[theora] DRM for Theora over RTP

Gisle Sælensminde gisle at snirklasjon.no
Tue May 25 15:55:20 PDT 2010

fboehm wrote:
> Hi,
> are there any open source DRM implementations for protecting Theora 
> streams over RTP?
> I only know of the ISMACryp specification which seems to be licence free 
> and so could be used in an open source project.
To wrap theora in RTP, you need to follow the internet draft, which you
can find at http://tools.ietf.org/html/draft-barbato-avt-rtp-theora-01 .
This is a draft, and has som gotchas. I recently implemented this in a
proprietary video conferencing system, and can share some of the stuff I
found out by doing that.

I send the RTP in plaintext myself, but for encrypting RTP streams you
have SRTP in addition to the ISMACryp. I don't know whether ISMACryp is
adapted to theora or need adaption in the first place. SRTP encrypts the
entire RTP payload, so it can be applied without codec-specific
adaptations. It is defined in rfc 3711, available at the following URL.


When it comes to DRM, you are on your own. To my knowledge nobody has
made any DRM system for  theora. Given that theora is an open codec,
developing a DRM scheme runs counter to the goal of the project. Those
who spend time and effort to develop a free codec, will probably not
think that developing a DRM scheme is a project worth spending their
limited time on, and those interested in cryptography know that DRM
theoretically cannot be more than security by obscurity, and is
therefore not interested. Nothing (legally or otherwise) stops you from
developing DRM for theora. You may be able to use or adapt ISMACryp, but
you are likely be the first to do that,  and very likely also the first
to implement DRM for a theora stream over RTP. Not many people have
implemented theora over RTP at all, and all I know about transfer the
streams in plaintext.


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