@misc{cryptoeprint:2007:085,
author = {Hongbo Yu, Xiaoyun Wang},
title = {MultiCollision Attack on the Compression Functions of MD4 and 3-Pass HAVAL},
howpublished = {Cryptology ePrint Archive, Report 2007/085},
year = {2007},
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.