Coprivacy: an introduction to the theory and applications of co-operative privacy

We introduce the novel concept of coprivacy or co-operative privacy to make privacy preservation attractive. A protocol is coprivate if the best option for a player to preserve her privacy is to help another player in preserving his privacy. Coprivacy makes an individual�s privacy preservation a goal that rationally interests other individuals: it is a matter of helping oneself by helping someone else. We formally define coprivacy in terms of Nash equilibria. We then extend the concept to: i) general coprivacy, where a helping player�s utility (i.e. interest) may include earning functionality and security in addition to privacy; ii) mixed coprivacy, where mixed strategies and mixed Nash equilibria are allowed with some restrictions; iii) correlated coprivacy, in which Nash equilibria are replaced by correlated equilibria. Coprivacy can be applied to any peer-to-peer (P2P) protocol. We illustrate coprivacy in P2P anonymous keyword search, in content privacy in social networks, in vehicular network communications and in controlled content distribution and digital oblivion enforcement.