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Re: Encrypted Media proposal (was RE: ISSUE-179: av_param - Chairs Solicit Alternate Proposals or Counter-Proposals)

From: Maciej Stachowiak <mjs@apple.com>
Date: Fri, 02 Mar 2012 11:43:43 -0800
Cc: Silvia Pfeiffer <silviapfeiffer1@gmail.com>, Mark Watson <watsonm@netflix.com>, "<public-html@w3.org>" <public-html@w3.org>
Message-id: <1AC967BC-3E58-4D03-AF58-DAE3CC24A546@apple.com>
To: Henri Sivonen <hsivonen@iki.fi>

On Mar 2, 2012, at 4:23 AM, Henri Sivonen wrote:

> 
> Aside:
> 
> PlayReady, Marlin and Widevine (and, from making inferences from the
> UI, Adobe's Flash DRM, too) support use cases that aren't essential
> for Web video. Web video could go a long way with streaming-only DRM.
> For streaming, it's enough for the DRM to work during streaming. That
> is, secrets in the CDM can be ephemeral. PlayReady, Marlin and
> Widevine are designed to support use cases where the end user holds
> onto encrypted media files for extended periods of time. This means
> that secrets in the CDM need to stay secret for extended periods of
> time and there's a lot of red tape about protecting those secrets for
> extended periods of time, since it's a big deal if the secrets leak.
> For the streaming use case, if the CDM secrets are compromised, the
> CDM could be updated soon with new and differently obfuscated secrets,
> since it's OK to invalidate keys related to past streams. Thus, the
> red tape around protecting CDM secrets doesn't need to be as severe as
> with PlayReady, Marlin or Widevine.
> 
> Even if we accepted the idea of CDMs that contain secrets, it seems
> like a bad idea to tie browsers to CDMs whose secret management
> regimes' level of red tape is geared towards use cases that aren't
> essential for streaming video on the Web.

I don't know about individual CDMs, but I believe the proposal is geared significantly towards support of DRM'd streams, thus the support for key rotation through an out-of-band channel. For DRM of downloaded, non-streamed resources, I don't believe this would be necessary, at least given the way many popular DRM schemes work.

Regards,
Maciej
Received on Friday, 2 March 2012 19:44:12 UTC

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