Instead of assigning a password for every private entry, I would prefer if registered users signed-in in order to view all the private entries. The general public can still access all entries in your journal not marked as private. Only registered users can view your private entries based on their user levels.
For instance, if the admin posts a new topic and designates it as level 2 privacy, then only users level 2 and above can read those entries after they've logged in. Level 1 users would still be denied access to those entries, but they can read anything assigned as level 1. Furthermore, all comments made on those private entries would be hidden from those without access.
Logs of who logs in and when would also be wonderful.
Keep up the good work.