Issuing Chained Licenses

Licenses can be created in two formats:

• The simple format is a self-contained license. When the license expires, the entire license is no longer valid and a new license must be issued before the content can be played again.

  

• A complex format, called a license chain, is a license that is composed of connected elements that include a root license and one or more leaf licenses, each of which contains a subset of rights.

  

License chaining is most useful in a subscription scenario when large numbers of licenses must be updated periodically. For example, a music subscription service with a library of 10,000 songs issues licenses that expire after 30 days. When consumers renew their subscriptions, they receive updated licenses valid for an additional 30 days.

• Using simple license format: One license is issued per song. After 30 days, the entire license expires, and so the subscription service must reissue 10,000 licenses each month to each consumer.
• Using a license chain: Initially, the subscription service issues one leaf license per song allowing the right to play the song, and one root license for all songs with an expiration date. After 30 days, the root license expires and so the subscription must reissue one license each month to each consumer. As a result, the overall process is much faster for both the subscription service and the consumer.

This section contains the following topics.

Topic	Description
How License Chaining Works	Describes how the elements in a license chain work together to decrypt content.
Specifying a License Chain When Protecting Content	Describes how to specify the elements in a license chain to protect content.
Issuing a License in a License Chain	Describes how to issue part or all of a license chain.

For additional information and sample code, see the Technical Articles on the Digital Rights Management page at the Microsoft Web site.

See Also

• Generating and Issuing Licenses