As personal information and context sharing applications gain traction more attention is drawn to the associated privacy issues. These applications address privacy using an unsatisfactory "whitelist" approach, similar to social networks "friends". Some of them also link location publishing with user interaction which is also a form of privacy control -the user has to explicitly say where he is. There are a few automatic location based-services (LBS) that track the user, but without more

more »

... privacy protection mechanisms they enable even bigger threats to the user. On previous work, an XMPP-based Context Distribution Architecture was defined, more suitable for the distribution of frequently changing context than other systems because it is based on the publish-subscribe pattern. In this paper the authors present an extension to this architecture that allows for the introduction of a complex degree of access control in context distribution. The devised changes enable the system to consider a number of interesting context privacy settings for context distribution control. Also, this control must be enforced in a way that it doesn't interfere with the real-time nature of the distribution process. After describing the enhancements to the architecture, a prototype of the system is presented. Finally, the delivery latency and additional processing introduced by the access control components is estimated by testing it against the existing system.