Digital Rights Management (DRM) for Silverlight 4

Note: This topic is specific to Silverlight 4. To learn about the DRM in Silverlight 3, see Digital Rights Management (Silverlight 3).

With Digital Rights Management (DRM) integrated into Silverlight applications, you can better protect content and more securely deliver content across platforms for a variety of scenarios, including streaming content, incremental downloads, lease content, and subscriptions.

DRM scheme

You can use DRM to help you deliver audio and video content, which makes it safer and better to protect content from unauthorized access and redistribution. This protection mechanism can be integrated into a variety of business scenarios, including:

Online scenarios: These scenarios require users to be online when playing media content:

Real-time streaming: real-time streaming is also known as "real streaming", which sends content directly to a computer or device without saving the file to the hard disk. Live streaming is available only when broadcasting. Examples of real-time streaming are Internet TV and radio.

Incremental Downloads: Incremental downloads enable users to play when the media is downloading. From a user's perspective, the main difference between incremental downloads and real-time streaming is that the content that is incrementally downloaded is stored on the user's computer or device (at least temporary storage).

Offline Scenarios: These scenarios allow users to be offline when they play content. These scenarios do require that the offline version of the Silverlight runtime be installed on the user's computer or device, and that the user is actually online (at least intermittently online) so that the content is initially downloaded and the subscription is renewed.

Download files offline (one-time purchase): Users download content from the Internet, and then use the offline Silverlight player to play the content. For example, an online video store charges a customer for downloading a video file that the user can play in the offline Silverlight player when needed. DRM software can limit the redistribution of video files to one or more devices (see the domain later in this article).

Leasing: You can specify a time limit in a DRM license to limit the playback of content. For example, an online video store might provide its video for rent. Once the leased content has been purchased and the license is downloaded, the license expires after 30 days from the date of issuance of the license or 24 hours after the first broadcast, whichever comes first.

Subscriptions: Enables customers to play content based on the subscription model. For example, customers at online video stores pay a monthly fee to watch up to 100 hours of TV content online and download up to 20 TV dramas. To renew its subscription, customers need to pay a monthly fee and need to connect to this service at least once a month, because the subscription license expires every 45 days.

Note the Windows XP operating system installed on FAT32 does not support the Silverlight DRM scheme.

Silverlight DRM Online Scenario

The following sections explain how to enable the online Silverlight DRM scheme. Many of the concepts described here also apply to offline scenarios, but offline scenarios, such as leases and subscriptions, are described later in the Silverlight DRM offline scenario.

This section examines the minimum components required to play DRM content in Silverlight. These components apply to both online and offline scenarios, but some scenarios require additional components, which are described in subsequent chapters.

Silverlight DRM Online Conceptual Overview

The following figure summarizes the processes required to play the DRM content in Silverlight and the server/client interaction required to drive these processes to completion. Each of these steps will be discussed in more detail later.