Subject: Re: [Perc] Consensus call: SSRCs are immutable

From: John Mattsson <[email-masked]>
Date: Thu, 26 Nov 2015 12:35:56 +0000

Jonathan Lennox wrote:
>I’d like to have a convincing story about how SSRC uniqueness is
>guaranteed before we make this decision.

+1

Two solutions would be (all endpoint<->KMF communication is assumed to be
over (D)TLS)
 
1. KMF assigns a SSRC prefix (maybe 22 bits) to each participant and each
endpoint can then use the remaining 10 bits to separate up to 1024
different streams. Each participant can be uniquely identified by the SSRC
prefix.
2. The endpoint generates a random SSRC and asks the KMF if it can be used.

The security properties of both these solutions are very easy to analyze
(as security should be) and it is easy to see that both mitigate the
splicing attack.

Would be good if someone arguing for a different solution could write that
done in more detail, with analysis of how good mitigation it would give
against splicing attacks and how any MDD interference is avoided.

JOHN MATTSSON
MSc Engineering Physics, MSc Business Administration and Economics
Ericsson IETF Security Coordinator
Senior Researcher, Security