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Issue w3c#80: Times in the record of key usage should be at session, not key, level
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‎encrypted-media-respec.html

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@@ -921,11 +921,11 @@ <h2><a>MediaKeys</a> Interface</h2>
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<dd>
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<p class="issue"><a href="https://github.com/w3c/encrypted-media/issues/85">Issue 85</a> - There are concerns about the architectural implications of <code>"tracked"</code> sessions that are pending a TAG discussion. The outcome of this discussion could result in modification (including removal) of the feature.</p>
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<p>
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A session for which the license and any key(s) it contains SHALL NOT be persisted and for which a <var>record of key usage times</var> SHALL be persisted.
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The <var>record of key usage times</var> consists of a record of the key IDs of the keys used in the session, the <var>first decryption time</var> for each key and the <var>latest decryption time</var> for each key.
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A <a def-id="message"></a> of type <a def-id="message-type-license-release"></a> containing a record of key usage will be generated when <a def-id="remove"></a> is called and on every <a def-id="load"></a> call until the record is acknowledged by a response passed to <a def-id="update"></a>. Because the license and keys are not persisted, this record implicitly proves that the keys are no longer available in the session.
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A session for which the license and any key(s) it contains SHALL NOT be persisted and for which a <var>record of key usage</var> SHALL be persisted.
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The <var>record of key usage</var> consists of a record of the key IDs of the keys available in the session, the time at which the session was first used
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to decrypt content, the <var>first decryption time</var> and the latest time at which the session was used to decrypt content, the <var>latest decryption time</var>.
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A <a def-id="message"></a> of type <a def-id="message-type-license-release"></a> containing the <var>record of key usage</var> will be generated when <a def-id="remove"></a> is called and on every <a def-id="load"></a> call until the record is acknowledged by a response passed to <a def-id="update"></a>. Because the license and keys are not persisted, this record implicitly proves that the keys are no longer available in the session.
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</p>
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<p class="issue"><a href="https://github.com/w3c/encrypted-media/issues/80">Issue 80</a> - It has been proposed that usage should be recorded by session, not key.</p>
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<p>
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The session MUST be loadable via its <a def-id="session-id"></a> once <a def-id="update"></a> is called successfully.
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The application is responsible for managing any such storage that may be generated by the CDM.
@@ -1148,7 +1148,14 @@ <h2><a>MediaKeySession</a> Interface</h2>
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</dd>
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<dt><a def-id="tracked-session"></a></dt>
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<dd>
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<p>Let <var>requested license type</var> be a non-persistable license that will persist a <var>record of key usage</var>.</p>
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<ol>
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<li>
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<p>Let this sessions <var>record of key usage</var> be <code>null</code>.</p>
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</li>
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<li>
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<p>Let <var>requested license type</var> be a non-persistable license that will persist the <var>record of key usage</var>.</p>
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</li>
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</ol>
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</dd>
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<dt><a def-id="persistent-license-session"></a></dt>
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<dd>
@@ -1296,7 +1303,19 @@ <h2><a>MediaKeySession</a> Interface</h2>
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<dt>If <var>sessionType</var> is <a def-id="temporary-session"></a> and <var>sanitized response</var> does not specify that session data, including any license, key(s), or similar session data it contains, should be stored</dt>
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<dd>Process <var>sanitized response</var>, not storing any session data.</dd>
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<dt>If <var>sessionType</var> is <a def-id="tracked-session"></a> and <var>sanitized response</var> contains a non-persistable license</dt>
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<dd>Process <var>sanitized response</var>, not storing any session data.
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<dd>
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<ol>
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<li>
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<p>
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Process <var>sanitized response</var>, not storing any session data.
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</p>
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</li>
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<li>
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<p>
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If processing <var>sanitized response</var> resulting in the addition of keys to the set of <a href="#known-key">known keys</a>, add these new keys to the session's <var>record of key usage</var>.
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</p>
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</li>
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</ol>
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</dd><dt>If <var>sessionType</var> is <a def-id="persistent-license-session"></a> and <var>sanitized response</var> contains a persistable license</dt>
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<dd>Process <var>sanitized response</var>, storing the license/key(s) and related session data contained in <var>sanitized response</var>.
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Such data MUST be stored such that only the <a def-id="origin"></a> of this object's <a def-id="document-concept"></a> can access it.
