The xauth(1) program is used to edit and to display the authorization information used in connecting to the X server. This program is usually to extract authorization records from one machine and merge them in on another (as is the case when using remote logins or to grant access to other users). Commands may be entered interactively, on the xauth command line, or in scripts. Note that this program does not contact the X server.
The xauth(1) man page is available at http://cando.dwr.co.gov/cgi-bin/man2html/xauth(1) or http://www.bsd.com/bsdi-man?proto=1.1&query=xauth&msection=1&apropos=0.