On Metadata Privacy in Instant Messaging

Users metadata collection is a concerning issue related to Instant Messaging (IM) due to the potential of privacy violation. Even with messages' content encryption, metadata such as relationships and other communication patterns are exchanged in clear text, incurring in information leakage. In this paper, we investigate popular IM solutions to identify existing metadata, propose a broader nomenclature encompassing similar information, and assess the impact of metadata leakage on users' privacy. We also present a hierarchy of metadata based on our proposed nomenclature to allow for fair comparison among related work and easy gathering of privacy needs of users.