Re: [AVTCORE] Review of draft-ietf-avtcore-rtp-security-options-04

[Magnus Westerlund <[e-mail]>]

Hi,

See below for proposal regarding Section 3.1.1.

On 2013-08-29 15:47, Alan Johnston wrote:
> On Thu, Aug 29, 2013 at 7:57 AM, Colin Perkins <[e-mail]
> <mailto:[e-mail]>> wrote:
>
>     >
>     > Numbers refer to sections in the document.
>     >
>     > 3.1.1:
>     >
>     > It is surprising no mention is made of RFC 4474 in this section
>     (or in the whole document) as DTLS-SRTP keying relies on an
>     integrity protected signaling channel provided by RFC 4474.  When
>     mentioning RFC 4474, it needs to be pointed out that RFC 4474 is
>     effectively being deprecated by the STIR work and has proved to be
>     undeployable and also ineffective for E.164 identities.
> 
>     I have added a reference to RFC 4474 in Sections 4.1.3 and 4.1.4 as
>     a result of Dan Wing's comments. I'm not familiar with the STIR
>     work, or the other issues, can you suggest text for Section 3.1.1?
> 
> 
> Here's the proposed charter for STIR:
> http://datatracker.ietf.org/wg/stir/charter/ 
> 
> draft-jennings-dispatch-rfc4474bis discusses the problems with RFC 4474
> and some proposed changes.
> 
> I would suggest text in this section mention that DTLS-SRTP relies on an
> integrity protected signaling channel based on RFC 4474, but that there
> is proposed underway in the IETF to try to make this workable.

I tried drafting some text for this. Feedback appreciated

   DTLS-SRTP key management can use the signalling protocol in four
   ways.  First, to agree on using DTLS-SRTP for media security.
   Secondly, to determine the network location (address and port) where
   each side is running a DTLS listener to let the parts perform the
   key-management handshakes that generate the keys used by SRTP.
   Thirdly, to exchange hashes of each side's certificates to bind these
   to the signalling, and ensure there is no man-in-the-middle attack.
   Finally to provide an assertable identity, e.g. [RFC4474] that can be
   used to prevent modification of the signalling and the exchange of
   certificate hashes.  That way enabling binding between the key-
   exchange and the signalling.

   This usage is well defined for SIP/SDP in [RFC5763], and in most
   cases can be adopted for use with other bi-directions signalling
   solutions.  It should be noted that there is work underway of
   revisiting the SIP Identity mechanism [RFC4474] in the STIR WG.

Cheers

Magnus Westerlund

----------------------------------------------------------------------
Multimedia Technologies, Ericsson Research EAB/TVM
----------------------------------------------------------------------
Ericsson AB                | Phone  [phone]
Färögatan 6                | Mobile [phone]
SE-164 80 Stockholm, Sweden| mailto: [e-mail]
----------------------------------------------------------------------