[Bug 26887] New: Allowing license servers and CDMs to control data persistence and secure release

https://www.w3.org/Bugs/Public/show_bug.cgi?id=26887

            Bug ID: 26887
           Summary: Allowing license servers and CDMs to control data
                    persistence and secure release
           Product: HTML WG
           Version: unspecified
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: major
          Priority: P2
         Component: Encrypted Media Extensions
          Assignee: adrianba@microsoft.com
          Reporter: jdsmith@microsoft.com
        QA Contact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-media@w3.org

Our current spec uses sessionType to control storage of session data, and
load() and remove() to support secure release.  These assume the app is in
control of the secure release process, and in many respects, the CDM need not
be aware.  Unfortunately, these features don’t work well with implementations
that have the license server and CDM control secure release using terms set in
the license itself.  This license server model has many positives.  It can
securely manage license persistence, expirations and secure release features,
directly and with little app complexity.  We believe supporting it will be
important for EME; however, there are issues between it and the current spec:  

1.    At most, sessionType could only be a hint to the process in the license
controlled model, as the license terms would determine whether the license
itself is stored, and whether it is subject to secure release requirements.
2.    Load() is problematic, since licenses under secure release may still be
temporary (in fact this may be desirable) and may be released even though
secure release messages are still pending.
3.    Status information on secure release is maintained in the CDM and
currently would be inaccessible to applications.  We could make this
information accessible, but the utility of any function we provide for this
might vary by CDM.

Some of these issues result from overloading the original intents for
MediaKeySession and sessionId.  These originally managed the short term
exchange of messages and have grown to now manage the lifetime of media content
playback on a given device.  The original short term intention was a much
better fit with license server controlled CDM implementations.

We believe the license server controlled model must be supported by EME.  I’d
like to get agreement on this and discuss whether it can be done with a common
EME abstraction or not.

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Received on Tuesday, 23 September 2014 00:08:33 UTC