Management rule permission is a feature for SharePoint 2010/2013 allows users to manage permissions in a dynamic way.
The feature allows the List administrator user to define rules permissions when list item is added or updated.
rules can be related to the properties of the list or properties of User profile service.
for each new task added / changed, assign this permissions to the item:
Assigned To: Contribute
Responsable of Assigned To : Read
Group Manager: Full Control
the application is bilingual: English and French.