@misc{cryptoeprint:2010:309,
author = {Raveen R. Goundar and Marc Joye and Atsuko Miyaji},
title = {Co-Z Addition Formulae and Binary Ladders on Elliptic Curves},
howpublished = {Cryptology ePrint Archive, Report 2010/309},
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.