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Re: Encrypted Media proposal: Summary of the discussion so far

From: Henri Sivonen <hsivonen@iki.fi>
Date: Mon, 12 Mar 2012 09:29:36 +0200
Message-ID: <CAJQvAucChbEu56VPnqfRZ=AKTQ8un8ngAKme--e3HicjeaUCcw@mail.gmail.com>
To: David Dorwin <ddorwin@google.com>
Cc: public-html@w3.org
On Fri, Mar 9, 2012 at 8:11 PM, David Dorwin <ddorwin@google.com> wrote:
> On Fri, Mar 9, 2012 at 2:59 AM, Henri Sivonen <hsivonen@iki.fi> wrote:
>> Are there disclosed specs / design documents explaining
>>  1) how you plan to encrypt WebM
>>  2) what kind of key passing messages you plan to use
>>  3) if the CDM includes secrets (private key or secret algorithms),
>> how you plan to share those secrets with other vendors
>> ?
> We're still early in the process. #1 will be handled separately by the WebM
> Project. #2 and #3 seem CDM-specific, so I'm not sure what you're asking.

Are there publicly-disclosed specs or design documents for any of
this? (I failed to see recent threads on the WebM mailing list
relevant to #1.)

For #2, what I'm asking is this: You will need to have some format and
semantics for the initData parameter of generateKeyRequest() and for
the key and initData parameters of addKey(). What format and semantics
do you plan to use for these? In particular, do you believe that what
you have chosen here is royalty-free? If you believe you have found a
royalty-free (but not clear key) initialization procedure, are you
willing to standardize it under the W3C Patent Policy?

For #3 what I'm asking is this: Presumably, your CDM will have an
embedded secret so that only a piece of software embedding that secret
can successfully use the data passed to addKey(). I'd expect this
secret to be at minimum a private key for an asymmetric encryption
algorithm. Even if the behavior of your CDM was published except for
this secret, another vendor wouldn't be able to develop an independent
implementation that works with a site that targets Chrome unless the
site is changed to cater to the secret embedded in another browser in
addition to catering to the secret embedded in Chrome. Are you
planning to share the secret part of your CDM with other browser
vendors in order to enable interoperability and to avoid lock-in? (In
other words, if the secret is just an RSA private key, are you willing
to share Chrome's private key with other browsers, such as Firefox and
Opera?) If so, under what terms?

Henri Sivonen
Received on Monday, 12 March 2012 07:30:10 UTC

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