Content Protection
Functional Description
Content protection of media assets involves mechanisms to prevent users of third parties consuming or acquiring content outside of authorised usage scenarios.
This generally includes a mechanism by which media data is encrypted using one or more encryption keys, and these key(s) are communicated from a licensing/key authority to the playback device out of band either in advance, at the start of playback, or during playback, subject to satisfying any licensing/authorisation requirements.
API Specification
A remote API would be required in the case where the required key(s) to play the content are not present on the device, and must be acquired to begin/continue playback.
In the case where an existing DRM system was being used, the API and endpoints used would be as specified for that system.
A possible API for a custom, simple DRM scheme suitable for use with MPEG-DASH CENC protected media on a TV-emulator device may include the following:
Get playback key(s):
Request encryption key(s) for an item of content.
{
"message" : "get_keys",
"cid" : "content ID",
"kid" : [ "key ID", ... ],
"auth" : { relevant authentication details/token(s) as may be defined in identity/auth module }
}
Get playback key(s) response:
{
"message" : "get_keys_response",
"cid" : "content ID",
"kid" : [ "key ID", ... ],
"keys" : [ "key value", ... ]
}
Where ‘cid’ (content ID) and ‘kid’ (key ID) are as defined and embedded within the MPEG-DASH CENC media.
In the case of MPEG-DASH CENC, content IDs, key IDs and key values can be assumed to be opaque 128-bit values.
In order to protect authentication details/token(s) and encryption key(s) in transit, communication between the device and the licensing/key authority should be suitably encrypted (i.e. using TLS).
Content could be explicitly marked as protected using the 2-IMMERSE scheme either by adding a tag to the MPD manifest within a 2-IMMERSE specific namespace, or by generating a unique 2-IMMERSE owned system ID and embedding that within the PSSH of the media.
