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Nov 19 / Kimberly Mason

Limited Public Sharing

Written by Audrey Austin

With the rise in popularity of smartphones and mobile applications come new ways in which people are able to share content and information. One of the more recent trends in mobile applications is providing location-based services. Some mobile applications that make use of location data are Facebook, Foursquare, Google Now, Google+, and Twitter. Soon, users may also be able to utilize location data, in conjunction with temporal data, to determine who can access their publicly available content.

Using cell phone towers, wifi, and global positioning satellite (GPS) data, mobile applications are able to tailor services to a user’s location and geo-tag photos, status updates, and messages. Some features are triggered automatically and others are initiated by the user. Google Now uses location data to calculate travel time to home or work and report on local weather (What is it, n.d.). Twitter allows users to opt-in to location sharing, which adds location information to Tweets and allows users to see Tweets from others who are nearby (Twitter, Inc., 2013). Facebook and Foursquare allow users to “check in” to physical locations, such as restaurants, hospitals, parks, and even cities. Photos tagged at these locations are then publicly available to other users. Facebook allows photos to be shared at varying levels of publicity: Public, Friends, selected friends (“Custom”), and private (“Only Me”) (Facebook, 2013). Google+ utilizes “circles” to organize contacts, and content can be shared with no one, individual users, one or more circles, or everyone (Circles: Share and receive updates from the right people, n.d.). Photos posted on Foursquare are publicly shared. Furthermore, each user grants to other users “a non-exclusive license to access your User Submissions …, and to use, edit, modify, reproduce, distribute, prepare derivative works of, display and perform such User Submissions” in addition to the license granted to Foursquare (Foursquare Labs, Inc., 2013). None of these social networks offer a way to limit access to publicly shared content.

Christin, et al (2013) recognized the potential for limited public sharing and developed the idea of “privacy bubbles” (Share with strangers: Privacy bubbles as user-centered privacy control for mobile content sharing applications). The authors’ premise was that strangers at a public place or event may wish to share some of the photos they take with fellow attendees, but not everyone on the Internet. Current social networks define “access to the uploaded content based on social distance” (Christin, Lopez, Reinhardt, Hollick, & Kauer, 2013, p. 105). In contrast, privacy bubbles would allow users to limit the population that has access to their content by time and location. They would choose which photos to share with others who visited the same general area at approximately the same time. The degree of privacy would be inversely proportional to the size of the radius of the area and length of time chosen for sharing the content. For example, a privacy bubble set to +/- 5 minutes and 20 feet is more restrictive than one that is set to +/- 20 minutes and 50 feet. As the users move around, “the persons authorized to access [their] photos are dynamically determined for each individual photo” (Christin, Lopez, Reinhardt, Hollick, & Kauer, 2013, p. 106). The ability to create privacy bubbles would coexist with existing privacy settings in the applications that adopted it.

In the age of “Big Data,” social media networking, and location-sharing smartphones, the ability for users to choose how others can access their information is essential. Current practices utilize existing relationships between users to determine levels of sharing, but there is a large gap between “all contacts” and “the entire Internet.” Privacy bubbles would help fill in that gap.

Question: What potential roadblocks exist for implementing a privacy bubble feature in new or popular mobile applications?

Note: The privacy bubbles described by Christin et al (2013) are not the same as the “Privacy Bubbles for Google+TM” application that is available in the Chrome Web Store.


Christin, D., Lopez, P. S., Reinhardt, A., Hollick, M., & Kauer, M. (2013). Share with strangers: Privacy bubbles as user-centered privacy control for mobile content sharing applications. Information Security Technical Report, 17(3), 105-116. doi:10.1016/j.istr.2012.10.004

Facebook. (2013). Data use policy: Sharing and finding you on Facebook. Retrieved from Facebook:

Foursquare Labs, Inc. (2013, January 29). Terms of Use. Retrieved from foursquare:

Google. (n.d.). Circles: Share and receive updates from the right people. Retrieved from Google+:

Google. (n.d.). What is it. Retrieved from Google Now:

Twitter, Inc. (2013). FAQs about the Tweet location feature. Retrieved from Twitter Help Center:

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