Since the migration operation executes on two machines, a user must be authenticated on both the source and target host. In particular, a user other than superuser must have the solaris.ldoms.read and solaris.ldoms.write authorizations as well as the file_dac_read and file_dac_search privileges on both machines. See Adding the Privileges Needed to Migrate Domains.
The ldm command line interface for migration allows the user to specify an optional alternate user name for authentication on the target host. If this is not specified, the user name of the user executing the migration command is used. In both cases, the user is prompted for a password for the target machine unless the -p option is used to initiate an automatic migration.