I want to make a protected processing imported layers from the sqlite database.
Is there in QGIS 2.0 a function or a plugin or do I have to insert directly into the data?
This can be a problem in SQLite. SQLite does not grant policy for user. And I think it's about privilegs in the database and not in the QGIS application. The application can control the privilegs to edit the attributes (Properties o layer>Fields>Edit line>Checkbox Editable).
Using qgis 2.18.x you can set al layer as 'read only'.
Go to project > project properties (or Ctrl+Shift+P). In the tab 'identify layers' you can check 'read only'.
Then the pencil (toggle editing) will be greyed out.