Cryptology ePrint Archive: BibTeX Citation of Report 2011/399

@misc{cryptoeprint:2011:399,
    author = {Luk Bettale and Jean-Charles Faugère and Ludovic Perret},
    title = {Cryptanalysis of HFE, Multi-HFE and Variants for Odd and Even Characteristic},
    howpublished = {Cryptology ePrint Archive, Report 2011/399},
    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.