&gt; What in the W3C EME standard cannot be freely implemented? As far as I know, EME is just a communications standard between the browser and components that are not part of the browser to allow those components to provide media data for the browser to display.<p>That, sadly, isn&#x27;t the case. (It would be much better if it were!) All the existing EME modules are embedded as part of the browser, and there definitely isn&#x27;t any standardised API to communicate with a module external to the browser.<p>All EME defines is an API on HTMLMediaElement to communicate with this abstract module, which yes, would allow the case of hiding the key from third parties to be addressed.