Subproject CO-PRIVACY/DBPRIVACY, led by IF-PAD/CSIC, will deal with coprivacy in peer-to-peer private information retrieval (PIR). Its specific objectives are:

  1. a) Model P2P PIR as a coprivate game, thereby ensuring rational cooperation between peers in submitting each other’s queries. b) Consider more general peer-to-peer interactions, such as multi-hop P2P PIR, in which a peer may decide to submit another peer’s query or forward the query to a third peer, and so on.
  2. Investigate how cryptography can be employed to enhance P2P PIR by offering group-based privacy to peers. Cryptography and group-based anonymity should not deter the rational cooperation implied by coprivacy. To remedy those shortcomings, one-round asymmetric group key agreement protocols will be designed (see our Eurocrypt 2009 paper) and ad hoc broadcast protocols. The idea is to go for privacy graduality (rather than full anonymity) to stimulate functionality and achieve coprivacy.
  3. Use the concept of general coprivacy to render P2P PIR attractive for the database, which would behave like a peer player with its own utility. The idea is to include in the game not only user privacy but also system security; the latter may open new possibilities, like liability investigation (e.g. tracing who has been querying details on a place where a bombing has recently happened) or fee charging (the database information items are not free and have different prices, and the database wishes to charge for each queried information).


  • Daniel Abril
  • Jordi Marés
  • Dr. Yasuo Narukawa
  • Dr. Guillermo Navarro
  • Dr. Vicenc Torra, principal investigator (PI) of the subproject