@@ -1331,7 +1350,7 @@ <h2><a>MediaKeySession</a> Interface</h2>
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<dd>
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<p>Run the following steps:</p>
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<ol>
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<li><p>Clear all stored session data associated with this object, including the <a def-id="sessionId"></a> and <var>record of key usage</var>.</p>
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<li><p>Clear all stored session data associated with this object, including the <a def-id="sessionId"></a> and the <var>record of key usage</var>.</p>
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<p class="note">A subsequent call to <a def-id="load"></a> with the value of this object's <a def-id="sessionId"></a> would fail because there is no data stored for that session ID.</p>
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</li>
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<li>
@@ -2044,12 +2063,12 @@ <h4>Encrypted Block Encountered</h4>
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<ol>
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<li>
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<p>
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If the <var>record of key usage</var> does not contain an entry for <var>block key ID</var>, add a new entry for <var>block key ID</var> with <var>first decrypt time</var> set to the current time.
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If the session's <var>record of key usage</var> is <code>null</code>, initialize the <var>record of key usage</var> to contain the key ids for all <a href="#known-key">known keys</a>, setting <var>first decrypt time</var> to the current time.
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</p>
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</li>
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<li>
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<p>
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Set the <var>latest decrypt time</var> of the entry for <var>block key ID</var> in the <var>record of key use</var> to the current time.
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Set the <var>latest decrypt time</var> of the <var>record of key usage</var> to the current time.
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</p>
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</li>
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</ol>
@@ -2360,7 +2379,7 @@ <h4>Behavior</h4>
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<li>
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<p>
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For sessions of type <a def-id="tracked-session"></a>, in the <a def-id="remove"></a> and <a def-id="load"></a> algorithms, the <var>message</var> reflecting
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the <var>record of key usage times</var> is a JSON object encoded in UTF-8 as described in <a href="#clear-key-release-format">License Release Format</a>.
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the <var>record of key usage</var> is a JSON object encoded in UTF-8 as described in <a href="#clear-key-release-format">License Release Format</a>.
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</p>
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</li>
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<li>
@@ -2457,18 +2476,12 @@ <h4>License Release Format</h4>
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<p>This section describes the format of the license release message to be provided via the <a def-id="message-event-message-attribute"></a> attribute of the <a def-id="message"></a> event.</p>
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<p>The format is a JSON object containing the following members:</p>
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<dl>
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<dt>"keys"</dt>
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<dd>
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An array of objects, each object containing the following members:
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<dl>
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<dt>"kid"</dt>
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<dd>The base64url encoding of the octet sequence containing a key ID value.</dd>
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<dt>"tfirst"</dt>
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<dd>The <var>first decrypt time</var> for this key ID expressed as a number giving the time, in milliseconds since 01 January, 1970 UTC.</dd>
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<dt>"tlatest"</dt>
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<dd>The <var>latest decrypt time</var> for this key ID expressed as a number giving the time, in milliseconds since 01 January, 1970 UTC.</dd>
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</dl>
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</dd>
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<dt>"kids"</dt>
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<dd>An array of <a def-id="key-id">key IDs</a>. Each element of the array is the base64url encoding of the octet sequence containing the key ID value.</dd>
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<dt>"tfirst"</dt>
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<dd>The <var>first decrypt time</var> expressed as a number giving the time, in milliseconds since 01 January, 1970 UTC.</dd>
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<dt>"tlatest"</dt>
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<dd>The <var>latest decrypt time</var> expressed as a number giving the time, in milliseconds since 01 January, 1970 UTC.</dd>
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</dl>
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<p>When contained in the ArrayBuffer <a def-id="message-event-message-attribute"></a> attribute of a <a>MediaKeyMessageEvent</a> object, the JSON string is encoded in UTF-8 as specified in the Encoding specification [[!ENCODING]].
@@ -2480,14 +2493,9 @@ <h5>Example</h5>
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<p>The following example is a license release for a temporary license for a single key ID. (Line breaks are for readability only.)</p>
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<pre class="example highlight">
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{
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"keys":
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[
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{
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"kid" : "67ef0gd8pvfd0",
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"tfirst" : 1430425323757,
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"tlatest" : 1430425383757
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}
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]
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"kids": [ "67ef0gd8pvfd0", "77ef0gd8pvfd0" ],
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"tfirst" : 1430425323757,
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"tlatest" : 1430425383757
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}
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</pre>
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</section>

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