@misc{cryptoeprint:2010:294,
author = {Kristin Lauter and Tonghai Yang},
title = {Computing genus 2 curves from invariants on the Hilbert moduli space},
howpublished = {Cryptology ePrint Archive, Report 2010/294},
year = {2010},
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.