aBlog2 was designed to work with aLogin2 as its authentication system. However there may be occassions where you'll want to use another authentication system. This process involves the modification of two files, localAuthority.php and localLoginChecks.php. Unfortunately, how much modification will be required by the specific circumstances of the application.
aBlog2 directly calls the files in localAuthority.php. You can modify these to meet your own needs, but unless you're also using aLogin2, you'll need to make sure you remove the call to checkAuthorityLevel since without aLogin2 this wouldn't be available.
This function receives a username, the password, a boolean which is true if we want to know if we have authority to post a reply and a local array that was passed to the blog at configuration time. It returns either true (authoritized to post) or false (not authoritized).
This function receives a username, the password, and a local array that was passed to the blog at configuration time. It returns true if authorized and false if not.
In addition to changing localAuthority.php, if you are using aLogin2 you can consider modifying localLoginChecks.php. See the localization section of the aLogin2 documentation on how to do this.