[Jingle] SRTP

Robert McQueen robert.mcqueen at collabora.co.uk
Tue Jul 22 20:18:31 CDT 2008


We decided (eventually) that SRTP shouldn't be represented as a
transport, because the encryption/keying/etc is specific to RTP (it
makes no sense to consider file transfer over SRTP, for example).
However, it should also not be a new content description, as the
codec/payload type negotiation is in common with the RTP content
description, and we don't really want to nest the RTP stuff inside
another namespace either.

Therefore, it should be an optional element which can be added to RTP
content descriptions. Mapping to SIP profiles like RTP/AVP and SRTP/AVP
is doable by inspecting whether or not this element is present. Diana
Cionoiu has a proposal for a <crypto> element to achieve this, which she
can follow up with.

I have no particularly strong feelings on whether this should be in a
separate XEP/namespace, or just an optional part of the RTP XEP-0167. I
think it should probably just go in XEP-0167.

(note that some kind of E2E encryption is necessary for exchanging an
SRTP key in your signalling to be meaningful, but we hope that working
stream transports/fallbacks in Jingle will enable TLS encrypted peer to
peer XMPP streams to be negotiated with Jingle)

Regards,
Rob


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