Re: [Cellar] shepherd review of Matroska: part 1

[Steve Lhomme <[e-mail]>]

On 2022-07-06 19:59, Michael Richardson wrote:
> 
> Steve Lhomme <[e-mail]> wrote:
>      > On 2022-06-12 10:01, Steve Lhomme wrote:
>      >>> } 5.1.4.1.34.9. ContentEncAlgo Element
>      >>> questions will be asked about 1DES, and 3DES.
>      >>> 1) We need a note about how legacy files might be encrypted, and we need
>      >>>     those definitions for history.
> 
>      > AFAIK Matroska files are not encrypted. WebM on the other hand is very
>      > common. But we're not making the WebM spec. Content Compression which is
>      > parallel to this is however common.
> 
>      > In WebM it also depends on the codec what kind of information is actually
>      > encrypted. The frame headers are usually not encrypted so they can be parsed
>      > without dealing with encryption. Only the actual content part is
>      > encrypted.
> 
> I think that what we need to explain is that *THIS DOCUMENT* does not define
> any encryption scheme.  That is reserves a container/element for schemes that
> third parties (WebM) have used, and yes, have an informational reference to
> that.

Would that do ?
https://github.com/ietf-wg-cellar/matroska-specification/pull/654

> That's all we need to say.
> 
>      > defined in Matroska. In the case of WebM, the AES-CTR
>      > (AESSettingsCipherMode=1) really tells the whole story of how the
>      > encrypted data fill the Block.
> 
> Yes, but not how/where the key comes from, which is where we will get into trouble.
> 
> --
> Michael Richardson <[e-mail]>   . o O ( IPv6 IøT consulting )
>             Sandelman Software Works Inc, Ottawa and Worldwide