Cryptology ePrint Archive: BibTeX Citation of Report 2004/015

@misc{cryptoeprint:2004:015,
    author = {Trond St{\o}len Gustavsen and Kristian Ranestad},
    title = {An AGM-type elliptic curve point counting algorithm in characteristic three},
    howpublished = {Cryptology ePrint Archive, Report 2004/015},
    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.