Abstract-As the online social networks (OSNs), such as Facebook, witness explosive growth, the privacy challenges gain critical consideration from governmental and law agencies due to concentration of vast amount of personal information within a single administrative domain. In this paper, we demonstrate a privacy-aware decentralized OSN called My3 12 , where users can exercise full access control on their data. Our system exploits trust relationships in the social network for providing the necessary decentralized storage infrastructure. By taking users' geographical locations and online time statistics into account, it also addresses availability and storage performance issues.

The participatory sensing paradigm, through the growing availability of cheap sensors in mobile devices, enables applications of great social and business interest, e.g., electrosmog exposure measurement and early earthquake detection. However, users' privacy concerns regarding their activity traces need to be adequately addressed as well. The existing static privacy-enabling approaches, which hide or obfuscate data, offer some protection at the expense of data value. These approaches do not offer privacy guarantees and heterogeneous user privacy requirements cannot be met by them. In this paper, we propose a user-side privacy-protection scheme; it adaptively adjusts its parameters, in order to meet personalized location-privacy protection requirements against adversaries in a measurable manner. As proved by simulation experiments with artificial-and real-data traces, when feasible, our approach not only always satisfies personal location-privacy concerns, but also maximizes data utility (in terms of error, data availability, area coverage), as compared to static privacyprotection schemes.

Abstract-Unprecedented growth of online social networks (OSNs) increasingly makes privacy advocates and government agencies worrisome alike. In this paper, we propose My3, a privacy-friendly decentralized alternative for online social networking. The My3 system exploits well-known interesting properties of the current online social networks in its novel design namely, locality of access, predictable access times, geolocalization of friends, unique access requirements of the social content, and implicit trust among friends. It allows users to exercise finer granular access control on the content, thus making My3 extremely privacy-preserving. Moreover, we propose different replication strategies that users may independently choose for meeting their personalized performance objectives. A detailed performance study evaluates the system regarding profile availability, access delay, freshness and storage load. By using real-world data traces, we prove that My3 offers high availability even with low average online time of users in the network.

Abstract-The explosive growth of online social networks (OSNs) and their wide popularity suggest the impact of OSNs on today's Internet. At the same time, concentration of vast amount of personal information within a single administrative domain causes critical privacy concerns. As a result, privacy-conscious users feel dis-empowered with today's OSNs. In this paper, we report on an on-going research work and introduce a privacyaware decentralized OSN called porkut. Our system exploits trust relationships in the social network for decentralized storage of OSN profiles and their content. By taking users' geographical locations and online time statistics into account, it also addresses availability and storage performance issues. We finally advocate indexing of social network content and present an approach for indexing in a privacy-preserving manner.

Abstract-As the Online Social Networks (OSNs) amass unprecedented amounts of personal information, the privacy concerns gain considerable attention from the community. Apart from privacy-enabling approaches for existing OSNs, a number of initiatives towards building decentralized OSN infrastructures have emerged. However, before this paradigm becomes a serious alternative to current centralized infrastructures, some key design challenges, often conflicting with each other, have to be addressed. In this paper, we explore such design objectives concerning various system properties, namely availability, replication degree, user online times, privacy, and experimentally study the tradeoffs among them based on real data sets from Facebook and Twitter. We introduce different mechanisms to model user online times in the OSN from their activity times. We demonstrate how different profile replica selection approaches significantly affect the system performance.