Why Johnny Can’t Blow the Whistle: Identifying and Reducing Usability Issues in Anonymity Systems

Abstract—Tor is one of the most widely used anonymity networks in the world. The anonymity provided to any individual Tor user is a function of the total number of Tor users. Adoption of anonymity tools, including Tor, can be hindered by a lack of usability. Therefore, enhancing Tor’s usability and making it easier for more people to use Tor successfully increases security for all Tor users. To enhance Tor usability we begin by identifying stop-points which may act as barriers to using the Tor Browser Bundle (TBB). We suggest changes based on our analysis of these stop-points. To follow through, in our second study we test whether the changes we recommended to the Tor Project are effective in increasing usability, and find a significant decrease in stop-points across the board. Based on these studies, we both suggest new design heuristics appropriate for improving the usability of anonymity systems and identify design heuristics which are particularly salient in the design of anonymity systems. I