Subject: RE: Transparency Top 10 list (was Re: [Sipping] Transparent B2BU A?)

From: "Mark Watson"<[email-masked]>
Date: Wed, 15 May 2002 15:48:04 +0100

> 4) The P-CSCF MAY (this is being fought now) obfuscate the 
> To: and From:
> fields in messages.
> 
> 5) The P-CSCF filters messages from the UA to assure that only an
> identity known to the P-CSCF is presented by the UA. This may interact
> with the preceding characteristic. This appears to be required to
> accomodate the authorization model of 3GPP, which authenticates only
> REGISTER transactions and uses them to establish a security 
> association
> between UA and P-CSCF.
> 

Actually, the P-CSCF does not obfuscate the To/From fields. There is a
discussion in Budapest at this very moment as to whether the UA in 3GPP
networks should be *required* to always include Anonymous in the To/From, on
the basis of simplifying the implementation of privacy services which will
need to be provided by the S-CSCF.

[As described in Jon Peterson's draft, the 'header privacy' service requires
the From: field to be modified, amongst other things].

For (5), the P-CSCF will need to implement an Authentication Service as
described in Jon Peterson's identity draft, but using the short term Network
Asserted Identity mechansism to communicate the identity, rather than
S/MIME.

The mechanism 3GPP uses to authenticate the sender of a message at the
P-CSCF differs between the original registration (which uses SIP & AKA), and
subsequent messages, which are authenticated by virtual of their arrival on
the security association set up as part of the initial registration.

Regards...Mark