[VOIPSEC] Why a secure keyechange for media encryption?

[Hadriel Kaplan]

Au contraire, firewalls do not make encryption problematic.  TLS works
through them all the time.  IPSec has had problems, but it's less common for
SIP anyway.  ALGs are not needed, if by an ALG you mean in your local NAT.
Phones can use stun/ICE or other protocols to fix their addressing, or let
an SBC do it for them (an SBC is neither an ALG nor a firewall). 

If you don't trust the hop-by-hop signaling path to remain secure, don't use
it - your signaling is almost as sensitive as your media - more for some,
less for others.  Send signaling directly to the far-end, or use s/mime to
encrypt the SDP (good luck with that).

-hadriel


> -----Original Message-----
> From: Voipsec-bounces at voipsa.org [mailto:Voipsec-bounces at voipsa.org] On
> Behalf Of Weidong Shao
> Sent: Friday, April 28, 2006 3:56 AM
> To: Michael Prochaska
> Cc: voipsec at voipsa.org
> Subject: Re: [VOIPSEC] Why a secure keyechange for media encryption?
> 
> you have a point here. It is nice to have encrypted signalling and then
> the
> media key can simply  be sent over the signaling channel.
> 
> But encrypted signaling is problematic with firewalls or ALGs (which are
> often necessary for NAT rewrite), and if there are multiple hops in the
> signaling path, you then need to have hop-by-hop signaling encryption.
> Then,
> the question is, how do you manage key management for each segment of
> signaling path?
> 
> Weidong
> 
> On 4/28/06, Michael Prochaska <tm021090 at fh-stpoelten.ac.at> wrote:
> >
> > hi,
> > i'm a student and are working on my diploma thesis (VOIP security with
> > open standards)at the moment.
> >
> > i know the question is a little bit provocative.
> >
> > in my eyes there are the following vulnarabilities / problems for
> > signaling:
> >
> > - SPIT
> > - unauthorised use of account
> > - identity forgery
> > - session highjacking
> > - loss of anonymity
> > - replay
> >
> > and the following vulnarabilities for the media stream:
> >
> > - replay
> > - eavesdropping
> >
> > any additions are welcome :-)
> >
> >
> > the outcome of this is that the signaling is "the bigger" problem.
> >
> > in which situations it might be usefull to encrypt and authorize only
> > the mediastream ? i thing the goal must be a secure signaling. when i
> > have a secure signaling, why not exchange the key plain over the
> > signaling channel?
> >
> > any comments are very welcome!
> >
> > best regards,
> > michael
> >
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