The Privacy Enhancing Common Social Features Discovery Project aims at providing mobile users the opportunity to discover common social features they may have with other (possibly stranger) users. In numerous applications, users need to make trust and/or access control decisions involving other (possibly stranger) users, and one important factor is often the existence of common social feature (e.g., friendship, interest, etc.). This motivates the need for secure, privacy-preserving and efficient techniques allowing users to assess whether or not they have mutual attributes. Main challenges involved in this project are:

  • Exploration of social graph with data authenticity guarantees
  • Secure distribution of explored data (see: PeerShare project)
  • Discovery of common attributes by means of Private Set Intersection (PSI) protocols


We have built a framework for privacy-preserving determination of common friends (or more generally distance between two nodes on the social graph). This framework can be used by mobile app developers. We have built two example applications.


Technical reports