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Windows Media DRM FAQ October 2005
This page provides answers to frequently asked questions about Microsoft Windows Media digital rights management (DRM). It includes the following sections:General. General questions about Windows Media DRM.
Security. Questions about Windows Media DRM security features.
Business Rules. Questions about the types of implementations that Windows Media DRM supports.
 Tip To search this FAQ, press CTRL+F.
General
Security
Business Rules
Scalable Platform
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General1.1 What is Windows Media DRM?Microsoft Windows Media digital rights management (DRM) is a flexible platform that makes it possible to protect and securely deliver content by subscription or individual request for playback on a computer, portable device, or network device. Windows Media DRM is comprised of multiple components, including:Windows Media DRM 10 for Portable Devices. Designed to allow devices such as portable audio and video players, set-top boxes, and mobile devices with audio and video capabilities to directly or indirectly acquire and play Windows Media–based protected content.
Windows Media DRM 10 for Network Devices. Designed to allow devices such as set-top boxes, DVD players, digital media receivers, and digital audio receivers to play back Windows Media–based protected content that resides on another computer on a home network.
Windows Media Rights Manager 10 Software Development Kit (SDK). Enables content owners to encrypt content with a key and deliver licenses to desktop computers and devices for playback of protected content.
Windows Media Format 9.5 SDK, DRM Addendum. Enables independent software vendors (ISVs) to develop applications that can play protected Windows Media–based content.
Windows Media Data Session Toolkit. Used to deliver protected digital media content to a computer through physical media in an easy and secure manner.
Windows Media Device Manager 10 SDK. Enables software vendors or equipment manufacturers to develop applications used to transfer content from computers to compatible portable devices.
Windows Media Portable Device DRM (PDDRM). Enables portable device manufacturers to develop devices that decrypt content protected by using Windows Media DRM.
First shipped in April 1999, the Windows Media DRM platform is widely deployed by content providers and is already installed on over 500 million desktops. More than 50 different music and video services are using Windows Media DRM today, which has powered tens of millions of transactions to date.
1.2 What is Windows Media DRM 10?The latest release of Windows Media DRM technology makes it possible to protect, deliver, and play individual, subscription, and promotional digital media content on computers, portable audio devices, Portable Media Center devices, or networked devices that are connected to an Internet protocol (IP) network. Windows Media DRM includes two new components, Windows Media DRM 10 for Portable Devices and Windows Media DRM 10 for Network Devices, as well as an updated Windows Media Rights Manager 10 SDK. These components allow for the seamless flow of content to almost any device, offer the widest range of purchase and rental options for digital media, and ensure the security of premium content as it flows from device to device.
1.3 What is Windows Media Rights Manager?
Windows Media Rights Manager is the technology that allows you to package Windows Media DRM files and issues licenses. You can use Windows Media Rights Manager to encrypt a given digital media file, lock it with a key, and bundle additional information from the content provider. This results in a packaged file that can only be played by the person who has obtained a license. Windows Media Rights Manager can also act as the license clearing house, authenticating the consumer's request for a license and issuing the license to the user. Windows Media Rights Manager is made available as an SDK, and the current available version is the Windows Media Rights Manager 10.1.2 SDK.
1.4 How does Windows Media DRM work?The basic Windows Media DRM process is as follows:Packaging Windows Media Rights Manager packages the digital media file. The packaged file has been encrypted and locked with a key. This key is stored in an encrypted license, which is distributed separately. (This feature is unique to Windows Media Rights Manager.) Other information is added to the digital media file, such as the URL where the license can be acquired. This packaged digital media file is saved in Windows Media Audio format (file with a .wma file name extension) or Windows Media Video format (file with a .wmv file name extension). Distribution The packaged file can be placed on a Web site for download, placed on a digital media server for streaming, distributed on a CD, or e-mailed to consumers. Windows Media DRM permits consumers to send copy-protected digital media files to their friends as well. Establishing a license server The content provider chooses a license clearing house that stores the specific rights or rules of the license and implements the Windows Media Rights Manager License Service. The role of the clearing house is to authenticate the consumer's request for a license. Digital media files and licenses are distributed and stored separately, making it easier to manage the entire system. License acquisition To play a packaged digital media file, the consumer must first acquire a license key to unlock the file. The process of acquiring a license begins automatically when the consumer attempts to acquire the packaged digital media file, acquires a pre-delivered license, or plays the file for the first time. Windows Media Rights Manager either sends the consumer to a registration page where information is requested or payment is required, or "silently" retrieves a license from a clearing house. Playing the digital media file To play the digital media file, the consumer needs a player that supports Windows Media DRM. The consumer can then play the file according to the rules or rights that are included in the license. Licenses can have different rights, such as start times and dates, duration, and counted operations. For instance, default rights may allow the consumer to play the digital media file on a specific computer and copy the file to a portable device. Licenses, however, are not transferable. If a consumer sends a packaged digital media file to a friend, this friend must acquire her own license to play the digital media file. This PC-by-PC licensing scheme ensures that the packaged digital media file can only be played by the computer that has been granted the license key for that file.
