4 February 2008
Developers, content providers, and operators are all involved in protecting mobile content. Digital Right Management (DRM) is an important issue in the mobile world and it is a complex environment to work with. Open Mobile Alliance DRM (OMA DRM) can be used to protect Flash Lite content. OMA DRM has two specifications 1.0 and 2.0. Both DRM solve the same problem – protecting content. I will briefly explain the differences in OMA DRM 1.0 and OMA DRM 2.0 and how to apply OMA DRM 1.0 Forward Lock to Flash Lite content. Note that this is not an easy topic and it is important to understand all entities involved in the process of protecting content.
But first a question: Why do would you want to apply DRM to Flash Lite content?
The idea is to increase protection of your Flash Lite files (SWF) and your intellectual property. Also you might find that DRM is a requirement for operators/carriers and aggregators to distribute your Flash Lite content. So it is important to understand how to use DRM and what options are available for Flash Lite content.
The Open Mobile Alliance is an international body that creates standards on which mobile handsets manufactures (OEM), operators and companies can base their solutions and be interoperable. An OMA DRM protected piece of mobile content that is compliant with these specifications will operate correctly on different mobile phones from different OEM. This is a very important concept since no matter which tool you use for protecting your content, it will work on handsets from different OEM.
OMA DRM 1.0 is defined by the following specification. The specification defines three different ways to protect content:
- Forward Lock – locks content to the individual handsets.
- Combined Delivery – locks content to the handsets. Playback rights can be applied to the content.
- Separate Delivery – playback rights can be applied and allows super distribution.
For more details of the different OMA DRM 1.0 protection methods and distribution you can read the following document from Forum Nokia:
The following MIME types are defined for OMA DRM, you will need to define them into your Web Server so that a OMA DRM protected Flash Lite file will be recognized by the mobile phone upon download.
application/vnd.oma.drm.rights+xml .dr application/vnd.oma.drm.rights+wbxml .drc application/vnd.oma.drm.content .dcf application/vnd.oma.drm.message .dm application/vnd.oma.drm.dd+xml .dd
Note: the "application/vnd.oma.drm.message" is the only one required for Forward Lock.
Refer to the documentation for more details.
OMA DRM 2.0 is defined by the specification on the OMA web site. It applies the same concepts of OMA DRM 1.0 but it offers a higher degree of protection (Separate Delivery method) by introducing stronger encryption methods and also offers protection methods for streaming media such as audio and video. OMA DRM 2.0 introduces other MIME types.
In this article I will concentrate on OMA DRM 1.0 and in particular on the Forward Lock protection method. This protection method is the most common on handsets and the simplest to implement. It is important to understand that not all protection methods are supported by the handsets for OMA DRM.
I will go through an example using the following scenario:
- Apply OMA DRM 1.0 Forward Lock to a Flash Lite file (.swf)
- Upload the Forward Lock file (.dm) to a mobile web page
- Download the Forward Lock file to a mobile phone
- Test the Forward Lock file by executing it and trying to send the file to another handset.
The most important aspect to understand about protecting content using OMA DRM is to have a clear definition of which type of content can be protected. Here is how Symbian defines active and passive content:
"Symbian Signed defines Passive Content (PC) as any SIS file that does not contain any executable (active) components." (Source)
The Flash Lite player is the active component and the Flash Lite file (SWF) is the passive content. This means that Flash Lite files (SWF) are considered, from a DRM point of view, the equivalent to an image file (.jpg, .gif, etc..), sound file (.acc, .mp3, etc..) or a video file (.3gp, .mp4, etc..). We can apply OMA DRM 1.0 protection to Flash Lite content.
Since OMA DRM 1.0 is a standard, it is supported by all major mobile handset manufacturers. They provide tools to apply OMA DRM 1.0 to selected content. Here is a list of tools from different manufacturers:
- Nokia: Nokia Multimedia Internet Toolkit 4.1 (Windows only)
- Sony Ericsson: DRM Packager (Windows and MAC OSX)
- Motorola: Moto DRM toolkit (Windows)
You can use any of these tools to apply OMA DRM 1.0 to Flash Lite content. In this article I will use the Nokia Multimedia Internet Toolkit 4.1 since it is integrated with all Nokia Software Development Kits (SDKs) both for Series 60 and Series 40 platforms. It allows you to test the protected Flash Lite content directly in the SDKs. You can download the NMIT 4.1 tool and the Nokia S60 or S40 SDK from Forum Nokia.
