Hello Linda and thanks for replying.
My place is an apartment in a building of ten floors with other thirty apartments. The problem lies in the entrance door to the building, which has a special key which may be reproduced only with the administrator's permission and a special matrix. The reason for this is discouraging owners to give out their keys to friends or workers or whoever does not belong to the building. The reason behind these measures, in turn, is the dangerousness of the city and its ever increasing crime rate. In other words, the less people have the entrance key, the better.
I have now added a clause to the house rules specifying that only one set of keys will be given to each group.
Thanks again,
Eloisa