Quote by Benqo:
I need specially a gallery plugin, which, as first point, is fully integrated to the weblog software
Geekary exists as an integrated photo gallery. Gallery also exists and though not designed with GL in mind does integrate nicely Also, Inmmemoriam will have a release ready to go by the end of august (no guarantees).
Quote by Benqo:
and, as the second point, uses a user management system, so that visitors are forced to register and login.
All three employ a configuarable permissions system of some type and all three make use of the GL user database.
There are others... you'll have to try them out and see what suits your needs best