web interface security

[thufir]

I disabled root and password based ssh for increased security.

Using fail2ban or other firewalls, I suppose a web server can blacklist 
certain IP's?

Whether it's a web server, or perhaps a web service, are there other 
options?  To whitelist only one, or a few, IP addresses?  How effective 
would a white list be?

Might there be something like ssh keys?  So that access to a web server 
or service requires a key?  

(This is somewhat off topic, it's for Elastix (asterisk) on CentoOS, but 
I am using Ubuntu to connect..)

thanks,

Thufir