Abstract. The Tor network is one of the largest deployed anonymity networks, consisting of 1500+ volunteer-run relays and probably hundreds of thousands of clients connecting every day. Its large user-base has made it attractive for researchers to analyze usage of a real deployed anonymity network. The recent growth of the network has also led to performance problems, as well as attempts by some governments to block access to the Tor network. Investigating these performance problems and learning about network blocking is best done by measuring usage data of the Tor network. However, analyzing a live anonymity system must be performed with great care, so that the users ’ privacy is not put at risk. In this paper we present a case study of measuring two different types of sensitive data in the Tor network: countries of connecting clients, and exiting traffic by port. Based on these examples we derive general guidelines for safely measuring potentially sensitive data, both in the Tor network and in other anonymity networks. 1

Abstract—During the last few years there has been an increasing number of people-centric sensing projects, which combine location information with other sensors available on mobile devices, such as the camera, the microphone or the accelerometer, giving birth to a different dimension in sensing our environment compared to the existing wireless sensor networks approach. In this paper, we envision a new scenario, where users develop their own participatory urban sensing projects at a large scale through the use of social networks. Consequently, users can participate in campaigns created by other users, according to their sensitivities and interests, exploiting the existing enormous social interconnections offered by existing social networking tools. We place our primary concern to protecting user privacy and address the need for new solutions in location anonymity and access control under this new complex and dynamic communication paradigm. I.

Abstract. The aim of this paper is to present a new idea on censorshipresilient communication Internet services, like blogs or web publishing. The motivation of this idea comes from the fact that in many situations guaranteeing this property is even matter of personal freedom. Our idea leverages: i) to split the actual content of a message and to scatter it through different points of retrieval; ii) to hide the content of a splitted message in a way that is clearly unidentifiable—hence involving encryption and steganography; iii) to allow the intended message recipient to correctly retrieve the original message. A further extension on this idea allows the recipient of the message to retrieve the message even if: i) some of the retrieval point are not available; ii) some retrieved data have been tampered with—their integrity has been violated. 1