Cryptology ePrint Archive: BibTeX Citation of Report 2005/028

@misc{cryptoeprint:2005:028,
    author = {Giuseppe Ateniese and Kevin Fu and Matthew Green and Susan Hohenberger},
    title = {Improved Proxy Re-Encryption Schemes with Applications to Secure Distributed Storage},
    howpublished = {Cryptology ePrint Archive, Report 2005/028},
    year = {2005},
    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.