Streaming Secure Files with Windows Media Rights Manager 7

Article
03/19/2007

Andrea Pruneda
Microsoft Digital Media Division

October 2000

Summary: This document describes how content providers can stream audio and video to consumers in a secure way by using Microsoft Windows Media Rights Manager 7. (4 printed pages)

Introduction

You can provide music and video to your consumers in different ways. In addition to letting consumers download multimedia files, you can also stream multimedia files to consumers. Streaming is a good choice when you want to make your content available, but you don't want to give copies of it to consumers. Streaming also forces consumers back to your Web site to play your multimedia files, which is advantageous when you want to make sure that consumers see branding, advertisements, and other information on your site.

However, streaming multimedia files rather than providing them for download does not necessarily ensure that the files are secure. Several programs are currently available that allow a consumer to capture an audio or video stream and save it to a file on their computer. Consumers can then play the resulting multimedia file at any time and share it with other people.

To ensure that your audio and video content is secure and protected, you can package your multimedia files (encrypt them) by using Microsoft® Windows Media™ Rights Manager 7. The resulting packaged files retain the quality of the original version, are resilient to packet loss, and require a license for playback. This license specifies what actions can be performed by the consumer, such as the number of times a consumer can play the packaged multimedia files.

Streaming packaged files provides several solutions to ensure security:

If a consumer saves a streamed file to their computer, the file remains protected. That is, the consumer must have a license to play the saved stream.
If consumers share a saved stream with others, they will not be able to play the file without first obtaining a license because it is required to play a packaged file.
You can provide a URL in the packaged file so that when a consumer tries to play a local copy of it and does not have a license, the consumer is redirected to a Web site from which they can obtain a license. For example, you might display a page with information about the particular song or video, or redirect the consumer to a location from which the file can be streamed again.

Using Windows Media Rights Manager

You can package your multimedia files by using the Windows Media Rights Manager 7 Software Development Kit (SDK). This SDK provides the tools you need to protect your multimedia files, set the rights you want to allow for each file, generate licenses for them, and issue licenses to consumers. Consumers can play packaged multimedia files by using any player that supports the Microsoft Windows Media Format SDK, such as Microsoft Windows Media Player 7.

After packaging your files, you can set up your Web site to stream them and to deliver licenses for them. You must consider how you want to issue licenses, what rights you want to allow, and which URL to display if a consumer saves a streamed file and then tries to play it.

The Windows Media Rights Manager SDK provides many different methods for you to issue licenses, but perhaps the best way to issue a license for a streamed file is to predeliver a license. That is, to issue the license after a consumer selects the multimedia file they want to play, but before it is streamed. For example, a consumer selects a song to play, you issue a license, and then stream the song. A predelivered license provides the best experience for consumers because they are not aware of the licensing process. Users simply select a file that is then streamed to their players.

You must also consider the rights you want to allow for your packaged multimedia files. When streaming, you should allow the right to play the file. However, since it is possible for the stream to be saved to the consumer's computer, you might limit the rights you allow. For example, you might allow only one playback, which is the minimum right the consumer needs to play a stream. If the consumer saves the stream and tries to play the resulting file on their computer, the license will not allow further playback.

You should also specify a license acquisition URL to display when a consumer tries to play a packaged file for which there is no valid license (or when the consumer tries to play a saved stream with a license that does not allow further playback). This URL typically displays a Web site where the consumer can acquire a license. However, for streamed files, you might specify a URL that points to a registration page on your Web site. Alternatively, you might display a page with information that tells the consumer that they cannot play a local copy of your multimedia stream and must instead play it from your Web site. You specify this license acquisition URL when you package your files.

Providing Additional Security in Windows Millennium Edition

In addition to the encryption of multimedia files, Windows Media Rights Manager can also help to protect the content from being captured as it is traveling through the computer to the sound card by making use of a feature called Secure Audio Path. Secure Audio Path is currently a feature of Microsoft Windows® Millennium Edition, and is planned to be a feature in future Microsoft operating systems.

Secure Audio Path creates the strongest protection available from Microsoft for digital audio. It provides an infrastructure for maintaining copyright protection on audio files by helping to ensure that the audio data reaches the sound card on a computer and is not diverted to an unauthorized program. Secure Audio Path is a system that can secure digital audio at the kernel level of the operating system. Protecting digital audio in this way makes it more difficult to bypass copyright protections.

Because Secure Audio Path isn't available for all platforms, you can detect which platform the consumer is using before you issue a license and only use this feature for consumers who are using Windows Millennium Edition.

A Suggested Configuration

The following packaging and licensing configuration is one possibility for streaming.

Packaging

Encrypt all of your multimedia files, regardless of whether you will stream them or provide them for download.
Set the license acquisition URL in each content header to a page that is worded specifically for undesired stream captures. When the consumer plays a captured stream and does not have a valid license, this URL is displayed. Inform the consumer that they must return to your Web site to play this item and cannot play a saved copy of it. The saved stream is not playable and essentially rendered useless.

Licensing

If consumer has Windows Millennium Edition, require Secure Audio Path in the license (set the corresponding property).
If the consumer is using a player that supports Windows Media Rights Manager 7, before streaming the multimedia file, predeliver a license that allows one play.

For More Information

To learn more about the Windows Media Rights Manager 7 SDK and the Windows Media Format SDK, see the Windows Media Rights Manager 7 SDK and Windows Media Format 7 SDK documentation. These components of the Windows Media SDK can be downloaded from the Windows Media Web site.

For features, articles, and answers to frequently asked questions about digital rights management and Windows Media Rights Manager, see the MSDN Online Library.

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