@misc{cryptoeprint:2012:096,
author = {Ewan Fleischmann and Christian Forler and Stefan Lucks and Jakob Wenzel},
title = {The Collision Security of MDC-4},
howpublished = {Cryptology ePrint Archive, Report 2012/096},
year = {2012},
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.