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Re: EME support for CENC with AES-CBC?

From: Joe Steele <steele@adobe.com>
Date: Tue, 17 Jun 2014 16:24:20 +0000
To: David Dorwin <ddorwin@google.com>, "Jerry Smith (WINDOWS)" <jdsmith@microsoft.com>
CC: "<public-html-media@w3.org>" <public-html-media@w3.org>
Message-ID: <8DE1E2AE-298D-476B-918F-8F8583DBF23E@adobe.com>
I am specifically interested in the AES-CBC. As far as I can tell, this has not been made official yet, which is why it would not be published yet as other than a draft proposal.  

I am trying to take the temperature of the group here. Assuming this proposal is accepted and latest version of the CENC spec includes it, does that imply that CDMs “may", “should" or “must" support it? Or should we constrain usage by the spec to a subset of what is supported, as has been suggested around PSSH. 


On Jun 16, 2014, at 6:03 PM, David Dorwin <ddorwin@google.com> wrote:

> Are you specifically interested in just CBC or is there something else in the amendment? (For what it's worth, it does not appear that amendment has been published.)
> The ISO Common Encryption EME Stream Format and Initialization Data spec is based on ISO/IEC 23001-7:2012 the AES-128 CTR encryption it specifies.
> On Mon, Jun 16, 2014 at 5:20 PM, Jerry Smith (WINDOWS) <jdsmith@microsoft.com> wrote:
> It would seem that when new encryption types are added to CENC, then these will need to be supported by CENC compatible CDMs.  If we agree on that, then the current model for IsTypeSupported() should be sufficient.
> Jerry
> -----Original Message-----
> From: Joe Steele [mailto:steele@adobe.com]
> Sent: Monday, June 16, 2014 1:57 PM
> To: <public-html-media@w3.org>
> Subject: EME support for CENC with AES-CBC?
> I am curious whether this group intends to say anything about support for the AES-CBC encryption mode for ISOBMFF with CENC. I have been reviewing the amendments to the CENC spec, specifically "Part 7: Common encryption format for ISO base media file format, AMENDMENT 1: AES-CBC-128 and key rotation". I am wondering how CDMs should expect to handle this - or if it is called out via isTypeSupported().
> This may have been discussed and I just cannot find the references to it.
> Joe

Received on Tuesday, 17 June 2014 16:24:54 UTC

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