I. Introduction
Online Social Networks (OSNs) evolved into ubiquitous platforms of communication over the past few years and revolutionized interpersonal communication between people. Social users produce and disseminate an unprecedented amount of textual and multimedia content that is stored in a central data storage. This central data storage is controlled by the OSN providers and come with a variety of serious concerns, which are amplified by the very personal nature of social-networking-related data.