@misc{cryptoeprint:2005:228,
author = {Xinxin Fan and Thomas Wollinger and Yumin Wang},
title = {Efficient Doubling on Genus 3 Curves over Binary Fields},
howpublished = {Cryptology ePrint Archive, Report 2005/228},
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.