Authentication in XMLRPC 3

Hi,

I have just discovered a new version of XMLRPC and started
to explore it.
I'am completely understand, how to deal with client part,
but I have
problems with server part.
I don't understand how to use authentication, I mean how I
can extract
username and password, which user passing to the XMLRPC
server?
In the previous version it could be done with
AuthenticatedXmlRpcHandler interface. Are there some analogs
in the
XMLRPC 3 version?

Thanks for any help
Eugene