I will use the NMIT 4.1 tool to apply Forward Lock DRM to a Flash Lite file with a step by step process. I will not go into details for each option but you can refer to the NMIT 4.1 User Guide to learn more about all the capabilities and features of the tool.
- Start the NMIT 4.1 tool. If you have the Nokia S60 and S40 SDK installed you will see the following screen.
Figure 1. Nokia Multimedia Internet Toolkit 4.1 start-up screen
- Select File > New. The Available Content Types screen will open
- Select the Deployment tab
- Select the DRM Message icon
- Press OK
Figure 2. NMIT 4.1 – Deployment screen
Figure 3 shows a screen where I will define the type of DRM to apply to the Flash Lite content. There are four sections on this screen.
- The first section, "1. Select Message Type" allows you to select which type of OMA DRM 1.0 to apply to the content. I use Forward Lock so no changes are needed since this is the default.
- The second section, "2. Load Media Content", allows you to load the file that you want to protect. In my case it is a Flash Lite file (SWF). Also leave the "Content-Transfer-Encoding" set to binary.
- The third section, "3. Edit Header", allows you to define the headers. Since Flash Lite content is now automatically recognized by the tool, I will enter the application/x-shockwave-flash information into the Content-Type line.
- The fourth section, "4. Specify Rights" is not used for Forward Lock DRM. In case you use another DRM protection method, you will have several options available. Refer to the tool manual for more information.
Figure 3. DRM definition window.
- Load your Flash Lite file using the "Load Content" button from the section "2. Load Media Content". I loaded the testdrm.swf. You can find this file in the Sample files linked from the beginning of this article.
- Add the application/x-shockwave-flash information into the Content-Type line in the "3. Edit Headers" section. This step is necessary since the tool does not recognize the Flash file format.
- Save the file. I saved as testdrm.dm.
At this point I have a so-called DRM message file ready for deployment. I will need to upload it to my web server for download and installation.
Figure 4. Apply OMA DRM 1.0 Forward Lock to the testdrm.swf
Important Note: The protection will only be applied once you download the .dm file from the mobile site to your phone. This is only one of the delivery methods used by OMA DRM. For other delivery methods please consult the documentation.
I created a simple mobile web page with a link to the testdrm.dm file. You can use Adobe Dreamweaver CS3 to create a mobile web page. Here is a step by step process:
- Upload the files, index.html and testdrm.dm to your web server.
- Browse to the mobile web page using the browser of your mobile phone.
- Select the link to the testdrm.dm file, Figure 5.
Figure 5. Select testdrm.dm
- Select the location where you want to save the file (see Figure 6).
Figure 6. Select location
- At this point the download of the file starts (see Figure 7).
Figure 7. Downloaded testdrm.dm
- Save the file to the phone (see Figure 8).
Figure 8. testdrm.dcf saved
- On the phone go to the location where the file was saved. On Nokia S60 devices, this is usually the Other directory. You can just select the Flash Lite player icon and you will see the testdrm.dcf file (see Figure 9).
Figure 9. testdrm.dcf in the Flash Lite
The yellow key icon indicates that the file is DRM protected.
You can now execute the Flash Lite content (see Figure 10).
Figure 10. Test testdrm.dm on the phone
To test that the file is protected with Forward Lock DRM, try to send the file via MMS or Bluetooth to another handsets (see Figure 11).
Figure 11. Send the file to another handset
You will see the following message "unable to send protected object" (see Figure 12).
Figure 12. The "unable to send protected object" message
If you do not have a Web Server to test this process you can just point your mobile browser to the following URL:
Or if you have a mobile phone with a 2D bar code reader just scan the following bar code:
Figure 13. Bar code generated with Nokia Mobile Code.
Where to Go from Here
This is a very simple process to protect your Flash Lite content by applying OMA DRM 1.0 Forward Lock. Since OMA DRM is interoperable, your content will work across many different Flash Lite-enabled mobile phones. It is important to understand that there are different protection methods and delivery processes for DRM protected content. A diligent reading of the documentation is very important to understand all the aspects of protecting and distributing your Flash Lite content.
This work is licensed under a Creative Commons Attribution-Noncommercial 3.0 Unported License.