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Re: ACTION-5: key release

From: Mark Watson <watsonm@netflix.com>
Date: Thu, 6 Sep 2012 16:08:21 +0000
To: "Sunyang (Eric)" <eric.sun@huawei.com>
CC: "<public-html-media@w3.org>" <public-html-media@w3.org>
Message-ID: <708DCEEB-A3DC-4EF4-B51D-BC6A8876C5EE@netflix.com>

On Sep 6, 2012, at 1:59 AM, Sunyang (Eric) wrote:

> Thanks for the solution.
> But why we need retrieve a "released" MediaKeySession£¬ then fire event on it?

The idea is to provide secure proof of key release. That is, server visibility of the complete key lifecycle as asserted by the CDM.

The key release message is an assertion from the CDM that it no longer has a copy of the key. It needs to be delivered reliably to the application server, so the CDM should store it until it received a key release ack from the application server. This includes storing it one shutdown/startup cycles. When the app starts up it needs to get any stored, unacknowledged key release messages from the CDM to deliver to the application server.

”­Mark

> 
> 
> Yang
> Huawei
> 
>> -----Original Message-----
>> From: Mark Watson [mailto:watsonm@netflix.com]
>> Sent: Tuesday, September 04, 2012 10:22 PM
>> To: <public-html-media@w3.org>
>> Subject: ACTION-5: key release
>> 
>> http://www.w3.org/html/wg/media/track/actions/5

>> 
>> All,
>> 
>> The status of this action is that I have provided a proposal as a comment to
>> the bug [1]. For ease of reference I've copied the proposal here, but please
>> make comments in the bug, or on the call today.
>> 
>> ”­Mark
>> 
>> If key release is supported, then
>> (i) when the MediaKeySession.close() method is called, the session enters a
>> "key release pending" state and a keymessage event is fired on the
>> MediaKeySession, containing the key release object
>> (ii) when the application receives the key release acknowledgement from the
>> server the session is updated with this message using the addKey() method
>> (or
>> update(), if we rename it as per bug 18531 [2]). The MediaKeySession enters
>> a
>> "key release complete" state
>> (iii) a new method is added to MediaKeys: MediaKeySession?
>> retrieveClosedSession() which will retrieve a MediaKeySession object in the
>> key
>> release pending state. Subsequent calls to this method will retrieve further
>> sessions in the 'key release pending state' until none are left (we could
>> consider returning a list of MediaKeySession objects). A keymessage event is
>> fired on each MediaKeySession retrieved with this method containing the key
>> release object.
>> 
>> [1] https://www.w3.org/Bugs/Public/show_bug.cgi?id=17199

>> [2] https://www.w3.org/Bugs/Public/show_bug.cgi?id=18531


Received on Thursday, 6 September 2012 16:08:51 GMT

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