Cryptology ePrint Archive: BibTeX Citation of Report 2008/218

@misc{cryptoeprint:2008:218,
    author = {Wouter Castryck and Steven Galbraith and Reza Rezaeian Farashahi},
    title = {Efficient arithmetic on elliptic curves using a mixed Edwards-Montgomery representation},
    howpublished = {Cryptology ePrint Archive, Report 2008/218},
    year = {2008},
    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.