Cryptology ePrint Archive: BibTeX Citation of Report 2011/286

@misc{cryptoeprint:2011:286,
    author = {Dmitry Khovratovich and Christian Rechberger and Alexandra Savelieva},
    title = {Bicliques for Preimages: Attacks on Skein-512 and the SHA-2 family},
    howpublished = {Cryptology ePrint Archive, Report 2011/286},
    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.