[VOIPSEC] Is it feasible that we just protect part(master key) of SDP to pass some Middle boxes (firewalls, SBCs and other ALGs) ?

[Randell Jesup]

Mark Baugher <mbaugher at cisco.com> writes:
>It's possible to use multipart/signed and have the entire SDP message  
>signed and the keys in the message encrypted.  I always favored that  
>approach.  There are other concerns, however, and the current  
>approach in SIP AFAICT is to use multipart/alternative so that a  
>legacy endpoint that does not understand SRTP can still process an  
>incoming call, see http://tools.ietf.org/wg/sipping/draft-jennings- 
>sipping-multipart-01.txt

        And because intermediate proxies may (have to) modify the 
SDP because they're SBCs (or they're gateways from one network to another,
like an IPv4<->IPv6 gateway, etc).

-- 
Randell Jesup, Worldgate (developers of the Ojo videophone), ex-Amiga OS team
rjesup at wgate.com