asterisk users - Feb 2011 - SIP friend name

Is there a way to configure a friend in sip.conf that allows a station
to register using a username other than the [name]?

I want to have something like this in sip.conf:

    [1234]
    username=something_really_long_and_random
    secret=something_else_really_long_and_random
    ...

Then allow a SIP REGISTER like so:

    REGISTER sip:10.0.0.200:5060 SIP/2.0
    Via: SIP/2.0/UDP 10.0.0.201;branch=z9hG4bK9238ea1821361589
    From: "Joe User"
<sip:something_really_long_and_random at 10.0.0.200>;tag=CA8D62BF-9750393E
    To: <sip:something_really_long_and_random at 10.0.0.200>
    CSeq: 2 REGISTER
    Call-ID: fbc4bb4b-91001d55-8c6da4c4 at 10.0.0.201
    Contact: <sip:something_really_long_and_random at
10.0.0.200>;methods="INVITE,
ACK, BYE, CANCEL, OPTIONS, INFO,     MESSAGE, SUBSCRIBE, NOTIFY,
PRACK, UPDATE, REFER"
    User-Agent: PolycomSoundPointIP-SPIP_501-UA/3.1.6.0017
    Accept-Language: en
    Authorization: Digest username="something_really_long_and_random",
realm="asterisk", nonce="35d57376",
uri="sip:10.0.0.201:5060",
response="5a0596db3c3f1823b783ae195074cc5c", algorithm=MD5
    Max-Forwards: 70
    Expires: 3600
    Content-Length: 0

And end up being able to reference the device via SIP/1234.

I've tried adding name, username, auth, authname, defaultname, and
fromname among others and none seem to do what I'm looking for.  Tried
reading through chan_sip.c but have not figured it out yet.  Figured
I'd ask.

Thanks in advance,

Paul

PS: I had a SIP entry with too easy a secret get exploited to the tune
of $500 worth of calls to Liberia...