Examine one user's entry in your bot, with:
.whois <handle>

and note the HOSTS line(s).

If you remove them, and add one back in this format:
nick!*@*

then that is what the bot will use to identify that user - just the nick.

This is very insecure, as any user can probably spoof another user's nick.
However, that is basically what (I think) you are asking for.
...something that happens automatically, with no password required from the user.

bind join c * join:fielproc join:fiel {nick host hand chan} {   global botradio nombreradio sloganradio   set fiel [encoding convertfrom utf-8 "$nombreradio $sloganradio  It gives you a warm welcome to its True Listener \0034 $nick \0031 in \0032 $chan."]   putmsg $chan "$fiel"}