Cryptology ePrint Archive: BibTeX Citation of Report 2003/257

@misc{cryptoeprint:2003:257,
    author = {Mathieu Ciet and Marc Joye and Kristin Lauter and Peter L. Montgomery},
    title = {Trading Inversions for Multiplications in Elliptic Curve Cryptography},
    howpublished = {Cryptology ePrint Archive, Report 2003/257},
    year = {2003},
    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.