[Tutor] cross platform authenticating

[John]

Hi,

Is there a general discussion (somewhere on the web) on how to

1. determine what authentication the platform requires
2. can #1 be determine dynamically 
3. If I know #1 will it be cross platform?

Googling reveals that there are many authenticating modules, LDAP, PAS, 
RADIUS, Active Directory, PAM, and something called pluggable authentication. 
But I don't see anything that tells me how to determine what the platform 
requires.  And what if there is no authentication required - like on a single 
computer.  Also if I am able to determine the authentication requirements 
will the modules then be cross platform - working on Linux, Mac, and Windows?

As you guys can see I'm just starting out in the authentication world.


Thanks in advance for any help,

Johnf