Cryptology ePrint Archive: BibTeX Citation of Report 2005/225

@misc{cryptoeprint:2005:225,
    author = {Roberto M. Avanzi and Clemens Heuberger and Helmut Prodinger},
    title = {Minimality of the Hamming Weight of the \tau-NAF for Koblitz Curves and Improved Combination with Point Halving},
    howpublished = {Cryptology ePrint Archive, Report 2005/225},
    year = {2005},
    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.