Sorry for my bad English Ben.
Thank you very much for your cooperation.
Yes, I had already tried that combination and others:
user: blank
user: live (as you suggested)
(hostname): blank
(hostname): live
root: root
root: blank
root: live
debian: live
etc., etc., etc.
/etc/lightdm/lightdm.conf :
#autologin-guest=false
autologin-user=user
autologin-user-timeout=0
#autologin-in-background="">#autologin-session=
#exit-on-failure=false
/etc/live/config.conf.d/live-setup.conf :
LIVE_USERNAME="user"
LIVE_HOSTNAME="distro"
LIVE_USER_FULLNAME="Distro Live user"
LIVE_USER_DEFAULT_GROUPS="audio cdrom dip floppy video plugdev netdev powerdev scanner bluetooth debian-tor"
Thanks again.