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Jau-Wu Huang 1
Digital Rights Management for Visual Content in Mobile Applications
Trimeche, M.; Chebil, F.;Nokia Research Center
Control, Communications and Signal Processing, 2004. First International
Symposium on, 2004. Pages:95 - 98
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Outline
Introduction DRM in OMA DRM for Mobile Visual Content
Encryption Watermarking Watermarking of images and video
Conclusion
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Introduction Secure distribution, storage,
exchange and management of copyright-protected contents Audio Video Game,…
A balance between content owner and consumer’s rights
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Conflicts of Rights
Content Owners I create the content Revenue flow for every single copy
sold No resale of content No copying of content Content used only by original buyer Limited use of content
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Conflicts of Rights(Cont.)
Consumers I paid for the content Fair use right to copy the content Resale the content in a different form Share contents with others Unlimited use of contents Why pay for something if I can get it
free
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DRM System End-to-end security
Every link in the delivery chain has to be secured 2 major content distribution channels
Distribution of electronic files via the Internet or digital bus interface
Distribution via pre-recorded or recordable physical media
Only accessible to authorized/authenticated person or compliance devices Rights are correctly executed and enforced
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DRM Formula DRM = Contents + Rights + Enforcement Contents
Audio track, VCD, DVD, … Rights
Copy once, copy never, unlimited listening, 10 downloads per day, …
Enforcement Rights executed as specified with technology
and legal support
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DRM in OMA OMA (Open Mobile Alliance)
Formed in June 2002 By “Open Mobile Architecture
Initiative” and “WAP Forum” Introduce/Promote open standards
and specifications for mobile industry OMA DRM V2.0 3GPP move the MDRM(Mobile DRM)
standardization to OMA
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DRM in OMA(Cont1.) Right expression
4 key components Principal (user, compliance devices) Rights (copy, play, download, view, print,…) Resource (the digital content) Condition (when, how, how much times,…)
Example Registered user 8043 can have 10 downloads
from compliance device 132 starting from time xxx to time yyy
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DRM in OMA(Cont2.) DRM package includes
Rights Define how the device is allowed to render
the content Copy, play, download…
The usage right REL(Right Expression Language)
A language to specify rights and their condition ODRL (Open Digital Right Language) Support an extensible language and data
dictionary
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DRM in OMA(Cont3.) Based on public key cryptography to
enhance security support 3 download modes
Forward Lock Allows single purchase and single delivery Content cannot forwarded to other devices Clear content WAP download
Combined Delivery Clear content + rights WAP download Device conforms to rights Enable usage rules to be sent for the media object Add a RO(Right Object) to the DRM message
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DRM in OMA(Cont4.) Separate Delivery
Protect higher-value media and enable right refreshment
encrypted content WAP download Rights + key separately delivered
Super distribution and separate channel Media is encrypted into DCF(DRM Content
Format) Use symmetric encryption
The rights hold the CEK(Content Encryption Key)
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DRM in MPEG MPEG-4 IPMP
Separate content stream (IPMP-ES) and associated rights (IPMP-Ds)
Provides an interface between DRM-specific content and MPEG-4 terminal
MPEG-21 IPMP An open interoperable framework for multimedia
delivery and exchange Content encapsulation in Digital Item (regardless of
format) REL standardized a way to associate rights with
content The MPEG-21 REL is an XML-based language
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DRM for Mobile Visual Content
Multimedia portable device Small display size (screen) Power management Processor utilization
Lower computational and memory capability Security issue Fulfill strict quality and bit rate
requirement in real-time streaming application
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Encryption
Content encryption Block cipher technology
DES (Data Encryption Standard)
Selective encryption Only encrypt the compressed code
stream header Only Intra frames could be encrypted
in video
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Watermarking
Embedded information into digital content irremovably and invisibly
Technology has its limitation Keep watermarking casting secret False alarm is more severe than
missing Can still be a valuable component in a
DRM system
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Watermarking(Cont.)
Fig. 2 shows that the use of watermarking to enhance DRM security MMS (Multimedia Message Service)
content Stamp watermarks into the media
object It’s only a stand-alone solution, not
part of any OMA Spec.
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Watermarking of images and video Capacity
Low-resolution image The carrier signal has lowered bandwidth A smaller capability for data hiding
Content adaptation Watermark has to resist content
adaptation It can consist of spatial subsampling of
images/video to fit display size, color space reductions, or format conversion, …
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Watermarking of images and video(Cont.)
Computational complexity Watermark has to be simple to
extract Security issue
Further study of preventing abuse and security leakage strategy have to be carried out in open mobile platform
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Conclusion
Propose a system that integrate watermarking technology to stamp media content in MMS
The limitations and requirements of the mobile visual content should be taken into consideration in mobile application