1.5 What are some of the features in Windows Media DRM?Windows Media DRM contains a number of features that protect the content file and enables new flexible business models.
SecurityIndividualization Windows Media DRM improves the security of the system by making each digital media player unique and linking the player to the host computer. This reduces the likelihood that a compromised player will be widely distributed on the Internet. With individualization, any compromised player can be identified and disabled in the licensing process. Application exclusion Windows Media DRM enables the license issuer to prohibit an application from playing certain packaged files. DRM component exclusion Windows Media DRM enables the license issuer to deny licenses to applications that use a DRM component that is known to be damaged or corrupted. Secure Audio Path Windows Media DRM ensures digital media file protection in the operating system from the player to the sound card driver in Microsoft Windows Millennium Edition, Microsoft Windows XP. This secure relationship reduces the likelihood that any unauthorized program will capture a digital media stream within a computer.
License AcquisitionLicense chaining This feature allows content services to create “root” licenses (which contain information that governs whether or not a file can be played, such as expiration date) and “leaf” licenses for the content itself. This is useful for subscription services because only the single root license needs to be updated for each renewal period as opposed to renewing hundreds or thousands of individual content licenses. License store performance The redesigned license store reduces the time necessary to manage licenses.
PlaybackStart and end times Content providers can create specific playback time periods for their digital media files. For example, a rental model could be established where consumers could play back a streaming media file during a three-day period. This time period may begin some time in the future and last for a limited duration. Playback duration Content providers can specify an amount of time during which playback of a given digital media file is permitted. This time period may begin the first time the file is played or saved to a computer. Counted operations The single play or limited play option allows the content provider to limit the number of times that the consumer can play a digital media file.
1.6 Why is digital rights management important?Digital media files can be easily copied and distributed without any reduction in quality. As a result, digital media files are being widely distributed on the Internet today, through both authorized and unauthorized distribution channels. Piracy is a concern when security measures are not in place to protect content. Digital rights management enables content providers to protect their content and maintain control over distribution. Content providers can protect and manage their rights by creating licenses for each digital media file. License registration procedures also give these companies important customer information. Such information helps content providers stay closer to their customers. Having a robust DRM system in place ensures that a wide variety of the highest-quality audio and video content is made available to consumers.
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Security2.1 How does Windows Media DRM protect digital content?Microsoft Windows Media DRM uses a wide range of cryptographic and anti-piracy techniques to protect digital media content and its own integrity. Microsoft Windows Media Rights Manager, the technology that packages files and issues licenses, encrypts a given media file with a full-strength encryption algorithm. No decryption key is contained in the Windows Media Format file container. Decrypting an isolated Windows Media file would require breaking industrial-strength cryptographic algorithms.
2.2 How does Windows Media DRM protect content owners' rights during the transfer of digital media files?Standard cryptographic protocols based on digital signatures are used for authentication throughout Windows Media DRM. For example, license servers use Windows Media DRM technologies to authenticate Windows Media DRM-based clients. These clients use digital certificates on their computers. The digital certificate's unique public key and version number identify the client. Licenses are issued only to authenticated clients. The digital media file key in the license is also encrypted in such a way that only the Windows Media DRM-based client software to which the key was issued can retrieve it. A digital signature further protects the usage rules from tampering.
2.3 How are media players protected with Windows Media DRM?Microsoft must first give authorization to any company before it can incorporate Windows Media DRM into its media player. After being authorized, the company is provided with a certificate, which can be revoked if their player is compromised. Windows Media DRM run-time software requires authentication of license applications before the license server serves packaged digital media files to the application. The authentication protocol also establishes a session key, which is used to protect the integrity and secrecy of the data exchanged between the run-time software and the media player.
2.4 What is individualization?Windows Media DRM individualizes the critical components of each run-time client. Individualization binds the run-time client to the computer on which the client was initially installed. Every consumer is given a different executable file and different certified license keys. This significantly reduces the danger of global breaks. If a specific DRM client becomes compromised, it can be barred from acquiring licenses for new digital media files.
2.5 How does Windows Media DRM support revocation?Windows Media DRM supports revocation at several stages. First, the license server can crosscheck a list of compromised run-time clients and refuse service to those clients until they upgrade to a newer and more secure client. Second, it is also possible to revoke third-party applications that were previously enabled to work with Windows Media DRM, but which have since been compromised.
