Hi Cyril,
Restriction feature are managed by restriction plugins (http://www.seblod.com/products?cck=seb_marketplace_item&seb_item_category=112&art_id=&seb_item_stores=&seb_item_type=commercial%2Cfree%2Cpack&seb_item_search_generic=&seb_item_ordering=0&boxchecked=0&search=seb_marketplace&task=search) that you can select on the content type edition interface on button 4.
It allows to restrict the display of a field in regards of dynamic data such as in regards of current language, permissions, user group...
Default workflow restriction plugin allows to display a field on admin or site side for add or edit form interface.
Regards.