Re: Question on transport protocol

[Derek Fawcus <dfawcus%cisco.com@localhost>]

On Tue, Jan 15, 2002 at 03:29:44 +0000, Derek Fawcus wrote:
> In the transport protocol,  section 8 (Service Request),  the last paragraph
> states:
> 
>    Note that after a key exchange with implicit server authentication,
>    the client MUST wait for response to its service request message
>    before sending any further data.
> 
> I'd like to ask why is the above contraint there?  I assume it's for some
> security reason,  but looking at the packet flow,  I can't see a reason
> for it.

A bit more about what I'm thinking...

The obvious problem with implicit server authentication is that it leaves
one open to a MITM attack.  However I don't see how the above constraint
helps here.  You'd have just done a sucessful DH exchange with the MITM,
and he can then fake all responses,  delaying till you get the SERVICE_ACCEPT
doesn't appear to gain any advantage in this case.

I there must assume it's for some other scenario,  if so then what?

DF