Cryptology ePrint Archive: BibTeX Citation of Report 2004/241

@misc{cryptoeprint:2004:241,
    author = {Colm O hEigeartaigh},
    title = {A Comparison of Point Counting methods for Hyperelliptic Curves over Prime Fields and Fields of Characteristic 2},
    howpublished = {Cryptology ePrint Archive, Report 2004/241},
    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.