2.6 Does Windows Media DRM support "renewability"?Yes. Renewability refers to the updating of DRM system components to enhance security. Windows Media DRM can be upgraded by a variety of triggers as Microsoft releases improved versions. These releases may be regular improvements in the overall security system or reactions to security threats. Content owners can also refuse to service requests from less secure clients unless the client upgrades or renews certain components.
2.7 What is Secure Audio Path?All personal computer operating systems are vulnerable to attacks that seek to replace device drivers. For example, a digital media file is vulnerable to interception on the way to the sound driver after the file has been decrypted and downloaded from the DRM system to a media player. With the release of Secure Audio Path technology in Microsoft Windows Millennium Edition and Windows XP, the data path inside the operating system is protected during transfer from the media player to the sound card. This reduces attacks that are based on false plug-ins because these components only have access to encrypted data. A certified Microsoft component verifies that all downstream components (including the sound card driver) are also certified. It does not decrypt the data stream if it detects unauthorized or compromised components in the execution path.
2.8 Does Secure Audio Path require specific hardware?
All Windows Hardware Quality Labs (WHQL)-certified signed audio drivers for Windows XP support Secure Audio Path. For more information about WHQL-certified signed audio drivers, see the Windows Hardware and Driver Central page.
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Business Rules3.1 How does Windows Media DRM support Live DRM?To deliver on-demand or live content, Windows Media DRM can provide real-time encryption when creating content with Windows Media Encoder 9 Series. Using these two Windows Media technologies together, files can be simultaneously encoded and encrypted prior to delivery so that no content is ever unprotected. Applying innovative license terms that are provided by Windows Media DRM enables new business models for live DRM content.
3.2 Does Windows Media DRM support super distribution?Yes. Digital media files are maintained in a protected format at all times. This protected file can be freely shared between customers. When customers without a license attempt to access the shared digital media file, they are prompted to get a license for that digital media file by following the business rules specified at the hosting Web site. Acquiring a new license to play a super-distributed media file requires an active Web connection.
3.3 Does Windows Media DRM support time-limited playback of digital media files?Yes. Licenses to play digital media files can specify start times, end times, and license duration limits. If customers with an expired license try to access a digital media file, they are directed back to the hosting Web site for another license. In Windows Media DRM, both start and expiration dates are supported, which creates great flexibility. For example, a digital media file could be distributed with a license that disables playback until the intended release date.
3.4 Does Windows Media DRM support limiting the number of times a digital media file can be played?Yes. Windows Media DRM version 1 supports counted operations (a specified number of times a file can be played back) through distribution of multiple single-play licenses. Windows Media DRM 7 and later versions support counted operations in one license.
3.5 Does Windows Media DRM support limits on the number of digital media file transfers to portable devices or portable media?Yes. Windows Media DRM adds a right in the license to enable or disable copying to a portable device or portable media. When enabled, the packaged digital media file can be copied to a portable device or portable media. The license is bound to a unique ID on the portable device or media.
3.6 Does Windows Media DRM support limiting the number of times a digital media file can be copied?Yes. A packaged media file can be freely copied between computers; however, each computer that plays the packaged digital media file needs a separate license. The license server can be configured to restrict the number of licenses that it issues for any given copy.
3.7 Does Windows Media DRM support creating CD-ROM copies of media content?Yes. Windows Media DRM has the ability to set the appropriate license right to "burn-to-CD." To copy a packaged Windows Media file onto a CD-ROM, the consumer must have a license that includes the right to do so. CD-ROM-copying applications are required to honor the rights set by the content owner and distributor. After content is copied to a CD-ROM, it is no longer packaged.
3.8 Can Windows Media DRM create different licenses for the same digital media file?Yes. For instance, consumers could acquire a movie with a single-play rental license. If they tried to play the movie a second time, they would be directed to a license clearing house or e-commerce Web site, where they may be presented with the option to purchase an unlimited playback license. In this case, the consumer downloads the digital media file only once but receives multiple licenses for that file.
3.9 Is it possible to programmatically acquire a license without using the normal SDK license acquisition HTTP post request?Yes. The license request can be obtained using client-side script, by requesting non-silent license acquisition. The Internet Service Provider (ISP) can then send this request to the license server by using any protocol.
3.10 What is the recommended way to silently identify a user on the server side when a license is requested?Silent identification of users is not supported by the SDK due to privacy concerns, so the SDK does not hand out the client ID to the license server.
