Solaris 8 machines use normal UNIX crypts. Change these passwords using the passwd command. Note that within a cluster, passwd changes must be performed on the cluster head.
There are no longer any Solaris 8 junkfood hosts, so you shouldn't have to worry about this unless you get access to a research cluster that still has some of these machines.
All Solaris 8 machines are scheduled to be retired by January 31, 2008.