@misc{cryptoeprint:2004:264,
author = {Philip Hawkes and Michael Paddon and Gregory G. Rose},
title = {Musings on the Wang et al. MD5 Collision},
howpublished = {Cryptology ePrint Archive, Report 2004/264},
year = {2004},
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.