Cryptology ePrint Archive: BibTeX Citation of Report 2011/674

@misc{cryptoeprint:2011:674,
    author = {Colleen M. Swanson and Douglas R. Stinson},
    title = {Extended Combinatorial Constructions for Peer-to-peer User-Private Information Retrieval},
    howpublished = {Cryptology ePrint Archive, Report 2011/674},
    year = {2011},
    note = {\url{http://eprint.iacr.org/}},
}

You will need the url.sty package (comes with most LaTeX installations) for the last line. Otherwise, remove the \url command.