
• Separate delivery
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Forward-lock (FL)
• A special case of
combined delivery
method where the
DRM message does
not contain a rights
object.
• The device is
allowed to render
the content but not
to forward it to
other devices.
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Forward-lock (FL)
• The Content Provider, using a DRM Packager, packages the
media object into one DRM Message and makes the URL
available to the device (e.g. by publishing it on a Web page).
• HTTP Download is used to deliver the DRM Message.
• The User is using the media object.
• The DRM agent ensures that the media object is not copied
to another device, via IrDA or Bluetooth, or sent from the
device in an MMS or email.
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Combined delivery (CD)
• Delivery of the rights
object and content together
in a single message.
• The DRM message includes
the media object and a
rights object.
• The device may render the
content according to the
rights object.
• If the device supports the
“combined delivery” method
it MUST also support the
“forward-lock” method.
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Combined delivery (CD)
• The Content Provider, using a DRM Packager,
packages the media object and the rights object
into one DRM Message.
• The DRM Message is made available to the device
(e.g. by publishing it on a Web page).
• To download the DRM Message (media object +
rights object).
• The User is using the media object. The DRM
agent ensures that the media object is used
according to the rights.
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Separate delivery (SD)
• Delivery of the rights
object and content via
separate transports.
• If the device supports the
“separate delivery” method
it MUST also support the
“combined delivery” and
“forward-lock” methods.
• If there are no rights
objects associated with a
piece of DRM content the
device MUST NOT consume
the content.
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Separate delivery
• In the separate delivery method the content
provider needs to convert the plaintext media
object into DRM content format (DCF).
• This conversion includes symmetric encryption of
the content making the DRM protected content
object useless to parties not having access to the
Content Encryption Key (CEK).
• The content in DRM format may be distributed via
an insecure transport whereas a more secure
transport (from DRM point of view) is used to
deliver the rights object with the CEK.
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Separate delivery
• In the separate delivery method the media object
is always encrypted and converted into the DCF
format.
• When a media object is distributed in encrypted
form, the key is with the rights object.
• The device should allow to forward the DCF file to
another device.
• The device must not forward rights objects from
the device.
16
Separate delivery
• The media object is
allowed to pass from
mobile device to
mobile device through
any channel, with the
rights object being
obtainable from the
Rights Issuer.
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DRM V1.0 Use Case
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Introduction of DRM V2.0
• 更進一步加密權限物件
• 藉由使用裝置的公開金鑰(public key)做為
內容物件加密的金鑰
– 將它們結合於目標裝置，來加強安全性。
• 整合的保護內容及權限物件，可減少被濫
用的風險
• 除了加強安全性，亦加入信任的元件(trust
element)
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The Trust Element of DRM V2.0
• DRM Agent
• Content Issuer
• Rights Issuer
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DRM Agent
• 此元件內嵌入一個信任的實體(trusted
entity)
• 負責執行DRM 內的許可權限及限制
• 控制對DRM 內容的存取
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Content Issuer
• 負責傳遞DRM 內容
• OMA DRM 中有定義DRM 內容的格式以傳
遞至DRM Agent
• 亦定義使用不同傳遞機制由Content
Issuer 傳遞至DRM Agent
• 可以確實地將DRM 內容包裝好或是可接收
已包裝好的內容
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Rights Issuer
• 對DRM 內容分配許可權限及限制的一個實
體
• 產生權限物件Rights Objects
• 一個權限物件是一份XML 文件，表達出對
相關DRM 內容的許可權限及限制
• 權限物件管理DRM 內容如何被使用
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DRM Website
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DRM Website
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Conclusion
• 所謂的DRM乃是藉由電腦程式，以軟體或硬體方
法限制數位內容使用方式的系統通稱
• 一種機密保護機制，防止被複製，或防止在傳遞
時被攔截轉拷
• 在「複製」所費不貲的年代中，出版商持有了複
製所需的資源及技術，壟斷了複製的權利，藉以
保障其利潤，這便是著作權的由來。
• 「合理使用」的權利會被 DRM 吞噬
• 使用者還是得接受大財團的剝削，讓自己的權益
平白受損。
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Reference
• OMA Digital Rights Management V1.0 Approved Enabler
• Digital Rights Management (OMA-Download-DRM-V1_020040615-A.pdf)
• Download Architecture(OMA-Download-ARCH-V1_0-20040625A.pdf)
• Introduction to DRM - Digital Right Management
• DRM Website
• 再論DRM
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Q&A
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