[AVT] draft-lehtovirta-srtp-rcc-01.txt for broadcast use

It is being proposed in the DVB standards group that this Internet draft
be adopted in their specifications for broadcasting to mobile devices
(DVB-H).

Currently their specification A100 "Service Purchase and Protection"
(see http://www.dvb-h-online.org/technology.htm) defines use of SRTP
with authentication being optional.

This internet draft appears to to enhance SRTP operation in a useful way
for this application but, as it instatiates the Rollover Counter
Carrying transform as an SRTP Authentication algorithm, its use seems to
require that authentication becomes mandatory. The minimum level of
authentication apparently allowed is authentication of every Rth SRTP
packet using HMAC-SHA-1-80.

Is this right, or have I misunderstood?

For this broadcasting application, I would like to retain the use of
authentication as optional, whilst using the method of carrying the ROC
defined in this internet draft. It seems that the only way to do this
would be to define an additional version of the RCC transform, which I
shall call "RCCv3".

I would envisage that RCCv3 would be similar to RCCv1, in that the
authentication tag field would only be present in every Rth RTP packet.
However, the content of the authentication tag field would consist only
of ROC_sender, rather than ROC_sender || MAC.

Would this be a sensible addition to the current draft, or is there a
better solution?

Regards,

Nigel

** Nigel Dallard                 e-mail: ndallard@ndsuk.com  ** 
** Senior Member                    www: http://www.nds.com  ** 
**   of Technical Staff             tel: +44 23 8030 7151    ** 
** NDS Ltd, Southampton, UK.     mobile: +44 7881 913151     ** 

This email message and any attachments thereto are intended only for use by the addressee(s) named above, and may contain legally privileged and/or confidential information. If the reader of this message is not the intended recipient, or the employee or agent responsible to deliver it to the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please immediately notify the postmaster@nds.com and destroy the original message

_______________________________________________
Audio/Video Transport Working Group
avt@ietf.org
https://www1.ietf.org/mailman/listinfo/avt