asterisk users - Dec 2005 - Passing authentication to an analog adapter

This is more of a curiosity and a thought than serious issue.  But, I 
wonder if I can get my Asterisk server to authenticate to my provider by 
throwing the authentication requests to the SIP analog-adapter they 
shipped me? (And I can't get in and see the authentication credentials 
in the adapter, of course.)

In other words, say I've got something like:

SIP
analog adapter <--> * server <--> provider

Such that the DHCP and DNS information the SIP adapter gathers comes 
from the asterisk server where it pretends to be the provider.

So then this happens:

- * tries to register with the provider
- gets the challenge
- the challenge is passed to the SIP adapter
- which answers the challenge correctly
- then * passes the answer to the provider and completes the registration

(AKA man-in-the-middle)

Is there such an authentication feature in *?  If not, I could see it 
being handy.

An alternative (although not as fun) would be to connect the analog 
adapter to a FXO card in the * server.

PS- I know some providers could treat this as a violation to their 
service agreement, btw.


Phil