With the advent of GPS-enabled smartphones, location-sharing services (LSSs) have emerged that share data collected through those mobile devices. However, research has shown that many users are uncomfortable with LSS operators managing their location histories, and that the ease with which contextual data can be shared with unintended audiences can lead to regrets that sometimes outweigh the benefits of these systems. In an effort to address these issues, we have developed SLS: a secure location sharing system that combines location-limited channels, multi-channel key establishment, and untrusted cloud storage to hide user locations from LSS operators while also limiting unintended audience sharing. In addition to describing the key agreement and location- sharing protocols used by the architecture, we discuss an iOS implementation of SLS that enables location sharing at tunable granularity through an intuitive policy interface on the user’s mobile device
