@misc{cryptoeprint:2008:230,
author = {Tao Xie and DengGuo Feng and FanBao Liu},
title = {A New Collision Differential For MD5 With Its Full Differential Path},
howpublished = {Cryptology ePrint Archive, Report 2008/230},
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.