Rational behavior in peer-to-peer profile obfuscation for anonymous keyword search

User profiling in web search has the advantage of enabling personalized web search: the quality of the results offered by the search engine to the user is increased by taking the user’s interests into account when presenting those results. The negative side is that the interests and the query history of users may contain information considered as private; hence, technology should be provided for users to avoid profiling if they wish so. There are several anti-profiling approaches in web search, from basic level countermeasures to private information retrieval and including profile obfuscation. Except private information retrieval (PIR), which hides the retrieved item from the database, the rest of approaches focus on anonymizing the user’s identity and fall into the category of anonymous keyword search (also named sometimes user-private information retrieval). Most current PIR protocols are ill-suited to provide PIR from a search engine or large database, due to their complexity and their assumption that the database actively cooperates in the PIR protocol. Peerto-peer profile obfuscation protocols appear as a competitive option provided that peers are rationally interested in helping each other. We present a game-theoretic analysis of P2P profile obfuscation protocols which shows under which conditions helping each other is in the peers’ rational interest.