The OMA DRM v1.0 specification enables content providers to associate certain rights to the content objects for defining how the content can be used. The Symbian platform supports the mandatory features of the OMA DRM v1.0 specification.
The Symbian platform supports the following OMA DRM 1.0 features:
Forward-lock
Combined delivery
Separate delivery
In addition, the Symbian platform supports time-based constraints for automated content, such as background images, UI themes, ring tones, and alarm tones. However, count-based constraints for automated content are not allowed.
The protection of themes and native applications covers not only the SIS package itself but also the data after the installation. The protection is achieved through encrypting essential theme and application data (chosen by the developer). Protected applications and themes can make use of DRM mechanisms, such as expiry dates or online rights refresh.
For file formats that are not DRM protected, the forwarding is restricted according to the closed content list.
Use the DRM CAF Agent API to implement the OMA DRM v1.0 features in applications.
Forward-lock is a simple mechanism that prevents content from leaving the mobile device. It provides basic copy protection that protects the rights of content owners. The content is delivered to the device in a DRM message without associating a rights object to the content. Forward-lock content can be opened and played freely in the given device but cannot be forwarded or used in any other device.
Combined delivery is similar to OMA forward-lock, but additional usage rights can be added to the content, such as one-time use, or use for a week. This allows the previewing of content, or the adoption of various new business models by applying different usage rights. The content and rights are delivered to the device within the same DRM message. The device enforces the usage of the content according to the rights. The device does not allow forwarding the right or the content to any other device.
Forward-lock and combined delivery protected content is received to the device as plain text, but is encrypted as soon as it is received. After the content has been encrypted, it can only be opened and consumed in the device where it was originally downloaded.
Separate delivery is similar to combined delivery but with added security. Content is delivered as encrypted files separately from usage rights, which are delivered via a different channel. Separate delivery also enables the superdistribution business model, in which DRM-protected content can be sent from mobile device to mobile device, for example sending the content as part of an MMS to a friend. The recipient can then acquire a license to get a preview or buy the content. This makes viral marketing a potentially powerful concept.
In separate delivery, the content is in the format defined in the OMA DRM Content Format specification. The content is encrypted using a symmetric encryption key called content encryption key (CEK). The content can be decrypted only with the same key that has been used for encryption. With separate delivery, the encrypted content is delivered to the device separately from the rights (typically over HTTP download or MMS). The rights object containing the CEK is delivered to the device using connectionless WAP Push over SMS.
Symbian applications that deal with combined delivery and separate delivery protected media objects are capable of enforcing the usage rights constraints that are defined in the rights objects. The applications are able to detect when the usage rights related to a combined delivery and separate delivery protected media object have become expired.
The content provider can specify a timeout value for the delivery of the rights object when delivering content over HTTP. The user is notified if the rights object does not arrive within the specified time. The rights object related to a separate delivery protected media object can also be updated when it expires.
The file types that are defined in OMA DRM v1.0 correspond to the following delivery methods:
Delivery message (.dm)
Contains the content. It is used in both OMA forward-lock and combined delivery. In an OMA forward-lock delivery message, the file contains only the protected content, whereas in a combined delivery message, the file contains both the rights (defined in ODRL) and the content. The MIME type for this file type is application/vnd.oma.drm.message.
DRM content format (.dcf)
Contains the encrypted content. It is used in separate delivery where the content is encrypted into the message without the rights. The key used to encrypt the content is sent separately with the rights to the device. The MIME type for this file type is application/vnd.oma.drm.content.
DRM rights object, binary (.drc)
Contains the rights object, specified in binary, as well as the key used to encrypt the content in the DCF file. The MIME type for this file type is application/vnd.oma.drm.rights+wbxml.
DRM rights object, clear text (.dr)
Contains the rights object, specified in clear text, as well as the key used to encrypt the content in the DCF file. The MIME type for this file type is application/vnd.oma.drm.rights+xml.
You can use the following methods to download DRM-protected files:
HTTP download
Multimedia messaging service (MMS)
You can use the following methods to download files in the DCF format:
MMS
HTTP
Bluetooth
IrDa
Multimedia card (MMC)
Any other connectivity method that supports file transfer
For more information, see Video distribution channels.