John,

Looking at the last diagram, and the discussion on keeping the
acquisition of assertions separate from presenting those, I have this
basic question (could also be due to my lack of knowledge of SAML
assertions :-)):

When a user needs to present the identity assertion, and the "over 21
assertion" from the ID agent, what prevents a man-in-the-middle from
mixing and matching assertions? Example: What if I have browser code to
take my ID assertion from the ID agent, and someone else's "Over 21"
assertion (which I probably captured by posing as a replying party), and
passed it on to the replying party. Is this scenario possible? Is there
a restriction on who can present an assertion in the assertion itself? 

Thanks and Regards,
Haripriya S.

 
>>> John Merrells <[EMAIL PROTECTED]> 06/06/06 3:27 am >>> 

On 5- Jun- 06, at 2:42 PM, Eric Rescorla wrote:

>
> I'm still not sure I get what you're saying. Let me see if I can
> try again looking at the flows of data.
>
>
> OPTION 1: What I take DIX to be doing

Yes, this interaction diagram is correct.

> Client                     IdP                   Relying Party
>
> -------------------------   Service Please ------------ >
> <-------------------------  Prove you're over 21--------
>
> <------- Auth exchange ------ >
> <-------  Over 21 credential--
>
> <-----------------  Auth exchange plus over 21 cred ---- >

Assuming that at some point earlier the user acquired an over 21  
assertion
from an appropriate authority.

Client            Identity Agent                   Authority

-------------------------   Service Please ------------ >
<---  Auth/Verify exchange, maybe even out of band ---- >
<-------  Over 21 credential----------------------------
<---------  Over 21 cred ---- >

John



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