Small world phenomenon

The small-world phenomenon states the principle that all people linked by short chains six degrees of separation, the median length among the completed paths was six providing the first concrete evidence for the abundance of short paths connecting pairs of individuals in society.

We have followed a particular strand of research running through the topic of complex networks, concerned with short paths and the ability of decentralized algorithms to find them .

Our results confirm the power-law, small-world, and scale-free properties of on-line social networks, We observe that the in-degree of user nodes tends to match the out-degree; that the networks contain a densely connected core of high-degree nodes; and that this core links small groups of strongly clustered, low-degree nodes at the fringes of the network. Finally, we discuss the implications of these structural properties for the design of social network based systems. Unlike the Web, which is largely organized around content, on-line social networks are organized around users. Participating users join a network, publish their profile and any content, and create links to any other users with whom they associate. The resulting social network provides a basis for maintaining social relationships, for finding users with similar interests, and for locating content and knowledge that has been contributed or endorsed by other users.

Authoritative pages on certain topics:
A lot of experiments concerning the network structure of a hyper-linked environment finds thats these environments can be a rich source of all information about the content of that environment
a set of algorithms developed to extract informations from link structure of such networks and focus on the use of links for analyzing the collection of pages and discover the most authoritative pages on such topics,

The need to decentralized social network (Safebook):
a competitive social networking service, which solves these vulnerabilities by its decentralized design, leveraging on the real life relationships of its users and means of cryptography.

A peer-to-peer architecture:
in order to avoid control over user data and behavior by a single entity such as the service provider

privacy and trust management for user data and communications in the OSN system leveraging the trust relations from the social network

end-to-end confidentiality, authentication, access control, privacy, data integrity and data availability.

End-to-end confidentiality:
has to guarantee that no other than requesting and responding parties can access the exchanged data, so that eavesdropping is impossible. Since
in Peer to Peer (P2P) systems messages are forwarded along a path of peers that possibly contains a malicious entity, a special focus has to put on man in the middle attacks, as they may be easy to mount in this environment.

Decentralization is provided thanks to a structured peer to peer substrate, while privacy and cooperation enforcement are assured through to the matryoshkas, concentric structures crossed by paths providing hop-by-hop trust anonymizing each OSN member and guaranteeing access to the data of users.

references :
Safebook: Feasibility of Transitive Cooperation for Privacy
on a Decentralized Social Network
http://www.eurecom.fr/fr/publication/2757/download/rs-publi-2757.pdf

Authoritative Sources in a Hyperlinked Environment
https://www.cs.cornell.edu/home/kleinber/auth.pdf