asterisk users - Jul 2007 - how to register several clients with different number but using single authentication account ?

Hi all,
I'm running some performance tests  over my Asterisk,to simplify the test,I
want to configure Asterisk to allow several clients registered with
different nubmers but using single authentication account,so that Asterisk
would not check the "to" "from" head when challenging
registartion &
invitation,.for example,I want Asterisk to allow following registration :

.........
To:<sip:1234 at 192.168.1.42>
From:<sip:1234 at 192.168.1.42>:tag=8a3d7e61
..........
Authorization:Digest Username="5678",realm="192.168.1.42
",nonce="4692235235jefsdfq23423fc",uri="sip:192.168.1.42",
response="234234234324sfdsf",algorithm=MD5

Does  Asterisk support that?How to configure?Please advise,thanks a lot.
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