John Hughes∗†, Benjamin C. Pierce‡, Thomas Arts∗, Ulf Norell∗†, ∗ Quviq AB, G¨oteborg, Sweden † Dept of Computer Science and Engineering, Chalmers University of Technology, G¨oteborg, Sweden ‡ Dept of Computer and Information Science, University of Pennsylvania, PA, USA Abstract—File synchronization services such as Dropbox are used by hundreds of millions of people to replicate vital data. ...