Cryptology ePrint Archive: BibTeX Citation of Report 2004/240

@misc{cryptoeprint:2004:240,
    author = {Seigo Arita and  Kazuto Matsuo and Koh-ichi Nagao and Mahoro Shimura},
    title = {A Weil Descent Attack against Elliptic Curve Cryptosystems over Quartic Extension Fields},
    howpublished = {Cryptology ePrint Archive, Report 2004/240},
    year = {2004},
    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.