Re: [Bug 20944] New: EME should do more to encourage/ensure CDM-level interop

On Sat, Mar 2, 2013 at 3:30 AM, Robert O'Callahan <robert@ocallahan.org>wrote:

> On Sat, Mar 2, 2013 at 4:39 AM, Glenn Adams <glenn@skynav.com> wrote:
>
>> It depends. But one cannot make this assumption (that it isn't necessary
>> to know the portion of the specification governed by an NDA which imposes
>> some obfuscation/secret).
>>
>
> If describing the operation of the CDM on-the-wire, except for secret
> keys, makes it easy to break the CDM, that CDM must be very poorly
> designed. (Just as any other cryptographic protocol whose security depends
> on secrecy of the protocol is anathema these days.) I hope and expect
> actual CDMs are better designed than that.
>

Agreed. Perhaps it would be useful to distinguish 3 cases for publishing
the details of a specific key system and encryption system implemented by a
CDM:

   1. All details are published as PAS.
   2. Most details are published as PAS, while some details require an NDA
   to access.
   3. No details are published as PAS, i.e., all details require an NDA to
   access.

I would suggest that it is desirable to maximize those systems that fall in
to the first category, while recognizing that some legacy systems may fall
into the second or third categories.

Regarding Fred's notion of "independently implementable", I would call all
of the above three categories of systems "independently implementable" in
the sense that two implementors given access to all necessary
specifications can implement any of them.

However, I'm sure that Fred's definition of "independently implementable"
is a subset of my definition, and could only be satisfied by the first
category above. Since Fred would appear to rule out systems that require
reference to any NDA governed specification material.

So, where are we today? Most existing systems fall into categories 2 or 3
above. I'm not aware of any complete DRM system that falls into category
(1), though there are certainly some useable components fall into category
(2), e.g., ISO/IEC 23001-7:2012.

It is clear that initial uses of EME by content service providers
encumbered by content license restrictions will need to make use of CDMs
that fall into category (2) or (3). One might suggest that with such an
initial usage, things will never get better, i.e., move further towards
category (1). I can't argue with certainty either way on this point. I can
say that it is possible that genuinely useful CDMs will appear in category
(1) that could be potentially accepted for use by content licensors. But I
can't say if or when that will happen. In my mind, it should not be a
pre-requisite for publishing EME, because this goes considerably beyond the
technical matters of EME and falls into the domain of deployment. However,
I recognize that this remains a concern, particularly for those parties
that wish that controlled access content could be reasonably accessible on
platforms that have made policy decisions about whether to permit portions
of their platform to be non-open. Given that such platforms find ways to
use proprietary processors for various purposes (i'm thinking of graphics
here), I don't see why they couldn't also find ways to use proprietary
processors for use with EME and open sourced user agents.