3.11 What, if anything, has to be deployed for the Windows Media Players to be able to play digital media files packaged by Windows Media DRM?Windows Media Player has a DRM component built-in. You don't have to do anything to make it work with a Windows Media DRM content file. For files protected with Secure Audio Path, the client computer must be running either the Microsoft Windows Millennium Edition or Microsoft Windows XP operating system.
3.12 How do I protect digital media files with Windows Media DRM so they can be played by older Windows Media Players, such as Windows Media Player 6.4? What are the drawbacks, if any?You can package the digital media files using Windows Media Rights Manager 10.1, the newly-released packager and license server. For Windows Media Player 6.4, you need to put a separate URL for version 1 license acquisition in the header. Windows Media Player 6.4 can use this URL to acquire a version 1 license for the content or this URL can point the user to an "upgrade Windows Media Player" page. The version 1 license has limited business model functionalities and lower security than later version licenses that are available to newer Windows Media Players. Windows Media Rights Manager 10.1 can issue all license versions.
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Scalable Platform4.1 How scalable is Windows Media Rights Manager?Windows Media Rights Manager is highly scalable. The server components in Windows Media Rights Manager are implemented as COM-based objects, which provide great flexibility and scalability in creating a Windows Media DRM system for specific business models. In addition, Windows Media Rights Manager supports high-volume delivery of digital media files and licenses. Scalability features include the following:Protecting content A single server can encrypt over 500,000 music files per day. The high performance of the encryption algorithm used in Windows Media Rights Manager makes it possible for server administrators to frequently change encryption keys and/or re-encrypt a given digital media file frequently. A digital media file can be re-encrypted with a different key for each download. Issuing licenses Windows Media Rights Manager can scale to issue licenses. On a Pentium 4, 2.4 gigahertz, 256 megabytes of random access memory, dual-processor desktop, it can issue 22.33 licenses per second.
4.2 Is Windows Media DRM open and extensible?Yes. The Windows Media DRM application programming interfaces (APIs) are open and published, which allows third parties to customize and extend their DRM systems. Microsoft only provides the core components. The various SDKs also allow third parties to build different media applications to support Windows Media, including Windows Media Rights Manager.
For more information on the SDKs that are available for Windows Media client and server development, see Windows Media SDK Components.
4.3 What input sources does Windows Media Rights Manager support?Windows Media Rights Manager uses standard Windows Media files, encrypting them in place. Therefore, any input source that can be converted to Windows Media Format can be used with Windows Media Rights Manager. Such sources include any analog or digital audio/video input that can be connected to a computer, raw waveform (WAV) and audio/video interleave (AVI) files, and direct encoding from CD.
4.4 What output formats does Windows Media Rights Manager support?Windows Media Rights Manager supports Windows Media Format, including Windows Media Audio format (with a .wma file name extension) and Windows Media Video format (with a .wmv file name extension).
4.5 Which operating systems support Windows Media DRM?The Windows Media DRM run-time client is supported on several operating systems. Depending on the operating system, either version 1 is supported or version 7 and later are supported. The difference between the two is that version 1 licenses offer more reach (for example, the Microsoft Windows 95 operating system) but fewer capabilities (for example, licensing models are more restrictive) and limited security functionalities. Version 7 and later licenses offer greater flexibility and security enhancements, but are available only to newer operating systems.
Regardless of which licenses the run-time client can use, Windows Media Rights Manager 10.1 can issue licenses in all of these formats (version 1, version 7.x, version 9, and version 10.x) to all run-time clients on these operating systems.
| Operating System | Windows Media Player supported | Windows Media DRM license supported |
|---|
Windows 95
| Windows Media Player 6.4
| Version 1 license
| Windows NT Server 4.0
| Windows Media Player 6.4
| Version 1 license
| Windows 98 SE
| Windows Media Player 7.1
Windows Media Player 9 Series
| Version 1 and version 7.x and later licenses
| Windows 2000
| Windows Media Player 7.1
Windows Media Player 9 Series
| Version 1 and version 7.x and later licenses
| Windows Millennium Edition
| Windows Media Player 7.1
Windows Media Player 9 Series
| Version 1 and version 7.x and later licenses
| Windows XP
| Windows Media Player 7.1
Windows Media Player 9 Series
Windows Media Player 10
| Version 1 and version 7.x and later licenses
| Mac OS 8.5
| Windows Media Player 7.01 for Mac
| Version 1 and version 7.x and later licenses
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4.6 Where is Windows Media DRM commercially available and deployed?
Windows Media DRM has been available since April 1999 and is used widely for promotional and commercial purposes. Examples include House of Blues, LAUNCH Media , NHL.com, Movielink.com, Pressplay, Worldwide Wrestling Federation, and many others. Pointers to these Web sites can be found at the Windows Media guide to audio and video on the Internet, WindowsMedia.com.
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