The confidentiality of correspondence has been historically characterized by letter exchanges. Think of the stamped royal letter protected with a wax seal. Everyone knows that a letter mailed in a glued envelope is more private than a standard postcard. This confidentiality with easily-understood privacy indicators has disappeared with the advent of digital correspondence.

In order to offer the public a better control over their private life, Caliopen proposes to associate a "privacy index" indicator to each element of it's interface. The user will be able to easily improve the level indicated by this index and thus be encouraged to better protect themselves and their contacts.

In order to do so, we have to define precise metrics to calculate those indices, that rely as much on technical data (protocol used, encryption...) than on human behaviour. We intend to present how much ambitious this is, the difficulties we face, and the leads we follow to realize that particular goal.